refactor: replace char_u with char

Work on https://github.com/neovim/neovim/issues/459

80 files changed, 613 insertions, 612 deletions

diff --git a/src/nvim/api/autocmd.c b/src/nvim/api/autocmd.c
index 1cf0211f43..99340a3c59 100644
--- a/src/nvim/api/autocmd.c
+++ b/src/nvim/api/autocmd.c
@@ -240,7 +240,7 @@ Array nvim_get_autocmds(Dict(get_autocmds) *opts, Error *err)
           assert(pattern_filters[i]);
 
           char *pat = pattern_filters[i];
-          int patlen = (int)STRLEN(pat);
+          int patlen = (int)strlen(pat);
 
           if (aupat_is_buflocal(pat, patlen)) {
             aupat_normalize_buflocal_pat(pattern_buflocal,
diff --git a/src/nvim/api/command.c b/src/nvim/api/command.c
index b3518f1b0f..ed0907e8f8 100644
--- a/src/nvim/api/command.c
+++ b/src/nvim/api/command.c
@@ -105,7 +105,7 @@ Dictionary nvim_parse_cmd(String str, Dictionary opts, Error *err)
 
   // Parse arguments
   Array args = ARRAY_DICT_INIT;
-  size_t length = STRLEN(ea.arg);
+  size_t length = strlen(ea.arg);
 
   // For nargs = 1 or '?', pass the entire argument list as a single argument,
   // otherwise split arguments by whitespace.
diff --git a/src/nvim/api/extmark.c b/src/nvim/api/extmark.c
index ae051d8cab..edcea52838 100644
--- a/src/nvim/api/extmark.c
+++ b/src/nvim/api/extmark.c
@@ -742,7 +742,7 @@ Integer nvim_buf_set_extmark(Buffer buffer, Integer ns_id, Integer line, Integer
       line = buf->b_ml.ml_line_count;
     }
   } else if (line < buf->b_ml.ml_line_count) {
-    len = ephemeral ? MAXCOL : STRLEN(ml_get_buf(buf, (linenr_T)line + 1, false));
+    len = ephemeral ? MAXCOL : strlen(ml_get_buf(buf, (linenr_T)line + 1, false));
   }
 
   if (col == -1) {
@@ -761,7 +761,7 @@ Integer nvim_buf_set_extmark(Buffer buffer, Integer ns_id, Integer line, Integer
 
   if (col2 >= 0) {
     if (line2 >= 0 && line2 < buf->b_ml.ml_line_count) {
-      len = ephemeral ? MAXCOL : STRLEN(ml_get_buf(buf, (linenr_T)line2 + 1, false));
+      len = ephemeral ? MAXCOL : strlen(ml_get_buf(buf, (linenr_T)line2 + 1, false));
     } else if (line2 == buf->b_ml.ml_line_count) {
       // We are trying to add an extmark past final newline
       len = 0;
@@ -1106,7 +1106,7 @@ static int init_sign_text(char **sign_text, char *text)
 {
   char *s;
 
-  char *endp = text + (int)STRLEN(text);
+  char *endp = text + (int)strlen(text);
 
   // Count cells and check for non-printable chars
   int cells = 0;
diff --git a/src/nvim/api/ui.c b/src/nvim/api/ui.c
index 27fb4b8e16..45c20d07e1 100644
--- a/src/nvim/api/ui.c
+++ b/src/nvim/api/ui.c
@@ -122,7 +122,7 @@ static char *mpack_array_dyn16(char **buf)
 static void mpack_str(char **buf, const char *str)
 {
   assert(sizeof(schar_T) - 1 < 0x20);
-  size_t len = STRLEN(str);
+  size_t len = strlen(str);
   mpack_w(buf, 0xa0 | len);
   memcpy(*buf, str, len);
   *buf += len;
diff --git a/src/nvim/api/vimscript.c b/src/nvim/api/vimscript.c
index f6d0e39327..1758f18926 100644
--- a/src/nvim/api/vimscript.c
+++ b/src/nvim/api/vimscript.c
@@ -304,7 +304,7 @@ Object nvim_call_dict_function(Object dict, String fn, Array args, Error *err)
     }
     fn = (String) {
       .data = di->di_tv.vval.v_string,
-      .size = STRLEN(di->di_tv.vval.v_string),
+      .size = strlen(di->di_tv.vval.v_string),
     };
   }
 
diff --git a/src/nvim/autocmd.c b/src/nvim/autocmd.c
index 9d37647a4e..dafbae5813 100644
--- a/src/nvim/autocmd.c
+++ b/src/nvim/autocmd.c
@@ -266,7 +266,7 @@ static void au_show_for_event(int group, event_T event, char *pat)
       // normalize pat into standard "<buffer>#N" form
       aupat_normalize_buflocal_pat(buflocal_pat, pat, patlen, aupat_get_buflocal_nr(pat, patlen));
       pat = (char *)buflocal_pat;
-      patlen = (int)STRLEN(buflocal_pat);
+      patlen = (int)strlen(buflocal_pat);
     }
 
     assert(*pat != NUL);
@@ -725,7 +725,7 @@ int check_ei(void)
 char *au_event_disable(char *what)
 {
   char *save_ei = xstrdup(p_ei);
-  char *new_ei = xstrnsave(p_ei, STRLEN(p_ei) + STRLEN(what));
+  char *new_ei = xstrnsave(p_ei, strlen(p_ei) + strlen(what));
   if (*what == ',' && *p_ei == NUL) {
     STRCPY(new_ei, what + 1);
   } else {
@@ -957,7 +957,7 @@ int do_autocmd_event(event_T event, char *pat, bool once, int nested, char *cmd,
       aupat_normalize_buflocal_pat(buflocal_pat, pat, patlen, buflocal_nr);
 
       pat = buflocal_pat;
-      patlen = (int)STRLEN(buflocal_pat);
+      patlen = (int)strlen(buflocal_pat);
     }
 
     if (delete) {
@@ -1018,7 +1018,7 @@ int autocmd_register(int64_t id, event_T event, char *pat, int patlen, int group
   int findgroup;
   char buflocal_pat[BUFLOCAL_PAT_LEN];  // for "<buffer=X>"
 
-  if (patlen > (int)STRLEN(pat)) {
+  if (patlen > (int)strlen(pat)) {
     return FAIL;
   }
 
@@ -1039,7 +1039,7 @@ int autocmd_register(int64_t id, event_T event, char *pat, int patlen, int group
     aupat_normalize_buflocal_pat(buflocal_pat, pat, patlen, buflocal_nr);
 
     pat = buflocal_pat;
-    patlen = (int)STRLEN(buflocal_pat);
+    patlen = (int)strlen(buflocal_pat);
   }
 
   // always goes at or after the last one, so start at the end.
@@ -1193,7 +1193,7 @@ size_t aucmd_pattern_length(char *pat)
     return (size_t)(endpat - pat);
   }
 
-  return STRLEN(pat);
+  return strlen(pat);
 }
 
 char *aucmd_next_pattern(char *pat, size_t patlen)
@@ -2012,7 +2012,7 @@ void auto_next_pat(AutoPatCmd *apc, int stop_at_last)
         s = _("%s Autocommands for \"%s\"");
 
         const size_t sourcing_name_len
-          = (STRLEN(s) + strlen(name) + (size_t)ap->patlen + 1);
+          = (strlen(s) + strlen(name) + (size_t)ap->patlen + 1);
 
         char *const namep = xmalloc(sourcing_name_len);
         snprintf(namep, sourcing_name_len, s, name, ap->pat);
diff --git a/src/nvim/buffer.c b/src/nvim/buffer.c
index 1cc68c9cee..1d8f4a257c 100644
--- a/src/nvim/buffer.c
+++ b/src/nvim/buffer.c
@@ -2170,7 +2170,7 @@ int buflist_findpat(const char *pattern, const char *pattern_end, bool unlisted,
     if (pat == NULL) {
       return -1;
     }
-    patend = pat + STRLEN(pat) - 1;
+    patend = pat + strlen(pat) - 1;
     toggledollar = (patend > pat && *patend == '$');
 
     // First try finding a listed buffer.  If not found and "unlisted"
@@ -2284,7 +2284,7 @@ int ExpandBufnames(char *pat, int *num_file, char ***file, int options)
 
   // Make a copy of "pat" and change "^" to "\(^\|[\/]\)".
   if (*pat == '^') {
-    patc = xmalloc(STRLEN(pat) + 11);
+    patc = xmalloc(strlen(pat) + 11);
     STRCPY(patc, "\\(^\\|[\\/]\\)");
     STRCPY(patc + 11, pat + 1);
   } else {
@@ -3037,7 +3037,7 @@ void fileinfo(int fullname, int shorthelp, int dont_truncate)
 
   if (fullname > 1) {       // 2 CTRL-G: include buffer number
     vim_snprintf(buffer, IOSIZE, "buf %d: ", curbuf->b_fnum);
-    p = buffer + STRLEN(buffer);
+    p = buffer + strlen(buffer);
   } else {
     p = buffer;
   }
@@ -3096,7 +3096,7 @@ void fileinfo(int fullname, int shorthelp, int dont_truncate)
                      (int64_t)curbuf->b_ml.ml_line_count,
                      n);
     validate_virtcol();
-    len = STRLEN(buffer);
+    len = strlen(buffer);
     col_print(buffer + len, IOSIZE - len,
               (int)curwin->w_cursor.col + 1, (int)curwin->w_virtcol + 1);
   }
@@ -3305,7 +3305,7 @@ void maketitle(void)
       }
       *icon_str = NUL;
       // Truncate name at 100 bytes.
-      len = (int)STRLEN(buf_p);
+      len = (int)strlen(buf_p);
       if (len > 100) {
         len -= 100;
         len += utf_cp_tail_off(buf_p, buf_p + len) + 1;
@@ -3412,7 +3412,7 @@ bool append_arg_number(win_T *wp, char *buf, int buflen, bool add_file)
     return false;
   }
 
-  char *p = buf + STRLEN(buf);  // go to the end of the buffer
+  char *p = buf + strlen(buf);  // go to the end of the buffer
 
   // Early out if the string is getting too long
   if (p - buf + 35 >= buflen) {
diff --git a/src/nvim/change.c b/src/nvim/change.c
index 6cd971cd74..ab550259c8 100644
--- a/src/nvim/change.c
+++ b/src/nvim/change.c
@@ -589,7 +589,7 @@ bool file_ff_differs(buf_T *buf, bool ignore_empty)
 /// Handles Replace mode and multi-byte characters.
 void ins_bytes(char *p)
 {
-  ins_bytes_len(p, STRLEN(p));
+  ins_bytes_len(p, strlen(p));
 }
 
 /// Insert string "p" with length "len" at the cursor position.
@@ -632,7 +632,7 @@ void ins_char_bytes(char *buf, size_t charlen)
   size_t col = (size_t)curwin->w_cursor.col;
   linenr_T lnum = curwin->w_cursor.lnum;
   char *oldp = ml_get(lnum);
-  size_t linelen = STRLEN(oldp) + 1;  // length of old line including NUL
+  size_t linelen = strlen(oldp) + 1;  // length of old line including NUL
 
   // The lengths default to the values for when not replacing.
   size_t oldlen = 0;        // nr of bytes inserted
@@ -731,7 +731,7 @@ void ins_char_bytes(char *buf, size_t charlen)
 /// Caller must have prepared for undo.
 void ins_str(char *s)
 {
-  int newlen = (int)STRLEN(s);
+  int newlen = (int)strlen(s);
   linenr_T lnum = curwin->w_cursor.lnum;
 
   if (virtual_active() && curwin->w_cursor.coladd > 0) {
@@ -740,7 +740,7 @@ void ins_str(char *s)
 
   colnr_T col = curwin->w_cursor.col;
   char *oldp = ml_get(lnum);
-  int oldlen = (int)STRLEN(oldp);
+  int oldlen = (int)strlen(oldp);
 
   char *newp = xmalloc((size_t)oldlen + (size_t)newlen + 1);
   if (col > 0) {
@@ -798,7 +798,7 @@ int del_bytes(colnr_T count, bool fixpos_arg, bool use_delcombine)
   colnr_T col = curwin->w_cursor.col;
   bool fixpos = fixpos_arg;
   char *oldp = ml_get(lnum);
-  colnr_T oldlen = (colnr_T)STRLEN(oldp);
+  colnr_T oldlen = (colnr_T)strlen(oldp);
 
   // Can't do anything when the cursor is on the NUL after the line.
   if (col >= oldlen) {
@@ -962,7 +962,7 @@ int copy_indent(int size, char *src)
     if (p == NULL) {
       // Allocate memory for the result: the copied indent, new indent
       // and the rest of the line.
-      line_len = (int)STRLEN(get_cursor_line_ptr()) + 1;
+      line_len = (int)strlen(get_cursor_line_ptr()) + 1;
       assert(ind_len + line_len >= 0);
       size_t line_size;
       STRICT_ADD(ind_len, line_len, &line_size, size_t);
@@ -1072,7 +1072,7 @@ int open_line(int dir, int flags, int second_line_indent, bool *did_do_comment)
       p = skipwhite(p_extra);
       first_char = (unsigned char)(*p);
     }
-    extra_len = (int)STRLEN(p_extra);
+    extra_len = (int)strlen(p_extra);
     saved_char = *p_extra;
     *p_extra = NUL;
   }
@@ -1155,7 +1155,7 @@ int open_line(int dir, int flags, int second_line_indent, bool *did_do_comment)
           }
         } else {      // Not a comment line
           // Find last non-blank in line
-          p = ptr + STRLEN(ptr) - 1;
+          p = ptr + strlen(ptr) - 1;
           while (p > ptr && ascii_iswhite(*p)) {
             p--;
           }
@@ -1205,7 +1205,7 @@ int open_line(int dir, int flags, int second_line_indent, bool *did_do_comment)
 
           while ((ptr[0] == '#' || was_backslashed)
                  && curwin->w_cursor.lnum < curbuf->b_ml.ml_line_count) {
-            if (*ptr && ptr[STRLEN(ptr) - 1] == '\\') {
+            if (*ptr && ptr[strlen(ptr) - 1] == '\\') {
               was_backslashed = true;
             } else {
               was_backslashed = false;
@@ -1331,7 +1331,7 @@ int open_line(int dir, int flags, int second_line_indent, bool *did_do_comment)
         if (lead_len > 0) {
           if (current_flag == COM_START) {
             lead_repl = (char *)lead_middle;
-            lead_repl_len = (int)STRLEN(lead_middle);
+            lead_repl_len = (int)strlen(lead_middle);
           }
 
           // If we have hit RETURN immediately after the start
@@ -1641,7 +1641,7 @@ int open_line(int dir, int flags, int second_line_indent, bool *did_do_comment)
     if (flags & OPENLINE_COM_LIST && second_line_indent > 0) {
       int i;
       int padding = second_line_indent
-                    - (newindent + (int)STRLEN(leader));
+                    - (newindent + (int)strlen(leader));
 
       // Here whitespace is inserted after the comment char.
       // Below, set_indent(newindent, SIN_INSERT) will insert the
@@ -1755,7 +1755,7 @@ int open_line(int dir, int flags, int second_line_indent, bool *did_do_comment)
       }
       ml_replace(curwin->w_cursor.lnum, saved_line, false);
 
-      int new_len = (int)STRLEN(saved_line);
+      int new_len = (int)strlen(saved_line);
 
       // TODO(vigoux): maybe there is issues there with expandtabs ?
       int cols_spliced = 0;
@@ -1795,7 +1795,7 @@ int open_line(int dir, int flags, int second_line_indent, bool *did_do_comment)
   if (did_append) {
     changed_lines(curwin->w_cursor.lnum, 0, curwin->w_cursor.lnum, 1L, true);
     // bail out and just get the final length of the line we just manipulated
-    bcount_t extra = (bcount_t)STRLEN(ml_get(curwin->w_cursor.lnum));
+    bcount_t extra = (bcount_t)strlen(ml_get(curwin->w_cursor.lnum));
     extmark_splice(curbuf, (int)curwin->w_cursor.lnum - 1, 0,
                    0, 0, 0, 1, 0, 1 + extra, kExtmarkUndo);
   }
@@ -2084,7 +2084,7 @@ int get_last_leader_offset(char *line, char **flags)
   char part_buf[COM_MAX_LEN];         // buffer for one option part
 
   // Repeat to match several nested comment strings.
-  int i = (int)STRLEN(line);
+  int i = (int)strlen(line);
   while (--i >= lower_check_bound) {
     // scan through the 'comments' option for a match
     int found_one = false;
@@ -2171,7 +2171,7 @@ int get_last_leader_offset(char *line, char **flags)
       while (ascii_iswhite(*com_leader)) {
         com_leader++;
       }
-      len1 = (int)STRLEN(com_leader);
+      len1 = (int)strlen(com_leader);
 
       for (list = curbuf->b_p_com; *list;) {
         char *flags_save = list;
@@ -2185,7 +2185,7 @@ int get_last_leader_offset(char *line, char **flags)
         while (ascii_iswhite(*string)) {
           string++;
         }
-        len2 = (int)STRLEN(string);
+        len2 = (int)strlen(string);
         if (len2 == 0) {
           continue;
         }
diff --git a/src/nvim/charset.c b/src/nvim/charset.c
index 693ff90179..0cc2189948 100644
--- a/src/nvim/charset.c
+++ b/src/nvim/charset.c
@@ -268,7 +268,7 @@ int buf_init_chartab(buf_T *buf, int global)
 void trans_characters(char *buf, int bufsize)
 {
   char_u *trs;                 // translated character
-  int len = (int)STRLEN(buf);  // length of string needing translation
+  int len = (int)strlen(buf);  // length of string needing translation
   int room = bufsize - len;    // room in buffer after string
 
   while (*buf != 0) {
@@ -1078,7 +1078,7 @@ void getvvcol(win_T *wp, pos_T *pos, colnr_T *start, colnr_T *cursor, colnr_T *e
     // Cannot put the cursor on part of a wide character.
     char *ptr = ml_get_buf(wp->w_buffer, pos->lnum, false);
 
-    if (pos->col < (colnr_T)STRLEN(ptr)) {
+    if (pos->col < (colnr_T)strlen(ptr)) {
       int c = utf_ptr2char(ptr + pos->col);
       if ((c != TAB) && vim_isprintc(c)) {
         endadd = (colnr_T)(char2cells(c) - 1);
@@ -1157,7 +1157,7 @@ char *skipwhite(const char *const p)
   FUNC_ATTR_PURE FUNC_ATTR_WARN_UNUSED_RESULT FUNC_ATTR_NONNULL_ALL
   FUNC_ATTR_NONNULL_RET
 {
-  return skipwhite_len(p, STRLEN(p));
+  return skipwhite_len(p, strlen(p));
 }
 
 /// Like `skipwhite`, but skip up to `len` characters.
diff --git a/src/nvim/cmdexpand.c b/src/nvim/cmdexpand.c
index 3e9edea372..65b07cc17b 100644
--- a/src/nvim/cmdexpand.c
+++ b/src/nvim/cmdexpand.c
@@ -511,7 +511,7 @@ char *ExpandOne(expand_T *xp, char *str, char *orig, int options, int mode)
   if (mode == WILD_ALL && xp->xp_numfiles > 0 && !got_int) {
     size_t len = 0;
     for (i = 0; i < xp->xp_numfiles; i++) {
-      len += STRLEN(xp->xp_files[i]) + 1;
+      len += strlen(xp->xp_files[i]) + 1;
     }
     ss = xmalloc(len);
     *ss = NUL;
@@ -672,7 +672,7 @@ int showmatches(expand_T *xp, int wildmenu)
       for (k = i; k < num_files; k += lines) {
         if (xp->xp_context == EXPAND_TAGS_LISTFILES) {
           msg_outtrans_attr(files_found[k], HL_ATTR(HLF_D));
-          p = (char_u *)files_found[k] + STRLEN(files_found[k]) + 1;
+          p = (char_u *)files_found[k] + strlen(files_found[k]) + 1;
           msg_advance(maxlen + 1);
           msg_puts((const char *)p);
           msg_advance(maxlen + 3);
@@ -2280,7 +2280,7 @@ static void ExpandGeneric(expand_T *xp, regmatch_T *regmatch, int *num_file, cha
       (*file)[count++] = str;
       if (func == get_menu_names) {
         // Test for separator added by get_menu_names().
-        str += STRLEN(str) - 1;
+        str += strlen(str) - 1;
         if (*str == '\001') {
           *str = '.';
         }
@@ -2362,7 +2362,7 @@ static void expand_shellcmd(char *filepat, int *num_file, char ***file, int flag
   for (s = path;; s = e) {
     e = vim_strchr(s, ENV_SEPCHAR);
     if (e == NULL) {
-      e = s + STRLEN(s);
+      e = s + strlen(s);
     }
 
     if (*s == NUL) {
@@ -2386,7 +2386,7 @@ static void expand_shellcmd(char *filepat, int *num_file, char ***file, int flag
     }
     STRLCPY(buf, s, l + 1);
     add_pathsep(buf);
-    l = STRLEN(buf);
+    l = strlen(buf);
     STRLCPY(buf + l, pat, MAXPATHL - l);
 
     // Expand matches in one directory of $PATH.
@@ -2493,7 +2493,7 @@ static int ExpandUserDefined(expand_T *xp, regmatch_T *regmatch, int *num_file,
   for (char *s = retstr; *s != NUL; s = e) {
     e = vim_strchr(s, '\n');
     if (e == NULL) {
-      e = s + STRLEN(s);
+      e = s + strlen(s);
     }
     const char keep = *e;
     *e = NUL;
@@ -2584,7 +2584,7 @@ void globpath(char *path, char *file, garray_T *ga, int expand_options)
   while (*path != NUL) {
     // Copy one item of the path to buf[] and concatenate the file name.
     copy_option_part(&path, (char *)buf, MAXPATHL, ",");
-    if (STRLEN(buf) + STRLEN(file) + 2 < MAXPATHL) {
+    if (STRLEN(buf) + strlen(file) + 2 < MAXPATHL) {
       add_pathsep((char *)buf);
       STRCAT(buf, file);  // NOLINT
 
@@ -2864,14 +2864,14 @@ void f_getcompletion(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
 
   if (strcmp(type, "cmdline") == 0) {
     set_one_cmd_context(&xpc, pattern);
-    xpc.xp_pattern_len = STRLEN(xpc.xp_pattern);
-    xpc.xp_col = (int)STRLEN(pattern);
+    xpc.xp_pattern_len = strlen(xpc.xp_pattern);
+    xpc.xp_col = (int)strlen(pattern);
     goto theend;
   }
 
   ExpandInit(&xpc);
   xpc.xp_pattern = (char *)pattern;
-  xpc.xp_pattern_len = STRLEN(xpc.xp_pattern);
+  xpc.xp_pattern_len = strlen(xpc.xp_pattern);
   xpc.xp_context = cmdcomplete_str_to_type(type);
   if (xpc.xp_context == EXPAND_NOTHING) {
     semsg(_(e_invarg2), type);
@@ -2880,17 +2880,17 @@ void f_getcompletion(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
 
   if (xpc.xp_context == EXPAND_MENUS) {
     set_context_in_menu_cmd(&xpc, "menu", xpc.xp_pattern, false);
-    xpc.xp_pattern_len = STRLEN(xpc.xp_pattern);
+    xpc.xp_pattern_len = strlen(xpc.xp_pattern);
   }
 
   if (xpc.xp_context == EXPAND_CSCOPE) {
     set_context_in_cscope_cmd(&xpc, (const char *)xpc.xp_pattern, CMD_cscope);
-    xpc.xp_pattern_len = STRLEN(xpc.xp_pattern);
+    xpc.xp_pattern_len = strlen(xpc.xp_pattern);
   }
 
   if (xpc.xp_context == EXPAND_SIGN) {
     set_context_in_sign_cmd(&xpc, xpc.xp_pattern);
-    xpc.xp_pattern_len = STRLEN(xpc.xp_pattern);
+    xpc.xp_pattern_len = strlen(xpc.xp_pattern);
   }
 
 theend:
diff --git a/src/nvim/cmdhist.c b/src/nvim/cmdhist.c
index 3747c91c4f..5a59f09113 100644
--- a/src/nvim/cmdhist.c
+++ b/src/nvim/cmdhist.c
@@ -91,7 +91,7 @@ static char *(history_names[]) = {
 char *get_history_arg(expand_T *xp, int idx)
 {
   const char *short_names = ":=@>?/";
-  const int short_names_count = (int)STRLEN(short_names);
+  const int short_names_count = (int)strlen(short_names);
   const int history_name_count = ARRAY_SIZE(history_names) - 1;
 
   if (idx < short_names_count) {
@@ -312,7 +312,7 @@ void add_to_history(int histype, char *new_entry, int in_map, int sep)
     hist_free_entry(hisptr);
 
     // Store the separator after the NUL of the string.
-    size_t len = STRLEN(new_entry);
+    size_t len = strlen(new_entry);
     hisptr->hisstr = xstrnsave(new_entry, len + 2);
     hisptr->timestamp = os_time();
     hisptr->additional_elements = NULL;
@@ -644,8 +644,8 @@ void ex_history(exarg_T *eap)
           snprintf((char *)IObuff, IOSIZE, "%c%6d  ", i == idx ? '>' : ' ',
                    hist[i].hisnum);
           if (vim_strsize(hist[i].hisstr) > Columns - 10) {
-            trunc_string(hist[i].hisstr, (char *)IObuff + STRLEN(IObuff),
-                         Columns - 10, IOSIZE - (int)STRLEN(IObuff));
+            trunc_string(hist[i].hisstr, (char *)IObuff + strlen(IObuff),
+                         Columns - 10, IOSIZE - (int)strlen(IObuff));
           } else {
             STRCAT(IObuff, hist[i].hisstr);
           }
diff --git a/src/nvim/cursor.c b/src/nvim/cursor.c
index cd651fcf4c..6c0475822b 100644
--- a/src/nvim/cursor.c
+++ b/src/nvim/cursor.c
@@ -67,7 +67,7 @@ int coladvance_force(colnr_T wcol)
 /// Try to advance the Cursor to the specified screen column.
 /// If virtual editing: fine tune the cursor position.
 /// Note that all virtual positions off the end of a line should share
-/// a curwin->w_cursor.col value (n.b. this is equal to STRLEN(line)),
+/// a curwin->w_cursor.col value (n.b. this is equal to strlen(line)),
 /// beginning at coladd 0.
 ///
 /// @return  OK if desired column is reached, FAIL if not
@@ -346,7 +346,7 @@ void check_cursor_col_win(win_T *win)
   colnr_T oldcoladd = win->w_cursor.col + win->w_cursor.coladd;
   unsigned int cur_ve_flags = get_ve_flags();
 
-  colnr_T len = (colnr_T)STRLEN(ml_get_buf(win->w_buffer, win->w_cursor.lnum, false));
+  colnr_T len = (colnr_T)strlen(ml_get_buf(win->w_buffer, win->w_cursor.lnum, false));
   if (len == 0) {
     win->w_cursor.col = 0;
   } else if (win->w_cursor.col >= len) {
@@ -412,7 +412,7 @@ void check_visual_pos(void)
     VIsual.col = 0;
     VIsual.coladd = 0;
   } else {
-    int len = (int)STRLEN(ml_get(VIsual.lnum));
+    int len = (int)strlen(ml_get(VIsual.lnum));
 
     if (VIsual.col > len) {
       VIsual.col = len;
diff --git a/src/nvim/cursor_shape.c b/src/nvim/cursor_shape.c
index 73ad99876a..6f4f17659a 100644
--- a/src/nvim/cursor_shape.c
+++ b/src/nvim/cursor_shape.c
@@ -220,7 +220,7 @@ char *parse_shape_opt(int what)
               endp = vim_strchr(p, '-');
               if (commap == NULL) {                       // last part
                 if (endp == NULL) {
-                  endp = p + STRLEN(p);                  // find end of part
+                  endp = p + strlen(p);                  // find end of part
                 }
               } else if (endp > commap || endp == NULL) {
                 endp = commap;
diff --git a/src/nvim/diff.c b/src/nvim/diff.c
index c5092dc866..9446d35630 100644
--- a/src/nvim/diff.c
+++ b/src/nvim/diff.c
@@ -729,7 +729,7 @@ static int diff_write_buffer(buf_T *buf, diffin_T *din)
 
   // xdiff requires one big block of memory with all the text.
   for (linenr_T lnum = 1; lnum <= buf->b_ml.ml_line_count; lnum++) {
-    len += (long)STRLEN(ml_get_buf(buf, lnum, false)) + 1;
+    len += (long)strlen(ml_get_buf(buf, lnum, false)) + 1;
   }
   char_u *ptr = try_malloc((size_t)len);
   if (ptr == NULL) {
@@ -1128,7 +1128,7 @@ static int diff_file(diffio_T *dio)
     return diff_file_internal(dio);
   } else {
     const size_t len = (strlen(tmp_orig) + strlen(tmp_new) + strlen(tmp_diff)
-                        + STRLEN(p_srr) + 27);
+                        + strlen(p_srr) + 27);
     char *const cmd = xmalloc(len);
 
     // We don't want $DIFF_OPTIONS to get in the way.
@@ -1267,7 +1267,7 @@ void ex_diffpatch(exarg_T *eap)
     emsg(_("E816: Cannot read patch output"));
   } else {
     if (curbuf->b_fname != NULL) {
-      newname = xstrnsave(curbuf->b_fname, STRLEN(curbuf->b_fname) + 4);
+      newname = xstrnsave(curbuf->b_fname, strlen(curbuf->b_fname) + 4);
       STRCAT(newname, ".new");
     }
 
@@ -1429,7 +1429,7 @@ void diff_win_options(win_T *wp, int addbuf)
   free_string_option(wp->w_p_fdc);
   wp->w_p_fdc = xstrdup("2");
   assert(diff_foldcolumn >= 0 && diff_foldcolumn <= 9);
-  snprintf(wp->w_p_fdc, STRLEN(wp->w_p_fdc) + 1, "%d", diff_foldcolumn);
+  snprintf(wp->w_p_fdc, strlen(wp->w_p_fdc) + 1, "%d", diff_foldcolumn);
   wp->w_p_fen = true;
   wp->w_p_fdl = 0;
   foldUpdateAll(wp);
@@ -2356,8 +2356,8 @@ bool diff_find_change(win_T *wp, linenr_T lnum, int *startp, int *endp)
 
       // Search for end of difference, if any.
       if ((line_org[si_org] != NUL) || (line_new[si_new] != NUL)) {
-        ei_org = (int)STRLEN(line_org);
-        ei_new = (int)STRLEN(line_new);
+        ei_org = (int)strlen(line_org);
+        ei_new = (int)strlen(line_new);
 
         while (ei_org >= *startp
                && ei_new >= si_new
@@ -2564,7 +2564,7 @@ void ex_diffgetput(exarg_T *eap)
     }
   } else {
     // Buffer number or pattern given. Ignore trailing white space.
-    p = eap->arg + STRLEN(eap->arg);
+    p = eap->arg + strlen(eap->arg);
     while (p > eap->arg && ascii_iswhite(p[-1])) {
       p--;
     }
diff --git a/src/nvim/digraph.c b/src/nvim/digraph.c
index 8e31d3feab..c0e7a6250e 100644
--- a/src/nvim/digraph.c
+++ b/src/nvim/digraph.c
@@ -1926,7 +1926,7 @@ void f_digraph_get(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
   if (digraphs == NULL) {
     return;
   }
-  if (STRLEN(digraphs) != 2) {
+  if (strlen(digraphs) != 2) {
     semsg(_(e_digraph_must_be_just_two_characters_str), digraphs);
     return;
   }
@@ -2036,7 +2036,7 @@ char *keymap_init(void)
 
     // Source the keymap file.  It will contain a ":loadkeymap" command
     // which will call ex_loadkeymap() below.
-    buflen = STRLEN(curbuf->b_p_keymap) + STRLEN(p_enc) + 14;
+    buflen = strlen(curbuf->b_p_keymap) + strlen(p_enc) + 14;
     buf = xmalloc(buflen);
 
     // try finding "keymap/'keymap'_'encoding'.vim"  in 'runtimepath'
@@ -2102,7 +2102,7 @@ void ex_loadkeymap(exarg_T *eap)
       s = skiptowhite(p);
       kp->to = xstrnsave(p, (size_t)(s - p));
 
-      if ((STRLEN(kp->from) + STRLEN(kp->to) >= KMAP_LLEN)
+      if ((strlen(kp->from) + strlen(kp->to) >= KMAP_LLEN)
           || (*kp->from == NUL)
           || (*kp->to == NUL)) {
         if (*kp->to == NUL) {
diff --git a/src/nvim/drawscreen.c b/src/nvim/drawscreen.c
index 5b83821927..957e8ae4da 100644
--- a/src/nvim/drawscreen.c
+++ b/src/nvim/drawscreen.c
@@ -1448,7 +1448,7 @@ win_update_start:
                  pos.lnum += cursor_above ? 1 : -1) {
               colnr_T t;
 
-              pos.col = (colnr_T)STRLEN(ml_get_buf(wp->w_buffer, pos.lnum, false));
+              pos.col = (colnr_T)strlen(ml_get_buf(wp->w_buffer, pos.lnum, false));
               getvvcol(wp, &pos, NULL, NULL, &t);
               if (toc < t) {
                 toc = t;
diff --git a/src/nvim/edit.c b/src/nvim/edit.c
index 1a8030d511..a165078bdf 100644
--- a/src/nvim/edit.c
+++ b/src/nvim/edit.c
@@ -1773,7 +1773,7 @@ void truncate_spaces(char *line)
   int i;
 
   // find start of trailing white space
-  for (i = (int)STRLEN(line) - 1; i >= 0 && ascii_iswhite(line[i]); i--) {
+  for (i = (int)strlen(line) - 1; i >= 0 && ascii_iswhite(line[i]); i--) {
     if (State & REPLACE_FLAG) {
       replace_join(0);              // remove a NUL from the replace stack
     }
@@ -2676,7 +2676,7 @@ int stuff_inserted(int c, long count, int no_esc)
   // when the last char is either "0" or "^" it will be quoted if no ESC
   // comes after it OR if it will inserted more than once and "ptr"
   // starts with ^D.  -- Acevedo
-  last_ptr = (esc_ptr ? esc_ptr : ptr + STRLEN(ptr)) - 1;
+  last_ptr = (esc_ptr ? esc_ptr : ptr + strlen(ptr)) - 1;
   if (last_ptr >= ptr && (*last_ptr == '0' || *last_ptr == '^')
       && (no_esc || (*ptr == Ctrl_D && count > 1))) {
     last = *last_ptr;
@@ -2938,7 +2938,7 @@ static void replace_do_bs(int limit_col)
     }
     (void)del_char_after_col(limit_col);
     if (l_State & VREPLACE_FLAG) {
-      orig_len = (int)STRLEN(get_cursor_pos_ptr());
+      orig_len = (int)strlen(get_cursor_pos_ptr());
     }
     replace_push(cc);
     replace_pop_ins();
@@ -3856,7 +3856,7 @@ static bool ins_bs(int c, int mode, int *inserted_space_p)
         return false;
       }
       Insstart.lnum--;
-      Insstart.col = (colnr_T)STRLEN(ml_get(Insstart.lnum));
+      Insstart.col = (colnr_T)strlen(ml_get(Insstart.lnum));
     }
     // In replace mode:
     // cc < 0: NL was inserted, delete it
@@ -4674,7 +4674,7 @@ bool ins_eol(int c)
 
   // NL in reverse insert will always start in the end of current line.
   if (revins_on) {
-    curwin->w_cursor.col += (colnr_T)STRLEN(get_cursor_pos_ptr());
+    curwin->w_cursor.col += (colnr_T)strlen(get_cursor_pos_ptr());
   }
 
   AppendToRedobuff(NL_STR);
diff --git a/src/nvim/eval.c b/src/nvim/eval.c
index ead01fcbad..1eaf29a4de 100644
--- a/src/nvim/eval.c
+++ b/src/nvim/eval.c
@@ -358,7 +358,7 @@ void eval_init(void)
 
   for (size_t i = 0; i < ARRAY_SIZE(vimvars); i++) {
     struct vimvar *p = &vimvars[i];
-    assert(STRLEN(p->vv_name) <= VIMVAR_KEY_LEN);
+    assert(strlen(p->vv_name) <= VIMVAR_KEY_LEN);
     STRCPY(p->vv_di.di_key, p->vv_name);
     if (p->vv_flags & VV_RO) {
       p->vv_di.di_flags = DI_FLAGS_RO | DI_FLAGS_FIX;
@@ -578,7 +578,7 @@ void var_redir_str(char *value, int value_len)
 
   int len;
   if (value_len == -1) {
-    len = (int)STRLEN(value);           // Append the entire string
+    len = (int)strlen(value);           // Append the entire string
   } else {
     len = value_len;                    // Append only "value_len" characters
   }
@@ -1078,7 +1078,7 @@ int call_vim_function(const char *func, int argc, typval_T *argv, typval_T *rett
   FUNC_ATTR_NONNULL_ALL
 {
   int ret;
-  int len = (int)STRLEN(func);
+  int len = (int)strlen(func);
   partial_T *pt = NULL;
 
   if (len >= 6 && !memcmp(func, "v:lua.", 6)) {
@@ -1667,7 +1667,7 @@ void set_var_lval(lval_T *lp, char *endp, typval_T *rettv, int copy, const bool
 
       // handle +=, -=, *=, /=, %= and .=
       di = NULL;
-      if (get_var_tv(lp->ll_name, (int)STRLEN(lp->ll_name),
+      if (get_var_tv(lp->ll_name, (int)strlen(lp->ll_name),
                      &tv, &di, true, false) == OK) {
         if ((di == NULL
              || (!var_check_ro(di->di_flags, lp->ll_name, TV_CSTRING)
@@ -1960,7 +1960,7 @@ void set_context_for_expression(expand_T *xp, char *arg, cmdidx_T cmdidx)
     xp->xp_context = EXPAND_USER_VARS;
     if (strpbrk(arg, "\"'+-*/%.=!?~|&$([<>,#") == NULL) {
       // ":let var1 var2 ...": find last space.
-      for (p = arg + STRLEN(arg); p >= arg;) {
+      for (p = arg + strlen(arg); p >= arg;) {
         xp->xp_pattern = p;
         MB_PTR_BACK(arg, p);
         if (ascii_iswhite(*p)) {
@@ -2077,7 +2077,7 @@ static size_t varnamebuflen = 0;
 char *cat_prefix_varname(int prefix, const char *name)
   FUNC_ATTR_NONNULL_ALL
 {
-  size_t len = STRLEN(name) + 3;
+  size_t len = strlen(name) + 3;
 
   if (len > varnamebuflen) {
     xfree(varnamebuf);
@@ -3828,7 +3828,7 @@ static int get_string_tv(char **arg, typval_T *rettv, int evaluate)
         if (p[1] != '*') {
           flags |= FSK_SIMPLIFY;
         }
-        extra = trans_special((const char_u **)&p, STRLEN(p), (char_u *)name, flags, false, NULL);
+        extra = trans_special((const char_u **)&p, strlen(p), (char_u *)name, flags, false, NULL);
         if (extra != 0) {
           name += extra;
           if (name >= rettv->vval.v_string + len) {
@@ -5019,7 +5019,7 @@ void common_function(typval_T *argvars, typval_T *rettv, bool is_funcref)
       // printable text.
       snprintf(sid_buf, sizeof(sid_buf), "<SNR>%" PRId64 "_",
                (int64_t)current_sctx.sc_sid);
-      name = xmalloc(STRLEN(sid_buf) + STRLEN(s + off) + 1);
+      name = xmalloc(strlen(sid_buf) + strlen(s + off) + 1);
       STRCPY(name, sid_buf);
       STRCAT(name, s + off);
     } else {
@@ -5594,10 +5594,10 @@ void set_buffer_lines(buf_T *buf, linenr_T lnum_arg, bool append, const typval_T
 
     if (!append && lnum <= curbuf->b_ml.ml_line_count) {
       // Existing line, replace it.
-      int old_len = (int)STRLEN(ml_get(lnum));
+      int old_len = (int)strlen(ml_get(lnum));
       if (u_savesub(lnum) == OK
           && ml_replace(lnum, (char *)line, true) == OK) {
-        inserted_bytes(lnum, 0, old_len, (int)STRLEN(line));
+        inserted_bytes(lnum, 0, old_len, (int)strlen(line));
         if (is_curbuf && lnum == curwin->w_cursor.lnum) {
           check_cursor_col();
         }
@@ -5838,7 +5838,7 @@ bool callback_call(Callback *const callback, const int argcount_in, typval_T *co
   switch (callback->type) {
   case kCallbackFuncref:
     name = callback->data.funcref;
-    int len = (int)STRLEN(name);
+    int len = (int)strlen(name);
     if (len >= 6 && !memcmp(name, "v:lua.", 6)) {
       name += 6;
       len = check_luafunc_name(name, false);
@@ -6365,7 +6365,7 @@ pos_T *var2fpos(const typval_T *const tv, const bool dollar_lnum, int *const ret
     if (charcol) {
       len = mb_charlen((char_u *)ml_get(pos.lnum));
     } else {
-      len = (int)STRLEN(ml_get(pos.lnum));
+      len = (int)strlen(ml_get(pos.lnum));
     }
 
     // We accept "$" for the column number: last column.
@@ -6451,7 +6451,7 @@ pos_T *var2fpos(const typval_T *const tv, const bool dollar_lnum, int *const ret
       if (charcol) {
         pos.col = (colnr_T)mb_charlen((char_u *)get_cursor_line_ptr());
       } else {
-        pos.col = (colnr_T)STRLEN(get_cursor_line_ptr());
+        pos.col = (colnr_T)strlen(get_cursor_line_ptr());
       }
     }
     return &pos;
@@ -6621,7 +6621,7 @@ int get_name_len(const char **const arg, char **alias, bool evaluate, bool verbo
     }
     *alias = temp_string;
     *arg = (const char *)skipwhite(p);
-    return (int)STRLEN(temp_string);
+    return (int)strlen(temp_string);
   }
 
   len += get_id_len(arg);
@@ -6747,7 +6747,7 @@ static char *make_expanded_name(const char *in_start, char *expr_start, char *ex
 
   char *temp_result = eval_to_string(expr_start + 1, &nextcmd, false);
   if (temp_result != NULL && nextcmd == NULL) {
-    retval = xmalloc(STRLEN(temp_result) + (size_t)(expr_start - in_start)
+    retval = xmalloc(strlen(temp_result) + (size_t)(expr_start - in_start)
                      + (size_t)(in_end - expr_end) + 1);
     STRCPY(retval, in_start);
     STRCAT(retval, temp_result);
@@ -7015,7 +7015,7 @@ char *set_cmdarg(exarg_T *eap, char *oldarg)
     len += 10;  // " ++ff=unix"
   }
   if (eap->force_enc != 0) {
-    len += STRLEN(eap->cmd + eap->force_enc) + 7;
+    len += strlen(eap->cmd + eap->force_enc) + 7;
   }
   if (eap->bad_char != 0) {
     len += 7 + 4;  // " ++bad=" + "keep" or "drop"
@@ -7037,20 +7037,20 @@ char *set_cmdarg(exarg_T *eap, char *oldarg)
   }
 
   if (eap->force_ff != 0) {
-    snprintf(newval + STRLEN(newval), newval_len, " ++ff=%s",
+    snprintf(newval + strlen(newval), newval_len, " ++ff=%s",
              eap->force_ff == 'u' ? "unix" :
              eap->force_ff == 'd' ? "dos" : "mac");
   }
   if (eap->force_enc != 0) {
-    snprintf(newval + STRLEN(newval), newval_len, " ++enc=%s",
+    snprintf(newval + strlen(newval), newval_len, " ++enc=%s",
              eap->cmd + eap->force_enc);
   }
   if (eap->bad_char == BAD_KEEP) {
-    STRCPY(newval + STRLEN(newval), " ++bad=keep");
+    STRCPY(newval + strlen(newval), " ++bad=keep");
   } else if (eap->bad_char == BAD_DROP) {
-    STRCPY(newval + STRLEN(newval), " ++bad=drop");
+    STRCPY(newval + strlen(newval), " ++bad=drop");
   } else if (eap->bad_char != 0) {
-    snprintf(newval + STRLEN(newval), newval_len, " ++bad=%c",
+    snprintf(newval + strlen(newval), newval_len, " ++bad=%c",
              eap->bad_char);
   }
   vimvars[VV_CMDARG].vv_str = newval;
@@ -8073,7 +8073,7 @@ repeat:
     // Append a path separator to a directory.
     if (os_isdir(*fnamep)) {
       // Make room for one or two extra characters.
-      *fnamep = xstrnsave(*fnamep, STRLEN(*fnamep) + 2);
+      *fnamep = xstrnsave(*fnamep, strlen(*fnamep) + 2);
       xfree(*bufp);          // free any allocated file name
       *bufp = *fnamep;
       add_pathsep(*fnamep);
@@ -8113,7 +8113,7 @@ repeat:
           home_replace(NULL, s, dirname, MAXPATHL, true);
           xfree(s);
         }
-        size_t namelen = STRLEN(dirname);
+        size_t namelen = strlen(dirname);
 
         // Do not call shorten_fname() here since it removes the prefix
         // even though the path does not have a prefix.
@@ -8149,7 +8149,7 @@ repeat:
   }
 
   char *tail = path_tail(*fnamep);
-  *fnamelen = STRLEN(*fnamep);
+  *fnamelen = strlen(*fnamep);
 
   // ":h" - head, remove "/file_name", can be repeated
   // Don't remove the first "/" or "c:\"
@@ -8266,7 +8266,7 @@ repeat:
           *usedlen = (size_t)(p + 1 - src);
           s = do_string_sub(str, pat, sub, NULL, flags);
           *fnamep = s;
-          *fnamelen = STRLEN(s);
+          *fnamelen = strlen(s);
           xfree(*bufp);
           *bufp = s;
           didit = true;
@@ -8294,7 +8294,7 @@ repeat:
     }
     xfree(*bufp);
     *bufp = *fnamep = p;
-    *fnamelen = STRLEN(p);
+    *fnamelen = strlen(p);
     *usedlen += 2;
   }
 
@@ -8325,7 +8325,7 @@ char *do_string_sub(char *str, char *pat, char *sub, typval_T *expr, char *flags
   regmatch.regprog = vim_regcomp(pat, RE_MAGIC + RE_STRING);
   if (regmatch.regprog != NULL) {
     char *tail = str;
-    char *end = str + STRLEN(str);
+    char *end = str + strlen(str);
     while (vim_regexec_nl(&regmatch, (char_u *)str, (colnr_T)(tail - str))) {
       // Skip empty match except for first match.
       if (regmatch.startp[0] == regmatch.endp[0]) {
@@ -8600,7 +8600,7 @@ void ex_checkhealth(exarg_T *eap)
     return;
   }
 
-  size_t bufsize = STRLEN(eap->arg) + sizeof("call health#check('')");
+  size_t bufsize = strlen(eap->arg) + sizeof("call health#check('')");
   char *buf = xmalloc(bufsize);
   snprintf(buf, bufsize, "call health#check('%s')", eap->arg);
 
@@ -8626,8 +8626,8 @@ void invoke_prompt_callback(void)
   }
   char *text = ml_get(lnum);
   char *prompt = (char *)prompt_text();
-  if (STRLEN(text) >= STRLEN(prompt)) {
-    text += STRLEN(prompt);
+  if (strlen(text) >= strlen(prompt)) {
+    text += strlen(prompt);
   }
   argv[0].v_type = VAR_STRING;
   argv[0].vval.v_string = xstrdup(text);
diff --git a/src/nvim/eval/encode.c b/src/nvim/eval/encode.c
index bb514fba47..599bbae0f5 100644
--- a/src/nvim/eval/encode.c
+++ b/src/nvim/eval/encode.c
@@ -219,7 +219,7 @@ bool encode_vim_list_to_buf(const list_T *const list, size_t *const ret_len, cha
     }
     len++;
     if (TV_LIST_ITEM_TV(li)->vval.v_string != NULL) {
-      len += STRLEN(TV_LIST_ITEM_TV(li)->vval.v_string);
+      len += strlen(TV_LIST_ITEM_TV(li)->vval.v_string);
     }
   });
   if (len) {
@@ -281,7 +281,7 @@ int encode_read_from_list(ListReaderState *const state, char *const buf, const s
       state->offset = 0;
       state->li_length = (TV_LIST_ITEM_TV(state->li)->vval.v_string == NULL
                           ? 0
-                          : STRLEN(TV_LIST_ITEM_TV(state->li)->vval.v_string));
+                          : strlen(TV_LIST_ITEM_TV(state->li)->vval.v_string));
     }
   }
   *read_bytes = nbuf;
diff --git a/src/nvim/eval/funcs.c b/src/nvim/eval/funcs.c
index b59caab34f..96f0c0dcd2 100644
--- a/src/nvim/eval/funcs.c
+++ b/src/nvim/eval/funcs.c
@@ -840,7 +840,7 @@ static void get_col(typval_T *argvars, typval_T *rettv, bool charcol)
     if (fp->col == MAXCOL) {
       // '> can be MAXCOL, get the length of the line then
       if (fp->lnum <= curbuf->b_ml.ml_line_count) {
-        col = (colnr_T)STRLEN(ml_get(fp->lnum)) + 1;
+        col = (colnr_T)strlen(ml_get(fp->lnum)) + 1;
       } else {
         col = MAXCOL;
       }
@@ -7808,7 +7808,7 @@ free_lstval:
     if (strval == NULL) {
       return;
     }
-    write_reg_contents_ex(regname, strval, (ssize_t)STRLEN(strval),
+    write_reg_contents_ex(regname, strval, (ssize_t)strlen(strval),
                           append, yank_type, (colnr_T)block_len);
   }
   if (pointreg != 0) {
@@ -8377,7 +8377,7 @@ static void f_strgetchar(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
     return;
   }
 
-  const size_t len = STRLEN(str);
+  const size_t len = strlen(str);
   size_t byteidx = 0;
 
   while (charidx >= 0 && byteidx < len) {
@@ -8483,7 +8483,7 @@ static void f_strwidth(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
 static void f_strcharpart(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
 {
   const char *const p = tv_get_string(&argvars[0]);
-  const size_t slen = STRLEN(p);
+  const size_t slen = strlen(p);
 
   int nbyte = 0;
   bool error = false;
@@ -8623,7 +8623,7 @@ static void f_strridx(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
     return;  // Type error; errmsg already given.
   }
 
-  const size_t haystack_len = STRLEN(haystack);
+  const size_t haystack_len = strlen(haystack);
   ptrdiff_t end_idx;
   if (argvars[2].v_type != VAR_UNKNOWN) {
     // Third argument: upper limit for index.
@@ -8754,7 +8754,7 @@ static void f_synID(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
 
   int id = 0;
   if (!transerr && lnum >= 1 && lnum <= curbuf->b_ml.ml_line_count
-      && col >= 0 && (size_t)col < STRLEN(ml_get(lnum))) {
+      && col >= 0 && (size_t)col < strlen(ml_get(lnum))) {
     id = syn_get_id(curwin, lnum, col, trans, NULL, false);
   }
 
@@ -8820,7 +8820,7 @@ static void f_synIDattr(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
     }
     break;
   case 'u':
-    if (STRLEN(what) >= 9) {
+    if (strlen(what) >= 9) {
       if (TOLOWER_ASC(what[5]) == 'l') {
         // underline
         p = highlight_has_attr(id, HL_UNDERLINE, modec);
@@ -8879,7 +8879,7 @@ static void f_synconcealed(typval_T *argvars, typval_T *rettv, EvalFuncData fptr
   CLEAR_FIELD(str);
 
   if (lnum >= 1 && lnum <= curbuf->b_ml.ml_line_count && col >= 0
-      && (size_t)col <= STRLEN(ml_get(lnum)) && curwin->w_p_cole > 0) {
+      && (size_t)col <= strlen(ml_get(lnum)) && curwin->w_p_cole > 0) {
     (void)syn_get_id(curwin, lnum, col, false, NULL, false);
     syntax_flags = get_syntax_info(&matchid);
 
@@ -8916,7 +8916,7 @@ static void f_synstack(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
   if (lnum >= 1
       && lnum <= curbuf->b_ml.ml_line_count
       && col >= 0
-      && (size_t)col <= STRLEN(ml_get(lnum))) {
+      && (size_t)col <= strlen(ml_get(lnum))) {
     tv_list_alloc_ret(rettv, kListLenMayKnow);
     (void)syn_get_id(curwin, lnum, col, false, NULL, true);
 
@@ -9470,7 +9470,7 @@ static void f_trim(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
     }
   }
 
-  const char *tail = head + STRLEN(head);
+  const char *tail = head + strlen(head);
   if (dir == 0 || dir == 2) {
     // Trim trailing characters
     for (; tail > head; tail = prev) {
@@ -9578,7 +9578,7 @@ static void f_virtcol(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
     if (fp->col < 0) {
       fp->col = 0;
     } else {
-      const size_t len = STRLEN(ml_get(fp->lnum));
+      const size_t len = strlen(ml_get(fp->lnum));
       if (fp->col > (colnr_T)len) {
         fp->col = (colnr_T)len;
       }
diff --git a/src/nvim/eval/userfunc.c b/src/nvim/eval/userfunc.c
index 70c9e02d5c..283dc23793 100644
--- a/src/nvim/eval/userfunc.c
+++ b/src/nvim/eval/userfunc.c
@@ -528,14 +528,14 @@ static char *fname_trans_sid(const char *const name, char *const fname_buf, char
       } else {
         snprintf(fname_buf + i, (size_t)(FLEN_FIXED + 1 - i), "%" PRId64 "_",
                  (int64_t)current_sctx.sc_sid);
-        i = (int)STRLEN(fname_buf);
+        i = (int)strlen(fname_buf);
       }
     }
-    if ((size_t)i + STRLEN(name + llen) < FLEN_FIXED) {
+    if ((size_t)i + strlen(name + llen) < FLEN_FIXED) {
       STRCPY(fname_buf + i, name + llen);
       fname = fname_buf;
     } else {
-      fname = xmalloc((size_t)i + STRLEN(name + llen) + 1);
+      fname = xmalloc((size_t)i + strlen(name + llen) + 1);
       *tofree = fname;
       memmove(fname, fname_buf, (size_t)i);
       STRCPY(fname + i, name + llen);
@@ -1516,7 +1516,7 @@ int call_func(const char *funcname, int len, typval_T *rettv, int argcount_in, t
         fp = find_func((char_u *)rfname);
       }
       // Try loading a package.
-      if (fp == NULL && script_autoload((const char *)rfname, STRLEN(rfname),
+      if (fp == NULL && script_autoload((const char *)rfname, strlen(rfname),
                                         true) && !aborting()) {
         // Loaded a package, search for the function again.
         fp = find_func((char_u *)rfname);
@@ -2167,7 +2167,7 @@ void ex_function(exarg_T *eap)
       theline = line_arg;
       p = vim_strchr(theline, '\n');
       if (p == NULL) {
-        line_arg += STRLEN(line_arg);
+        line_arg += strlen(line_arg);
       } else {
         *p = NUL;
         line_arg = p + 1;
@@ -2209,14 +2209,14 @@ void ex_function(exarg_T *eap)
       if (heredoc_trimmed == NULL
           || (is_heredoc && skipwhite(theline) == theline)
           || STRNCMP(theline, heredoc_trimmed,
-                     STRLEN(heredoc_trimmed)) == 0) {
+                     strlen(heredoc_trimmed)) == 0) {
         if (heredoc_trimmed == NULL) {
           p = theline;
         } else if (is_heredoc) {
           p = skipwhite(theline) == theline
-            ? theline : theline + STRLEN(heredoc_trimmed);
+            ? theline : theline + strlen(heredoc_trimmed);
         } else {
-          p = theline + STRLEN(heredoc_trimmed);
+          p = theline + strlen(heredoc_trimmed);
         }
         if (strcmp(p, skip_until) == 0) {
           XFREE_CLEAR(skip_until);
@@ -2383,7 +2383,7 @@ void ex_function(exarg_T *eap)
 
   // If there are no errors, add the function
   if (fudi.fd_dict == NULL) {
-    v = find_var((const char *)name, STRLEN(name), &ht, false);
+    v = find_var((const char *)name, strlen(name), &ht, false);
     if (v != NULL && v->di_tv.v_type == VAR_FUNC) {
       emsg_funcname(N_("E707: Function name conflicts with variable: %s"),
                     (char_u *)name);
@@ -2458,7 +2458,7 @@ void ex_function(exarg_T *eap)
       // Check that the autoload name matches the script name.
       int j = FAIL;
       if (SOURCING_NAME != NULL) {
-        scriptname = (char_u *)autoload_name((const char *)name, STRLEN(name));
+        scriptname = (char_u *)autoload_name((const char *)name, strlen(name));
         p = vim_strchr((char *)scriptname, '/');
         plen = (int)STRLEN(p);
         slen = (int)STRLEN(SOURCING_NAME);
@@ -2474,7 +2474,7 @@ void ex_function(exarg_T *eap)
       }
     }
 
-    fp = xcalloc(1, offsetof(ufunc_T, uf_name) + STRLEN(name) + 1);
+    fp = xcalloc(1, offsetof(ufunc_T, uf_name) + strlen(name) + 1);
 
     if (fudi.fd_dict != NULL) {
       if (fudi.fd_di == NULL) {
@@ -3085,7 +3085,7 @@ char *get_return_cmd(void *rettv)
 
   STRCPY(IObuff, ":return ");
   STRLCPY(IObuff + 8, s, IOSIZE - 8);
-  if (STRLEN(s) + 8 >= IOSIZE) {
+  if (strlen(s) + 8 >= IOSIZE) {
     STRCPY(IObuff + IOSIZE - 4, "...");
   }
   xfree(tofree);
diff --git a/src/nvim/eval/vars.c b/src/nvim/eval/vars.c
index 004a239fda..1c07fc4d45 100644
--- a/src/nvim/eval/vars.c
+++ b/src/nvim/eval/vars.c
@@ -710,7 +710,7 @@ static char *ex_let_one(char *arg, typval_T *const tv, const bool copy, const bo
         }
       }
       if (p != NULL) {
-        write_reg_contents(*arg == '@' ? '"' : *arg, p, (ssize_t)STRLEN(p), false);
+        write_reg_contents(*arg == '@' ? '"' : *arg, p, (ssize_t)strlen(p), false);
         arg_end = arg + 1;
       }
       xfree(ptofree);
@@ -1801,7 +1801,7 @@ void f_setbufvar(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
       // reset notion of buffer
       aucmd_restbuf(&aco);
     } else {
-      const size_t varname_len = STRLEN(varname);
+      const size_t varname_len = strlen(varname);
       char *const bufvarname = xmalloc(varname_len + 3);
       buf_T *const save_curbuf = curbuf;
       curbuf = buf;
diff --git a/src/nvim/ex_cmds.c b/src/nvim/ex_cmds.c
index 96bef4902c..97080ad81d 100644
--- a/src/nvim/ex_cmds.c
+++ b/src/nvim/ex_cmds.c
@@ -330,7 +330,7 @@ static int linelen(int *has_tab)
   first = skipwhite(line);
 
   // find the character after the last non-blank character
-  for (last = first + STRLEN(first);
+  for (last = first + strlen(first);
        last > first && ascii_iswhite(last[-1]); last--) {}
   char save = *last;
   *last = NUL;
@@ -550,7 +550,7 @@ void ex_sort(exarg_T *eap)
   // Also get the longest line length for allocating "sortbuf".
   for (lnum = eap->line1; lnum <= eap->line2; lnum++) {
     s = ml_get(lnum);
-    len = (int)STRLEN(s);
+    len = (int)strlen(s);
     if (maxlen < len) {
       maxlen = len;
     }
@@ -651,7 +651,7 @@ void ex_sort(exarg_T *eap)
     }
 
     s = ml_get(get_lnum);
-    size_t bytelen = STRLEN(s) + 1;  // include EOL in bytelen
+    size_t bytelen = strlen(s) + 1;  // include EOL in bytelen
     old_count += (bcount_t)bytelen;
     if (!unique || i == 0 || string_compare(s, sortbuf1) != 0) {
       // Copy the line into a buffer, it may become invalid in
@@ -796,7 +796,7 @@ void ex_retab(exarg_T *eap)
 
             // len is actual number of white characters used
             len = num_spaces + num_tabs;
-            old_len = (long)STRLEN(ptr);
+            old_len = (long)strlen(ptr);
             const long new_len = old_len - col + start_col + len + 1;
             if (new_len <= 0 || new_len >= MAXCOL) {
               emsg(_(e_resulting_text_too_long));
@@ -1142,9 +1142,9 @@ void do_bang(int addr_count, exarg_T *eap, bool forceit, bool do_in, bool do_out
   bool ins_prevcmd = forceit;
   trailarg = arg;
   do {
-    len = STRLEN(trailarg) + 1;
+    len = strlen(trailarg) + 1;
     if (newcmd != NULL) {
-      len += STRLEN(newcmd);
+      len += strlen(newcmd);
     }
     if (ins_prevcmd) {
       if (prevcmd == NULL) {
@@ -1152,7 +1152,7 @@ void do_bang(int addr_count, exarg_T *eap, bool forceit, bool do_in, bool do_out
         xfree(newcmd);
         return;
       }
-      len += STRLEN(prevcmd);
+      len += strlen(prevcmd);
     }
     t = xmalloc(len);
     *t = NUL;
@@ -1162,7 +1162,7 @@ void do_bang(int addr_count, exarg_T *eap, bool forceit, bool do_in, bool do_out
     if (ins_prevcmd) {
       STRCAT(t, prevcmd);
     }
-    p = t + STRLEN(t);
+    p = t + strlen(t);
     STRCAT(t, trailarg);
     xfree(newcmd);
     newcmd = t;
@@ -1201,7 +1201,7 @@ void do_bang(int addr_count, exarg_T *eap, bool forceit, bool do_in, bool do_out
   }
   // Add quotes around the command, for shells that need them.
   if (*p_shq != NUL) {
-    newcmd = xmalloc(STRLEN(prevcmd) + 2 * STRLEN(p_shq) + 1);
+    newcmd = xmalloc(strlen(prevcmd) + 2 * STRLEN(p_shq) + 1);
     STRCPY(newcmd, p_shq);
     STRCAT(newcmd, prevcmd);
     STRCAT(newcmd, p_shq);
@@ -1542,23 +1542,23 @@ char *make_filter_cmd(char *cmd, char *itmp, char *otmp)
   bool is_pwsh = STRNCMP(invocation_path_tail((char_u *)p_sh, NULL), "pwsh", 4) == 0
                  || STRNCMP(invocation_path_tail((char_u *)p_sh, NULL), "powershell", 10) == 0;
 
-  size_t len = STRLEN(cmd) + 1;  // At least enough space for cmd + NULL.
+  size_t len = strlen(cmd) + 1;  // At least enough space for cmd + NULL.
 
   len += is_fish_shell ?  sizeof("begin; " "; end") - 1
                        :  is_pwsh ? sizeof("Start-Process ")
                                   : sizeof("(" ")") - 1;
 
   if (itmp != NULL) {
-    len += is_pwsh  ? STRLEN(itmp) + sizeof(" -RedirectStandardInput ")
-                    : STRLEN(itmp) + sizeof(" { " " < " " } ") - 1;
+    len += is_pwsh  ? strlen(itmp) + sizeof(" -RedirectStandardInput ")
+                    : strlen(itmp) + sizeof(" { " " < " " } ") - 1;
   }
   if (otmp != NULL) {
-    len += STRLEN(otmp) + STRLEN(p_srr) + 2;  // two extra spaces ("  "),
+    len += strlen(otmp) + strlen(p_srr) + 2;  // two extra spaces ("  "),
   }
 
   const char *const cmd_args = strchr(cmd, ' ');
   len += (is_pwsh && cmd_args)
-      ? STRLEN(" -ArgumentList ") + 2  // two extra quotes
+      ? strlen(" -ArgumentList ") + 2  // two extra quotes
       : 0;
 
   char *const buf = xmalloc(len);
@@ -1568,7 +1568,7 @@ char *make_filter_cmd(char *cmd, char *itmp, char *otmp)
     if (cmd_args == NULL) {
       xstrlcat(buf, cmd, len);
     } else {
-      xstrlcpy(buf + STRLEN(buf), cmd, (size_t)(cmd_args - cmd + 1));
+      xstrlcpy(buf + strlen(buf), cmd, (size_t)(cmd_args - cmd + 1));
       xstrlcat(buf, " -ArgumentList \"", len);
       xstrlcat(buf, cmd_args + 1, len);  // +1 to skip the leading space.
       xstrlcat(buf, "\"", len);
@@ -2372,7 +2372,7 @@ int do_ecmd(int fnum, char *ffname, char *sfname, exarg_T *eap, linenr_T newlnum
   if ((command != NULL || newlnum > (linenr_T)0)
       && *get_vim_var_str(VV_SWAPCOMMAND) == NUL) {
     // Set v:swapcommand for the SwapExists autocommands.
-    const size_t len = (command != NULL) ? STRLEN(command) + 3 : 30;
+    const size_t len = (command != NULL) ? strlen(command) + 3 : 30;
     char *const p = xmalloc(len);
     if (command != NULL) {
       vim_snprintf(p, len, ":%s\r", command);
@@ -2941,7 +2941,7 @@ void ex_append(exarg_T *eap)
       }
       p = vim_strchr(eap->nextcmd, NL);
       if (p == NULL) {
-        p = eap->nextcmd + STRLEN(eap->nextcmd);
+        p = eap->nextcmd + strlen(eap->nextcmd);
       }
       theline = xstrnsave(eap->nextcmd, (size_t)(p - eap->nextcmd));
       if (*p != NUL) {
@@ -3329,7 +3329,7 @@ static char *sub_grow_buf(char **new_start, int needed_len)
     // Check if the temporary buffer is long enough to do the
     // substitution into.  If not, make it larger (with a bit
     // extra to avoid too many calls to xmalloc()/free()).
-    size_t len = STRLEN(*new_start);
+    size_t len = strlen(*new_start);
     needed_len += (int)len;
     if (needed_len > new_start_len) {
       new_start_len = needed_len + 50;
@@ -3777,7 +3777,7 @@ static int do_sub(exarg_T *eap, proftime_T timeout, long cmdpreview_ns, handle_T
           // we continue looking for a match on the next line.
           // Avoids that ":s/\nB\@=//gc" get stuck.
           if (nmatch > 1) {
-            matchcol = (colnr_T)STRLEN(sub_firstline);
+            matchcol = (colnr_T)strlen(sub_firstline);
             nmatch = 1;
             skip_match = true;
           }
@@ -3878,7 +3878,7 @@ static int do_sub(exarg_T *eap, proftime_T timeout, long cmdpreview_ns, handle_T
                 // Position the cursor relative to the end of the line, the
                 // previous substitute may have inserted or deleted characters
                 // before the cursor.
-                len_change = (int)STRLEN(new_line) - (int)STRLEN(orig_line);
+                len_change = (int)strlen(new_line) - (int)strlen(orig_line);
                 curwin->w_cursor.col += len_change;
                 ml_replace(lnum, new_line, false);
               }
@@ -3971,7 +3971,7 @@ static int do_sub(exarg_T *eap, proftime_T timeout, long cmdpreview_ns, handle_T
             // Avoids that ":%s/\nB\@=//gc" and ":%s/\n/,\r/gc"
             // get stuck when pressing 'n'.
             if (nmatch > 1) {
-              matchcol = (colnr_T)STRLEN(sub_firstline);
+              matchcol = (colnr_T)strlen(sub_firstline);
               skip_match = true;
             }
             goto skip;
@@ -4081,7 +4081,7 @@ static int do_sub(exarg_T *eap, proftime_T timeout, long cmdpreview_ns, handle_T
           }
           size_t copy_len = (size_t)(regmatch.startpos[0].col - copycol);
           new_end = sub_grow_buf(&new_start,
-                                 (colnr_T)STRLEN(p1) - regmatch.endpos[0].col
+                                 (colnr_T)strlen(p1) - regmatch.endpos[0].col
                                  + (colnr_T)copy_len + sublen + 1);
 
           // copy the text up to the part that matched
@@ -4115,7 +4115,7 @@ static int do_sub(exarg_T *eap, proftime_T timeout, long cmdpreview_ns, handle_T
           bcount_t replaced_bytes = 0;
           lpos_T start = regmatch.startpos[0], end = regmatch.endpos[0];
           for (i = 0; i < nmatch - 1; i++) {
-            replaced_bytes += (bcount_t)STRLEN(ml_get((linenr_T)(lnum_start + i))) + 1;
+            replaced_bytes += (bcount_t)strlen(ml_get((linenr_T)(lnum_start + i))) + 1;
           }
           replaced_bytes += end.col - start.col;
 
@@ -4158,7 +4158,7 @@ static int do_sub(exarg_T *eap, proftime_T timeout, long cmdpreview_ns, handle_T
               p1 += utfc_ptr2len(p1) - 1;
             }
           }
-          colnr_T new_endcol = (colnr_T)STRLEN(new_start);
+          colnr_T new_endcol = (colnr_T)strlen(new_start);
           current_match.end.col = new_endcol;
           current_match.end.lnum = lnum;
 
@@ -4214,8 +4214,8 @@ skip:
             // have changed the number of characters.  Same for
             // "prev_matchcol".
             STRCAT(new_start, sub_firstline + copycol);
-            matchcol = (colnr_T)STRLEN(sub_firstline) - matchcol;
-            prev_matchcol = (colnr_T)STRLEN(sub_firstline)
+            matchcol = (colnr_T)strlen(sub_firstline) - matchcol;
+            prev_matchcol = (colnr_T)strlen(sub_firstline)
                             - prev_matchcol;
 
             if (u_savesub(lnum) != OK) {
@@ -4260,8 +4260,8 @@ skip:
             xfree(sub_firstline);                // free the temp buffer
             sub_firstline = new_start;
             new_start = NULL;
-            matchcol = (colnr_T)STRLEN(sub_firstline) - matchcol;
-            prev_matchcol = (colnr_T)STRLEN(sub_firstline)
+            matchcol = (colnr_T)strlen(sub_firstline) - matchcol;
+            prev_matchcol = (colnr_T)strlen(sub_firstline)
                             - prev_matchcol;
             copycol = 0;
           }
diff --git a/src/nvim/ex_cmds2.c b/src/nvim/ex_cmds2.c
index e551cbee0b..1248251556 100644
--- a/src/nvim/ex_cmds2.c
+++ b/src/nvim/ex_cmds2.c
@@ -703,7 +703,7 @@ void ex_compiler(exarg_T *eap)
     do_cmdline_cmd("echo globpath(&rtp, 'compiler/*.vim')");  // NOLINT
     do_cmdline_cmd("echo globpath(&rtp, 'compiler/*.lua')");  // NOLINT
   } else {
-    size_t bufsize = STRLEN(eap->arg) + 14;
+    size_t bufsize = strlen(eap->arg) + 14;
     buf = xmalloc(bufsize);
     if (eap->forceit) {
       // ":compiler! {name}" sets global options
diff --git a/src/nvim/ex_docmd.c b/src/nvim/ex_docmd.c
index 5defabc05a..52841b6021 100644
--- a/src/nvim/ex_docmd.c
+++ b/src/nvim/ex_docmd.c
@@ -1302,7 +1302,7 @@ static void parse_register(exarg_T *eap)
         if (!eap->skip) {
           set_expr_line(xstrdup(eap->arg));
         }
-        eap->arg += STRLEN(eap->arg);
+        eap->arg += strlen(eap->arg);
       }
       eap->arg = skipwhite(eap->arg);
     }
@@ -1536,7 +1536,7 @@ static int execute_cmd0(int *retv, exarg_T *eap, char **errormsg, bool preview)
           || eap->cmdidx == CMD_bunload) {
         p = skiptowhite_esc(eap->arg);
       } else {
-        p = eap->arg + STRLEN(eap->arg);
+        p = eap->arg + strlen(eap->arg);
         while (p > eap->arg && ascii_iswhite(p[-1])) {
           p--;
         }
@@ -2824,7 +2824,7 @@ bool checkforcmd(char **pp, char *cmd, int len)
 /// invisible otherwise.
 static void append_command(char *cmd)
 {
-  size_t len = STRLEN(IObuff);
+  size_t len = strlen(IObuff);
   char *s = cmd;
   char *d;
 
@@ -3666,7 +3666,7 @@ char *replace_makeprg(exarg_T *eap, char *arg, char **cmdlinep)
     // Replace $* by given arguments
     if ((new_cmdline = strrep(program, "$*", arg)) == NULL) {
       // No $* in arg, build "<makeprg> <arg>" instead
-      new_cmdline = xmalloc(STRLEN(program) + STRLEN(arg) + 2);
+      new_cmdline = xmalloc(strlen(program) + strlen(arg) + 2);
       STRCPY(new_cmdline, program);
       STRCAT(new_cmdline, " ");
       STRCAT(new_cmdline, arg);
@@ -3805,7 +3805,7 @@ int expand_filename(exarg_T *eap, char **cmdlinep, char **errormsgp)
         p = NULL;
       }
       if (p != NULL) {
-        (void)repl_cmdline(eap, eap->arg, STRLEN(eap->arg), p, cmdlinep);
+        (void)repl_cmdline(eap, eap->arg, strlen(eap->arg), p, cmdlinep);
       }
     }
 
@@ -3833,7 +3833,7 @@ int expand_filename(exarg_T *eap, char **cmdlinep, char **errormsgp)
       if (p == NULL) {
         return FAIL;
       }
-      (void)repl_cmdline(eap, eap->arg, STRLEN(eap->arg), p, cmdlinep);
+      (void)repl_cmdline(eap, eap->arg, strlen(eap->arg), p, cmdlinep);
       xfree(p);
     }
   }
@@ -3851,10 +3851,10 @@ static char *repl_cmdline(exarg_T *eap, char *src, size_t srclen, char *repl, ch
   // The new command line is build in new_cmdline[].
   // First allocate it.
   // Careful: a "+cmd" argument may have been NUL terminated.
-  size_t len = STRLEN(repl);
-  size_t i = (size_t)(src - *cmdlinep) + STRLEN(src + srclen) + len + 3;
+  size_t len = strlen(repl);
+  size_t i = (size_t)(src - *cmdlinep) + strlen(src + srclen) + len + 3;
   if (eap->nextcmd != NULL) {
-    i += STRLEN(eap->nextcmd);    // add space for next command
+    i += strlen(eap->nextcmd);    // add space for next command
   }
   char *new_cmdline = xmalloc(i);
   size_t offset = (size_t)(src - *cmdlinep);
@@ -3872,7 +3872,7 @@ static char *repl_cmdline(exarg_T *eap, char *src, size_t srclen, char *repl, ch
   src = new_cmdline + i;                // remember where to continue
 
   if (eap->nextcmd != NULL) {           // append next command
-    i = STRLEN(new_cmdline) + 1;
+    i = strlen(new_cmdline) + 1;
     STRCPY(new_cmdline + i, eap->nextcmd);
     eap->nextcmd = new_cmdline + i;
   }
@@ -4913,7 +4913,7 @@ void ex_splitview(exarg_T *eap)
   }
 
   if (eap->cmdidx == CMD_sfind || eap->cmdidx == CMD_tabfind) {
-    fname = (char *)find_file_in_path((char_u *)eap->arg, STRLEN(eap->arg),
+    fname = (char *)find_file_in_path((char_u *)eap->arg, strlen(eap->arg),
                                       FNAME_MESS, true, (char_u *)curbuf->b_ffname);
     if (fname == NULL) {
       goto theend;
@@ -5106,7 +5106,7 @@ static void ex_resize(exarg_T *eap)
 /// ":find [+command] <file>" command.
 static void ex_find(exarg_T *eap)
 {
-  char *fname = (char *)find_file_in_path((char_u *)eap->arg, STRLEN(eap->arg),
+  char *fname = (char *)find_file_in_path((char_u *)eap->arg, strlen(eap->arg),
                                           FNAME_MESS, true, (char_u *)curbuf->b_ffname);
   if (eap->addr_count > 0) {
     // Repeat finding the file "count" times.  This matters when it
@@ -6292,7 +6292,7 @@ static void ex_normal(exarg_T *eap)
       }
     }
     if (len > 0) {
-      arg = xmalloc(STRLEN(eap->arg) + (size_t)len + 1);
+      arg = xmalloc(strlen(eap->arg) + (size_t)len + 1);
       len = 0;
       for (p = eap->arg; *p != NUL; p++) {
         arg[len++] = *p;
@@ -6471,7 +6471,7 @@ static void ex_findpat(exarg_T *eap)
     }
   }
   if (!eap->skip) {
-    find_pattern_in_path((char_u *)eap->arg, 0, STRLEN(eap->arg), whole, !eap->forceit,
+    find_pattern_in_path((char_u *)eap->arg, 0, strlen(eap->arg), whole, !eap->forceit,
                          *eap->cmd == 'd' ?  FIND_DEFINE : FIND_ANY,
                          n, action, eap->line1, eap->line2);
   }
@@ -6612,7 +6612,7 @@ ssize_t find_cmdline_var(const char_u *src, size_t *usedlen)
   };
 
   for (size_t i = 0; i < ARRAY_SIZE(spec_str); i++) {
-    size_t len = STRLEN(spec_str[i]);
+    size_t len = strlen(spec_str[i]);
     if (STRNCMP(src, spec_str[i], len) == 0) {
       *usedlen = len;
       assert(i <= SSIZE_MAX);
@@ -6879,7 +6879,7 @@ char_u *eval_vars(char_u *src, char_u *srcstart, size_t *usedlen, linenr_T *lnum
     }
 
     // Length of new string.
-    resultlen = STRLEN(result);
+    resultlen = strlen(result);
     // Remove the file name extension.
     if (src[*usedlen] == '<') {
       (*usedlen)++;
@@ -6942,11 +6942,11 @@ char *expand_sfile(char *arg)
         p += srclen;
         continue;
       }
-      size_t len = STRLEN(result) - srclen + STRLEN(repl) + 1;
+      size_t len = strlen(result) - srclen + strlen(repl) + 1;
       char *newres = xmalloc(len);
       memmove(newres, result, (size_t)(p - result));
       STRCPY(newres + (p - result), repl);
-      len = STRLEN(newres);
+      len = strlen(newres);
       STRCAT(newres, p + srclen);
       xfree(repl);
       xfree(result);
diff --git a/src/nvim/ex_eval.c b/src/nvim/ex_eval.c
index f40149d07a..c2648b9bfc 100644
--- a/src/nvim/ex_eval.c
+++ b/src/nvim/ex_eval.c
@@ -376,13 +376,13 @@ char *get_exception_string(void *value, except_type_T type, char *cmdname, int *
     *should_free = true;
     mesg = ((msglist_T *)value)->throw_msg;
     if (cmdname != NULL && *cmdname != NUL) {
-      size_t cmdlen = STRLEN(cmdname);
-      ret = xstrnsave("Vim(", 4 + cmdlen + 2 + STRLEN(mesg));
+      size_t cmdlen = strlen(cmdname);
+      ret = xstrnsave("Vim(", 4 + cmdlen + 2 + strlen(mesg));
       STRCPY(&ret[4], cmdname);
       STRCPY(&ret[4 + cmdlen], "):");
       val = ret + 4 + cmdlen + 2;
     } else {
-      ret = xstrnsave("Vim:", 4 + STRLEN(mesg));
+      ret = xstrnsave("Vim:", 4 + strlen(mesg));
       val = ret + 4;
     }
 
@@ -410,7 +410,7 @@ char *get_exception_string(void *value, except_type_T type, char *cmdname, int *
 
           STRCAT(val, p);
           p[-2] = NUL;
-          snprintf(val + STRLEN(p), strlen(" (%s)"), " (%s)", &mesg[1]);
+          snprintf(val + strlen(p), strlen(" (%s)"), " (%s)", &mesg[1]);
           p[-2] = '"';
         }
         break;
diff --git a/src/nvim/ex_getln.c b/src/nvim/ex_getln.c
index 2b7797ddc8..4a398badec 100644
--- a/src/nvim/ex_getln.c
+++ b/src/nvim/ex_getln.c
@@ -1411,7 +1411,7 @@ static int may_do_command_line_next_incsearch(int firstc, long count, incsearch_
 
 static void command_line_next_histidx(CommandLineState *s, bool next_match)
 {
-  int j = (int)STRLEN(s->lookfor);
+  int j = (int)strlen(s->lookfor);
   for (;;) {
     // one step backwards
     if (!next_match) {
@@ -1920,7 +1920,7 @@ static int command_line_handle_key(CommandLineState *s)
         STRCPY(ccline.cmdbuff, p);
       }
 
-      ccline.cmdpos = ccline.cmdlen = (int)STRLEN(ccline.cmdbuff);
+      ccline.cmdpos = ccline.cmdlen = (int)strlen(ccline.cmdbuff);
       redrawcmd();
       return command_line_changed(s);
     }
@@ -2027,7 +2027,7 @@ static int command_line_not_changed(CommandLineState *s)
 /// as a trailing \|, which can happen while typing a pattern.
 static int empty_pattern(char *p)
 {
-  size_t n = STRLEN(p);
+  size_t n = strlen(p);
 
   // remove trailing \v and the like
   while (n >= 2 && p[n - 2] == '\\'
@@ -2803,7 +2803,7 @@ static void color_expr_cmdline(const CmdlineInfo *const colored_ccline,
   ParserLine parser_lines[] = {
     {
       .data = (const char *)colored_ccline->cmdbuff,
-      .size = STRLEN(colored_ccline->cmdbuff),
+      .size = strlen(colored_ccline->cmdbuff),
       .allocated = false,
     },
     { NULL, 0, false },
@@ -3377,7 +3377,7 @@ void unputcmdline(void)
 }
 
 // Put the given string, of the given length, onto the command line.
-// If len is -1, then STRLEN() is used to calculate the length.
+// If len is -1, then strlen() is used to calculate the length.
 // If 'redraw' is true then the new part of the command line, and the remaining
 // part will be redrawn, otherwise it will not.  If this function is called
 // twice in a row, then 'redraw' should be false and redrawcmd() should be
@@ -3863,7 +3863,7 @@ char *vim_strsave_fnameescape(const char *const fname, const int what)
 /// Put a backslash before the file name in "pp", which is in allocated memory.
 void escape_fname(char **pp)
 {
-  char_u *p = xmalloc(STRLEN(*pp) + 2);
+  char_u *p = xmalloc(strlen(*pp) + 2);
   p[0] = '\\';
   STRCPY(p + 1, *pp);
   xfree(*pp);
@@ -4010,7 +4010,7 @@ static int set_cmdline_str(const char *str, int pos)
     return 1;
   }
 
-  int len = (int)STRLEN(str);
+  int len = (int)strlen(str);
   realloc_cmdbuff(len + 1);
   p->cmdlen = len;
   STRCPY(p->cmdbuff, str);
@@ -4347,7 +4347,7 @@ static int open_cmdwin(void)
       ccline.cmdpos = 0;
       cmdwin_result = Ctrl_C;
     } else {
-      ccline.cmdlen = (int)STRLEN(ccline.cmdbuff);
+      ccline.cmdlen = (int)strlen(ccline.cmdbuff);
       ccline.cmdbufflen = ccline.cmdlen + 1;
       ccline.cmdpos = curwin->w_cursor.col;
       if (ccline.cmdpos > ccline.cmdlen) {
@@ -4420,7 +4420,7 @@ char *script_get(exarg_T *const eap, size_t *const lenp)
   const char *const cmd = (const char *)eap->arg;
 
   if (cmd[0] != '<' || cmd[1] != '<' || eap->getline == NULL) {
-    *lenp = STRLEN(eap->arg);
+    *lenp = strlen(eap->arg);
     return eap->skip ? NULL : xmemdupz(eap->arg, *lenp);
   }
 
diff --git a/src/nvim/file_search.c b/src/nvim/file_search.c
index b3491e98c2..ff23fdf66f 100644
--- a/src/nvim/file_search.c
+++ b/src/nvim/file_search.c
@@ -433,16 +433,16 @@ void *vim_findfile_init(char *path, char *filename, char *stopdirs, int level, i
   }
 
   // create an absolute path
-  if (STRLEN(search_ctx->ffsc_start_dir)
-      + STRLEN(search_ctx->ffsc_fix_path) + 3 >= MAXPATHL) {
+  if (strlen(search_ctx->ffsc_start_dir)
+      + strlen(search_ctx->ffsc_fix_path) + 3 >= MAXPATHL) {
     emsg(_(e_pathtoolong));
     goto error_return;
   }
   STRCPY(ff_expand_buffer, search_ctx->ffsc_start_dir);
   add_pathsep(ff_expand_buffer);
   {
-    size_t eb_len = STRLEN(ff_expand_buffer);
-    char_u *buf = xmalloc(eb_len + STRLEN(search_ctx->ffsc_fix_path) + 1);
+    size_t eb_len = strlen(ff_expand_buffer);
+    char_u *buf = xmalloc(eb_len + strlen(search_ctx->ffsc_fix_path) + 1);
 
     STRCPY(buf, ff_expand_buffer);
     STRCPY(buf + eb_len, search_ctx->ffsc_fix_path);
@@ -466,13 +466,13 @@ void *vim_findfile_init(char *path, char *filename, char *stopdirs, int level, i
         xstrlcat(ff_expand_buffer, search_ctx->ffsc_fix_path, eb_len + (size_t)len + 1);
         add_pathsep(ff_expand_buffer);
       } else {
-        len = (int)STRLEN(search_ctx->ffsc_fix_path);
+        len = (int)strlen(search_ctx->ffsc_fix_path);
       }
 
       if (search_ctx->ffsc_wc_path != NULL) {
         wc_path = xstrdup(search_ctx->ffsc_wc_path);
-        temp = xmalloc(STRLEN(search_ctx->ffsc_wc_path)
-                       + STRLEN(search_ctx->ffsc_fix_path + len)
+        temp = xmalloc(strlen(search_ctx->ffsc_wc_path)
+                       + strlen(search_ctx->ffsc_fix_path + len)
                        + 1);
         STRCPY(temp, search_ctx->ffsc_fix_path + len);
         STRCAT(temp, search_ctx->ffsc_wc_path);
@@ -569,7 +569,7 @@ char_u *vim_findfile(void *search_ctx_arg)
 
   // store the end of the start dir -- needed for upward search
   if (search_ctx->ffsc_start_dir != NULL) {
-    path_end = (char_u *)&search_ctx->ffsc_start_dir[STRLEN(search_ctx->ffsc_start_dir)];
+    path_end = (char_u *)&search_ctx->ffsc_start_dir[strlen(search_ctx->ffsc_start_dir)];
   }
 
   // upward search loop
@@ -652,7 +652,7 @@ char_u *vim_findfile(void *search_ctx_arg)
         // if we have a start dir copy it in
         if (!vim_isAbsName(stackp->ffs_fix_path)
             && search_ctx->ffsc_start_dir) {
-          if (STRLEN(search_ctx->ffsc_start_dir) + 1 >= MAXPATHL) {
+          if (strlen(search_ctx->ffsc_start_dir) + 1 >= MAXPATHL) {
             ff_free_stack_element(stackp);
             goto fail;
           }
@@ -758,8 +758,8 @@ char_u *vim_findfile(void *search_ctx_arg)
               continue;                 // not a directory
             }
             // prepare the filename to be checked for existence below
-            if (STRLEN(stackp->ffs_filearray[i]) + 1
-                + STRLEN(search_ctx->ffsc_file_to_search) >= MAXPATHL) {
+            if (strlen(stackp->ffs_filearray[i]) + 1
+                + strlen(search_ctx->ffsc_file_to_search) >= MAXPATHL) {
               ff_free_stack_element(stackp);
               goto fail;
             }
@@ -902,8 +902,8 @@ char_u *vim_findfile(void *search_ctx_arg)
         break;
       }
 
-      if (STRLEN(search_ctx->ffsc_start_dir) + 1
-          + STRLEN(search_ctx->ffsc_fix_path) >= MAXPATHL) {
+      if (strlen(search_ctx->ffsc_start_dir) + 1
+          + strlen(search_ctx->ffsc_fix_path) >= MAXPATHL) {
         goto fail;
       }
       STRCPY(file_path, search_ctx->ffsc_start_dir);
@@ -1091,7 +1091,7 @@ static int ff_check_visited(ff_visited_T **visited_list, char *fname, char *wc_p
   }
 
   // New file/dir.  Add it to the list of visited files/dirs.
-  vp = xmalloc(sizeof(ff_visited_T) + STRLEN(ff_expand_buffer));
+  vp = xmalloc(sizeof(ff_visited_T) + strlen(ff_expand_buffer));
 
   if (!url) {
     vp->file_id_valid = true;
@@ -1397,7 +1397,7 @@ char_u *find_file_in_path_option(char_u *ptr, size_t len, int options, int first
       // When FNAME_REL flag given first use the directory of the file.
       // Otherwise or when this fails use the current directory.
       for (int run = 1; run <= 2; run++) {
-        size_t l = STRLEN(ff_file_to_find);
+        size_t l = strlen(ff_file_to_find);
         if (run == 1
             && rel_to_curdir
             && (options & FNAME_REL)
@@ -1405,7 +1405,7 @@ char_u *find_file_in_path_option(char_u *ptr, size_t len, int options, int first
             && STRLEN(rel_fname) + l < MAXPATHL) {
           STRCPY(NameBuff, rel_fname);
           STRCPY(path_tail((char *)NameBuff), ff_file_to_find);
-          l = STRLEN(NameBuff);
+          l = strlen(NameBuff);
         } else {
           STRCPY(NameBuff, ff_file_to_find);
           run = 2;
diff --git a/src/nvim/fileio.c b/src/nvim/fileio.c
index 0bc7f736bc..f2db4086c1 100644
--- a/src/nvim/fileio.c
+++ b/src/nvim/fileio.c
@@ -346,7 +346,7 @@ int readfile(char *fname, char *sfname, linenr_T from, linenr_T lines_to_skip,
   }
   // If the name is too long we might crash further on, quit here.
   if (fname != NULL && *fname != NUL) {
-    size_t namelen = STRLEN(fname);
+    size_t namelen = strlen(fname);
 
     // If the name is too long we might crash further on, quit here.
     if (namelen >= MAXPATHL) {
@@ -1782,12 +1782,12 @@ failed:
         c = true;
       }
       if (conv_error != 0) {
-        sprintf((char *)IObuff + STRLEN(IObuff),
-                _("[CONVERSION ERROR in line %" PRId64 "]"), (int64_t)conv_error);
+        snprintf(IObuff + strlen(IObuff), IOSIZE - strlen(IObuff),
+                 _("[CONVERSION ERROR in line %" PRId64 "]"), (int64_t)conv_error);
         c = true;
       } else if (illegal_byte > 0) {
-        sprintf((char *)IObuff + STRLEN(IObuff),
-                _("[ILLEGAL BYTE in line %" PRId64 "]"), (int64_t)illegal_byte);
+        snprintf(IObuff + strlen(IObuff), IOSIZE - strlen(IObuff),
+                 _("[ILLEGAL BYTE in line %" PRId64 "]"), (int64_t)illegal_byte);
         c = true;
       } else if (error) {
         STRCAT(IObuff, _("[READ ERRORS]"));
@@ -1958,7 +1958,7 @@ static linenr_T readfile_linenr(linenr_T linecnt, char_u *p, char_u *endp)
 void prep_exarg(exarg_T *eap, const buf_T *buf)
   FUNC_ATTR_NONNULL_ALL
 {
-  const size_t cmd_len = 15 + STRLEN(buf->b_p_fenc);
+  const size_t cmd_len = 15 + strlen(buf->b_p_fenc);
   eap->cmd = xmalloc(cmd_len);
 
   snprintf(eap->cmd, cmd_len, "e ++enc=%s", buf->b_p_fenc);
@@ -2022,7 +2022,7 @@ static char *next_fenc(char **pp, bool *alloced)
   p = vim_strchr((*pp), ',');
   if (p == NULL) {
     r = enc_canonize(*pp);
-    *pp += STRLEN(*pp);
+    *pp += strlen(*pp);
   } else {
     r = xstrnsave(*pp, (size_t)(p - *pp));
     *pp = p + 1;
@@ -2203,7 +2203,7 @@ int buf_write(buf_T *buf, char *fname, char *sfname, linenr_T start, linenr_T en
   }
 
   // Avoid a crash for a long name.
-  if (STRLEN(fname) >= MAXPATHL) {
+  if (strlen(fname) >= MAXPATHL) {
     emsg(_(e_longname));
     return FAIL;
   }
@@ -2733,7 +2733,7 @@ int buf_write(buf_T *buf, char *fname, char *sfname, linenr_T start, linenr_T en
               // delete an existing one, and try to use another name instead.
               // Change one character, just before the extension.
               //
-              wp = backup + STRLEN(backup) - 1 - STRLEN(backup_ext);
+              wp = backup + strlen(backup) - 1 - strlen(backup_ext);
               if (wp < backup) {                // empty file name ???
                 wp = backup;
               }
@@ -2861,7 +2861,7 @@ nobackup:
           // delete an existing one, try to use another name.
           // Change one character, just before the extension.
           if (!p_bk && os_path_exists(backup)) {
-            p = backup + STRLEN(backup) - 1 - STRLEN(backup_ext);
+            p = backup + strlen(backup) - 1 - strlen(backup_ext);
             if (p < backup) {           // empty file name ???
               p = backup;
             }
@@ -3172,7 +3172,7 @@ restore_backup:
       // Keep it fast!
       ptr = ml_get_buf(buf, lnum, false) - 1;
       if (write_undo_file) {
-        sha256_update(&sha_ctx, (char_u *)ptr + 1, (uint32_t)(STRLEN(ptr + 1) + 1));
+        sha256_update(&sha_ctx, (char_u *)ptr + 1, (uint32_t)(strlen(ptr + 1) + 1));
       }
       while ((c = *++ptr) != NUL) {
         if (c == NL) {
@@ -4527,7 +4527,7 @@ int vim_rename(const char *from, const char *to)
 
     // Find a name that doesn't exist and is in the same directory.
     // Rename "from" to "tempname" and then rename "tempname" to "to".
-    if (STRLEN(from) >= MAXPATHL - 5) {
+    if (strlen(from) >= MAXPATHL - 5) {
       return -1;
     }
     STRCPY(tempname, from);
@@ -4892,7 +4892,7 @@ int buf_check_timestamp(buf_T *buf)
     if (!helpmesg) {
       mesg2 = "";
     }
-    const size_t tbuf_len = STRLEN(path) + STRLEN(mesg) + STRLEN(mesg2) + 2;
+    const size_t tbuf_len = strlen(path) + strlen(mesg) + strlen(mesg2) + 2;
     char *const tbuf = xmalloc(tbuf_len);
     snprintf(tbuf, tbuf_len, mesg, path);
     // Set warningmsg here, before the unimportant and output-specific
@@ -5489,7 +5489,7 @@ char *file_pat_to_reg_pat(const char *pat, const char *pat_end, char *allow_dirs
     *allow_dirs = false;
   }
   if (pat_end == NULL) {
-    pat_end = pat + STRLEN(pat);
+    pat_end = pat + strlen(pat);
   }
 
   if (pat_end == pat) {
diff --git a/src/nvim/fold.c b/src/nvim/fold.c
index 2e8d282ede..d46470d413 100644
--- a/src/nvim/fold.c
+++ b/src/nvim/fold.c
@@ -996,7 +996,7 @@ void foldAdjustVisual(void)
   }
   if (hasFolding(end->lnum, NULL, &end->lnum)) {
     ptr = ml_get(end->lnum);
-    end->col = (colnr_T)STRLEN(ptr);
+    end->col = (colnr_T)strlen(ptr);
     if (end->col > 0 && *p_sel == 'o') {
       end->col--;
     }
@@ -1589,7 +1589,7 @@ static void foldAddMarker(buf_T *buf, pos_T pos, const char *marker, size_t mark
   if (u_save(lnum - 1, lnum + 1) == OK) {
     // Check if the line ends with an unclosed comment
     skip_comment(line, false, false, &line_is_comment);
-    newline = xmalloc(line_len + markerlen + STRLEN(cms) + 1);
+    newline = xmalloc(line_len + markerlen + strlen(cms) + 1);
     STRCPY(newline, line);
     // Append the marker to the end of the line
     if (p == NULL || line_is_comment) {
@@ -1599,7 +1599,7 @@ static void foldAddMarker(buf_T *buf, pos_T pos, const char *marker, size_t mark
       STRCPY(newline + line_len, cms);
       memcpy(newline + line_len + (p - cms), marker, markerlen);
       STRCPY(newline + line_len + (p - cms) + markerlen, p + 2);
-      added = markerlen + STRLEN(cms) - 2;
+      added = markerlen + strlen(cms) - 2;
     }
     ml_replace_buf(buf, lnum, newline, false);
     if (added) {
@@ -1655,14 +1655,14 @@ static void foldDelMarker(buf_T *buf, linenr_T lnum, char *marker, size_t marker
       char *cms2 = strstr(cms, "%s");
       if (p - line >= cms2 - cms
           && STRNCMP(p - (cms2 - cms), cms, cms2 - cms) == 0
-          && STRNCMP(p + len, cms2 + 2, STRLEN(cms2 + 2)) == 0) {
+          && STRNCMP(p + len, cms2 + 2, strlen(cms2 + 2)) == 0) {
         p -= cms2 - cms;
-        len += STRLEN(cms) - 2;
+        len += strlen(cms) - 2;
       }
     }
     if (u_save(lnum - 1, lnum + 1) == OK) {
       // Make new line: text-before-marker + text-after-marker
-      char *newline = xmalloc(STRLEN(line) - len + 1);
+      char *newline = xmalloc(strlen(line) - len + 1);
       assert(p >= line);
       memcpy(newline, line, (size_t)(p - line));
       STRCPY(newline + (p - line), p + len);
@@ -1789,7 +1789,7 @@ static void foldtext_cleanup(char *str)
 {
   // Ignore leading and trailing white space in 'commentstring'.
   char *cms_start = skipwhite(curbuf->b_p_cms);
-  size_t cms_slen = STRLEN(cms_start);
+  size_t cms_slen = strlen(cms_start);
   while (cms_slen > 0 && ascii_iswhite(cms_start[cms_slen - 1])) {
     cms_slen--;
   }
@@ -2985,7 +2985,7 @@ static void parseMarker(win_T *wp)
 {
   foldendmarker = vim_strchr(wp->w_p_fmr, ',');
   foldstartmarkerlen = (size_t)(foldendmarker++ - wp->w_p_fmr);
-  foldendmarkerlen = STRLEN(foldendmarker);
+  foldendmarkerlen = strlen(foldendmarker);
 }
 
 // foldlevelMarker() {{{2
@@ -3262,13 +3262,13 @@ void f_foldtext(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
     }
     int count = foldend - foldstart + 1;
     char *txt = NGETTEXT("+-%s%3ld line: ", "+-%s%3ld lines: ", count);
-    size_t len = STRLEN(txt)
-                 + STRLEN(dashes)  // for %s
+    size_t len = strlen(txt)
+                 + strlen(dashes)  // for %s
                  + 20              // for %3ld
                  + STRLEN(s);      // concatenated
     char *r = xmalloc(len);
     snprintf(r, len, txt, dashes, count);
-    len = STRLEN(r);
+    len = strlen(r);
     STRCAT(r, s);
     // remove 'foldmarker' and 'commentstring'
     foldtext_cleanup(r + len);
diff --git a/src/nvim/garray.c b/src/nvim/garray.c
index adc3eda5ca..6c63ce5a7c 100644
--- a/src/nvim/garray.c
+++ b/src/nvim/garray.c
@@ -198,7 +198,7 @@ void ga_concat(garray_T *gap, const char *restrict s)
     return;
   }
 
-  ga_concat_len(gap, s, STRLEN(s));
+  ga_concat_len(gap, s, strlen(s));
 }
 
 /// Concatenate a string to a growarray which contains characters
diff --git a/src/nvim/getchar.c b/src/nvim/getchar.c
index 0f0e3aece1..c7cfc91591 100644
--- a/src/nvim/getchar.c
+++ b/src/nvim/getchar.c
@@ -148,7 +148,7 @@ static char_u *get_buffcont(buffheader_T *buffer, int dozero)
   // compute the total length of the string
   for (const buffblock_T *bp = buffer->bh_first.b_next;
        bp != NULL; bp = bp->b_next) {
-    count += STRLEN(bp->b_str);
+    count += strlen(bp->b_str);
   }
 
   if (count || dozero) {
@@ -225,13 +225,13 @@ static void add_buff(buffheader_T *const buf, const char *const s, ptrdiff_t sle
   } else if (buf->bh_index != 0) {
     memmove(buf->bh_first.b_next->b_str,
             buf->bh_first.b_next->b_str + buf->bh_index,
-            STRLEN(buf->bh_first.b_next->b_str + buf->bh_index) + 1);
+            strlen(buf->bh_first.b_next->b_str + buf->bh_index) + 1);
   }
   buf->bh_index = 0;
 
   size_t len;
   if (buf->bh_space >= (size_t)slen) {
-    len = STRLEN(buf->bh_curr->b_str);
+    len = strlen(buf->bh_curr->b_str);
     STRLCPY(buf->bh_curr->b_str + len, s, slen + 1);
     buf->bh_space -= (size_t)slen;
   } else {
@@ -259,7 +259,7 @@ static void delete_buff_tail(buffheader_T *buf, int slen)
   if (buf->bh_curr == NULL) {
     return;  // nothing to delete
   }
-  len = (int)STRLEN(buf->bh_curr->b_str);
+  len = (int)strlen(buf->bh_curr->b_str);
   if (len >= slen) {
     buf->bh_curr->b_str[len - slen] = NUL;
     buf->bh_space += (size_t)slen;
@@ -845,7 +845,7 @@ int ins_typebuf(char *str, int noremap, int offset, bool nottyped, bool silent)
     typebuf.tb_change_cnt = 1;
   }
 
-  addlen = (int)STRLEN(str);
+  addlen = (int)strlen(str);
 
   if (offset == 0 && addlen <= typebuf.tb_off) {
     // Easy case: there is room in front of typebuf.tb_buf[typebuf.tb_off]
diff --git a/src/nvim/hardcopy.c b/src/nvim/hardcopy.c
index b530e2c5ec..c46f95b64f 100644
--- a/src/nvim/hardcopy.c
+++ b/src/nvim/hardcopy.c
@@ -663,7 +663,7 @@ void ex_hardcopy(exarg_T *eap)
 
   // Estimate the total lines to be printed
   for (lnum = eap->line1; lnum <= eap->line2; lnum++) {
-    bytes_to_print += STRLEN(skipwhite((char *)ml_get(lnum)));
+    bytes_to_print += strlen(skipwhite(ml_get(lnum)));
   }
   if (bytes_to_print == 0) {
     msg(_("No text to be printed"));
@@ -739,10 +739,10 @@ void ex_hardcopy(exarg_T *eap)
           }
 
           if (settings.n_collated_copies > 1) {
-            sprintf((char *)IObuff + STRLEN(IObuff),
-                    _(" Copy %d of %d"),
-                    collated_copies + 1,
-                    settings.n_collated_copies);
+            snprintf(IObuff + strlen(IObuff), IOSIZE - strlen(IObuff),
+                     _(" Copy %d of %d"),
+                     collated_copies + 1,
+                     settings.n_collated_copies);
           }
           prt_message((char_u *)IObuff);
 
@@ -759,7 +759,7 @@ void ex_hardcopy(exarg_T *eap)
             if (prtpos.column == 0) {
               // finished a file line
               prtpos.bytes_printed +=
-                STRLEN(skipwhite((char *)ml_get(prtpos.file_line)));
+                strlen(skipwhite(ml_get(prtpos.file_line)));
               if (++prtpos.file_line > eap->line2) {
                 break;                 // reached the end
               }
@@ -1278,7 +1278,7 @@ static void prt_write_file_raw_len(char_u *buffer, size_t bytes)
 
 static void prt_write_file(char *buffer)
 {
-  prt_write_file_len((char_u *)buffer, STRLEN(buffer));
+  prt_write_file_len((char_u *)buffer, strlen(buffer));
 }
 
 static void prt_write_file_len(char_u *buffer, size_t bytes)
@@ -1475,7 +1475,7 @@ static void prt_resource_name(char *filename, void *cookie)
 {
   char_u *resource_filename = cookie;
 
-  if (STRLEN(filename) >= MAXPATHL) {
+  if (strlen(filename) >= MAXPATHL) {
     *resource_filename = NUL;
   } else {
     STRCPY(resource_filename, filename);
@@ -1653,14 +1653,14 @@ static bool prt_open_resource(struct prt_ps_resource_S *resource)
   int offset = 0;
 
   if (prt_resfile_strncmp(offset, PRT_RESOURCE_HEADER,
-                          (int)STRLEN(PRT_RESOURCE_HEADER)) != 0) {
+                          (int)strlen(PRT_RESOURCE_HEADER)) != 0) {
     semsg(_("E618: file \"%s\" is not a PostScript resource file"),
           resource->filename);
     return false;
   }
 
   // Skip over any version numbers and following ws
-  offset += (int)STRLEN(PRT_RESOURCE_HEADER);
+  offset += (int)strlen(PRT_RESOURCE_HEADER);
   offset = prt_resfile_skip_nonws(offset);
   if (offset == -1) {
     return false;
@@ -1670,22 +1670,22 @@ static bool prt_open_resource(struct prt_ps_resource_S *resource)
     return false;
   }
   if (prt_resfile_strncmp(offset, PRT_RESOURCE_RESOURCE,
-                          (int)STRLEN(PRT_RESOURCE_RESOURCE)) != 0) {
+                          (int)strlen(PRT_RESOURCE_RESOURCE)) != 0) {
     semsg(_("E619: file \"%s\" is not a supported PostScript resource file"),
           resource->filename);
     return false;
   }
-  offset += (int)STRLEN(PRT_RESOURCE_RESOURCE);
+  offset += (int)strlen(PRT_RESOURCE_RESOURCE);
 
   // Decide type of resource in the file
   if (prt_resfile_strncmp(offset, PRT_RESOURCE_PROCSET,
-                          (int)STRLEN(PRT_RESOURCE_PROCSET)) == 0) {
+                          (int)strlen(PRT_RESOURCE_PROCSET)) == 0) {
     resource->type = PRT_RESOURCE_TYPE_PROCSET;
   } else if (prt_resfile_strncmp(offset, PRT_RESOURCE_ENCODING,
-                                 (int)STRLEN(PRT_RESOURCE_ENCODING)) == 0) {
+                                 (int)strlen(PRT_RESOURCE_ENCODING)) == 0) {
     resource->type = PRT_RESOURCE_TYPE_ENCODING;
   } else if (prt_resfile_strncmp(offset, PRT_RESOURCE_CMAP,
-                                 (int)STRLEN(PRT_RESOURCE_CMAP)) == 0) {
+                                 (int)strlen(PRT_RESOURCE_CMAP)) == 0) {
     resource->type = PRT_RESOURCE_TYPE_CMAP;
   } else {
     semsg(_("E619: file \"%s\" is not a supported PostScript resource file"),
@@ -2021,7 +2021,7 @@ static int prt_match_encoding(char *p_encoding, struct prt_ps_mbfont_S *p_cmap,
 
   *pp_mbenc = NULL;
   // Look for recognised encoding
-  enc_len = (int)STRLEN(p_encoding);
+  enc_len = (int)strlen(p_encoding);
   p_mbenc = p_cmap->encodings;
   for (mbenc = 0; mbenc < p_cmap->num_encodings; mbenc++) {
     if (STRNICMP(p_mbenc->encoding, p_encoding, enc_len) == 0) {
@@ -2044,7 +2044,7 @@ static int prt_match_charset(char *p_charset, struct prt_ps_mbfont_S *p_cmap,
   if (*p_charset == NUL) {
     p_charset = p_cmap->defcs;
   }
-  char_len = (int)STRLEN(p_charset);
+  char_len = (int)strlen(p_charset);
   p_mbchar = p_cmap->charsets;
   for (mbchar = 0; mbchar < p_cmap->num_charsets; mbchar++) {
     if (STRNICMP(p_mbchar->charset, p_charset, char_len) == 0) {
@@ -2135,8 +2135,8 @@ int mch_print_init(prt_settings_T *psettings, char_u *jobname, int forceit)
     }
 
     // CMap name ends with (optional) encoding name and -H for horizontal
-    if (p_mbenc->cmap_encoding != NULL && STRLEN(prt_cmap)
-        + STRLEN(p_mbenc->cmap_encoding) + 3 < sizeof(prt_cmap)) {
+    if (p_mbenc->cmap_encoding != NULL && strlen(prt_cmap)
+        + strlen(p_mbenc->cmap_encoding) + 3 < sizeof(prt_cmap)) {
       STRCAT(prt_cmap, p_mbenc->cmap_encoding);
       STRCAT(prt_cmap, "-");
     }
@@ -2200,7 +2200,7 @@ int mch_print_init(prt_settings_T *psettings, char_u *jobname, int forceit)
     paper_strlen = 2;
   }
   for (i = 0; i < (int)PRT_MEDIASIZE_LEN; i++) {
-    if (STRLEN(prt_mediasize[i].name) == (unsigned)paper_strlen
+    if (strlen(prt_mediasize[i].name) == (unsigned)paper_strlen
         && STRNICMP(prt_mediasize[i].name, paper_name,
                     paper_strlen) == 0) {
       break;
diff --git a/src/nvim/hashtab.c b/src/nvim/hashtab.c
index 308f64f011..3d0ab192b9 100644
--- a/src/nvim/hashtab.c
+++ b/src/nvim/hashtab.c
@@ -87,7 +87,7 @@ void hash_clear_all(hashtab_T *ht, unsigned int off)
 ///                  is changed in any way.
 hashitem_T *hash_find(const hashtab_T *const ht, const char *const key)
 {
-  return hash_lookup(ht, key, STRLEN(key), hash_hash((char_u *)key));
+  return hash_lookup(ht, key, strlen(key), hash_hash((char_u *)key));
 }
 
 /// Like hash_find, but key is not NUL-terminated
diff --git a/src/nvim/help.c b/src/nvim/help.c
index 507c5904b3..a24b17e34e 100644
--- a/src/nvim/help.c
+++ b/src/nvim/help.c
@@ -75,7 +75,7 @@ void ex_help(exarg_T *eap)
   }
 
   // remove trailing blanks
-  p = arg + STRLEN(arg) - 1;
+  p = arg + strlen(arg) - 1;
   while (p > arg && ascii_iswhite(*p) && p[-1] != '\\') {
     *p-- = NUL;
   }
@@ -95,7 +95,7 @@ void ex_help(exarg_T *eap)
   if (n != FAIL && lang != NULL) {
     // Find first item with the requested language.
     for (i = 0; i < num_matches; i++) {
-      len = (int)STRLEN(matches[i]);
+      len = (int)strlen(matches[i]);
       if (len > 3 && matches[i][len - 3] == '@'
           && STRICMP(matches[i] + len - 2, lang) == 0) {
         break;
@@ -219,7 +219,7 @@ void ex_helpclose(exarg_T *eap)
 /// @return  NULL if not found.
 char *check_help_lang(char *arg)
 {
-  int len = (int)STRLEN(arg);
+  int len = (int)strlen(arg);
 
   if (len >= 3 && arg[len - 3] == '@' && ASCII_ISALPHA(arg[len - 2])
       && ASCII_ISALPHA(arg[len - 1])) {
@@ -278,7 +278,7 @@ int help_heuristic(char *matched_string, int offset, int wrong_case)
   if (matched_string[0] == '+' && matched_string[1] != NUL) {
     offset += 100;
   }
-  return 100 * num_letters + (int)STRLEN(matched_string) + offset;
+  return 100 * num_letters + (int)strlen(matched_string) + offset;
 }
 
 /// Compare functions for qsort() below, that checks the help heuristics number
@@ -515,16 +515,16 @@ int find_help_tags(const char *arg, int *num_matches, char ***matches, bool keep
       if (*IObuff == '`') {
         if (d > IObuff + 2 && d[-1] == '`') {
           // remove the backticks from `command`
-          memmove(IObuff, IObuff + 1, STRLEN(IObuff));
+          memmove(IObuff, IObuff + 1, strlen(IObuff));
           d[-2] = NUL;
         } else if (d > IObuff + 3 && d[-2] == '`' && d[-1] == ',') {
           // remove the backticks and comma from `command`,
-          memmove(IObuff, IObuff + 1, STRLEN(IObuff));
+          memmove(IObuff, IObuff + 1, strlen(IObuff));
           d[-3] = NUL;
         } else if (d > IObuff + 4 && d[-3] == '`'
                    && d[-2] == '\\' && d[-1] == '.') {
           // remove the backticks and dot from `command`\.
-          memmove(IObuff, IObuff + 1, STRLEN(IObuff));
+          memmove(IObuff, IObuff + 1, strlen(IObuff));
           d[-4] = NUL;
         }
       }
@@ -567,7 +567,7 @@ void cleanup_help_tags(int num_file, char **file)
   *p = NUL;
 
   for (int i = 0; i < num_file; i++) {
-    int len = (int)STRLEN(file[i]) - 3;
+    int len = (int)strlen(file[i]) - 3;
     if (len <= 0) {
       continue;
     }
@@ -577,7 +577,7 @@ void cleanup_help_tags(int num_file, char **file)
       int j;
       for (j = 0; j < num_file; j++) {
         if (j != i
-            && (int)STRLEN(file[j]) == len + 3
+            && (int)strlen(file[j]) == len + 3
             && STRNCMP(file[i], file[j], len + 1) == 0) {
           break;
         }
@@ -591,7 +591,7 @@ void cleanup_help_tags(int num_file, char **file)
 
   if (*buf != NUL) {
     for (int i = 0; i < num_file; i++) {
-      int len = (int)STRLEN(file[i]) - 3;
+      int len = (int)strlen(file[i]) - 3;
       if (len <= 0) {
         continue;
       }
@@ -915,7 +915,7 @@ static void helptags_one(char *dir, const char *ext, const char *tagfname, bool
   ga_init(&ga, (int)sizeof(char_u *), 100);
   if (add_help_tags
       || path_full_compare("$VIMRUNTIME/doc", dir, false, true) == kEqualFiles) {
-    size_t s_len = 18 + STRLEN(tagfname);
+    size_t s_len = 18 + strlen(tagfname);
     s = xmalloc(s_len);
     snprintf(s, s_len, "help-tags\t%s\t1\n", tagfname);
     GA_APPEND(char *, &ga, s);
@@ -979,7 +979,7 @@ static void helptags_one(char *dir, const char *ext, const char *tagfname, bool
                   || s[1] == '\0')) {
             *p2 = '\0';
             p1++;
-            size_t s_len= (size_t)(p2 - p1) + STRLEN(fname) + 2;
+            size_t s_len= (size_t)(p2 - p1) + strlen(fname) + 2;
             s = xmalloc(s_len);
             GA_APPEND(char *, &ga, s);
             snprintf(s, s_len, "%s\t%s", p1, fname);
@@ -1087,7 +1087,7 @@ static void do_helptags(char *dirname, bool add_help_tags, bool ignore_writeerr)
   int j;
   ga_init(&ga, 1, 10);
   for (int i = 0; i < filecount; i++) {
-    len = (int)STRLEN(files[i]);
+    len = (int)strlen(files[i]);
     if (len <= 4) {
       continue;
     }
diff --git a/src/nvim/highlight.c b/src/nvim/highlight.c
index e42cb66422..d507f07bca 100644
--- a/src/nvim/highlight.c
+++ b/src/nvim/highlight.c
@@ -407,7 +407,7 @@ void update_ns_hl(int ns_id)
   int *hl_attrs = **alloc;
 
   for (int hlf = 0; hlf < HLF_COUNT; hlf++) {
-    int id = syn_check_group(hlf_names[hlf], STRLEN(hlf_names[hlf]));
+    int id = syn_check_group(hlf_names[hlf], strlen(hlf_names[hlf]));
     bool optional = (hlf == HLF_INACTIVE || hlf == HLF_NFLOAT);
     hl_attrs[hlf] = hl_get_ui_attr(ns_id, hlf, id, optional);
   }
diff --git a/src/nvim/highlight_group.c b/src/nvim/highlight_group.c
index 2cb8fabfb4..fed39c6ed7 100644
--- a/src/nvim/highlight_group.c
+++ b/src/nvim/highlight_group.c
@@ -1084,7 +1084,7 @@ void do_highlight(const char *line, const bool forceit, const bool init)
         int i;
         while (arg[off] != NUL) {
           for (i = ARRAY_SIZE(hl_attr_table); --i >= 0;) {
-            len = (int)STRLEN(hl_name_table[i]);
+            len = (int)strlen(hl_name_table[i]);
             if (STRNICMP(arg + off, hl_name_table[i], len) == 0) {
               attr |= hl_attr_table[i];
               off += len;
@@ -1519,7 +1519,7 @@ static bool highlight_list_arg(const int id, bool didh, const int type, int iarg
       }
     }
 
-    (void)syn_list_header(didh, vim_strsize((char *)ts) + (int)STRLEN(name) + 1, id, false);
+    (void)syn_list_header(didh, vim_strsize((char *)ts) + (int)strlen(name) + 1, id, false);
     didh = true;
     if (!got_int) {
       if (*name != NUL) {
@@ -1723,7 +1723,7 @@ int syn_name2id(const char *name)
     // if we look up @aaa.bbb, we have to consider @aaa as well
     return syn_check_group(name, strlen(name));
   } else {
-    return syn_name2id_len(name, STRLEN(name));
+    return syn_name2id_len(name, strlen(name));
   }
 }
 
@@ -2007,7 +2007,7 @@ void highlight_changed(void)
 
   /// Translate builtin highlight groups into attributes for quick lookup.
   for (int hlf = 0; hlf < HLF_COUNT; hlf++) {
-    id = syn_check_group(hlf_names[hlf], STRLEN(hlf_names[hlf]));
+    id = syn_check_group(hlf_names[hlf], strlen(hlf_names[hlf]));
     if (id == 0) {
       abort();
     }
diff --git a/src/nvim/if_cscope.c b/src/nvim/if_cscope.c
index 719899d0b8..a637e480ea 100644
--- a/src/nvim/if_cscope.c
+++ b/src/nvim/if_cscope.c
@@ -415,7 +415,7 @@ static int cs_add_common(char *arg1, char *arg2, char *flags)
   fname = xmalloc(MAXPATHL + 1);
 
   expand_env(arg1, fname, MAXPATHL);
-  size_t len = STRLEN(fname);
+  size_t len = strlen(fname);
   fbuf = fname;
   (void)modify_fname(":p", false, &usedlen, &fname, &fbuf, &len);
   if (fname == NULL) {
@@ -1180,7 +1180,7 @@ static cscmd_T *cs_lookup_cmd(exarg_T *eap)
   }
 
   // Store length of eap->arg before it gets modified by strtok().
-  eap_arg_len = (int)STRLEN(eap->arg);
+  eap_arg_len = (int)strlen(eap->arg);
 
   if ((stok = strtok(eap->arg, (const char *)" ")) == NULL) {  // NOLINT(runtime/threadsafe_fn)
     return NULL;
diff --git a/src/nvim/indent_c.c b/src/nvim/indent_c.c
index c7f37790b6..5eed2601d5 100644
--- a/src/nvim/indent_c.c
+++ b/src/nvim/indent_c.c
@@ -204,7 +204,7 @@ bool cin_is_cinword(const char *line)
 {
   bool retval = false;
 
-  size_t cinw_len = STRLEN(curbuf->b_p_cinw) + 1;
+  size_t cinw_len = strlen(curbuf->b_p_cinw) + 1;
   char_u *cinw_buf = xmalloc(cinw_len);
   line = skipwhite((char *)line);
 
@@ -485,7 +485,7 @@ bool cin_isscopedecl(const char_u *p)
 {
   const char_u *s = cin_skipcomment(p);
 
-  const size_t cinsd_len = STRLEN(curbuf->b_p_cinsd) + 1;
+  const size_t cinsd_len = strlen(curbuf->b_p_cinsd) + 1;
   char_u *cinsd_buf = xmalloc(cinsd_len);
 
   bool found = false;
@@ -1322,7 +1322,7 @@ static int cin_ends_in(const char_u *s, const char_u *find, const char_u *ignore
 /// Return true when "s" starts with "word" and then a non-ID character.
 static int cin_starts_with(const char_u *s, const char *word)
 {
-  int l = (int)STRLEN(word);
+  int l = (int)strlen(word);
 
   return STRNCMP(s, word, l) == 0 && !vim_isIDc(s[l]);
 }
@@ -1901,7 +1901,7 @@ int get_c_indent(void)
   // For unknown reasons the cursor might be past the end of the line, thus
   // check for that.
   if ((State & MODE_INSERT)
-      && curwin->w_cursor.col < (colnr_T)STRLEN(linecopy)
+      && curwin->w_cursor.col < (colnr_T)strlen(linecopy)
       && linecopy[curwin->w_cursor.col] == ')') {
     linecopy[curwin->w_cursor.col] = NUL;
   }
@@ -2010,17 +2010,17 @@ int get_c_indent(void)
       (void)copy_option_part(&p, lead_end, COM_MAX_LEN, ",");
       if (what == COM_START) {
         STRCPY(lead_start, lead_end);
-        lead_start_len = (int)STRLEN(lead_start);
+        lead_start_len = (int)strlen(lead_start);
         start_off = off;
         start_align = align;
       } else if (what == COM_MIDDLE) {
         STRCPY(lead_middle, lead_end);
-        lead_middle_len = (int)STRLEN(lead_middle);
+        lead_middle_len = (int)strlen(lead_middle);
       } else if (what == COM_END) {
         // If our line starts with the middle comment string, line it
         // up with the comment opener per the 'comments' option.
         if (STRNCMP(theline, lead_middle, lead_middle_len) == 0
-            && STRNCMP(theline, lead_end, STRLEN(lead_end)) != 0) {
+            && STRNCMP(theline, lead_end, strlen(lead_end)) != 0) {
           done = true;
           if (curwin->w_cursor.lnum > 1) {
             // If the start comment string matches in the previous
@@ -2051,7 +2051,7 @@ int get_c_indent(void)
         // If our line starts with the end comment string, line it up
         // with the middle comment
         if (STRNCMP(theline, lead_middle, lead_middle_len) != 0
-            && STRNCMP(theline, lead_end, STRLEN(lead_end)) == 0) {
+            && STRNCMP(theline, lead_end, strlen(lead_end)) == 0) {
           amount = get_indent_lnum(curwin->w_cursor.lnum - 1);
           // XXX
           if (off != 0) {
diff --git a/src/nvim/insexpand.c b/src/nvim/insexpand.c
index a5e7929525..a4b0d68ffe 100644
--- a/src/nvim/insexpand.c
+++ b/src/nvim/insexpand.c
@@ -652,7 +652,7 @@ static char_u *ins_compl_infercase_gettext(char_u *str, int char_len, int compl_
       ga_grow(&gap, IOSIZE);
       *p = NUL;
       STRCPY(gap.ga_data, IObuff);
-      gap.ga_len = (int)STRLEN(IObuff);
+      gap.ga_len = (int)strlen(IObuff);
     } else {
       p += utf_char2bytes(wca[i++], p);
     }
@@ -775,7 +775,7 @@ static int ins_compl_add(char *const str, int len, char *const fname, char *cons
     return FAIL;
   }
   if (len < 0) {
-    len = (int)STRLEN(str);
+    len = (int)strlen(str);
   }
 
   // If the same match is already present, don't add it.
@@ -784,7 +784,7 @@ static int ins_compl_add(char *const str, int len, char *const fname, char *cons
     do {
       if (!match_at_original_text(match)
           && STRNCMP(match->cp_str, str, len) == 0
-          && ((int)STRLEN(match->cp_str) <= len || match->cp_str[len] == NUL)) {
+          && ((int)strlen(match->cp_str) <= len || match->cp_str[len] == NUL)) {
         FREE_CPTEXT(cptext, cptext_allocated);
         return NOTDONE;
       }
@@ -997,7 +997,7 @@ bool ins_compl_has_shown_match(void)
 bool ins_compl_long_shown_match(void)
 {
   return compl_shown_match != NULL && compl_shown_match->cp_str != NULL
-         && (colnr_T)STRLEN(compl_shown_match->cp_str) > curwin->w_cursor.col - compl_col;
+         && (colnr_T)strlen(compl_shown_match->cp_str) > curwin->w_cursor.col - compl_col;
 }
 
 /// Set variables that store noselect and noinsert behavior from the
@@ -1124,7 +1124,7 @@ static int ins_compl_build_pum(void)
     XFREE_CLEAR(compl_leader);
   }
 
-  const int lead_len = compl_leader != NULL ? (int)STRLEN(compl_leader) : 0;
+  const int lead_len = compl_leader != NULL ? (int)strlen(compl_leader) : 0;
 
   do {
     if (!match_at_original_text(compl)
@@ -2724,7 +2724,7 @@ static int process_next_cpt_value(ins_compl_next_state_T *st, int *compl_type_ar
       // buffer, so that word at start of buffer is found
       // correctly.
       st->first_match_pos.lnum = st->ins_buf->b_ml.ml_line_count;
-      st->first_match_pos.col = (colnr_T)STRLEN(ml_get(st->first_match_pos.lnum));
+      st->first_match_pos.col = (colnr_T)strlen(ml_get(st->first_match_pos.lnum));
     }
     st->last_match_pos = st->first_match_pos;
     compl_type = 0;
@@ -2806,7 +2806,7 @@ done:
 static void get_next_include_file_completion(int compl_type)
 {
   find_pattern_in_path((char_u *)compl_pattern, compl_direction,
-                       STRLEN(compl_pattern), false, false,
+                       strlen(compl_pattern), false, false,
                        ((compl_type == CTRL_X_PATH_DEFINES
                          && !(compl_cont_status & CONT_SOL))
                         ? FIND_DEFINE : FIND_ANY),
@@ -2889,7 +2889,7 @@ static void get_next_cmdline_completion(void)
   char **matches;
   int num_matches;
   if (expand_cmdline(&compl_xp, (char_u *)compl_pattern,
-                     (int)STRLEN(compl_pattern),
+                     (int)strlen(compl_pattern),
                      &num_matches, &matches) == EXPAND_OK) {
     ins_compl_add_matches(num_matches, matches, false);
   }
@@ -3810,7 +3810,7 @@ static int get_filename_compl_info(char_u *line, int startcol, colnr_T curs_col)
 static int get_cmdline_compl_info(char *line, colnr_T curs_col)
 {
   compl_pattern = xstrnsave(line, (size_t)curs_col);
-  set_cmd_context(&compl_xp, (char_u *)compl_pattern, (int)STRLEN(compl_pattern), curs_col, false);
+  set_cmd_context(&compl_xp, (char_u *)compl_pattern, (int)strlen(compl_pattern), curs_col, false);
   if (compl_xp.xp_context == EXPAND_UNSUCCESSFUL
       || compl_xp.xp_context == EXPAND_NOTHING) {
     // No completion possible, use an empty pattern to get a
diff --git a/src/nvim/keycodes.c b/src/nvim/keycodes.c
index a3763ea9bb..9ec37fd564 100644
--- a/src/nvim/keycodes.c
+++ b/src/nvim/keycodes.c
@@ -539,7 +539,7 @@ char_u *get_special_key_name(int c, int modifiers)
       }
     }
   } else {            // use name of special key
-    size_t len = STRLEN(key_names_table[table_idx].name);
+    size_t len = strlen(key_names_table[table_idx].name);
 
     if ((int)len + idx + 2 <= MAX_KEY_NAME_LEN) {
       STRCPY(string + idx, key_names_table[table_idx].name);
@@ -1050,7 +1050,7 @@ char *vim_strsave_escape_ks(char *p)
   // Need a buffer to hold up to three times as much.  Four in case of an
   // illegal utf-8 byte:
   // 0xc0 -> 0xc3 - 0x80 -> 0xc3 K_SPECIAL KS_SPECIAL KE_FILLER
-  char_u *res = xmalloc(STRLEN(p) * 4 + 1);
+  char_u *res = xmalloc(strlen(p) * 4 + 1);
   char_u *d = res;
   for (char_u *s = (char_u *)p; *s != NUL;) {
     if (s[0] == K_SPECIAL && s[1] != NUL && s[2] != NUL) {
diff --git a/src/nvim/lua/executor.c b/src/nvim/lua/executor.c
index 78ac051308..128f133b23 100644
--- a/src/nvim/lua/executor.c
+++ b/src/nvim/lua/executor.c
@@ -1049,7 +1049,7 @@ static int nlua_debug(lua_State *lstate)
       return 0;
     }
     if (luaL_loadbuffer(lstate, (const char *)input.vval.v_string,
-                        STRLEN(input.vval.v_string), "=(debug command)")) {
+                        strlen(input.vval.v_string), "=(debug command)")) {
       nlua_error(lstate, _("E5115: Error while loading debug string: %.*s"));
     } else if (nlua_pcall(lstate, 0, 0)) {
       nlua_error(lstate, _("E5116: Error while calling debug string: %.*s"));
@@ -1641,7 +1641,7 @@ void ex_luado(exarg_T *const eap)
       break;
     }
     if (lua_isstring(lstate, -1)) {
-      size_t old_line_len = STRLEN(old_line);
+      size_t old_line_len = strlen(old_line);
 
       size_t new_line_len;
       const char *const new_line = lua_tolstring(lstate, -1, &new_line_len);
@@ -2001,7 +2001,7 @@ int nlua_do_ucmd(ucmd_T *cmd, exarg_T *eap, bool preview)
 
   // Split args by unescaped whitespace |<f-args>| (nargs dependent)
   if (cmd->uc_argt & EX_NOSPC) {
-    if ((cmd->uc_argt & EX_NEEDARG) || STRLEN(eap->arg)) {
+    if ((cmd->uc_argt & EX_NEEDARG) || strlen(eap->arg)) {
       // For commands where nargs is 1 or "?" and argument is passed, fargs = { args }
       lua_rawseti(lstate, -2, 1);
     } else {
@@ -2011,7 +2011,7 @@ int nlua_do_ucmd(ucmd_T *cmd, exarg_T *eap, bool preview)
   } else if (eap->args == NULL) {
     // For commands with more than one possible argument, split if argument list isn't available.
     lua_pop(lstate, 1);  // Pop the reference of opts.args
-    size_t length = STRLEN(eap->arg);
+    size_t length = strlen(eap->arg);
     size_t end = 0;
     size_t len = 0;
     int i = 1;
diff --git a/src/nvim/main.c b/src/nvim/main.c
index a73c465042..a317789f73 100644
--- a/src/nvim/main.c
+++ b/src/nvim/main.c
@@ -1156,7 +1156,7 @@ static void command_line_scan(mparm_T *parmp)
         p_verbose = get_number_arg(argv[0], &argv_idx, 10);
         if (argv[0][argv_idx] != NUL) {
           set_option_value_give_err("verbosefile", 0L, argv[0] + argv_idx, 0);
-          argv_idx = (int)STRLEN(argv[0]);
+          argv_idx = (int)strlen(argv[0]);
         }
         break;
       case 'w':    // "-w{number}" set window height
@@ -1226,7 +1226,7 @@ static void command_line_scan(mparm_T *parmp)
               a = argv[0];
             }
 
-            size_t s_size = STRLEN(a) + 9;
+            size_t s_size = strlen(a) + 9;
             char *s = xmalloc(s_size);
             snprintf(s, s_size, "so %s", a);
             parmp->cmds_tofree[parmp->n_commands] = true;
@@ -1375,7 +1375,7 @@ scripterror:
 
   // If there is a "+123" or "-c" command, set v:swapcommand to the first one.
   if (parmp->n_commands > 0) {
-    const size_t swcmd_len = STRLEN(parmp->commands[0]) + 3;
+    const size_t swcmd_len = strlen(parmp->commands[0]) + 3;
     char *const swcmd = xmalloc(swcmd_len);
     snprintf(swcmd, swcmd_len, ":%s\r", parmp->commands[0]);
     set_vim_var_string(VV_SWAPCOMMAND, swcmd, -1);
diff --git a/src/nvim/mapping.c b/src/nvim/mapping.c
index 9f169427f5..a10146c110 100644
--- a/src/nvim/mapping.c
+++ b/src/nvim/mapping.c
@@ -262,7 +262,7 @@ static bool set_maparg_lhs_rhs(const char *const orig_lhs, const size_t orig_lhs
   if (replaced == NULL) {
     return false;
   }
-  mapargs->lhs_len = STRLEN(replaced);
+  mapargs->lhs_len = strlen(replaced);
   STRLCPY(mapargs->lhs, replaced, sizeof(mapargs->lhs));
   if (did_simplify) {
     replaced = replace_termcodes(orig_lhs, orig_lhs_len, &bufarg, flags | REPTERM_NO_SIMPLIFY,
@@ -270,7 +270,7 @@ static bool set_maparg_lhs_rhs(const char *const orig_lhs, const size_t orig_lhs
     if (replaced == NULL) {
       return false;
     }
-    mapargs->alt_lhs_len = STRLEN(replaced);
+    mapargs->alt_lhs_len = strlen(replaced);
     STRLCPY(mapargs->alt_lhs, replaced, sizeof(mapargs->alt_lhs));
   } else {
     mapargs->alt_lhs_len = 0;
@@ -299,7 +299,7 @@ static void set_maparg_rhs(const char *const orig_rhs, const size_t orig_rhs_len
       char *rhs_buf = NULL;
       char *replaced = replace_termcodes(orig_rhs, orig_rhs_len, &rhs_buf, REPTERM_DO_LT, NULL,
                                          cpo_flags);
-      mapargs->rhs_len = STRLEN(replaced);
+      mapargs->rhs_len = strlen(replaced);
       // NB: replace_termcodes may produce an empty string even if orig_rhs is non-empty
       // (e.g. a single ^V, see :h map-empty-rhs)
       mapargs->rhs_is_noop = orig_rhs_len != 0 && mapargs->rhs_len == 0;
@@ -709,7 +709,7 @@ static int buf_do_map(int maptype, MapArguments *args, int mode, bool is_abbrev,
             }
           } else {                          // do we have a match?
             if (round) {              // second round: Try unmap "rhs" string
-              n = (int)STRLEN(mp->m_str);
+              n = (int)strlen(mp->m_str);
               p = (char_u *)mp->m_str;
             } else {
               n = mp->m_keylen;
@@ -2091,7 +2091,7 @@ static void get_maparg(typval_T *argvars, typval_T *rettv, int exact)
   const int mode = get_map_mode((char **)&which, 0);
 
   char_u *keys_simplified
-    = (char_u *)replace_termcodes(keys, STRLEN(keys), &keys_buf, flags, &did_simplify,
+    = (char_u *)replace_termcodes(keys, strlen(keys), &keys_buf, flags, &did_simplify,
                                   CPO_TO_CPO_FLAGS);
   mapblock_T *mp = NULL;
   int buffer_local;
@@ -2101,7 +2101,7 @@ static void get_maparg(typval_T *argvars, typval_T *rettv, int exact)
     // When the lhs is being simplified the not-simplified keys are
     // preferred for printing, like in do_map().
     (void)replace_termcodes(keys,
-                            STRLEN(keys),
+                            strlen(keys),
                             &alt_keys_buf, flags | REPTERM_NO_SIMPLIFY, NULL,
                             CPO_TO_CPO_FLAGS);
     rhs = check_map((char_u *)alt_keys_buf, mode, exact, false, abbr, &mp, &buffer_local, &rhs_lua);
diff --git a/src/nvim/mark.c b/src/nvim/mark.c
index 6f8aecb3ff..83ac61f7d2 100644
--- a/src/nvim/mark.c
+++ b/src/nvim/mark.c
@@ -658,7 +658,7 @@ static void fname2fnum(xfmark_T *fm)
       int len;
 
       expand_env("~/", NameBuff, MAXPATHL);
-      len = (int)STRLEN(NameBuff);
+      len = (int)strlen(NameBuff);
       STRLCPY(NameBuff + len, fm->fname + 2, MAXPATHL - len);
     } else {
       STRLCPY(NameBuff, fm->fname, MAXPATHL);
diff --git a/src/nvim/mbyte.c b/src/nvim/mbyte.c
index dc74e23874..1c2fd6c7db 100644
--- a/src/nvim/mbyte.c
+++ b/src/nvim/mbyte.c
@@ -1556,7 +1556,7 @@ void show_utf8(void)
     sprintf((char *)IObuff + rlen, "%02x ",
             (line[i] == NL) ? NUL : line[i]);          // NUL is stored as NL
     clen--;
-    rlen += (int)STRLEN(IObuff + rlen);
+    rlen += (int)strlen(IObuff + rlen);
     if (rlen > IOSIZE - 20) {
       break;
     }
diff --git a/src/nvim/memline.c b/src/nvim/memline.c
index 9d1ad5903d..b374010f80 100644
--- a/src/nvim/memline.c
+++ b/src/nvim/memline.c
@@ -627,7 +627,7 @@ static void set_b0_fname(ZERO_BL *b0p, buf_T *buf)
     if (b0p->b0_fname[0] == '~') {
       // If there is no user name or it is too long, don't use "~/"
       int retval = os_get_username(uname, B0_UNAME_SIZE);
-      size_t ulen = STRLEN(uname);
+      size_t ulen = strlen(uname);
       size_t flen = STRLEN(b0p->b0_fname);
       if (retval == FAIL || ulen + flen > B0_FNAME_SIZE_CRYPT - 1) {
         STRLCPY(b0p->b0_fname, buf->b_ffname, B0_FNAME_SIZE_CRYPT);
@@ -678,7 +678,7 @@ static void add_b0_fenc(ZERO_BL *b0p, buf_T *buf)
   int n;
   int size = B0_FNAME_SIZE_NOCRYPT;
 
-  n = (int)STRLEN(buf->b_p_fenc);
+  n = (int)strlen(buf->b_p_fenc);
   if ((int)STRLEN(b0p->b0_fname) + n + 1 > size) {
     b0p->b0_flags &= (uint8_t) ~B0_HAS_FENC;
   } else {
@@ -736,7 +736,7 @@ void ml_recover(bool checkext)
   if (fname == NULL) {              // When there is no file name
     fname = "";
   }
-  len = (int)STRLEN(fname);
+  len = (int)strlen(fname);
   if (checkext && len >= 4
       && STRNICMP(fname + len - 4, ".s", 2) == 0
       && vim_strchr("abcdefghijklmnopqrstuvw", TOLOWER_ASC(fname[len - 2])) != NULL
@@ -1221,7 +1221,7 @@ int recover_names(char_u *fname, int list, int nr, char **fname_out)
 
   // Do the loop for every directory in 'directory'.
   // First allocate some memory to put the directory name in.
-  dir_name = xmalloc(STRLEN(p_dir) + 1);
+  dir_name = xmalloc(strlen(p_dir) + 1);
   dirp = p_dir;
   while (*dirp) {
     // Isolate a directory name from *dirp and put it in dir_name (we know
@@ -3029,7 +3029,7 @@ int resolve_symlink(const char *fname, char *buf)
       STRCPY(tmp, buf);
     } else {
       char_u *tail = (char_u *)path_tail(tmp);
-      if (STRLEN(tail) + STRLEN(buf) >= MAXPATHL) {
+      if (STRLEN(tail) + strlen(buf) >= MAXPATHL) {
         return FAIL;
       }
       STRCPY(tail, buf);
diff --git a/src/nvim/menu.c b/src/nvim/menu.c
index d8b7e872d9..b38e832c77 100644
--- a/src/nvim/menu.c
+++ b/src/nvim/menu.c
@@ -220,7 +220,7 @@ void ex_menu(exarg_T *eap)
       map_buf = NULL;  // Menu tips are plain text.
     } else {
       map_buf = NULL;
-      map_to = replace_termcodes(map_to, STRLEN(map_to), &map_buf,
+      map_to = replace_termcodes(map_to, strlen(map_to), &map_buf,
                                  REPTERM_DO_LT, NULL, CPO_TO_CPO_FLAGS);
     }
     menuarg.modes = modes;
@@ -286,7 +286,7 @@ static int add_menu_path(const char *const menu_path, vimmenu_T *menuarg, const
     // Get name of this element in the menu hierarchy, and the simplified
     // name (without mnemonic and accelerator text).
     next_name = menu_name_skip(name);
-    map_to = menutrans_lookup(name, (int)STRLEN(name));
+    map_to = menutrans_lookup(name, (int)strlen(name));
     if (map_to != NULL) {
       en_name = name;
       name = map_to;
@@ -424,7 +424,7 @@ static int add_menu_path(const char *const menu_path, vimmenu_T *menuarg, const
         }
 
         if (c != 0) {
-          menu->strings[i] = xmalloc(STRLEN(call_data) + 5);
+          menu->strings[i] = xmalloc(strlen(call_data) + 5);
           menu->strings[i][0] = c;
           if (d == 0) {
             STRCPY(menu->strings[i] + 1, call_data);
@@ -433,7 +433,7 @@ static int add_menu_path(const char *const menu_path, vimmenu_T *menuarg, const
             STRCPY(menu->strings[i] + 2, call_data);
           }
           if (c == Ctrl_C) {
-            int len = (int)STRLEN(menu->strings[i]);
+            int len = (int)strlen(menu->strings[i]);
 
             menu->strings[i][len] = Ctrl_BSL;
             menu->strings[i][len + 1] = Ctrl_G;
@@ -1054,7 +1054,7 @@ char *get_menu_names(expand_T *xp, int idx)
   while (menu != NULL
          && (menu_is_hidden(menu->dname)
              || (expand_emenu && menu_is_separator(menu->dname))
-             || menu->dname[STRLEN(menu->dname) - 1] == '.')) {
+             || menu->dname[strlen(menu->dname) - 1] == '.')) {
     menu = menu->next;
   }
 
@@ -1276,7 +1276,7 @@ static char *get_menu_mode_str(int modes)
 // Returns the name in allocated memory.
 static char *popup_mode_name(char *name, int idx)
 {
-  size_t len = STRLEN(name);
+  size_t len = strlen(name);
   assert(len >= 4);
 
   char *mode_chars = menu_mode_chars[idx];
@@ -1365,7 +1365,7 @@ bool menu_is_toolbar(const char *const name)
 /// with '-'
 int menu_is_separator(char *name)
 {
-  return name[0] == '-' && name[STRLEN(name) - 1] == '-';
+  return name[0] == '-' && name[strlen(name) - 1] == '-';
 }
 
 /// True if a popup menu or starts with \ref MNU_HIDDEN_CHAR
diff --git a/src/nvim/message.c b/src/nvim/message.c
index 2d23797bc8..46f6adec47 100644
--- a/src/nvim/message.c
+++ b/src/nvim/message.c
@@ -433,7 +433,7 @@ void trunc_string(char *s, char *buf, int room_in, int buflen)
   }
 
   // Last part: End of the string.
-  half = i = (int)STRLEN(s);
+  half = i = (int)strlen(s);
   for (;;) {
     do {
       half = half - utf_head_off(s, s + half - 1) - 1;
@@ -449,7 +449,7 @@ void trunc_string(char *s, char *buf, int room_in, int buflen)
   if (i <= e + 3) {
     // text fits without truncating
     if (s != buf) {
-      len = (int)STRLEN(s);
+      len = (int)strlen(s);
       if (len >= buflen) {
         len = buflen - 1;
       }
@@ -463,7 +463,7 @@ void trunc_string(char *s, char *buf, int room_in, int buflen)
   } else if (e + 3 < buflen) {
     // set the middle and copy the last part
     memmove(buf + e, "...", (size_t)3);
-    len = (int)STRLEN(s + i) + 1;
+    len = (int)strlen(s + i) + 1;
     if (len >= buflen - e - 3) {
       len = buflen - e - 3 - 1;
     }
@@ -553,7 +553,7 @@ static char *get_emsg_source(void)
     }
 
     const char *const p = _("Error detected while processing %s:");
-    const size_t buf_len = STRLEN(sname) + strlen(p) + 1;
+    const size_t buf_len = strlen(sname) + strlen(p) + 1;
     char *const buf = xmalloc(buf_len);
     snprintf(buf, buf_len, p, sname);
     xfree(tofree);
@@ -909,7 +909,7 @@ char *msg_may_trunc(bool force, char *s)
 
   room = (Rows - cmdline_row - 1) * Columns + sc_col - 1;
   if ((force || (shortmess(SHM_TRUNC) && !exmode_active))
-      && (int)STRLEN(s) - room > 0 && p_ch > 0) {
+      && (int)strlen(s) - room > 0 && p_ch > 0) {
     int size = vim_strsize(s);
 
     // There may be room anyway when there are multibyte chars.
@@ -968,7 +968,7 @@ static void add_msg_hist_multiattr(const char *s, int len, int attr, bool multil
   struct msg_hist *p = xmalloc(sizeof(struct msg_hist));
   if (s) {
     if (len < 0) {
-      len = (int)STRLEN(s);
+      len = (int)strlen(s);
     }
     // remove leading and trailing newlines
     while (len > 0 && *s == '\n') {
@@ -1506,7 +1506,7 @@ int msg_outtrans(char *str)
 
 int msg_outtrans_attr(const char *str, int attr)
 {
-  return msg_outtrans_len_attr(str, (int)STRLEN(str), attr);
+  return msg_outtrans_len_attr(str, (int)strlen(str), attr);
 }
 
 int msg_outtrans_len(const char *str, int len)
@@ -1588,7 +1588,7 @@ int msg_outtrans_len_attr(const char *msgstr, int len, int attr)
         }
         plain_start = str + 1;
         msg_puts_attr((const char *)s, attr == 0 ? HL_ATTR(HLF_8) : attr);
-        retval += (int)STRLEN(s);
+        retval += (int)strlen(s);
       } else {
         retval++;
       }
@@ -1819,7 +1819,7 @@ void msg_prt_line(char *s, int list)
   if (list) {
     // find start of trailing whitespace
     if (curwin->w_p_lcs_chars.trail) {
-      trail = s + STRLEN(s);
+      trail = s + strlen(s);
       while (trail > s && ascii_iswhite(trail[-1])) {
         trail--;
       }
@@ -2003,7 +2003,7 @@ void msg_puts_title(const char *s)
 /// Does not handle multi-byte characters!
 void msg_outtrans_long_attr(char *longstr, int attr)
 {
-  msg_outtrans_long_len_attr(longstr, (int)STRLEN(longstr), attr);
+  msg_outtrans_long_len_attr(longstr, (int)strlen(longstr), attr);
 }
 
 void msg_outtrans_long_len_attr(char *longstr, int len, int attr)
@@ -3291,7 +3291,7 @@ static void redir_write(const char *const str, const ptrdiff_t maxlen)
       }
     }
 
-    size_t len = maxlen == -1 ? STRLEN(s) : (size_t)maxlen;
+    size_t len = maxlen == -1 ? strlen(s) : (size_t)maxlen;
     if (capture_ga) {
       ga_concat_len(capture_ga, str, len);
     }
@@ -3633,9 +3633,9 @@ static char *console_dialog_alloc(const char *message, char *buttons, bool has_h
     MB_PTR_ADV(r);
   }
 
-  len += (int)(STRLEN(message)
+  len += (int)(strlen(message)
                + 2                          // for the NL's
-               + STRLEN(buttons)
+               + strlen(buttons)
                + 3);                        // for the ": " and NUL
   lenhotkey++;                               // for the NUL
 
@@ -3685,7 +3685,7 @@ static void copy_hotkeys_and_msg(const char *message, char *buttons, int default
   *confirm_msg = '\n';
   STRCPY(confirm_msg + 1, message);
 
-  char *msgp = confirm_msg + 1 + STRLEN(message);
+  char *msgp = confirm_msg + 1 + strlen(message);
 
   // Define first default hotkey. Keep the hotkey string NUL
   // terminated to avoid reading past the end.
@@ -3709,7 +3709,7 @@ static void copy_hotkeys_and_msg(const char *message, char *buttons, int default
       *msgp++ = ' ';                    // '\n' -> ', '
 
       // Advance to next hotkey and set default hotkey
-      hotkeys_ptr += STRLEN(hotkeys_ptr);
+      hotkeys_ptr += strlen(hotkeys_ptr);
       hotkeys_ptr[copy_char(r + 1, hotkeys_ptr, true)] = NUL;
 
       if (default_button_idx) {
diff --git a/src/nvim/msgpack_rpc/server.c b/src/nvim/msgpack_rpc/server.c
index 532e684f93..6f2d71629c 100644
--- a/src/nvim/msgpack_rpc/server.c
+++ b/src/nvim/msgpack_rpc/server.c
@@ -173,7 +173,7 @@ int server_start(const char *addr)
   ((SocketWatcher **)watchers.ga_data)[watchers.ga_len++] = watcher;
 
   // Update v:servername, if not set.
-  if (STRLEN(get_vim_var_str(VV_SEND_SERVER)) == 0) {
+  if (strlen(get_vim_var_str(VV_SEND_SERVER)) == 0) {
     set_vservername(&watchers);
   }
 
diff --git a/src/nvim/normal.c b/src/nvim/normal.c
index 326469bd38..249d5b6c0b 100644
--- a/src/nvim/normal.c
+++ b/src/nvim/normal.c
@@ -2752,7 +2752,7 @@ bool add_to_showcmd(int c)
     STRCPY(p, "<20>");
   }
   size_t old_len = STRLEN(showcmd_buf);
-  size_t extra_len = STRLEN(p);
+  size_t extra_len = strlen(p);
   size_t limit = ui_has(kUIMessages) ? SHOWCMD_BUFLEN - 1 : SHOWCMD_COLS;
   if (old_len + extra_len > limit) {
     size_t overflow = old_len + extra_len - limit;
@@ -4057,7 +4057,7 @@ static void nv_colon(cmdarg_T *cap)
     } else if (cap->oap->op_type != OP_NOP
                && (cap->oap->start.lnum > curbuf->b_ml.ml_line_count
                    || cap->oap->start.col >
-                   (colnr_T)STRLEN(ml_get(cap->oap->start.lnum))
+                   (colnr_T)strlen(ml_get(cap->oap->start.lnum))
                    || did_emsg)) {
       // The start of the operator has become invalid by the Ex command.
       clearopbeep(cap->oap);
@@ -4216,7 +4216,7 @@ static size_t nv_K_getcmd(cmdarg_T *cap, char *kp, bool kp_help, bool kp_ex, cha
   }
   STRCAT(buf, " ");
   if (cap->count0 != 0 && (isman || isman_s)) {
-    snprintf(buf + STRLEN(buf), buf_size - STRLEN(buf), "%" PRId64,
+    snprintf(buf + strlen(buf), buf_size - strlen(buf), "%" PRId64,
              (int64_t)cap->count0);
     STRCAT(buf, " ");
   }
@@ -4282,7 +4282,7 @@ static void nv_ident(cmdarg_T *cap)
     return;
   }
   bool kp_ex = (*kp == ':');  // 'keywordprg' is an ex command
-  size_t buf_size = n * 2 + 30 + STRLEN(kp);
+  size_t buf_size = n * 2 + 30 + strlen(kp);
   char *buf = xmalloc(buf_size);
   buf[0] = NUL;
 
@@ -4342,7 +4342,7 @@ static void nv_ident(cmdarg_T *cap)
       p = (char *)vim_strsave_shellescape((char_u *)ptr, true, true);
     }
     xfree(ptr);
-    char *newbuf = xrealloc(buf, STRLEN(buf) + STRLEN(p) + 1);
+    char *newbuf = xrealloc(buf, strlen(buf) + strlen(p) + 1);
     buf = newbuf;
     STRCAT(buf, p);
     xfree(p);
@@ -4426,7 +4426,7 @@ bool get_visual_text(cmdarg_T *cap, char **pp, size_t *lenp)
   }
   if (VIsual_mode == 'V') {
     *pp = get_cursor_line_ptr();
-    *lenp = STRLEN(*pp);
+    *lenp = strlen(*pp);
   } else {
     if (lt(curwin->w_cursor, VIsual)) {
       *pp = (char *)ml_get_pos(&curwin->w_cursor);
@@ -6151,7 +6151,7 @@ static void nv_gi_cmd(cmdarg_T *cap)
   if (curbuf->b_last_insert.mark.lnum != 0) {
     curwin->w_cursor = curbuf->b_last_insert.mark;
     check_cursor_lnum();
-    int i = (int)STRLEN(get_cursor_line_ptr());
+    int i = (int)strlen(get_cursor_line_ptr());
     if (curwin->w_cursor.col > (colnr_T)i) {
       if (virtual_active()) {
         curwin->w_cursor.coladd += curwin->w_cursor.col - i;
@@ -6834,7 +6834,7 @@ bool unadjust_for_sel(void)
       mark_mb_adjustpos(curbuf, pp);
     } else if (pp->lnum > 1) {
       pp->lnum--;
-      pp->col = (colnr_T)STRLEN(ml_get(pp->lnum));
+      pp->col = (colnr_T)strlen(ml_get(pp->lnum));
       return true;
     }
   }
@@ -6971,7 +6971,7 @@ void set_cursor_for_append_to_line(void)
     coladvance(MAXCOL);
     State = save_State;
   } else {
-    curwin->w_cursor.col += (colnr_T)STRLEN(get_cursor_pos_ptr());
+    curwin->w_cursor.col += (colnr_T)strlen(get_cursor_pos_ptr());
   }
 }
 
diff --git a/src/nvim/ops.c b/src/nvim/ops.c
index 10e957287e..420f6cf840 100644
--- a/src/nvim/ops.c
+++ b/src/nvim/ops.c
@@ -2260,7 +2260,7 @@ void op_insert(oparg_T *oap, long count1)
     if (oap->op_type == OP_APPEND) {
       firstline += bd.textlen;
     }
-    pre_textlen = (long)STRLEN(firstline);
+    pre_textlen = (long)strlen(firstline);
   }
 
   if (oap->op_type == OP_APPEND) {
@@ -2386,7 +2386,7 @@ void op_insert(oparg_T *oap, long count1)
     // Subsequent calls to ml_get() flush the firstline data - take a
     // copy of the required string.
     firstline = ml_get(oap->start.lnum);
-    const size_t len = STRLEN(firstline);
+    const size_t len = strlen(firstline);
     colnr_T add = bd.textcol;
     colnr_T offset = 0;  // offset when cursor was moved in insert mode
     if (oap->op_type == OP_APPEND) {
@@ -2408,7 +2408,7 @@ void op_insert(oparg_T *oap, long count1)
     } else {
       firstline += add;
     }
-    ins_len = (long)STRLEN(firstline) - pre_textlen - offset;
+    ins_len = (long)strlen(firstline) - pre_textlen - offset;
     if (pre_textlen >= 0 && ins_len > 0) {
       ins_text = xstrnsave(firstline, (size_t)ins_len);
       // block handled here
@@ -2992,7 +2992,7 @@ void do_put(int regname, yankreg_T *reg, int dir, long count, int flags)
 
         // curwin->w_cursor.col marks the byte position of the cursor in the
         // currunt line. It increases up to a max of
-        // STRLEN(ml_get(curwin->w_cursor.lnum)). With 'virtualedit' and the
+        // strlen(ml_get(curwin->w_cursor.lnum)). With 'virtualedit' and the
         // cursor past the end of the line, curwin->w_cursor.coladd is
         // incremented instead of curwin->w_cursor.col.
         char_u *cursor_pos = (char_u *)get_cursor_pos_ptr();
@@ -3174,7 +3174,7 @@ void do_put(int regname, yankreg_T *reg, int dir, long count, int flags)
     goto end;
   }
 
-  yanklen = (int)STRLEN(y_array[0]);
+  yanklen = (int)strlen(y_array[0]);
 
   if (cur_ve_flags == VE_ALL && y_type == kMTCharWise) {
     if (gchar_cursor() == TAB) {
@@ -3259,7 +3259,7 @@ void do_put(int regname, yankreg_T *reg, int dir, long count, int flags)
       }
       // get the old line and advance to the position to insert at
       oldp = get_cursor_line_ptr();
-      oldlen = STRLEN(oldp);
+      oldlen = strlen(oldp);
       chartabsize_T cts;
       init_chartabsize_arg(&cts, curwin, curwin->w_cursor.lnum, 0, oldp, oldp);
 
@@ -3292,7 +3292,7 @@ void do_put(int regname, yankreg_T *reg, int dir, long count, int flags)
         }
       }
 
-      yanklen = (int)STRLEN(y_array[i]);
+      yanklen = (int)strlen(y_array[i]);
 
       if ((flags & PUT_BLOCK_INNER) == 0) {
         // calculate number of spaces required to fill right side of
@@ -3380,7 +3380,7 @@ void do_put(int regname, yankreg_T *reg, int dir, long count, int flags)
       curwin->w_cursor.col++;
 
       // in Insert mode we might be after the NUL, correct for that
-      len = (colnr_T)STRLEN(get_cursor_line_ptr());
+      len = (colnr_T)strlen(get_cursor_line_ptr());
       if (curwin->w_cursor.col > len) {
         curwin->w_cursor.col = len;
       }
@@ -3444,7 +3444,7 @@ void do_put(int regname, yankreg_T *reg, int dir, long count, int flags)
         totlen = (size_t)(count * yanklen);
         do {
           oldp = ml_get(lnum);
-          oldlen = STRLEN(oldp);
+          oldlen = strlen(oldp);
           if (lnum > start_lnum) {
             pos_T pos = {
               .lnum = lnum,
@@ -3515,8 +3515,8 @@ void do_put(int regname, yankreg_T *reg, int dir, long count, int flags)
           // Then append y_array[0] to first line.
           lnum = new_cursor.lnum;
           ptr = ml_get(lnum) + col;
-          totlen = STRLEN(y_array[y_size - 1]);
-          newp = xmalloc((size_t)(STRLEN(ptr) + totlen + 1));
+          totlen = strlen(y_array[y_size - 1]);
+          newp = xmalloc((size_t)(strlen(ptr) + totlen + 1));
           STRCPY(newp, y_array[y_size - 1]);
           STRCAT(newp, ptr);
           // insert second line
@@ -3550,7 +3550,7 @@ void do_put(int regname, yankreg_T *reg, int dir, long count, int flags)
             curwin->w_cursor.lnum = lnum;
             ptr = ml_get(lnum);
             if (cnt == count && i == y_size - 1) {
-              lendiff = (int)STRLEN(ptr);
+              lendiff = (int)strlen(ptr);
             }
             if (*ptr == '#' && preprocs_left()) {
               indent = 0;                   // Leave # lines at start
@@ -3567,7 +3567,7 @@ void do_put(int regname, yankreg_T *reg, int dir, long count, int flags)
             curwin->w_cursor = old_pos;
             // remember how many chars were removed
             if (cnt == count && i == y_size - 1) {
-              lendiff -= (int)STRLEN(ml_get(lnum));
+              lendiff -= (int)strlen(ml_get(lnum));
             }
           }
         }
@@ -3577,9 +3577,9 @@ void do_put(int regname, yankreg_T *reg, int dir, long count, int flags)
         if (y_type == kMTCharWise
             || (y_type == kMTLineWise && flags & PUT_LINE_SPLIT)) {
           for (i = 0; i < y_size - 1; i++) {
-            totsize += (bcount_t)STRLEN(y_array[i]) + 1;
+            totsize += (bcount_t)strlen(y_array[i]) + 1;
           }
-          lastsize = (int)STRLEN(y_array[y_size - 1]);
+          lastsize = (int)strlen(y_array[y_size - 1]);
           totsize += lastsize;
         }
         if (y_type == kMTCharWise) {
@@ -3623,7 +3623,7 @@ error:
       // Put the '] mark on the first byte of the last inserted character.
       // Correct the length for change in indent.
       curbuf->b_op_end.lnum = new_lnum;
-      len = STRLEN(y_array[y_size - 1]);
+      len = strlen(y_array[y_size - 1]);
       col = (colnr_T)len - lendiff;
       if (col > 1) {
         curbuf->b_op_end.col = col - 1;
@@ -4019,7 +4019,7 @@ int do_join(size_t count, int insert_space, int save_undo, int use_formatoptions
     if (t == 0 && setmark && (cmdmod.cmod_flags & CMOD_LOCKMARKS) == 0) {
       // Set the '[ mark.
       curwin->w_buffer->b_op_start.lnum = curwin->w_cursor.lnum;
-      curwin->w_buffer->b_op_start.col = (colnr_T)STRLEN(curr);
+      curwin->w_buffer->b_op_start.col = (colnr_T)strlen(curr);
     }
     if (remove_comments) {
       // We don't want to remove the comment leader if the
@@ -4065,7 +4065,7 @@ int do_join(size_t count, int insert_space, int save_undo, int use_formatoptions
                      0, spaces[t], spaces[t],
                      kExtmarkUndo);
     }
-    currsize = (int)STRLEN(curr);
+    currsize = (int)strlen(curr);
     sumsize += currsize + spaces[t];
     endcurr1 = endcurr2 = NUL;
     if (insert_space && currsize > 0) {
@@ -4130,7 +4130,7 @@ int do_join(size_t count, int insert_space, int save_undo, int use_formatoptions
     if (insert_space && t > 1) {
       curr = skipwhite(curr);
     }
-    currsize = (int)STRLEN(curr);
+    currsize = (int)strlen(curr);
   }
 
   ml_replace(curwin->w_cursor.lnum, newp, false);
@@ -4362,20 +4362,20 @@ void op_addsub(oparg_T *oap, linenr_T Prenum1, bool g_cmd)
       } else if (oap->motion_type == kMTLineWise) {
         curwin->w_cursor.col = 0;
         pos.col = 0;
-        length = (colnr_T)STRLEN(ml_get(pos.lnum));
+        length = (colnr_T)strlen(ml_get(pos.lnum));
       } else {
         // oap->motion_type == kMTCharWise
         if (pos.lnum == oap->start.lnum && !oap->inclusive) {
           dec(&(oap->end));
         }
-        length = (colnr_T)STRLEN(ml_get(pos.lnum));
+        length = (colnr_T)strlen(ml_get(pos.lnum));
         pos.col = 0;
         if (pos.lnum == oap->start.lnum) {
           pos.col += oap->start.col;
           length -= oap->start.col;
         }
         if (pos.lnum == oap->end.lnum) {
-          length = (int)STRLEN(ml_get(oap->end.lnum));
+          length = (int)strlen(ml_get(oap->end.lnum));
           if (oap->end.col >= length) {
             oap->end.col = length - 1;
           }
@@ -4923,7 +4923,7 @@ void *get_reg_contents(int regname, int flags)
   // Compute length of resulting string.
   size_t len = 0;
   for (size_t i = 0; i < reg->y_size; i++) {
-    len += STRLEN(reg->y_array[i]);
+    len += strlen(reg->y_array[i]);
     // Insert a newline between lines and after last line if
     // y_type is kMTLineWise.
     if (reg->y_type == kMTLineWise || i < reg->y_size - 1) {
@@ -4937,7 +4937,7 @@ void *get_reg_contents(int regname, int flags)
   len = 0;
   for (size_t i = 0; i < reg->y_size; i++) {
     STRCPY(retval + len, reg->y_array[i]);
-    len += STRLEN(retval + len);
+    len += strlen(retval + len);
 
     // Insert a NL between lines and after the last line if y_type is
     // kMTLineWise.
@@ -5039,7 +5039,7 @@ void write_reg_contents_ex(int name, const char *str, ssize_t len, bool must_app
                            MotionType yank_type, colnr_T block_len)
 {
   if (len < 0) {
-    len = (ssize_t)STRLEN(str);
+    len = (ssize_t)strlen(str);
   }
 
   // Special case: '/' search pattern
@@ -5059,7 +5059,7 @@ void write_reg_contents_ex(int name, const char *str, ssize_t len, bool must_app
         semsg(_(e_nobufnr), (int64_t)num);
       }
     } else {
-      buf = buflist_findnr(buflist_findpat(str, str + STRLEN(str),
+      buf = buflist_findnr(buflist_findpat(str, str + strlen(str),
                                            true, false, false));
     }
     if (buf == NULL) {
@@ -5186,7 +5186,7 @@ static void str_to_reg(yankreg_T *y_ptr, MotionType yank_type, const char *str,
       }
 
       // When appending, copy the previous line and free it after.
-      size_t extra = append ? STRLEN(pp[--lnum]) : 0;
+      size_t extra = append ? strlen(pp[--lnum]) : 0;
       char *s = xmallocz(line_len + extra);
       if (extra > 0) {
         memcpy(s, pp[lnum], extra);
@@ -5486,7 +5486,7 @@ void cursor_pos_info(dict_T *dict)
 
     bom_count = bomb_size();
     if (dict == NULL && bom_count > 0) {
-      const size_t len = STRLEN(IObuff);
+      const size_t len = strlen(IObuff);
       vim_snprintf((char *)IObuff + len, IOSIZE - len,
                    _("(+%" PRId64 " for BOM)"), (int64_t)bom_count);
     }
@@ -5845,10 +5845,10 @@ void do_pending_operator(cmdarg_T *cap, int old_col, bool gui_yank)
         if (lt(VIsual, curwin->w_cursor)) {
           VIsual.col = 0;
           curwin->w_cursor.col =
-            (colnr_T)STRLEN(ml_get(curwin->w_cursor.lnum));
+            (colnr_T)strlen(ml_get(curwin->w_cursor.lnum));
         } else {
           curwin->w_cursor.col = 0;
-          VIsual.col = (colnr_T)STRLEN(ml_get(VIsual.lnum));
+          VIsual.col = (colnr_T)strlen(ml_get(VIsual.lnum));
         }
         VIsual_mode = 'v';
       } else if (VIsual_mode == 'v') {
@@ -5878,7 +5878,7 @@ void do_pending_operator(cmdarg_T *cap, int old_col, bool gui_yank)
              || oap->motion_type == kMTLineWise)
             && hasFolding(curwin->w_cursor.lnum, NULL,
                           &curwin->w_cursor.lnum)) {
-          curwin->w_cursor.col = (colnr_T)STRLEN(get_cursor_line_ptr());
+          curwin->w_cursor.col = (colnr_T)strlen(get_cursor_line_ptr());
         }
       }
       oap->end = curwin->w_cursor;
@@ -5896,7 +5896,7 @@ void do_pending_operator(cmdarg_T *cap, int old_col, bool gui_yank)
           curwin->w_cursor.col = 0;
         }
         if (hasFolding(oap->start.lnum, NULL, &oap->start.lnum)) {
-          oap->start.col = (colnr_T)STRLEN(ml_get(oap->start.lnum));
+          oap->start.col = (colnr_T)strlen(ml_get(oap->start.lnum));
         }
       }
       oap->end = oap->start;
@@ -6080,7 +6080,7 @@ void do_pending_operator(cmdarg_T *cap, int old_col, bool gui_yank)
       if (inindent(0)) {
         oap->motion_type = kMTLineWise;
       } else {
-        oap->end.col = (colnr_T)STRLEN(ml_get(oap->end.lnum));
+        oap->end.col = (colnr_T)strlen(ml_get(oap->end.lnum));
         if (oap->end.col) {
           oap->end.col--;
           oap->inclusive = true;
@@ -6474,7 +6474,7 @@ bool prepare_yankreg_from_object(yankreg_T *reg, String regtype, size_t lines)
 
 void finish_yankreg_from_object(yankreg_T *reg, bool clipboard_adjust)
 {
-  if (reg->y_size > 0 && STRLEN(reg->y_array[reg->y_size - 1]) == 0) {
+  if (reg->y_size > 0 && strlen(reg->y_array[reg->y_size - 1]) == 0) {
     // a known-to-be charwise yank might have a final linebreak
     // but otherwise there is no line after the final newline
     if (reg->y_type != kMTCharWise) {
@@ -6495,7 +6495,7 @@ void finish_yankreg_from_object(yankreg_T *reg, bool clipboard_adjust)
   if (reg->y_type == kMTBlockWise) {
     size_t maxlen = 0;
     for (size_t i = 0; i < reg->y_size; i++) {
-      size_t rowlen = STRLEN(reg->y_array[i]);
+      size_t rowlen = strlen(reg->y_array[i]);
       if (rowlen > maxlen) {
         maxlen = rowlen;
       }
@@ -6582,7 +6582,7 @@ static bool get_clipboard(int name, yankreg_T **target, bool quiet)
     reg->y_array[tv_idx++] = xstrdupnul((const char *)TV_LIST_ITEM_TV(li)->vval.v_string);
   });
 
-  if (reg->y_size > 0 && STRLEN(reg->y_array[reg->y_size - 1]) == 0) {
+  if (reg->y_size > 0 && strlen(reg->y_array[reg->y_size - 1]) == 0) {
     // a known-to-be charwise yank might have a final linebreak
     // but otherwise there is no line after the final newline
     if (reg->y_type != kMTCharWise) {
@@ -6601,7 +6601,7 @@ static bool get_clipboard(int name, yankreg_T **target, bool quiet)
   if (reg->y_type == kMTBlockWise) {
     size_t maxlen = 0;
     for (size_t i = 0; i < reg->y_size; i++) {
-      size_t rowlen = STRLEN(reg->y_array[i]);
+      size_t rowlen = strlen(reg->y_array[i]);
       if (rowlen > maxlen) {
         maxlen = rowlen;
       }
@@ -6851,13 +6851,13 @@ bcount_t get_region_bytecount(buf_T *buf, linenr_T start_lnum, linenr_T end_lnum
     return end_col - start_col;
   }
   const char *first = (const char *)ml_get_buf(buf, start_lnum, false);
-  bcount_t deleted_bytes = (bcount_t)STRLEN(first) - start_col + 1;
+  bcount_t deleted_bytes = (bcount_t)strlen(first) - start_col + 1;
 
   for (linenr_T i = 1; i <= end_lnum - start_lnum - 1; i++) {
     if (start_lnum + i > max_lnum) {
       return deleted_bytes;
     }
-    deleted_bytes += (bcount_t)STRLEN(ml_get_buf(buf, start_lnum + i, false)) + 1;
+    deleted_bytes += (bcount_t)strlen(ml_get_buf(buf, start_lnum + i, false)) + 1;
   }
   if (end_lnum > max_lnum) {
     return deleted_bytes;
diff --git a/src/nvim/option.c b/src/nvim/option.c
index ab4db30aaf..de9510cf8a 100644
--- a/src/nvim/option.c
+++ b/src/nvim/option.c
@@ -1266,7 +1266,7 @@ int do_set(char *arg, int opt_flags)
               // we need to remove the backslashes.
 
               // get a bit too much
-              newlen = (unsigned)STRLEN(arg) + 1;
+              newlen = (unsigned)strlen(arg) + 1;
               if (adding || prepending || removing) {
                 newlen += (unsigned)STRLEN(origval) + 1;
               }
@@ -1312,7 +1312,7 @@ int do_set(char *arg, int opt_flags)
                 s = option_expand(opt_idx, newval);
                 if (s != NULL) {
                   xfree(newval);
-                  newlen = (unsigned)STRLEN(s) + 1;
+                  newlen = (unsigned)strlen(s) + 1;
                   if (adding || prepending || removing) {
                     newlen += (unsigned)STRLEN(origval) + 1;
                   }
@@ -1357,10 +1357,10 @@ int do_set(char *arg, int opt_flags)
                     i--;
                   }
                   memmove(newval + i + comma, newval,
-                          STRLEN(newval) + 1);
+                          strlen(newval) + 1);
                   memmove(newval, origval, (size_t)i);
                 } else {
-                  i = (int)STRLEN(newval);
+                  i = (int)strlen(newval);
                   STRMOVE(newval + i + comma, origval);
                 }
                 if (comma) {
@@ -1507,7 +1507,7 @@ skip:
 
     if (errmsg != NULL) {
       STRLCPY(IObuff, _(errmsg), IOSIZE);
-      i = (int)STRLEN(IObuff) + 2;
+      i = (int)strlen(IObuff) + 2;
       if (i + (arg - startarg) < IOSIZE) {
         // append the argument with the error
         STRCAT(IObuff, ": ");
@@ -1694,7 +1694,7 @@ static char *option_expand(int opt_idx, char *val)
 
   // If val is longer than MAXPATHL no meaningful expansion can be done,
   // expand_env() would truncate the string.
-  if (val == NULL || STRLEN(val) > MAXPATHL) {
+  if (val == NULL || strlen(val) > MAXPATHL) {
     return NULL;
   }
 
@@ -2753,7 +2753,7 @@ int findoption_len(const char *const arg, const size_t len)
   } else {
     // Nvim: handle option aliases.
     if (STRNCMP(options[opt_idx].fullname, "viminfo", 7) == 0) {
-      if (STRLEN(options[opt_idx].fullname) == 7) {
+      if (strlen(options[opt_idx].fullname) == 7) {
         return findoption_len("shada", 5);
       }
       assert(strcmp(options[opt_idx].fullname, "viminfofile") == 0);
@@ -3274,7 +3274,7 @@ static void showoptions(int all, int opt_flags)
           len = 1;                      // a toggle option fits always
         } else {
           option_value2string(p, opt_flags);
-          len = (int)STRLEN(p->fullname) + vim_strsize((char *)NameBuff) + 1;
+          len = (int)strlen(p->fullname) + vim_strsize((char *)NameBuff) + 1;
         }
         if ((len <= INC - GAP && run == 1)
             || (len > INC - GAP && run == 2)) {
@@ -3565,7 +3565,7 @@ static int put_setstring(FILE *fd, char *cmd, char *name, char **valuep, uint64_
         }
       }
     } else if ((flags & P_EXPAND) != 0) {
-      size_t size = (size_t)STRLEN(*valuep) + 1;
+      size_t size = (size_t)strlen(*valuep) + 1;
 
       // replace home directory in the whole option value into "buf"
       buf = xmalloc(size);
diff --git a/src/nvim/optionstr.c b/src/nvim/optionstr.c
index 9d21603754..7278b1a12d 100644
--- a/src/nvim/optionstr.c
+++ b/src/nvim/optionstr.c
@@ -464,7 +464,7 @@ static char *check_mousescroll(char *string)
 
   for (;;) {
     char *end = vim_strchr(string, ',');
-    size_t length = end ? (size_t)(end - string) : STRLEN(string);
+    size_t length = end ? (size_t)(end - string) : strlen(string);
 
     // Both "ver:" and "hor:" are 4 bytes long.
     // They should be followed by at least one digit.
@@ -532,7 +532,7 @@ static int check_signcolumn(char *val)
   }
 
   // check for 'auto:<NUMBER>-<NUMBER>'
-  if (STRLEN(val) == 8
+  if (strlen(val) == 8
       && !STRNCMP(val, "auto:", 5)
       && ascii_isdigit(val[5])
       && val[6] == '-'
@@ -1258,7 +1258,7 @@ char *did_set_string_option(int opt_idx, char **varp, char *oldval, char *errbuf
     if (*p_pt) {
       p = NULL;
       (void)replace_termcodes(p_pt,
-                              STRLEN(p_pt),
+                              strlen(p_pt),
                               &p, REPTERM_FROM_PART | REPTERM_DO_LT, NULL,
                               CPO_TO_CPO_FLAGS);
       if (p != NULL) {
@@ -1641,7 +1641,7 @@ static int opt_strings_flags(char *val, char **values, unsigned *flagp, bool lis
         return FAIL;
       }
 
-      size_t len = STRLEN(values[i]);
+      size_t len = strlen(values[i]);
       if (STRNCMP(values[i], val, len) == 0
           && ((list && val[len] == ',') || val[len] == NUL)) {
         val += len + (val[len] == ',');
diff --git a/src/nvim/os/env.c b/src/nvim/os/env.c
index 34ed3aaf6e..bcc0fba8d0 100644
--- a/src/nvim/os/env.c
+++ b/src/nvim/os/env.c
@@ -451,7 +451,7 @@ void init_homedir(void)
       var = NULL;
       const char *exp = os_getenv(os_buf);
       if (exp != NULL && *exp != NUL
-          && STRLEN(exp) + STRLEN(p) < MAXPATHL) {
+          && strlen(exp) + strlen(p) < MAXPATHL) {
         vim_snprintf(os_buf, MAXPATHL, "%s%s", exp, p + 1);
         var = os_buf;
       }
@@ -800,7 +800,7 @@ static char *vim_version_dir(const char *vimdir)
 /// @return The new pend including dirname or just pend
 static char *remove_tail(char *path, char *pend, char *dirname)
 {
-  size_t len = STRLEN(dirname);
+  size_t len = strlen(dirname);
   char *new_tail = pend - len - 1;
 
   if (new_tail >= path
@@ -1146,7 +1146,7 @@ char *home_replace_save(buf_T *buf, const char *src)
 {
   size_t len = 3;             // space for "~/" and trailing NUL
   if (src != NULL) {          // just in case
-    len += STRLEN(src);
+    len += strlen(src);
   }
   char *dst = xmalloc(len);
   home_replace(buf, src, dst, len, true);
diff --git a/src/nvim/os/shell.c b/src/nvim/os/shell.c
index cf66899493..ca3e32e871 100644
--- a/src/nvim/os/shell.c
+++ b/src/nvim/os/shell.c
@@ -178,7 +178,7 @@ int os_expand_wildcards(int num_pat, char **pat, int *num_file, char ***file, in
   // STYLE_ECHO:       space separated.
   //       A shell we don't know, stay safe and use "echo".
   if (num_pat == 1 && *pat[0] == '`'
-      && (len = STRLEN(pat[0])) > 2
+      && (len = strlen(pat[0])) > 2
       && *(pat[0] + len - 1) == '`') {
     shell_style = STYLE_BT;
   } else if ((len = STRLEN(p_sh)) >= 3) {
@@ -198,7 +198,7 @@ int os_expand_wildcards(int num_pat, char **pat, int *num_file, char ***file, in
   // Worst case: "unset nonomatch; print -N >" plus two is 29
   len = STRLEN(tempname) + 29;
   if (shell_style == STYLE_VIMGLOB) {
-    len += STRLEN(sh_vimglob_func);
+    len += strlen(sh_vimglob_func);
   }
 
   for (i = 0; i < num_pat; i++) {
@@ -519,7 +519,7 @@ int os_expand_wildcards(int num_pat, char **pat, int *num_file, char ***file, in
       continue;
     }
 
-    p = xmalloc(STRLEN((*file)[i]) + 1 + dir);
+    p = xmalloc(strlen((*file)[i]) + 1 + dir);
     STRCPY(p, (*file)[i]);
     if (dir) {
       add_pathsep((char *)p);             // add '/' to a directory name
@@ -1319,7 +1319,7 @@ static char *shell_xescape_xquote(const char *cmd)
   if (*p_sxe != NUL && strcmp(p_sxq, "(") == 0) {
     ecmd = (char *)vim_strsave_escaped_ext((char_u *)cmd, p_sxe, '^', false);
   }
-  size_t ncmd_size = strlen(ecmd) + STRLEN(p_sxq) * 2 + 1;
+  size_t ncmd_size = strlen(ecmd) + strlen(p_sxq) * 2 + 1;
   char *ncmd = xmalloc(ncmd_size);
 
   // When 'shellxquote' is ( append ).
diff --git a/src/nvim/os/users.c b/src/nvim/os/users.c
index 0c662e8843..7b0f3ddaed 100644
--- a/src/nvim/os/users.c
+++ b/src/nvim/os/users.c
@@ -210,7 +210,7 @@ char *get_users(expand_T *xp, int idx)
 ///         2 is name fully matches a user name.
 int match_user(char *name)
 {
-  int n = (int)STRLEN(name);
+  int n = (int)strlen(name);
   int result = 0;
 
   init_users();
diff --git a/src/nvim/path.c b/src/nvim/path.c
index 38112be3ce..d02525c3ff 100644
--- a/src/nvim/path.c
+++ b/src/nvim/path.c
@@ -811,8 +811,8 @@ static bool is_unique(char *maybe_unique, garray_T *gap, int i)
     if (j == i) {
       continue;  // don't compare it with itself
     }
-    size_t candidate_len = STRLEN(maybe_unique);
-    size_t other_path_len = STRLEN(other_paths[j]);
+    size_t candidate_len = strlen(maybe_unique);
+    size_t other_path_len = strlen(other_paths[j]);
     if (other_path_len < candidate_len) {
       continue;  // it's different when it's shorter
     }
@@ -849,7 +849,7 @@ static void expand_path_option(char_u *curdir, garray_T *gap)
       }
       char_u *p = (char_u *)path_tail(curbuf->b_ffname);
       size_t len = (size_t)(p - (char_u *)curbuf->b_ffname);
-      if (len + STRLEN(buf) >= MAXPATHL) {
+      if (len + strlen(buf) >= MAXPATHL) {
         continue;
       }
       if (buf[1] == NUL) {
@@ -866,7 +866,7 @@ static void expand_path_option(char_u *curdir, garray_T *gap)
     } else if (!path_is_absolute((char_u *)buf)) {
       // Expand relative path to their full path equivalent
       size_t len = STRLEN(curdir);
-      if (len + STRLEN(buf) + 3 > MAXPATHL) {
+      if (len + strlen(buf) + 3 > MAXPATHL) {
         continue;
       }
       STRMOVE(buf + len + 1, buf);
@@ -988,7 +988,7 @@ static void uniquefy_paths(garray_T *gap, char_u *pattern)
         && vim_regexec(&regmatch, path_cutoff, (colnr_T)0)
         && is_unique(path_cutoff, gap, i)) {
       sort_again = true;
-      memmove(path, path_cutoff, STRLEN(path_cutoff) + 1);
+      memmove(path, path_cutoff, strlen(path_cutoff) + 1);
     } else {
       // Here all files can be reached without path, so get shortest
       // unique path.  We start at the end of the path. */
@@ -998,7 +998,7 @@ static void uniquefy_paths(garray_T *gap, char_u *pattern)
             && is_unique(pathsep_p + 1, gap, i)
             && path_cutoff != NULL && pathsep_p + 1 >= path_cutoff) {
           sort_again = true;
-          memmove(path, pathsep_p + 1, STRLEN(pathsep_p));
+          memmove(path, pathsep_p + 1, strlen(pathsep_p));
           break;
         }
       }
@@ -1045,7 +1045,7 @@ static void uniquefy_paths(garray_T *gap, char_u *pattern)
       continue;
     }
 
-    rel_path = xmalloc(STRLEN(short_name) + STRLEN(PATHSEPSTR) + 2);
+    rel_path = xmalloc(strlen(short_name) + strlen(PATHSEPSTR) + 2);
     STRCPY(rel_path, ".");
     add_pathsep(rel_path);
     STRCAT(rel_path, short_name);
@@ -1360,7 +1360,7 @@ static int expand_backtick(garray_T *gap, char *pat, int flags)
   int cnt = 0;
 
   // Create the command: lop off the backticks.
-  char *cmd = xstrnsave(pat + 1, STRLEN(pat) - 2);
+  char *cmd = xstrnsave(pat + 1, strlen(pat) - 2);
 
   if (*cmd == '=') {          // `={expr}`: Expand expression
     buffer = eval_to_string(cmd + 1, &p, true);
@@ -1415,7 +1415,7 @@ void slash_adjust(char_u *p)
 
   if (*p == '`') {
     // don't replace backslash in backtick quoted strings
-    const size_t len = STRLEN(p);
+    const size_t len = strlen(p);
     if (len > 2 && *(p + len - 1) == '`') {
       return;
     }
@@ -1678,7 +1678,7 @@ char *find_file_name_in_path(char *ptr, size_t len, int options, long count, cha
     tofree = eval_includeexpr(ptr, len);
     if (tofree != NULL) {
       ptr = tofree;
-      len = STRLEN(ptr);
+      len = strlen(ptr);
     }
   }
 
@@ -1693,7 +1693,7 @@ char *find_file_name_in_path(char *ptr, size_t len, int options, long count, cha
       tofree = eval_includeexpr(ptr, len);
       if (tofree != NULL) {
         ptr = tofree;
-        len = STRLEN(ptr);
+        len = strlen(ptr);
         file_name = (char *)find_file_in_path((char_u *)ptr, len, options & ~FNAME_MESS,
                                               true, (char_u *)rel_fname);
       }
@@ -2066,7 +2066,7 @@ char *path_shorten_fname(char *full_path, char *dir_name)
   }
 
   assert(dir_name != NULL);
-  size_t len = STRLEN(dir_name);
+  size_t len = strlen(dir_name);
 
   // If dir_name is a path head, full_path can always be made relative.
   if (len == (size_t)path_head_length() && is_path_head((char_u *)dir_name)) {
@@ -2232,7 +2232,7 @@ int match_suffix(char *fname)
 #define MAXSUFLEN 30  // maximum length of a file suffix
   char suf_buf[MAXSUFLEN];
 
-  size_t fnamelen = STRLEN(fname);
+  size_t fnamelen = strlen(fname);
   size_t setsuflen = 0;
   for (char_u *setsuf = p_su; *setsuf;) {
     setsuflen = copy_option_part((char **)&setsuf, (char *)suf_buf, MAXSUFLEN, ".,");
diff --git a/src/nvim/popupmenu.c b/src/nvim/popupmenu.c
index 4de3713f4f..5483c9cb94 100644
--- a/src/nvim/popupmenu.c
+++ b/src/nvim/popupmenu.c
@@ -542,7 +542,7 @@ void pum_redraw(void)
                   size++;
                 }
               }
-              grid_puts_len(&pum_grid, rt, (int)STRLEN(rt), row, grid_col - size + 1, attr);
+              grid_puts_len(&pum_grid, rt, (int)strlen(rt), row, grid_col - size + 1, attr);
               xfree(rt_start);
               xfree(st);
               grid_col -= width;
diff --git a/src/nvim/quickfix.c b/src/nvim/quickfix.c
index 9494308ef0..eeba7fe3c3 100644
--- a/src/nvim/quickfix.c
+++ b/src/nvim/quickfix.c
@@ -548,9 +548,9 @@ static void free_efm_list(efm_T **efm_first)
 /// a regular expression pattern.
 static size_t efm_regpat_bufsz(char *efm)
 {
-  size_t sz = (FMT_PATTERNS * 3) + (STRLEN(efm) << 2);
+  size_t sz = (FMT_PATTERNS * 3) + (strlen(efm) << 2);
   for (int i = FMT_PATTERNS - 1; i >= 0;) {
-    sz += STRLEN(fmt_pat[i--].pattern);
+    sz += strlen(fmt_pat[i--].pattern);
   }
 #ifdef BACKSLASH_IN_FILENAME
   sz += 12;  // "%f" can become twelve chars longer (see efm_to_regpat)
@@ -652,7 +652,7 @@ static int qf_get_next_str_line(qfstate_T *state)
   }
 
   char *p = vim_strchr(p_str, '\n');
-  size_t len = (p != NULL) ? (size_t)(p - p_str) + 1 : STRLEN(p_str);
+  size_t len = (p != NULL) ? (size_t)(p - p_str) + 1 : strlen(p_str);
 
   if (len > IOSIZE - 2) {
     state->linebuf = qf_grow_linebuf(state, len);
@@ -688,7 +688,7 @@ static int qf_get_next_list_line(qfstate_T *state)
     return QF_END_OF_INPUT;
   }
 
-  size_t len = STRLEN(TV_LIST_ITEM_TV(p_li)->vval.v_string);
+  size_t len = strlen(TV_LIST_ITEM_TV(p_li)->vval.v_string);
   if (len > IOSIZE - 2) {
     state->linebuf = qf_grow_linebuf(state, len);
   } else {
@@ -713,7 +713,7 @@ static int qf_get_next_buf_line(qfstate_T *state)
   char *p_buf = ml_get_buf(state->buf, state->buflnum, false);
   state->buflnum += 1;
 
-  size_t len = STRLEN(p_buf);
+  size_t len = strlen(p_buf);
   if (len > IOSIZE - 2) {
     state->linebuf = qf_grow_linebuf(state, len);
   } else {
@@ -738,7 +738,7 @@ retry:
   }
 
   bool discard = false;
-  state->linelen = STRLEN(IObuff);
+  state->linelen = strlen(IObuff);
   if (state->linelen == IOSIZE - 1
       && !(IObuff[state->linelen - 1] == '\n')) {
     // The current line exceeds IObuff, continue reading using growbuf
@@ -761,7 +761,7 @@ retry:
         }
         break;
       }
-      state->linelen = STRLEN(state->growbuf + growbuflen);
+      state->linelen = strlen(state->growbuf + growbuflen);
       growbuflen += state->linelen;
       if (state->growbuf[growbuflen - 1] == '\n') {
         break;
@@ -786,7 +786,7 @@ retry:
         }
         break;
       }
-      if (STRLEN(IObuff) < IOSIZE - 1 || IObuff[IOSIZE - 2] == '\n') {
+      if (strlen(IObuff) < IOSIZE - 1 || IObuff[IOSIZE - 2] == '\n') {
         break;
       }
     }
@@ -1175,7 +1175,7 @@ static void qf_store_title(qf_list_T *qfl, const char *title)
   XFREE_CLEAR(qfl->qf_title);
 
   if (title != NULL) {
-    size_t len = STRLEN(title) + 1;
+    size_t len = strlen(title) + 1;
     char *p = xmallocz(len);
 
     qfl->qf_title = p;
@@ -1424,7 +1424,7 @@ static int qf_parse_fmt_o(regmatch_T *rmp, int midx, qffields_T *fields)
     return QF_FAIL;
   }
   size_t len = (size_t)(rmp->endp[midx] - rmp->startp[midx]);
-  size_t dsize = STRLEN(fields->module) + len + 1;
+  size_t dsize = strlen(fields->module) + len + 1;
   if (dsize > CMDBUFFSIZE) {
     dsize = CMDBUFFSIZE;
   }
@@ -1609,8 +1609,8 @@ static int qf_parse_multiline_pfx(int idx, qf_list_T *qfl, qffields_T *fields)
       return QF_FAIL;
     }
     if (*fields->errmsg) {
-      size_t textlen = STRLEN(qfprev->qf_text);
-      size_t errlen  = STRLEN(fields->errmsg);
+      size_t textlen = strlen(qfprev->qf_text);
+      size_t errlen  = strlen(fields->errmsg);
       qfprev->qf_text = xrealloc(qfprev->qf_text, textlen + errlen + 2);
       qfprev->qf_text[textlen] = '\n';
       STRCPY(qfprev->qf_text + textlen + 1, fields->errmsg);
@@ -2791,7 +2791,7 @@ static void qf_jump_print_msg(qf_info_T *qi, int qf_index, qfline_T *qf_ptr, buf
            qf_ptr->qf_cleared ? _(" (line deleted)") : "",
            qf_types(qf_ptr->qf_type, qf_ptr->qf_nr));
   // Add the message, skipping leading whitespace and newlines.
-  int len = (int)STRLEN(IObuff);
+  int len = (int)strlen(IObuff);
   qf_fmt_text(skipwhite(qf_ptr->qf_text), (char *)IObuff + len, IOSIZE - len);
 
   // Output the message.  Overwrite to avoid scrolling when the 'O'
@@ -3064,7 +3064,7 @@ static void qf_list_entry(qfline_T *qfp, int qf_idx, bool cursel)
   } else {
     qf_range_text(qfp, (char *)IObuff, IOSIZE);
   }
-  vim_snprintf((char *)IObuff + STRLEN(IObuff), IOSIZE, "%s", qf_types(qfp->qf_type, qfp->qf_nr));
+  vim_snprintf((char *)IObuff + strlen(IObuff), IOSIZE, "%s", qf_types(qfp->qf_type, qfp->qf_nr));
   msg_puts_attr((const char *)IObuff, qfLineAttr);
   msg_puts_attr(":", qfSepAttr);
   if (qfp->qf_pattern != NULL) {
@@ -3076,7 +3076,7 @@ static void qf_list_entry(qfline_T *qfp, int qf_idx, bool cursel)
 
   char *tbuf = IObuff;
   size_t tbuflen = IOSIZE;
-  size_t len = STRLEN(qfp->qf_text) + 3;
+  size_t len = strlen(qfp->qf_text) + 3;
 
   if (len > IOSIZE) {
     tbuf = xmalloc(len);
@@ -3198,18 +3198,18 @@ static void qf_fmt_text(const char *restrict text, char *restrict buf, int bufsi
 static void qf_range_text(const qfline_T *qfp, char *buf, int bufsize)
 {
   vim_snprintf(buf, (size_t)bufsize, "%" PRIdLINENR, qfp->qf_lnum);
-  int len = (int)STRLEN(buf);
+  int len = (int)strlen(buf);
 
   if (qfp->qf_end_lnum > 0 && qfp->qf_lnum != qfp->qf_end_lnum) {
     vim_snprintf(buf + len, (size_t)(bufsize - len), "-%" PRIdLINENR, qfp->qf_end_lnum);
-    len += (int)STRLEN(buf + len);
+    len += (int)strlen(buf + len);
   }
   if (qfp->qf_col > 0) {
     vim_snprintf(buf + len, (size_t)(bufsize - len), " col %d", qfp->qf_col);
-    len += (int)STRLEN(buf + len);
+    len += (int)strlen(buf + len);
     if (qfp->qf_end_col > 0 && qfp->qf_col != qfp->qf_end_col) {
       vim_snprintf(buf + len, (size_t)(bufsize - len), "-%d", qfp->qf_end_col);
-      len += (int)STRLEN(buf + len);
+      len += (int)strlen(buf + len);
     }
   }
   buf[len] = NUL;
@@ -3230,7 +3230,7 @@ static void qf_msg(qf_info_T *qi, int which, char *lead)
                count);
 
   if (title != NULL) {
-    size_t len = STRLEN(buf);
+    size_t len = strlen(buf);
 
     if (len < 34) {
       memset(buf + len, ' ', 34 - len);
@@ -3915,7 +3915,7 @@ static int qf_buf_add_line(qf_list_T *qfl, buf_T *buf, linenr_T lnum, const qfli
     int len;
     if (qfp->qf_module != NULL) {
       STRLCPY(IObuff, qfp->qf_module, IOSIZE);
-      len = (int)STRLEN(IObuff);
+      len = (int)strlen(IObuff);
     } else if (qfp->qf_fnum != 0
                && (errbuf = buflist_findnr(qfp->qf_fnum)) != NULL
                && errbuf->b_fname != NULL) {
@@ -3935,7 +3935,7 @@ static int qf_buf_add_line(qf_list_T *qfl, buf_T *buf, linenr_T lnum, const qfli
         }
         STRLCPY(IObuff, errbuf->b_fname, IOSIZE);
       }
-      len = (int)STRLEN(IObuff);
+      len = (int)strlen(IObuff);
     } else {
       len = 0;
     }
@@ -3944,14 +3944,14 @@ static int qf_buf_add_line(qf_list_T *qfl, buf_T *buf, linenr_T lnum, const qfli
     }
     if (qfp->qf_lnum > 0) {
       qf_range_text(qfp, (char *)IObuff + len, IOSIZE - len);
-      len += (int)STRLEN(IObuff + len);
+      len += (int)strlen(IObuff + len);
 
       snprintf((char *)IObuff + len, (size_t)(IOSIZE - len), "%s", qf_types(qfp->qf_type,
                                                                             qfp->qf_nr));
-      len += (int)STRLEN(IObuff + len);
+      len += (int)strlen(IObuff + len);
     } else if (qfp->qf_pattern != NULL) {
       qf_fmt_text(qfp->qf_pattern, (char *)IObuff + len, IOSIZE - len);
-      len += (int)STRLEN(IObuff + len);
+      len += (int)strlen(IObuff + len);
     }
     if (len < IOSIZE - 2) {
       IObuff[len++] = '|';
@@ -4210,9 +4210,9 @@ static char *make_get_auname(cmdidx_T cmdidx)
 static char *make_get_fullcmd(const char *makecmd, const char *fname)
   FUNC_ATTR_NONNULL_ALL FUNC_ATTR_NONNULL_RET
 {
-  size_t len = STRLEN(p_shq) * 2 + STRLEN(makecmd) + 1;
+  size_t len = STRLEN(p_shq) * 2 + strlen(makecmd) + 1;
   if (*p_sp != NUL) {
-    len += STRLEN(p_sp) + STRLEN(fname) + 3;
+    len += strlen(p_sp) + strlen(fname) + 3;
   }
   char *const cmd = xmalloc(len);
   snprintf(cmd, len, "%s%s%s", (char *)p_shq, (char *)makecmd, (char *)p_shq);
@@ -4342,9 +4342,9 @@ static char *get_mef_name(void)
     } else {
       off += 19;
     }
-    name = xmalloc(STRLEN(p_mef) + 30);
+    name = xmalloc(strlen(p_mef) + 30);
     STRCPY(name, p_mef);
-    snprintf(name + (p - p_mef), STRLEN(name), "%d%d", start, off);
+    snprintf(name + (p - p_mef), strlen(name), "%d%d", start, off);
     STRCAT(name, p + 2);
     // Don't accept a symbolic link, it's a security risk.
     FileInfo file_info;
@@ -5137,7 +5137,7 @@ static bool vgr_match_buflines(qf_list_T *qfl, char *fname, buf_T *buf, char *sp
   FUNC_ATTR_NONNULL_ARG(1, 3, 4, 5, 6)
 {
   bool found_match = false;
-  const size_t pat_len = STRLEN(spat);
+  const size_t pat_len = strlen(spat);
 
   for (linenr_T lnum = 1; lnum <= buf->b_ml.ml_line_count && *tomatch > 0; lnum++) {
     colnr_T col = 0;
@@ -5174,7 +5174,7 @@ static bool vgr_match_buflines(qf_list_T *qfl, char *fname, buf_T *buf, char *sp
           break;
         }
         col = regmatch->endpos[0].col + (col == regmatch->endpos[0].col);
-        if (col > (colnr_T)STRLEN(ml_get_buf(buf, lnum, false))) {
+        if (col > (colnr_T)strlen(ml_get_buf(buf, lnum, false))) {
           break;
         }
       }
@@ -5217,7 +5217,7 @@ static bool vgr_match_buflines(qf_list_T *qfl, char *fname, buf_T *buf, char *sp
           break;
         }
         col = (colnr_T)matches[pat_len - 1] + col + 1;
-        if (col > (colnr_T)STRLEN(str)) {
+        if (col > (colnr_T)strlen(str)) {
           break;
         }
       }
@@ -6952,7 +6952,7 @@ static void hgr_search_file(qf_list_T *qfl, char *fname, regmatch_T *p_regmatch)
     char *line = (char *)IObuff;
 
     if (vim_regexec(p_regmatch, line, (colnr_T)0)) {
-      int l = (int)STRLEN(line);
+      int l = (int)strlen(line);
 
       // remove trailing CR, LF, spaces, etc.
       while (l > 0 && line[l - 1] <= ' ') {
@@ -7009,9 +7009,9 @@ static void hgr_search_files_in_dir(qf_list_T *qfl, char *dirname, regmatch_T *p
     for (int fi = 0; fi < fcount && !got_int; fi++) {
       // Skip files for a different language.
       if (lang != NULL
-          && STRNICMP(lang, fnames[fi] + STRLEN(fnames[fi]) - 3, 2) != 0
+          && STRNICMP(lang, fnames[fi] + strlen(fnames[fi]) - 3, 2) != 0
           && !(STRNICMP(lang, "en", 2) == 0
-               && STRNICMP("txt", fnames[fi] + STRLEN(fnames[fi]) - 3, 3)
+               && STRNICMP("txt", fnames[fi] + strlen(fnames[fi]) - 3, 3)
                == 0)) {
         continue;
       }
diff --git a/src/nvim/regexp.c b/src/nvim/regexp.c
index 9a8890a28a..a2ea096cb9 100644
--- a/src/nvim/regexp.c
+++ b/src/nvim/regexp.c
@@ -227,8 +227,8 @@ static int get_char_class(char **pp)
 
   if ((*pp)[1] == ':') {
     for (i = 0; i < (int)ARRAY_SIZE(class_names); i++) {
-      if (STRNCMP(*pp + 2, class_names[i], STRLEN(class_names[i])) == 0) {
-        *pp += STRLEN(class_names[i]) + 2;
+      if (STRNCMP(*pp + 2, class_names[i], strlen(class_names[i])) == 0) {
+        *pp += strlen(class_names[i]) + 2;
         return i;
       }
     }
@@ -1545,8 +1545,8 @@ char *regtilde(char *source, int magic, bool preview)
     if ((*p == '~' && magic) || (*p == '\\' && *(p + 1) == '~' && !magic)) {
       if (reg_prev_sub != NULL) {
         // length = len(newsub) - 1 + len(prev_sub) + 1
-        prevlen = (int)STRLEN(reg_prev_sub);
-        tmpsub = xmalloc(STRLEN(newsub) + (size_t)prevlen);
+        prevlen = (int)strlen(reg_prev_sub);
+        tmpsub = xmalloc(strlen(newsub) + (size_t)prevlen);
         // copy prefix
         len = (int)(p - newsub);              // not including ~
         memmove(tmpsub, newsub, (size_t)len);
@@ -1767,7 +1767,7 @@ static int vim_regsub_both(char_u *source, typval_T *expr, char_u *dest, int des
     if (copy) {
       if (eval_result[nested] != NULL) {
         STRCPY(dest, eval_result[nested]);
-        dst += STRLEN(eval_result[nested]);
+        dst += strlen(eval_result[nested]);
         XFREE_CLEAR(eval_result[nested]);
       }
     } else {
@@ -1865,7 +1865,7 @@ static int vim_regsub_both(char_u *source, typval_T *expr, char_u *dest, int des
           eval_result[nested] = (char *)s;
         }
 
-        dst += STRLEN(eval_result[nested]);
+        dst += strlen(eval_result[nested]);
       }
 
       can_f_submatch = prev_can_f_submatch;
@@ -2172,7 +2172,7 @@ char *reg_submatch(int no)
       } else {
         // Multiple lines: take start line from start col, middle
         // lines completely and end line up to end col.
-        len = (ssize_t)STRLEN(s);
+        len = (ssize_t)strlen(s);
         if (round == 2) {
           STRCPY(retval, s);
           retval[len] = '\n';
@@ -2184,7 +2184,7 @@ char *reg_submatch(int no)
           if (round == 2) {
             STRCPY(retval + len, s);
           }
-          len += (ssize_t)STRLEN(s);
+          len += (ssize_t)strlen(s);
           if (round == 2) {
             retval[len] = '\n';
           }
diff --git a/src/nvim/regexp_bt.c b/src/nvim/regexp_bt.c
index 59a6ed28af..ac33fc0f13 100644
--- a/src/nvim/regexp_bt.c
+++ b/src/nvim/regexp_bt.c
@@ -5594,7 +5594,7 @@ static char_u *regprop(char_u *op)
   case MOPEN + 7:
   case MOPEN + 8:
   case MOPEN + 9:
-    sprintf(buf + STRLEN(buf), "MOPEN%d", OP(op) - MOPEN);
+    snprintf(buf + strlen(buf), sizeof(buf) - strlen(buf), "MOPEN%d", OP(op) - MOPEN);
     p = NULL;
     break;
   case MCLOSE + 0:
@@ -5609,7 +5609,7 @@ static char_u *regprop(char_u *op)
   case MCLOSE + 7:
   case MCLOSE + 8:
   case MCLOSE + 9:
-    sprintf(buf + STRLEN(buf), "MCLOSE%d", OP(op) - MCLOSE);
+    snprintf(buf + strlen(buf), sizeof(buf) - strlen(buf), "MCLOSE%d", OP(op) - MCLOSE);
     p = NULL;
     break;
   case BACKREF + 1:
@@ -5621,7 +5621,7 @@ static char_u *regprop(char_u *op)
   case BACKREF + 7:
   case BACKREF + 8:
   case BACKREF + 9:
-    sprintf(buf + STRLEN(buf), "BACKREF%d", OP(op) - BACKREF);
+    snprintf(buf + strlen(buf), sizeof(buf) - strlen(buf), "BACKREF%d", OP(op) - BACKREF);
     p = NULL;
     break;
   case NOPEN:
@@ -5639,7 +5639,7 @@ static char_u *regprop(char_u *op)
   case ZOPEN + 7:
   case ZOPEN + 8:
   case ZOPEN + 9:
-    sprintf(buf + STRLEN(buf), "ZOPEN%d", OP(op) - ZOPEN);
+    snprintf(buf + strlen(buf), sizeof(buf) - strlen(buf), "ZOPEN%d", OP(op) - ZOPEN);
     p = NULL;
     break;
   case ZCLOSE + 1:
@@ -5651,7 +5651,7 @@ static char_u *regprop(char_u *op)
   case ZCLOSE + 7:
   case ZCLOSE + 8:
   case ZCLOSE + 9:
-    sprintf(buf + STRLEN(buf), "ZCLOSE%d", OP(op) - ZCLOSE);
+    snprintf(buf + strlen(buf), sizeof(buf) - strlen(buf), "ZCLOSE%d", OP(op) - ZCLOSE);
     p = NULL;
     break;
   case ZREF + 1:
@@ -5663,7 +5663,7 @@ static char_u *regprop(char_u *op)
   case ZREF + 7:
   case ZREF + 8:
   case ZREF + 9:
-    sprintf(buf + STRLEN(buf), "ZREF%d", OP(op) - ZREF);
+    snprintf(buf + strlen(buf), sizeof(buf) - strlen(buf), "ZREF%d", OP(op) - ZREF);
     p = NULL;
     break;
   case STAR:
@@ -5703,7 +5703,8 @@ static char_u *regprop(char_u *op)
   case BRACE_COMPLEX + 7:
   case BRACE_COMPLEX + 8:
   case BRACE_COMPLEX + 9:
-    sprintf(buf + STRLEN(buf), "BRACE_COMPLEX%d", OP(op) - BRACE_COMPLEX);
+    snprintf(buf + strlen(buf), sizeof(buf) - strlen(buf), "BRACE_COMPLEX%d",
+             OP(op) - BRACE_COMPLEX);
     p = NULL;
     break;
   case MULTIBYTECODE:
@@ -5713,7 +5714,7 @@ static char_u *regprop(char_u *op)
     p = "NEWL";
     break;
   default:
-    sprintf(buf + STRLEN(buf), "corrupt %d", OP(op));
+    snprintf(buf + strlen(buf), sizeof(buf) - strlen(buf), "corrupt %d", OP(op));
     p = NULL;
     break;
   }
diff --git a/src/nvim/runtime.c b/src/nvim/runtime.c
index 78a157f9fb..223865b918 100644
--- a/src/nvim/runtime.c
+++ b/src/nvim/runtime.c
@@ -250,7 +250,7 @@ int do_in_path(char *path, char *name, int flags, DoInRuntimepathCB callback, vo
     while (*rtp != NUL && ((flags & DIP_ALL) || !did_one)) {
       // Copy the path from 'runtimepath' to buf[].
       copy_option_part(&rtp, buf, MAXPATHL, ",");
-      size_t buflen = STRLEN(buf);
+      size_t buflen = strlen(buf);
 
       // Skip after or non-after directories.
       if (flags & (DIP_NOAFTER | DIP_AFTER)) {
@@ -265,9 +265,9 @@ int do_in_path(char *path, char *name, int flags, DoInRuntimepathCB callback, vo
       if (name == NULL) {
         (*callback)(buf, cookie);
         did_one = true;
-      } else if (buflen + STRLEN(name) + 2 < MAXPATHL) {
+      } else if (buflen + strlen(name) + 2 < MAXPATHL) {
         add_pathsep(buf);
-        tail = buf + STRLEN(buf);
+        tail = buf + strlen(buf);
 
         // Loop over all patterns in "name"
         char *np = name;
@@ -397,10 +397,10 @@ int do_in_cached_path(char *name, int flags, DoInRuntimepathCB callback, void *c
 
     if (name == NULL) {
       (*callback)(item.path, cookie);
-    } else if (buflen + STRLEN(name) + 2 < MAXPATHL) {
+    } else if (buflen + strlen(name) + 2 < MAXPATHL) {
       STRCPY(buf, item.path);
       add_pathsep(buf);
-      tail = buf + STRLEN(buf);
+      tail = buf + strlen(buf);
 
       // Loop over all patterns in "name"
       char *np = name;
@@ -545,7 +545,7 @@ int do_in_path_and_pp(char *path, char *name, int flags, DoInRuntimepathCB callb
 
   if ((done == FAIL || (flags & DIP_ALL)) && (flags & DIP_START)) {
     char *start_dir = "pack/*/start/*/%s%s";  // NOLINT
-    size_t len = STRLEN(start_dir) + STRLEN(name) + 6;
+    size_t len = strlen(start_dir) + strlen(name) + 6;
     char *s = xmallocz(len);  // TODO(bfredl): get rid of random allocations
     char *suffix = (flags & DIP_AFTER) ? "after/" : "";
 
@@ -556,7 +556,7 @@ int do_in_path_and_pp(char *path, char *name, int flags, DoInRuntimepathCB callb
 
     if (done == FAIL || (flags & DIP_ALL)) {
       start_dir = "start/*/%s%s";  // NOLINT
-      len = STRLEN(start_dir) + STRLEN(name) + 6;
+      len = strlen(start_dir) + strlen(name) + 6;
       s = xmallocz(len);
 
       vim_snprintf(s, len, start_dir, suffix, name);
@@ -568,7 +568,7 @@ int do_in_path_and_pp(char *path, char *name, int flags, DoInRuntimepathCB callb
 
   if ((done == FAIL || (flags & DIP_ALL)) && (flags & DIP_OPT)) {
     char *opt_dir = "pack/*/opt/*/%s";  // NOLINT
-    size_t len = STRLEN(opt_dir) + STRLEN(name);
+    size_t len = strlen(opt_dir) + strlen(name);
     char *s = xmallocz(len);
 
     vim_snprintf(s, len, opt_dir, name);
@@ -578,7 +578,7 @@ int do_in_path_and_pp(char *path, char *name, int flags, DoInRuntimepathCB callb
 
     if (done == FAIL || (flags & DIP_ALL)) {
       opt_dir = "opt/*/%s";  // NOLINT
-      len = STRLEN(opt_dir) + STRLEN(name);
+      len = strlen(opt_dir) + strlen(name);
       s = xmallocz(len);
 
       vim_snprintf(s, len, opt_dir, name);
@@ -630,13 +630,13 @@ static void expand_pack_entry(RuntimeSearchPath *search_path, Map(String, handle
   static char buf[MAXPATHL];
   char *(start_pat[]) = { "/pack/*/start/*", "/start/*" };  // NOLINT
   for (int i = 0; i < 2; i++) {
-    if (pack_entry_len + STRLEN(start_pat[i]) + 1 > sizeof buf) {
+    if (pack_entry_len + strlen(start_pat[i]) + 1 > sizeof buf) {
       continue;
     }
     STRLCPY(buf, pack_entry, sizeof buf);
     STRLCPY(buf + pack_entry_len, start_pat[i], sizeof buf - pack_entry_len);
     expand_rtp_entry(search_path, rtp_used, buf, false);
-    size_t after_size = STRLEN(buf) + 7;
+    size_t after_size = strlen(buf) + 7;
     char *after = xmallocz(after_size);
     xstrlcpy(after, buf, after_size);
     xstrlcat(after, "/after", after_size);
@@ -669,7 +669,7 @@ RuntimeSearchPath runtime_search_path_build(void)
     char *cur_entry = entry;
     copy_option_part(&entry, buf, MAXPATHL, ",");
 
-    String the_entry = { .data = cur_entry, .size = STRLEN(buf) };
+    String the_entry = { .data = cur_entry, .size = strlen(buf) };
 
     kv_push(pack_entries, the_entry);
     map_put(String, handle_T)(&pack_used, the_entry, 0);
@@ -679,7 +679,7 @@ RuntimeSearchPath runtime_search_path_build(void)
   for (rtp_entry = p_rtp; *rtp_entry != NUL;) {
     char *cur_entry = rtp_entry;
     copy_option_part(&rtp_entry, buf, MAXPATHL, ",");
-    size_t buflen = STRLEN(buf);
+    size_t buflen = strlen(buf);
 
     if (path_is_after(buf, buflen)) {
       rtp_entry = cur_entry;
@@ -713,7 +713,7 @@ RuntimeSearchPath runtime_search_path_build(void)
   // "after" dirs in rtp
   for (; *rtp_entry != NUL;) {
     copy_option_part(&rtp_entry, buf, MAXPATHL, ",");
-    expand_rtp_entry(&search_path, &rtp_used, buf, path_is_after(buf, STRLEN(buf)));
+    expand_rtp_entry(&search_path, &rtp_used, buf, path_is_after(buf, strlen(buf)));
   }
 
   // strings are not owned
@@ -891,7 +891,7 @@ static int add_pack_dir_to_rtp(char *fname, bool is_pack)
 
   if (insp == NULL) {
     // Both "fname" and "after" not found, append at the end.
-    insp = (const char *)p_rtp + STRLEN(p_rtp);
+    insp = (const char *)p_rtp + strlen(p_rtp);
   }
 
   // check if rtp/pack/name/start/name/after exists
@@ -901,8 +901,8 @@ static int add_pack_dir_to_rtp(char *fname, bool is_pack)
     afterlen = strlen(afterdir) + 1;  // add one for comma
   }
 
-  const size_t oldlen = STRLEN(p_rtp);
-  const size_t addlen = STRLEN(fname) + 1;  // add one for comma
+  const size_t oldlen = strlen(p_rtp);
+  const size_t addlen = strlen(fname) + 1;  // add one for comma
   const size_t new_rtp_capacity = oldlen + addlen + afterlen + 1;
   // add one for NUL ------------------------------------------^
   char *const new_rtp = try_malloc(new_rtp_capacity);
@@ -969,7 +969,7 @@ static int load_pack_plugin(bool opt, char *fname)
   static const char *ftpat = "%s/ftdetect/*.vim";  // NOLINT
 
   char *const ffname = fix_fname(fname);
-  size_t len = strlen(ffname) + STRLEN(ftpat);
+  size_t len = strlen(ffname) + strlen(ftpat);
   char *pat = xmallocz(len);
 
   vim_snprintf(pat, len, "%s/plugin/**/*.vim", ffname);  // NOLINT
@@ -1061,7 +1061,7 @@ static void add_pack_start_dir(char *fname, void *cookie)
   static char buf[MAXPATHL];
   char *(start_pat[]) = { "/start/*", "/pack/*/start/*" };  // NOLINT
   for (int i = 0; i < 2; i++) {
-    if (STRLEN(fname) + STRLEN(start_pat[i]) + 1 > MAXPATHL) {
+    if (strlen(fname) + strlen(start_pat[i]) + 1 > MAXPATHL) {
       continue;
     }
     STRLCPY(buf, fname, MAXPATHL);
@@ -1140,7 +1140,7 @@ void ex_packadd(exarg_T *eap)
       continue;
     }
 
-    const size_t len = STRLEN(plugpat) + STRLEN(eap->arg) + 5;
+    const size_t len = strlen(plugpat) + strlen(eap->arg) + 5;
     char *pat = xmallocz(len);
     vim_snprintf(pat, len, plugpat, round == 1 ? "start" : "opt", eap->arg);
     // The first round don't give a "not found" error, in the second round
@@ -1166,14 +1166,14 @@ int ExpandRTDir(char *pat, int flags, int *num_file, char ***file, char *dirname
 {
   *num_file = 0;
   *file = NULL;
-  size_t pat_len = STRLEN(pat);
+  size_t pat_len = strlen(pat);
 
   garray_T ga;
   ga_init(&ga, (int)sizeof(char *), 10);
 
   // TODO(bfredl): this is bullshit, exandpath should not reinvent path logic.
   for (int i = 0; dirnames[i] != NULL; i++) {
-    size_t size = STRLEN(dirnames[i]) + pat_len + 7;
+    size_t size = strlen(dirnames[i]) + pat_len + 7;
     char *s = xmalloc(size);
     snprintf(s, size, "%s/%s*.vim", dirnames[i], pat);
     globpath(p_rtp, s, &ga, 0);
@@ -1186,7 +1186,7 @@ int ExpandRTDir(char *pat, int flags, int *num_file, char ***file, char *dirname
 
   if (flags & DIP_START) {
     for (int i = 0; dirnames[i] != NULL; i++) {
-      size_t size = STRLEN(dirnames[i]) + pat_len + 22;
+      size_t size = strlen(dirnames[i]) + pat_len + 22;
       char *s = xmalloc(size);
       snprintf(s, size, "pack/*/start/*/%s/%s*.vim", dirnames[i], pat);  // NOLINT
       globpath(p_pp, s, &ga, 0);
@@ -1198,7 +1198,7 @@ int ExpandRTDir(char *pat, int flags, int *num_file, char ***file, char *dirname
     }
 
     for (int i = 0; dirnames[i] != NULL; i++) {
-      size_t size = STRLEN(dirnames[i]) + pat_len + 22;
+      size_t size = strlen(dirnames[i]) + pat_len + 22;
       char *s = xmalloc(size);
       snprintf(s, size, "start/*/%s/%s*.vim", dirnames[i], pat);  // NOLINT
       globpath(p_pp, s, &ga, 0);
@@ -1212,7 +1212,7 @@ int ExpandRTDir(char *pat, int flags, int *num_file, char ***file, char *dirname
 
   if (flags & DIP_OPT) {
     for (int i = 0; dirnames[i] != NULL; i++) {
-      size_t size = STRLEN(dirnames[i]) + pat_len + 20;
+      size_t size = strlen(dirnames[i]) + pat_len + 20;
       char *s = xmalloc(size);
       snprintf(s, size, "pack/*/opt/*/%s/%s*.vim", dirnames[i], pat);  // NOLINT
       globpath(p_pp, s, &ga, 0);
@@ -1224,7 +1224,7 @@ int ExpandRTDir(char *pat, int flags, int *num_file, char ***file, char *dirname
     }
 
     for (int i = 0; dirnames[i] != NULL; i++) {
-      size_t size = STRLEN(dirnames[i]) + pat_len + 20;
+      size_t size = strlen(dirnames[i]) + pat_len + 20;
       char *s = xmalloc(size);
       snprintf(s, size, "opt/*/%s/%s*.vim", dirnames[i], pat);  // NOLINT
       globpath(p_pp, s, &ga, 0);
@@ -1239,7 +1239,7 @@ int ExpandRTDir(char *pat, int flags, int *num_file, char ***file, char *dirname
   for (int i = 0; i < ga.ga_len; i++) {
     char *match = ((char **)ga.ga_data)[i];
     char *s = match;
-    char *e = s + STRLEN(s);
+    char *e = s + strlen(s);
     if (e - s > 4 && (STRNICMP(e - 4, ".vim", 4) == 0
                       || ((flags & DIP_LUA)
                           && STRNICMP(e - 4, ".lua", 4) == 0))) {
@@ -1277,7 +1277,7 @@ int ExpandPackAddDir(char *pat, int *num_file, char ***file)
 
   *num_file = 0;
   *file = NULL;
-  size_t pat_len = STRLEN(pat);
+  size_t pat_len = strlen(pat);
   ga_init(&ga, (int)sizeof(char *), 10);
 
   size_t buflen = pat_len + 26;
@@ -1291,7 +1291,7 @@ int ExpandPackAddDir(char *pat, int *num_file, char ***file)
   for (int i = 0; i < ga.ga_len; i++) {
     char *match = ((char **)ga.ga_data)[i];
     s = path_tail(match);
-    memmove(match, s, STRLEN(s) + 1);
+    memmove(match, s, strlen(s) + 1);
   }
 
   if (GA_EMPTY(&ga)) {
@@ -1728,7 +1728,7 @@ typedef struct {
 static char *get_str_line(int c, void *cookie, int indent, bool do_concat)
 {
   GetStrLineCookie *p = cookie;
-  if (STRLEN(p->buf) <= p->offset) {
+  if (strlen(p->buf) <= p->offset) {
     return NULL;
   }
   const char *line = p->buf + p->offset;
@@ -2290,7 +2290,7 @@ char *getsourceline(int c, void *cookie, int indent, bool do_concat)
       ga_init(&ga, (int)sizeof(char), 400);
       ga_concat(&ga, line);
       while (sp->nextline != NULL
-             && concat_continued_line(&ga, 400, sp->nextline, STRLEN(sp->nextline))) {
+             && concat_continued_line(&ga, 400, sp->nextline, strlen(sp->nextline))) {
         xfree(sp->nextline);
         sp->nextline = get_one_sourceline(sp);
       }
@@ -2353,7 +2353,7 @@ retry:
 
       break;
     }
-    len = ga.ga_len + (int)STRLEN(buf + ga.ga_len);
+    len = ga.ga_len + (int)strlen(buf + ga.ga_len);
 #ifdef USE_CRNL
     // Ignore a trailing CTRL-Z, when in Dos mode. Only recognize the
     // CTRL-Z by its own, or after a NL.
diff --git a/src/nvim/screen.c b/src/nvim/screen.c
index 8e10f2d62d..0ec6834364 100644
--- a/src/nvim/screen.c
+++ b/src/nvim/screen.c
@@ -1022,7 +1022,7 @@ void draw_tabline(void)
       if (modified || wincount > 1) {
         if (wincount > 1) {
           vim_snprintf((char *)NameBuff, MAXPATHL, "%d", wincount);
-          len = (int)STRLEN(NameBuff);
+          len = (int)strlen(NameBuff);
           if (col + len >= Columns - 3) {
             break;
           }
@@ -1394,7 +1394,7 @@ char *set_chars_option(win_T *wp, char **varp, bool apply)
     while (*p) {
       int i;
       for (i = 0; i < entries; i++) {
-        const size_t len = STRLEN(tab[i].name);
+        const size_t len = strlen(tab[i].name);
         if (STRNCMP(p, tab[i].name, len) == 0
             && p[len] == ':'
             && p[len + 1] != NUL) {
@@ -1436,8 +1436,8 @@ char *set_chars_option(win_T *wp, char **varp, bool apply)
       }
 
       if (i == entries) {
-        const size_t len = STRLEN("multispace");
-        const size_t len2 = STRLEN("leadmultispace");
+        const size_t len = strlen("multispace");
+        const size_t len2 = strlen("leadmultispace");
         if (is_listchars
             && STRNCMP(p, "multispace", len) == 0
             && p[len] == ':'
diff --git a/src/nvim/search.c b/src/nvim/search.c
index 8477efed92..336dd50292 100644
--- a/src/nvim/search.c
+++ b/src/nvim/search.c
@@ -817,7 +817,7 @@ int searchit(win_T *win, buf_T *buf, pos_T *pos, pos_T *end_pos, Direction dir,
             if (endpos.col == 0) {
               if (pos->lnum > 1) {              // just in case
                 pos->lnum--;
-                pos->col = (colnr_T)STRLEN(ml_get_buf(buf, pos->lnum, false));
+                pos->col = (colnr_T)strlen(ml_get_buf(buf, pos->lnum, false));
               }
             } else {
               pos->col--;
@@ -934,7 +934,7 @@ int searchit(win_T *win, buf_T *buf, pos_T *pos, pos_T *end_pos, Direction dir,
   // A pattern like "\n\zs" may go past the last line.
   if (pos->lnum > buf->b_ml.ml_line_count) {
     pos->lnum = buf->b_ml.ml_line_count;
-    pos->col = (int)STRLEN(ml_get_buf(buf, pos->lnum, false));
+    pos->col = (int)strlen(ml_get_buf(buf, pos->lnum, false));
     if (pos->col > 0) {
       pos->col--;
     }
@@ -1085,7 +1085,7 @@ int do_search(oparg_T *oap, int dirc, int search_delim, char_u *pat, long count,
       p = (char_u *)skip_regexp((char *)pat, search_delim, p_magic, &strcopy);
       if (strcopy != (char *)ps) {
         // made a copy of "pat" to change "\?" to "?"
-        searchcmdlen += (int)(STRLEN(pat) - STRLEN(strcopy));
+        searchcmdlen += (int)(STRLEN(pat) - strlen(strcopy));
         pat = (char_u *)strcopy;
         searchstr = (char_u *)strcopy;
       }
@@ -2444,7 +2444,7 @@ int current_search(long count, bool forward)
       } else {  // try again from end of buffer
                 // searching backwards, so set pos to last line and col
         pos.lnum = curwin->w_buffer->b_ml.ml_line_count;
-        pos.col  = (colnr_T)STRLEN(ml_get(curwin->w_buffer->b_ml.ml_line_count));
+        pos.col  = (colnr_T)strlen(ml_get(curwin->w_buffer->b_ml.ml_line_count));
       }
     }
   }
diff --git a/src/nvim/sha256.c b/src/nvim/sha256.c
index 53c9cb7c81..012f145875 100644
--- a/src/nvim/sha256.c
+++ b/src/nvim/sha256.c
@@ -17,7 +17,7 @@
 #include <stdio.h>         // for snprintf().
 
 #include "nvim/sha256.h"   // for context_sha256_T
-#include "nvim/vim.h"      // for STRCPY()/STRLEN().
+#include "nvim/vim.h"      // for STRCPY()/strlen().
 
 #ifdef INCLUDE_GENERATED_DECLARATIONS
 # include "sha256.c.generated.h"
diff --git a/src/nvim/shada.c b/src/nvim/shada.c
index 74d8b30347..f735829030 100644
--- a/src/nvim/shada.c
+++ b/src/nvim/shada.c
@@ -884,7 +884,7 @@ static const void *shada_hist_iter(const void *const iter, const uint8_t history
           .histtype = history_type,
           .string = hist_he.hisstr,
           .sep = (char)(history_type == HIST_SEARCH
-                        ? hist_he.hisstr[STRLEN(hist_he.hisstr) + 1]
+                        ? hist_he.hisstr[strlen(hist_he.hisstr) + 1]
                         : 0),
           .additional_elements = hist_he.additional_elements,
         }
@@ -4000,7 +4000,7 @@ static bool shada_removable(const char *name)
     (void)copy_option_part(&p, part, ARRAY_SIZE(part), ", ");
     if (part[0] == 'r') {
       home_replace(NULL, part + 1, (char *)NameBuff, MAXPATHL, true);
-      size_t n = STRLEN(NameBuff);
+      size_t n = strlen(NameBuff);
       if (mb_strnicmp(NameBuff, new_name, n) == 0) {
         retval = true;
         break;
diff --git a/src/nvim/sign.c b/src/nvim/sign.c
index ed546cf303..5ce9ee4546 100644
--- a/src/nvim/sign.c
+++ b/src/nvim/sign.c
@@ -78,10 +78,10 @@ static signgroup_T *sign_group_ref(const char *groupname)
   signgroup_T *group;
 
   hash = hash_hash((char_u *)groupname);
-  hi = hash_lookup(&sg_table, (char *)groupname, STRLEN(groupname), hash);
+  hi = hash_lookup(&sg_table, (char *)groupname, strlen(groupname), hash);
   if (HASHITEM_EMPTY(hi)) {
     // new group
-    group = xmalloc(sizeof(signgroup_T) + STRLEN(groupname));
+    group = xmalloc(sizeof(signgroup_T) + strlen(groupname));
 
     STRCPY(group->sg_name, groupname);
     group->sg_refcount = 1;
@@ -868,7 +868,7 @@ static int sign_define_init_text(sign_T *sp, char *text)
   int cells;
   size_t len;
 
-  endp = text + (int)STRLEN(text);
+  endp = text + (int)strlen(text);
   for (s = text; s + 1 < endp; s++) {
     if (*s == '\\') {
       // Remove a backslash, so that it is possible
@@ -951,7 +951,7 @@ static int sign_define_by_name(char *name, char *icon, char *linehl, char *text,
     if (*linehl == NUL) {
       sp->sn_line_hl = 0;
     } else {
-      sp->sn_line_hl = syn_check_group(linehl, STRLEN(linehl));
+      sp->sn_line_hl = syn_check_group(linehl, strlen(linehl));
     }
   }
 
@@ -959,7 +959,7 @@ static int sign_define_by_name(char *name, char *icon, char *linehl, char *text,
     if (*texthl == NUL) {
       sp->sn_text_hl = 0;
     } else {
-      sp->sn_text_hl = syn_check_group(texthl, STRLEN(texthl));
+      sp->sn_text_hl = syn_check_group(texthl, strlen(texthl));
     }
   }
 
@@ -967,7 +967,7 @@ static int sign_define_by_name(char *name, char *icon, char *linehl, char *text,
     if (*culhl == NUL) {
       sp->sn_cul_hl = 0;
     } else {
-      sp->sn_cul_hl = syn_check_group(culhl, STRLEN(culhl));
+      sp->sn_cul_hl = syn_check_group(culhl, strlen(culhl));
     }
   }
 
@@ -975,7 +975,7 @@ static int sign_define_by_name(char *name, char *icon, char *linehl, char *text,
     if (*numhl == NUL) {
       sp->sn_num_hl = 0;
     } else {
-      sp->sn_num_hl = syn_check_group(numhl, STRLEN(numhl));
+      sp->sn_num_hl = syn_check_group(numhl, strlen(numhl));
     }
   }
 
@@ -1139,7 +1139,7 @@ static linenr_T sign_jump(int sign_id, char *sign_group, buf_T *buf)
       emsg(_("E934: Cannot jump to a buffer that does not have a name"));
       return -1;
     }
-    size_t cmdlen = STRLEN(buf->b_fname) + 24;
+    size_t cmdlen = strlen(buf->b_fname) + 24;
     char *cmd = xmallocz(cmdlen);
     snprintf(cmd, cmdlen, "e +%" PRId64 " %s",
              (int64_t)lnum, buf->b_fname);
diff --git a/src/nvim/spell.c b/src/nvim/spell.c
index 42891fd3fb..53fa920358 100644
--- a/src/nvim/spell.c
+++ b/src/nvim/spell.c
@@ -109,7 +109,7 @@
 #include "nvim/syntax.h"          // for syn_get_id, syntax_present
 #include "nvim/types.h"           // for char_u
 #include "nvim/undo.h"            // for u_save_cursor
-#include "nvim/vim.h"             // for curwin, STRLEN, STRLCPY, STRNCMP
+#include "nvim/vim.h"             // for curwin, strlen, STRLCPY, STRNCMP
 
 // Result values.  Lower number is accepted over higher one.
 #define SP_BANNED       (-1)
@@ -1550,7 +1550,7 @@ static void spell_load_lang(char_u *lang)
     }
   } else if (sl.sl_slang != NULL) {
     // At least one file was loaded, now load ALL the additions.
-    STRCPY(fname_enc + STRLEN(fname_enc) - 3, "add.spl");
+    STRCPY(fname_enc + strlen(fname_enc) - 3, "add.spl");
     do_in_runtimepath((char *)fname_enc, DIP_ALL, spell_load_cb, &sl);
   }
 }
@@ -1888,7 +1888,7 @@ char *did_set_spelllang(win_T *wp)
     // Get one language name.
     copy_option_part(&splp, (char *)lang, MAXWLEN, ",");
     region = NULL;
-    len = (int)STRLEN(lang);
+    len = (int)strlen(lang);
 
     if (!valid_spelllang((char *)lang)) {
       continue;
@@ -2165,7 +2165,7 @@ static void use_midword(slang_T *lp, win_T *wp)
       wp->w_s->b_spell_ismw_mb = xstrnsave(p, (size_t)l);
     } else {
       // Append multi-byte chars to "b_spell_ismw_mb".
-      const int n = (int)STRLEN(wp->w_s->b_spell_ismw_mb);
+      const int n = (int)strlen(wp->w_s->b_spell_ismw_mb);
       char *bp = xstrnsave(wp->w_s->b_spell_ismw_mb, (size_t)n + (size_t)l);
       xfree(wp->w_s->b_spell_ismw_mb);
       wp->w_s->b_spell_ismw_mb = bp;
@@ -2572,9 +2572,9 @@ void ex_spellrepall(exarg_T *eap)
     emsg(_("E752: No previous spell replacement"));
     return;
   }
-  int addlen = (int)(STRLEN(repl_to) - STRLEN(repl_from));
+  int addlen = (int)(strlen(repl_to) - strlen(repl_from));
 
-  size_t frompatlen = STRLEN(repl_from) + 7;
+  size_t frompatlen = strlen(repl_from) + 7;
   char_u *frompat = xmalloc(frompatlen);
   snprintf((char *)frompat, frompatlen, "\\V\\<%s\\>", repl_from);
   p_ws = false;
@@ -2592,11 +2592,11 @@ void ex_spellrepall(exarg_T *eap)
     // when changing "etc" to "etc.".
     char_u *line = (char_u *)get_cursor_line_ptr();
     if (addlen <= 0 || STRNCMP(line + curwin->w_cursor.col,
-                               repl_to, STRLEN(repl_to)) != 0) {
+                               repl_to, strlen(repl_to)) != 0) {
       char_u *p = xmalloc(STRLEN(line) + (size_t)addlen + 1);
       memmove(p, line, (size_t)curwin->w_cursor.col);
       STRCPY(p + curwin->w_cursor.col, repl_to);
-      STRCAT(p, line + curwin->w_cursor.col + STRLEN(repl_from));
+      STRCAT(p, line + curwin->w_cursor.col + strlen(repl_from));
       ml_replace(curwin->w_cursor.lnum, (char *)p, false);
       changed_bytes(curwin->w_cursor.lnum, curwin->w_cursor.col);
 
@@ -2606,7 +2606,7 @@ void ex_spellrepall(exarg_T *eap)
       }
       sub_nsubs++;
     }
-    curwin->w_cursor.col += (colnr_T)STRLEN(repl_to);
+    curwin->w_cursor.col += (colnr_T)strlen(repl_to);
   }
 
   p_ws = save_ws;
@@ -3247,7 +3247,7 @@ void spell_dump_compl(char *pat, int ic, Direction *dir, int dumpflags_arg)
     // When matching with a pattern and there are no prefixes only use
     // parts of the tree that match "pat".
     if (pat != NULL && slang->sl_pbyts == NULL) {
-      patlen = (int)STRLEN(pat);
+      patlen = (int)strlen(pat);
     } else {
       patlen = -1;
     }
@@ -3611,7 +3611,7 @@ char *did_set_spell_option(bool is_spellfile)
   char *errmsg = NULL;
 
   if (is_spellfile) {
-    int l = (int)STRLEN(curwin->w_s->b_p_spf);
+    int l = (int)strlen(curwin->w_s->b_p_spf);
     if (l > 0
         && (l < 4 || strcmp(curwin->w_s->b_p_spf + l - 4, ".add") != 0)) {
       errmsg = e_invarg;
diff --git a/src/nvim/spellfile.c b/src/nvim/spellfile.c
index 7da5a7ca4f..611c43e85e 100644
--- a/src/nvim/spellfile.c
+++ b/src/nvim/spellfile.c
@@ -2157,8 +2157,8 @@ static afffile_T *spell_read_aff(spellinfo_T *spin, char_u *fname)
       } else if (spell_info_item(items[0]) && itemcnt > 1) {
         p = getroom(spin,
                     (spin->si_info == NULL ? 0 : STRLEN(spin->si_info))
-                    + STRLEN(items[0])
-                    + STRLEN(items[1]) + 3, false);
+                    + strlen(items[0])
+                    + strlen(items[1]) + 3, false);
         if (spin->si_info != NULL) {
           STRCPY(p, spin->si_info);
           STRCAT(p, "\n");
@@ -2231,7 +2231,7 @@ static afffile_T *spell_read_aff(spellinfo_T *spin, char_u *fname)
                  && compflags == NULL) {
         // Turn flag "c" into COMPOUNDRULE compatible string "c+",
         // "Na" into "Na+", "1234" into "1234+".
-        p = getroom(spin, STRLEN(items[1]) + 2, false);
+        p = getroom(spin, strlen(items[1]) + 2, false);
         STRCPY(p, items[1]);
         STRCAT(p, "+");
         compflags = (char_u *)p;
@@ -2247,7 +2247,7 @@ static afffile_T *spell_read_aff(spellinfo_T *spin, char_u *fname)
         if (compflags != NULL || *skipdigits((char *)items[1]) != NUL) {
           // Concatenate this string to previously defined ones,
           // using a slash to separate them.
-          l = (int)STRLEN(items[1]) + 1;
+          l = (int)strlen(items[1]) + 1;
           if (compflags != NULL) {
             l += (int)STRLEN(compflags) + 1;
           }
@@ -2358,7 +2358,7 @@ static afffile_T *spell_read_aff(spellinfo_T *spin, char_u *fname)
           cur_aff = getroom(spin, sizeof(*cur_aff), true);
           cur_aff->ah_flag = affitem2flag(aff->af_flagtype, (char_u *)items[1],
                                           fname, lnum);
-          if (cur_aff->ah_flag == 0 || STRLEN(items[1]) >= AH_KEY_LEN) {
+          if (cur_aff->ah_flag == 0 || strlen(items[1]) >= AH_KEY_LEN) {
             break;
           }
           if (cur_aff->ah_flag == aff->af_bad
@@ -4640,7 +4640,7 @@ static int write_vim_spell(spellinfo_T *spin, char *fname)
     size_t l = STRLEN(spin->si_compflags);
     assert(spin->si_comppat.ga_len >= 0);
     for (size_t i = 0; i < (size_t)spin->si_comppat.ga_len; i++) {
-      l += STRLEN(((char **)(spin->si_comppat.ga_data))[i]) + 1;
+      l += strlen(((char **)(spin->si_comppat.ga_data))[i]) + 1;
     }
     put_bytes(fd, l + 7, 4);                            // <sectionlen>
 
@@ -4652,9 +4652,9 @@ static int write_vim_spell(spellinfo_T *spin, char *fname)
     put_bytes(fd, (uintmax_t)spin->si_comppat.ga_len, 2);  // <comppatcount>
     for (size_t i = 0; i < (size_t)spin->si_comppat.ga_len; i++) {
       char *p = ((char **)(spin->si_comppat.ga_data))[i];
-      assert(STRLEN(p) < INT_MAX);
-      putc((int)STRLEN(p), fd);                         // <comppatlen>
-      fwv &= fwrite(p, STRLEN(p), 1, fd);               // <comppattext>
+      assert(strlen(p) < INT_MAX);
+      putc((int)strlen(p), fd);                         // <comppatlen>
+      fwv &= fwrite(p, strlen(p), 1, fd);               // <comppattext>
     }
     // <compflags>
     fwv &= fwrite(spin->si_compflags, STRLEN(spin->si_compflags), 1, fd);
@@ -5355,8 +5355,8 @@ static void mkspell(int fcount, char **fnames, bool ascii, bool over_write, bool
       afile[i] = NULL;
 
       if (incount > 1) {
-        len = (int)STRLEN(innames[i]);
-        if (STRLEN(path_tail((char *)innames[i])) < 5
+        len = (int)strlen(innames[i]);
+        if (strlen(path_tail(innames[i])) < 5
             || innames[i][len - 3] != '_') {
           semsg(_("E755: Invalid region in %s"), innames[i]);
           goto theend;
diff --git a/src/nvim/spellsuggest.c b/src/nvim/spellsuggest.c
index 16af1b72a3..f2a0da188e 100644
--- a/src/nvim/spellsuggest.c
+++ b/src/nvim/spellsuggest.c
@@ -66,7 +66,7 @@ typedef struct suginfo_S {
 /// One word suggestion.  Used in "si_ga".
 typedef struct {
   char *st_word;      ///< suggested word, allocated string
-  int st_wordlen;     ///< STRLEN(st_word)
+  int st_wordlen;     ///< strlen(st_word)
   int st_orglen;      ///< length of replaced text
   int st_score;       ///< lower is better
   int st_altscore;    ///< used when st_score compares equal
@@ -1633,7 +1633,7 @@ static void suggest_trie_walk(suginfo_T *su, langp_T *lp, char_u *fword, bool so
             if (!try_compound && !fword_ends) {
               STRCAT(preword, " ");
             }
-            sp->ts_prewordlen = (char_u)STRLEN(preword);
+            sp->ts_prewordlen = (char_u)strlen(preword);
             sp->ts_splitoff = sp->ts_twordlen;
             sp->ts_splitfidx = sp->ts_fidx;
 
@@ -3070,7 +3070,7 @@ static void add_suggestion(suginfo_T *su, garray_T *gap, const char *goodword, i
 
   // Minimize "badlen" for consistency.  Avoids that changing "the the" to
   // "thee the" is added next to changing the first "the" the "thee".
-  const char *pgood = goodword + STRLEN(goodword);
+  const char *pgood = goodword + strlen(goodword);
   char_u *pbad = su->su_badptr + badlenarg;
   for (;;) {
     goodlen = (int)(pgood - goodword);
@@ -3345,8 +3345,8 @@ static int soundalike_score(char *goodstart, char *badstart)
     }
   }
 
-  goodlen = (int)STRLEN(goodsound);
-  badlen = (int)STRLEN(badsound);
+  goodlen = (int)strlen(goodsound);
+  badlen = (int)strlen(badsound);
 
   // Return quickly if the lengths are too different to be fixed by two
   // changes.
diff --git a/src/nvim/statusline.c b/src/nvim/statusline.c
index 5f686ef96f..94462d4073 100644
--- a/src/nvim/statusline.c
+++ b/src/nvim/statusline.c
@@ -100,7 +100,7 @@ void win_redr_status(win_T *wp)
     }
     if (wp->w_buffer->b_p_ro) {
       snprintf((char *)p + len, MAXPATHL - (size_t)len, "%s", _("[RO]"));
-      // len += (int)STRLEN(p + len);  // dead assignment
+      // len += (int)strlen(p + len);  // dead assignment
     }
 
     this_ru_col = ru_col - (Columns - width);
@@ -137,9 +137,9 @@ void win_redr_status(win_T *wp)
               this_ru_col + col, fillchar, fillchar, attr);
 
     if (get_keymap_str(wp, "<%s>", (char *)NameBuff, MAXPATHL)
-        && this_ru_col - len > (int)(STRLEN(NameBuff) + 1)) {
+        && this_ru_col - len > (int)(strlen(NameBuff) + 1)) {
       grid_puts(&default_grid, NameBuff, row,
-                (int)((size_t)this_ru_col - STRLEN(NameBuff) - 1), attr);
+                (int)((size_t)this_ru_col - strlen(NameBuff) - 1), attr);
     }
 
     win_redr_ruler(wp, true);
@@ -286,7 +286,7 @@ void win_redr_ruler(win_T *wp, bool always)
     vim_snprintf(buffer, RULER_BUF_LEN, "%" PRId64 ",",
                  (wp->w_buffer->b_ml.ml_flags &
                   ML_EMPTY) ? (int64_t)0L : (int64_t)wp->w_cursor.lnum);
-    size_t len = STRLEN(buffer);
+    size_t len = strlen(buffer);
     col_print(buffer + len, RULER_BUF_LEN - len,
               empty_line ? 0 : (int)wp->w_cursor.col + 1,
               (int)virtcol + 1);
@@ -294,7 +294,7 @@ void win_redr_ruler(win_T *wp, bool always)
     // Add a "50%" if there is room for it.
     // On the last line, don't print in the last column (scrolls the
     // screen up on some terminals).
-    int i = (int)STRLEN(buffer);
+    int i = (int)strlen(buffer);
     get_rel_pos(wp, buffer + i + 1, RULER_BUF_LEN - i - 1);
     int o = i + vim_strsize(buffer + i + 1);
     if (wp->w_status_height == 0 && !is_stl_global) {  // can't use last char of screen
@@ -344,7 +344,7 @@ void win_redr_ruler(win_T *wp, bool always)
       ScreenGrid *grid = part_of_status ? &default_grid : &msg_grid_adj;
       grid_puts(grid, buffer, row, this_ru_col + off, attr);
       grid_fill(grid, row, row + 1,
-                this_ru_col + off + (int)STRLEN(buffer), off + width, fillchar,
+                this_ru_col + off + (int)strlen(buffer), off + width, fillchar,
                 fillchar, attr);
     }
 
@@ -717,7 +717,7 @@ int build_stl_str_hl(win_T *wp, char *out, size_t outlen, char *fmt, int use_san
   // Get the byte value now, in case we need it below. This is more
   // efficient than making a copy of the line.
   int byteval;
-  const size_t len = STRLEN(line_ptr);
+  const size_t len = strlen(line_ptr);
   if (wp->w_cursor.col > (colnr_T)len) {
     // Line may have changed since checking the cursor column, or the lnum
     // was adjusted above.
@@ -1190,8 +1190,8 @@ int build_stl_str_hl(win_T *wp, char *out, size_t outlen, char *fmt, int use_san
           && strchr((const char *)str, '%') != NULL
           && evaldepth < MAX_STL_EVAL_DEPTH) {
         size_t parsed_usefmt = (size_t)(block_start - usefmt);
-        size_t str_length = STRLEN(str);
-        size_t fmt_length = STRLEN(fmt_p);
+        size_t str_length = strlen(str);
+        size_t fmt_length = strlen(fmt_p);
         size_t new_fmt_len = parsed_usefmt + str_length + fmt_length + 3;
         char *new_fmt = xmalloc(new_fmt_len * sizeof(char));
         char *new_fmt_p = new_fmt;
@@ -1328,7 +1328,7 @@ int build_stl_str_hl(win_T *wp, char *out, size_t outlen, char *fmt, int use_san
       // in the temporary buffer
       // (including the brackets and null terminating character)
       if (*wp->w_buffer->b_p_ft != NUL
-          && STRLEN(wp->w_buffer->b_p_ft) < TMPLEN - 3) {
+          && strlen(wp->w_buffer->b_p_ft) < TMPLEN - 3) {
         vim_snprintf(buf_tmp, sizeof(buf_tmp), "[%s]",
                      wp->w_buffer->b_p_ft);
         str = buf_tmp;
@@ -1341,7 +1341,7 @@ int build_stl_str_hl(win_T *wp, char *out, size_t outlen, char *fmt, int use_san
       // in the temporary buffer
       // (including the comma and null terminating character)
       if (*wp->w_buffer->b_p_ft != NUL
-          && STRLEN(wp->w_buffer->b_p_ft) < TMPLEN - 2) {
+          && strlen(wp->w_buffer->b_p_ft) < TMPLEN - 2) {
         vim_snprintf(buf_tmp, sizeof(buf_tmp), ",%s", wp->w_buffer->b_p_ft);
         // Uppercase the file extension
         for (char *t = buf_tmp; *t != 0; t++) {
@@ -1561,7 +1561,7 @@ int build_stl_str_hl(win_T *wp, char *out, size_t outlen, char *fmt, int use_san
 
       // Advance the output buffer position to the end of the
       // number we just printed
-      out_p += STRLEN(out_p);
+      out_p += strlen(out_p);
 
       // Otherwise, there was nothing to print so mark the item as empty
     } else {
@@ -1669,7 +1669,7 @@ int build_stl_str_hl(win_T *wp, char *out, size_t outlen, char *fmt, int use_san
 
       if (width + 1 < maxwidth) {
         // Advance the pointer to the end of the string
-        trunc_p = trunc_p + STRLEN(trunc_p);
+        trunc_p = trunc_p + strlen(trunc_p);
       }
 
       // Fill up for half a double-wide character.
@@ -1705,7 +1705,7 @@ int build_stl_str_hl(win_T *wp, char *out, size_t outlen, char *fmt, int use_san
     // add characters at the separate marker (if there is one) to
     // fill up the available space.
   } else if (width < maxwidth
-             && STRLEN(out) + (size_t)(maxwidth - width) + 1 < outlen) {
+             && strlen(out) + (size_t)(maxwidth - width) + 1 < outlen) {
     // Find how many separators there are, which we will use when
     // figuring out how many groups there are.
     int num_separators = 0;
diff --git a/src/nvim/strings.c b/src/nvim/strings.c
index ee6172e7fc..b73221d4da 100644
--- a/src/nvim/strings.c
+++ b/src/nvim/strings.c
@@ -341,7 +341,7 @@ char *strcase_save(const char *const orig, bool upper)
     int newl = utf_char2len(uc);
     if (newl != l) {
       // TODO(philix): use xrealloc() in strcase_save()
-      char *s = xmalloc(STRLEN(res) + (size_t)(1 + newl - l));
+      char *s = xmalloc(strlen(res) + (size_t)(1 + newl - l));
       memcpy(s, res, (size_t)(p - res));
       STRCPY(s + (p - res) + newl, p + l);
       p = s + (p - res);
@@ -504,8 +504,8 @@ bool has_non_ascii_len(const char *const s, const size_t len)
 char *concat_str(const char *restrict str1, const char *restrict str2)
   FUNC_ATTR_NONNULL_RET FUNC_ATTR_MALLOC FUNC_ATTR_NONNULL_ALL
 {
-  size_t l = STRLEN(str1);
-  char *dest = xmalloc(l + STRLEN(str2) + 1);
+  size_t l = strlen(str1);
+  char *dest = xmalloc(l + strlen(str2) + 1);
   STRCPY(dest, str1);
   STRCPY(dest + l, str2);
   return dest;
@@ -1473,7 +1473,7 @@ char *reverse_text(char *s)
   FUNC_ATTR_NONNULL_RET
 {
   // Reverse the pattern.
-  size_t len = STRLEN(s);
+  size_t len = strlen(s);
   char *rev = xmalloc(len + 1);
   size_t rev_i = len;
   for (size_t s_i = 0; s_i < len; s_i++) {
@@ -1498,7 +1498,7 @@ char *reverse_text(char *s)
 char *strrep(const char *src, const char *what, const char *rep)
 {
   char *pos = (char *)src;
-  size_t whatlen = STRLEN(what);
+  size_t whatlen = strlen(what);
 
   // Count occurrences
   size_t count = 0;
@@ -1511,8 +1511,8 @@ char *strrep(const char *src, const char *what, const char *rep)
     return NULL;
   }
 
-  size_t replen = STRLEN(rep);
-  char *ret = xmalloc(STRLEN(src) + count * (replen - whatlen) + 1);
+  size_t replen = strlen(rep);
+  char *ret = xmalloc(strlen(src) + count * (replen - whatlen) + 1);
   char *ptr = ret;
   while ((pos = strstr(src, what)) != NULL) {
     size_t idx = (size_t)(pos - src);
diff --git a/src/nvim/syntax.c b/src/nvim/syntax.c
index ce952147f7..575d475b87 100644
--- a/src/nvim/syntax.c
+++ b/src/nvim/syntax.c
@@ -2295,7 +2295,7 @@ static void update_si_end(stateitem_T *sip, int startcol, bool force)
       // a "oneline" never continues in the next line
       sip->si_ends = true;
       sip->si_m_endpos.lnum = current_lnum;
-      sip->si_m_endpos.col = (colnr_T)STRLEN(syn_getcurline());
+      sip->si_m_endpos.col = (colnr_T)strlen(syn_getcurline());
     } else {
       // continues in the next line
       sip->si_ends = false;
@@ -2646,7 +2646,7 @@ static void syn_add_start_off(lpos_T *result, regmmatch_T *regmatch, synpat_T *s
   if (result->lnum > syn_buf->b_ml.ml_line_count) {
     // a "\n" at the end of the pattern may take us below the last line
     result->lnum = syn_buf->b_ml.ml_line_count;
-    col = (int)STRLEN(ml_get_buf(syn_buf, result->lnum, false));
+    col = (int)strlen(ml_get_buf(syn_buf, result->lnum, false));
   }
   if (off != 0) {
     base = (char_u *)ml_get_buf(syn_buf, result->lnum, false);
@@ -3734,11 +3734,11 @@ static void add_keyword(char *const name, const int id, const int flags,
 {
   char name_folded[MAXKEYWLEN + 1];
   const char *const name_ic = (curwin->w_s->b_syn_ic)
-      ? (char *)str_foldcase((char_u *)name, (int)STRLEN(name), (char_u *)name_folded,
+      ? (char *)str_foldcase((char_u *)name, (int)strlen(name), (char_u *)name_folded,
                              sizeof(name_folded))
       : name;
 
-  keyentry_T *const kp = xmalloc(sizeof(keyentry_T) + STRLEN(name_ic));
+  keyentry_T *const kp = xmalloc(sizeof(keyentry_T) + strlen(name_ic));
   STRCPY(kp->keyword, name_ic);
   kp->k_syn.id = (int16_t)id;
   kp->k_syn.inc_tag = current_syn_inc_tag;
@@ -4063,7 +4063,7 @@ static void syn_cmd_keyword(exarg_T *eap, int syncing)
     }
     if (syn_id != 0) {
       // Allocate a buffer, for removing backslashes in the keyword.
-      keyword_copy = xmalloc(STRLEN(rest) + 1);
+      keyword_copy = xmalloc(strlen(rest) + 1);
     }
     if (keyword_copy != NULL) {
       syn_opt_arg.flags = 0;
@@ -4099,7 +4099,7 @@ static void syn_cmd_keyword(exarg_T *eap, int syncing)
         syn_incl_toplevel(syn_id, &syn_opt_arg.flags);
 
         // 2: Add an entry for each keyword.
-        for (kw = keyword_copy; --cnt >= 0; kw += STRLEN(kw) + 1) {
+        for (kw = keyword_copy; --cnt >= 0; kw += strlen(kw) + 1) {
           for (p = vim_strchr(kw, '[');;) {
             if (p != NULL) {
               *p = NUL;
diff --git a/src/nvim/tag.c b/src/nvim/tag.c
index 36f797da06..a8d8eebb0d 100644
--- a/src/nvim/tag.c
+++ b/src/nvim/tag.c
@@ -1217,7 +1217,7 @@ static int find_tagfunc_tags(char_u *pat, garray_T *ga, int *match_count, int fl
       }
       // Other elements will be stored as "\tKEY:VALUE"
       // Allocate space for the key and the colon
-      len += STRLEN(dict_key) + 1;
+      len += strlen(dict_key) + 1;
     });
 
     if (has_extra) {
diff --git a/src/nvim/terminal.c b/src/nvim/terminal.c
index 46f141492b..326c868be8 100644
--- a/src/nvim/terminal.c
+++ b/src/nvim/terminal.c
@@ -693,7 +693,7 @@ void terminal_paste(long count, char **y_array, size_t y_size)
     return;
   }
   vterm_keyboard_start_paste(curbuf->terminal->vt);
-  size_t buff_len = STRLEN(y_array[0]);
+  size_t buff_len = strlen(y_array[0]);
   char_u *buff = xmalloc(buff_len);
   for (int i = 0; i < count; i++) {  // -V756
     // feed the lines to the terminal
@@ -702,7 +702,7 @@ void terminal_paste(long count, char **y_array, size_t y_size)
         // terminate the previous line
         terminal_send(curbuf->terminal, "\n", 1);
       }
-      size_t len = STRLEN(y_array[j]);
+      size_t len = strlen(y_array[j]);
       if (len > buff_len) {
         buff = xrealloc(buff, len);
         buff_len = len;
diff --git a/src/nvim/textformat.c b/src/nvim/textformat.c
index 5c53f84700..25728ef0f1 100644
--- a/src/nvim/textformat.c
+++ b/src/nvim/textformat.c
@@ -431,7 +431,7 @@ void internal_format(int textwidth, int second_indent, int flags, bool format_on
       // Check if cursor is not past the NUL off the line, cindent
       // may have added or removed indent.
       curwin->w_cursor.col += startcol;
-      len = (colnr_T)STRLEN(get_cursor_line_ptr());
+      len = (colnr_T)strlen(get_cursor_line_ptr());
       if (curwin->w_cursor.col > len) {
         curwin->w_cursor.col = len;
       }
@@ -644,7 +644,7 @@ void auto_format(bool trailblank, bool prev_line)
   // in 'formatoptions' and there is a single character before the cursor.
   // Otherwise the line would be broken and when typing another non-white
   // next they are not joined back together.
-  wasatend = (pos.col == (colnr_T)STRLEN(old));
+  wasatend = (pos.col == (colnr_T)strlen(old));
   if (*old != NUL && !trailblank && wasatend) {
     dec_cursor();
     cc = gchar_cursor();
@@ -698,7 +698,7 @@ void auto_format(bool trailblank, bool prev_line)
   // formatted.
   if (!wasatend && has_format_option(FO_WHITE_PAR)) {
     new = get_cursor_line_ptr();
-    len = (colnr_T)STRLEN(new);
+    len = (colnr_T)strlen(new);
     if (curwin->w_cursor.col == len) {
       pnew = xstrnsave(new, (size_t)len + 2);
       pnew[len] = ' ';
@@ -1115,7 +1115,7 @@ void format_lines(linenr_T line_count, bool avoid_fex)
         }
         first_par_line = false;
         // If the line is getting long, format it next time
-        if (STRLEN(get_cursor_line_ptr()) > (size_t)max_len) {
+        if (strlen(get_cursor_line_ptr()) > (size_t)max_len) {
           force_format = true;
         } else {
           force_format = false;
diff --git a/src/nvim/undo.c b/src/nvim/undo.c
index 891a42380e..0a5a3133df 100644
--- a/src/nvim/undo.c
+++ b/src/nvim/undo.c
@@ -771,7 +771,7 @@ static bool serialize_header(bufinfo_T *bi, char_u *hash)
 
   // Write buffer-specific data.
   undo_write_bytes(bi, (uintmax_t)buf->b_ml.ml_line_count, 4);
-  size_t len = buf->b_u_line_ptr ? STRLEN(buf->b_u_line_ptr) : 0;
+  size_t len = buf->b_u_line_ptr ? strlen(buf->b_u_line_ptr) : 0;
   undo_write_bytes(bi, len, 4);
   if (len > 0 && !undo_write(bi, (char_u *)buf->b_u_line_ptr, len)) {
     return false;
@@ -1034,7 +1034,7 @@ static bool serialize_uep(bufinfo_T *bi, u_entry_T *uep)
   undo_write_bytes(bi, (uintmax_t)uep->ue_size, 4);
 
   for (size_t i = 0; i < (size_t)uep->ue_size; i++) {
-    size_t len = STRLEN(uep->ue_array[i]);
+    size_t len = strlen(uep->ue_array[i]);
     if (!undo_write_bytes(bi, len, 4)) {
       return false;
     }
@@ -2638,7 +2638,7 @@ void ex_undolist(exarg_T *eap)
       vim_snprintf((char *)IObuff, IOSIZE, "%6ld %7d  ", uhp->uh_seq, changes);
       undo_fmt_time((char_u *)IObuff + STRLEN(IObuff), IOSIZE - STRLEN(IObuff), uhp->uh_time);
       if (uhp->uh_save_nr > 0) {
-        while (STRLEN(IObuff) < 33) {
+        while (strlen(IObuff) < 33) {
           STRCAT(IObuff, " ");
         }
         vim_snprintf_add((char *)IObuff, IOSIZE, "  %3ld", uhp->uh_save_nr);
@@ -2995,7 +2995,7 @@ void u_undoline(void)
   ml_replace(curbuf->b_u_line_lnum, curbuf->b_u_line_ptr, true);
   changed_bytes(curbuf->b_u_line_lnum, 0);
   extmark_splice_cols(curbuf, (int)curbuf->b_u_line_lnum - 1, 0, (colnr_T)STRLEN(oldp),
-                      (colnr_T)STRLEN(curbuf->b_u_line_ptr), kExtmarkUndo);
+                      (colnr_T)strlen(curbuf->b_u_line_ptr), kExtmarkUndo);
   xfree(curbuf->b_u_line_ptr);
   curbuf->b_u_line_ptr = (char *)oldp;
 
diff --git a/src/nvim/usercmd.c b/src/nvim/usercmd.c
index 6d6ba2466e..c3cf0b6df8 100644
--- a/src/nvim/usercmd.c
+++ b/src/nvim/usercmd.c
@@ -435,7 +435,7 @@ static void uc_list(char *name, size_t name_len)
       }
 
       msg_outtrans_attr(cmd->uc_name, HL_ATTR(HLF_D));
-      len = (int)STRLEN(cmd->uc_name) + 4;
+      len = (int)strlen(cmd->uc_name) + 4;
 
       do {
         msg_putchar(' ');
@@ -476,14 +476,14 @@ static void uc_list(char *name, size_t name_len)
           // -count=N
           snprintf((char *)IObuff + len, IOSIZE, "%" PRId64 "c",
                    (int64_t)cmd->uc_def);
-          len += (int)STRLEN(IObuff + len);
+          len += (int)strlen(IObuff + len);
         } else if (a & EX_DFLALL) {
           IObuff[len++] = '%';
         } else if (cmd->uc_def >= 0) {
           // -range=N
           snprintf((char *)IObuff + len, IOSIZE, "%" PRId64 "",
                    (int64_t)cmd->uc_def);
-          len += (int)STRLEN(IObuff + len);
+          len += (int)strlen(IObuff + len);
         } else {
           IObuff[len++] = '.';
         }
@@ -498,7 +498,7 @@ static void uc_list(char *name, size_t name_len)
         if (addr_type_complete[j].expand != ADDR_LINES
             && addr_type_complete[j].expand == cmd->uc_addr_type) {
           STRCPY(IObuff + len, addr_type_complete[j].shortname);
-          len += (int)STRLEN(IObuff + len);
+          len += (int)strlen(IObuff + len);
           break;
         }
       }
@@ -511,7 +511,7 @@ static void uc_list(char *name, size_t name_len)
       char *cmd_compl = get_command_complete(cmd->uc_compl);
       if (cmd_compl != NULL) {
         STRCPY(IObuff + len, get_command_complete(cmd->uc_compl));
-        len += (int)STRLEN(IObuff + len);
+        len += (int)strlen(IObuff + len);
       }
 
       do {
@@ -559,7 +559,7 @@ int parse_addr_type_arg(char *value, int vallen, cmd_addr_T *addr_type_arg)
   int i, a, b;
 
   for (i = 0; addr_type_complete[i].expand != ADDR_NONE; i++) {
-    a = (int)STRLEN(addr_type_complete[i].name) == vallen;
+    a = (int)strlen(addr_type_complete[i].name) == vallen;
     b = STRNCMP(value, addr_type_complete[i].name, vallen) == 0;
     if (a && b) {
       *addr_type_arg = addr_type_complete[i].expand;
@@ -607,7 +607,7 @@ int parse_compl_arg(const char *value, int vallen, int *complp, uint32_t *argt,
     if (get_command_complete(i) == NULL) {
       continue;
     }
-    if ((int)STRLEN(command_complete[i]) == valend
+    if ((int)strlen(command_complete[i]) == valend
         && STRNCMP(value, command_complete[i], valend) == 0) {
       *complp = i;
       if (i == EXPAND_BUFFERS) {
@@ -816,7 +816,7 @@ int uc_add_command(char *name, size_t name_len, const char *rep, uint32_t argt,
   char *rep_buf = NULL;
   garray_T *gap;
 
-  replace_termcodes(rep, STRLEN(rep), &rep_buf, 0, NULL, CPO_TO_CPO_FLAGS);
+  replace_termcodes(rep, strlen(rep), &rep_buf, 0, NULL, CPO_TO_CPO_FLAGS);
   if (rep_buf == NULL) {
     // Can't replace termcodes - try using the string as is
     rep_buf = xstrdup(rep);
@@ -837,7 +837,7 @@ int uc_add_command(char *name, size_t name_len, const char *rep, uint32_t argt,
     size_t len;
 
     cmd = USER_CMD_GA(gap, i);
-    len = STRLEN(cmd->uc_name);
+    len = strlen(cmd->uc_name);
     cmp = STRNCMP(name, cmd->uc_name, name_len);
     if (cmp == 0) {
       if (name_len < len) {
@@ -1198,7 +1198,7 @@ static char *uc_split_args(char *arg, char **args, size_t *arglens, size_t argc,
 
 static size_t add_cmd_modifier(char *buf, char *mod_str, bool *multi_mods)
 {
-  size_t result = STRLEN(mod_str);
+  size_t result = strlen(mod_str);
   if (*multi_mods) {
     result++;
   }
@@ -1405,13 +1405,13 @@ static size_t uc_check_code(char *code, size_t len, char *buf, ucmd_T *cmd, exar
 
     switch (quote) {
     case 0:     // No quoting, no splitting
-      result = STRLEN(eap->arg);
+      result = strlen(eap->arg);
       if (buf != NULL) {
         STRCPY(buf, eap->arg);
       }
       break;
     case 1:     // Quote, but don't split
-      result = STRLEN(eap->arg) + 2;
+      result = strlen(eap->arg) + 2;
       for (p = eap->arg; *p; p++) {
         if (*p == '\\' || *p == '"') {
           result++;
@@ -1475,7 +1475,7 @@ static size_t uc_check_code(char *code, size_t len, char *buf, ucmd_T *cmd, exar
     size_t num_len;
 
     snprintf(num_buf, sizeof(num_buf), "%" PRId64, (int64_t)num);
-    num_len = STRLEN(num_buf);
+    num_len = strlen(num_buf);
     result = num_len;
 
     if (quote) {
@@ -1637,7 +1637,7 @@ int do_ucmd(exarg_T *eap, bool preview)
       break;
     }
 
-    totlen += STRLEN(p);            // Add on the trailing characters
+    totlen += strlen(p);            // Add on the trailing characters
     buf = xmalloc(totlen + 1);
   }
 
diff --git a/src/nvim/window.c b/src/nvim/window.c
index 63a6eb9fb6..f6301457f3 100644
--- a/src/nvim/window.c
+++ b/src/nvim/window.c
@@ -746,7 +746,7 @@ void win_set_minimal_style(win_T *wp)
   parse_winhl_opt(wp);
 
   // signcolumn: use 'auto'
-  if (wp->w_p_scl[0] != 'a' || STRLEN(wp->w_p_scl) >= 8) {
+  if (wp->w_p_scl[0] != 'a' || strlen(wp->w_p_scl) >= 8) {
     free_string_option(wp->w_p_scl);
     wp->w_p_scl = xstrdup("auto");
   }
@@ -6467,10 +6467,10 @@ char_u *file_name_in_line(char_u *line, int col, int options, long count, char_u
     // Also accept " line 999" with and without the same translation as
     // used in last_set_msg().
     p = ptr + len;
-    if (STRNCMP(p, line_english, STRLEN(line_english)) == 0) {
-      p += STRLEN(line_english);
-    } else if (STRNCMP(p, line_transl, STRLEN(line_transl)) == 0) {
-      p += STRLEN(line_transl);
+    if (STRNCMP(p, line_english, strlen(line_english)) == 0) {
+      p += strlen(line_english);
+    } else if (STRNCMP(p, line_transl, strlen(line_transl)) == 0) {
+      p += strlen(line_transl);
     } else {
       p = skipwhite(p);
     }