refactor: replace char_u with char 4 (#19987)

* refactor: replace char_u with char

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

66 files changed, 499 insertions, 509 deletions

diff --git a/src/nvim/change.c b/src/nvim/change.c
index fd079f8eef..85ab92e49b 100644
--- a/src/nvim/change.c
+++ b/src/nvim/change.c
@@ -653,9 +653,9 @@ void ins_char_bytes(char *buf, size_t charlen)
       // cells.  May result in adding spaces to fill a gap.
       colnr_T vcol;
       getvcol(curwin, &curwin->w_cursor, NULL, &vcol, NULL);
-      colnr_T new_vcol = vcol + win_chartabsize(curwin, (char *)buf, vcol);
+      colnr_T new_vcol = vcol + win_chartabsize(curwin, buf, vcol);
       while (oldp[col + oldlen] != NUL && vcol < new_vcol) {
-        vcol += win_chartabsize(curwin, (char *)oldp + col + oldlen, vcol);
+        vcol += win_chartabsize(curwin, oldp + col + oldlen, vcol);
         // Don't need to remove a TAB that takes us to the right
         // position.
         if (vcol > new_vcol && oldp[col + oldlen] == TAB) {
diff --git a/src/nvim/charset.c b/src/nvim/charset.c
index 2632279565..4efd8a4ad1 100644
--- a/src/nvim/charset.c
+++ b/src/nvim/charset.c
@@ -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 (char *)skipwhite_len((char_u *)p, STRLEN(p));
+  return skipwhite_len(p, STRLEN(p));
 }
 
 /// Like `skipwhite`, but skip up to `len` characters.
@@ -1168,27 +1168,27 @@ char *skipwhite(const char *const p)
 ///
 /// @return Pointer to character after the skipped whitespace, or the `len`-th
 ///         character in the string.
-char_u *skipwhite_len(const char_u *p, size_t len)
+char *skipwhite_len(const char *p, size_t len)
   FUNC_ATTR_PURE FUNC_ATTR_WARN_UNUSED_RESULT FUNC_ATTR_NONNULL_ALL
   FUNC_ATTR_NONNULL_RET
 {
   for (; len > 0 && ascii_iswhite(*p); len--) {
     p++;
   }
-  return (char_u *)p;
+  return (char *)p;
 }
 
 // getwhitecols: return the number of whitespace
 // columns (bytes) at the start of a given line
 intptr_t getwhitecols_curline(void)
 {
-  return getwhitecols(get_cursor_line_ptr());
+  return getwhitecols((char *)get_cursor_line_ptr());
 }
 
-intptr_t getwhitecols(const char_u *p)
+intptr_t getwhitecols(const char *p)
   FUNC_ATTR_PURE
 {
-  return (char_u *)skipwhite((char *)p) - p;
+  return skipwhite(p) - p;
 }
 
 /// Skip over digits
@@ -1232,10 +1232,10 @@ const char *skipbin(const char *q)
 ///
 /// @return Pointer to the character after the skipped digits and hex
 ///         characters.
-char_u *skiphex(char_u *q)
+char *skiphex(char *q)
   FUNC_ATTR_PURE
 {
-  char_u *p = q;
+  char *p = q;
   while (ascii_isxdigit(*p)) {
     // skip to next non-digit
     p++;
@@ -1248,10 +1248,10 @@ char_u *skiphex(char_u *q)
 /// @param q
 ///
 /// @return Pointer to the digit or (NUL after the string).
-char_u *skiptodigit(char_u *q)
+char *skiptodigit(char *q)
   FUNC_ATTR_PURE
 {
-  char_u *p = q;
+  char *p = q;
   while (*p != NUL && !ascii_isdigit(*p)) {
     // skip to next digit
     p++;
@@ -1282,10 +1282,10 @@ const char *skiptobin(const char *q)
 /// @param q
 ///
 /// @return Pointer to the hex character or (NUL after the string).
-char_u *skiptohex(char_u *q)
+char *skiptohex(char *q)
   FUNC_ATTR_PURE
 {
-  char_u *p = q;
+  char *p = q;
   while (*p != NUL && !ascii_isxdigit(*p)) {
     // skip to next digit
     p++;
@@ -1298,13 +1298,13 @@ char_u *skiptohex(char_u *q)
 /// @param[in]  p  Text to skip over.
 ///
 /// @return Pointer to the next whitespace or NUL character.
-char_u *skiptowhite(const char_u *p)
+char *skiptowhite(const char *p)
   FUNC_ATTR_NONNULL_ALL FUNC_ATTR_PURE
 {
   while (*p != ' ' && *p != '\t' && *p != NUL) {
     p++;
   }
-  return (char_u *)p;
+  return (char *)p;
 }
 
 /// skiptowhite_esc: Like skiptowhite(), but also skip escaped chars
@@ -1329,11 +1329,11 @@ char *skiptowhite_esc(char *p)
 /// @param[in]  p  Text to skip over.
 ///
 /// @return Pointer to the next '\n' or NUL character.
-char_u *skip_to_newline(const char_u *const p)
+char *skip_to_newline(const char *const p)
   FUNC_ATTR_PURE FUNC_ATTR_WARN_UNUSED_RESULT FUNC_ATTR_NONNULL_ALL
   FUNC_ATTR_NONNULL_RET
 {
-  return (char_u *)xstrchrnul((const char *)p, NL);
+  return xstrchrnul(p, NL);
 }
 
 /// Gets a number from a string and skips over it, signalling overflow.
@@ -1422,10 +1422,10 @@ int32_t getdigits_int32(char **pp, bool strict, long def)
 /// Check that "lbuf" is empty or only contains blanks.
 ///
 /// @param  lbuf  line buffer to check
-bool vim_isblankline(char_u *lbuf)
+bool vim_isblankline(char *lbuf)
   FUNC_ATTR_PURE
 {
-  char_u *p = (char_u *)skipwhite((char *)lbuf);
+  char *p = skipwhite(lbuf);
   return *p == NUL || *p == '\r' || *p == '\n';
 }
 
@@ -1664,8 +1664,9 @@ int hex2nr(int c)
 }
 
 /// Convert two hex characters to a byte.
-/// Return -1 if one of the characters is not hex.
-int hexhex2nr(const char_u *p)
+///
+/// @return  -1 if one of the characters is not hex.
+int hexhex2nr(const char *p)
   FUNC_ATTR_PURE
 {
   if (!ascii_isxdigit(p[0]) || !ascii_isxdigit(p[1])) {
@@ -1707,10 +1708,10 @@ bool rem_backslash(const char *str)
 /// Halve the number of backslashes in a file name argument.
 ///
 /// @param p
-void backslash_halve(char_u *p)
+void backslash_halve(char *p)
 {
   for (; *p; p++) {
-    if (rem_backslash((char *)p)) {
+    if (rem_backslash(p)) {
       STRMOVE(p, p + 1);
     }
   }
@@ -1721,11 +1722,11 @@ void backslash_halve(char_u *p)
 /// @param p
 ///
 /// @return String with the number of backslashes halved.
-char_u *backslash_halve_save(const char_u *p)
+char *backslash_halve_save(const char *p)
   FUNC_ATTR_NONNULL_ALL FUNC_ATTR_NONNULL_RET
 {
   // TODO(philix): simplify and improve backslash_halve_save algorithm
-  char_u *res = vim_strsave(p);
+  char *res = xstrdup(p);
   backslash_halve(res);
   return res;
 }
diff --git a/src/nvim/cmdexpand.c b/src/nvim/cmdexpand.c
index dbf169c801..5c54404aab 100644
--- a/src/nvim/cmdexpand.c
+++ b/src/nvim/cmdexpand.c
@@ -387,7 +387,7 @@ static char_u *ExpandOne_start(int mode, expand_T *xp, char_u *str, int options)
 }
 
 /// Return the longest common part in the list of cmdline completion matches.
-static char_u *find_longest_match(expand_T *xp, int options)
+static char *find_longest_match(expand_T *xp, int options)
 {
   size_t len = 0;
 
@@ -417,7 +417,7 @@ static char_u *find_longest_match(expand_T *xp, int options)
     }
   }
 
-  return (char_u *)xstrndup(xp->xp_files[0], len);
+  return xstrndup(xp->xp_files[0], len);
 }
 
 /// Do wildcard expansion on the string 'str'.
@@ -500,7 +500,7 @@ char_u *ExpandOne(expand_T *xp, char_u *str, char_u *orig, int options, int mode
 
   // Find longest common part
   if (mode == WILD_LONGEST && xp->xp_numfiles > 0) {
-    ss = find_longest_match(xp, options);
+    ss = (char_u *)find_longest_match(xp, options);
     findex = -1;  // next p_wc gets first one
   }
 
@@ -670,7 +670,7 @@ int showmatches(expand_T *xp, int wildmenu)
       lastlen = 999;
       for (k = i; k < num_files; k += lines) {
         if (xp->xp_context == EXPAND_TAGS_LISTFILES) {
-          msg_outtrans_attr((char_u *)files_found[k], HL_ATTR(HLF_D));
+          msg_outtrans_attr(files_found[k], HL_ATTR(HLF_D));
           p = (char_u *)files_found[k] + STRLEN(files_found[k]) + 1;
           msg_advance(maxlen + 1);
           msg_puts((const char *)p);
@@ -691,15 +691,15 @@ int showmatches(expand_T *xp, int wildmenu)
             // $HOME has been replaced with ~/.
             char_u *exp_path = expand_env_save_opt((char_u *)files_found[k], true);
             char_u *path = exp_path != NULL ? exp_path : (char_u *)files_found[k];
-            char_u *halved_slash = backslash_halve_save(path);
-            j = os_isdir(halved_slash);
+            char_u *halved_slash = (char_u *)backslash_halve_save((char *)path);
+            j = os_isdir((char *)halved_slash);
             xfree(exp_path);
             if (halved_slash != path) {
               xfree(halved_slash);
             }
           } else {
             // Expansion was done here, file names are literal.
-            j = os_isdir((char_u *)files_found[k]);
+            j = os_isdir(files_found[k]);
           }
           if (showtail) {
             p = (char_u *)L_SHOWFILE(k);
@@ -711,7 +711,7 @@ int showmatches(expand_T *xp, int wildmenu)
           j = false;
           p = (char_u *)L_SHOWFILE(k);
         }
-        lastlen = msg_outtrans_attr(p, j ? attr : 0);
+        lastlen = msg_outtrans_attr((char *)p, j ? attr : 0);
       }
       if (msg_col > 0) {        // when not wrapped around
         msg_clr_eos();
@@ -1239,7 +1239,7 @@ static const char *set_context_by_cmdname(const char *cmd, cmdidx_T cmdidx, cons
     if (*arg == NUL || !ends_excmd(*arg)) {
       // also complete "None"
       set_context_in_echohl_cmd(xp, arg);
-      arg = (const char *)skipwhite((char *)skiptowhite((const char_u *)arg));
+      arg = (const char *)skipwhite(skiptowhite(arg));
       if (*arg != NUL) {
         xp->xp_context = EXPAND_NOTHING;
         arg = (const char *)skip_regexp((char *)arg + 1, (uint8_t)(*arg), p_magic, NULL);
@@ -1592,7 +1592,7 @@ static const char *set_context_by_cmdname(const char *cmd, cmdidx_T cmdidx, cons
 
 #ifdef HAVE_WORKING_LIBINTL
   case CMD_language:
-    p = (const char *)skiptowhite((const char_u *)arg);
+    p = (const char *)skiptowhite(arg);
     if (*p == NUL) {
       xp->xp_context = EXPAND_LANGUAGE;
       xp->xp_pattern = (char *)arg;
@@ -2161,19 +2161,19 @@ static int ExpandFromContext(expand_T *xp, char_u *pat, int *num_file, char ***f
   }
   if (xp->xp_context == EXPAND_COLORS) {
     char *directories[] = { "colors", NULL };
-    return ExpandRTDir(pat, DIP_START + DIP_OPT + DIP_LUA, num_file, file, directories);
+    return ExpandRTDir((char *)pat, DIP_START + DIP_OPT + DIP_LUA, num_file, file, directories);
   }
   if (xp->xp_context == EXPAND_COMPILER) {
     char *directories[] = { "compiler", NULL };
-    return ExpandRTDir(pat, DIP_LUA, num_file, file, directories);
+    return ExpandRTDir((char *)pat, DIP_LUA, num_file, file, directories);
   }
   if (xp->xp_context == EXPAND_OWNSYNTAX) {
     char *directories[] = { "syntax", NULL };
-    return ExpandRTDir(pat, 0, num_file, file, directories);
+    return ExpandRTDir((char *)pat, 0, num_file, file, directories);
   }
   if (xp->xp_context == EXPAND_FILETYPE) {
     char *directories[] = { "syntax", "indent", "ftplugin", NULL };
-    return ExpandRTDir(pat, DIP_LUA, num_file, file, directories);
+    return ExpandRTDir((char *)pat, DIP_LUA, num_file, file, directories);
   }
   if (xp->xp_context == EXPAND_USER_LIST) {
     return ExpandUserList(xp, num_file, file);
@@ -2182,7 +2182,7 @@ static int ExpandFromContext(expand_T *xp, char_u *pat, int *num_file, char ***f
     return ExpandUserLua(xp, num_file, file);
   }
   if (xp->xp_context == EXPAND_PACKADD) {
-    return ExpandPackAddDir(pat, num_file, file);
+    return ExpandPackAddDir((char *)pat, num_file, file);
   }
 
   // When expanding a function name starting with s:, match the <SNR>nr_
@@ -2573,7 +2573,7 @@ static int ExpandUserLua(expand_T *xp, int *num_file, char ***file)
 
 /// Expand `file` for all comma-separated directories in `path`.
 /// Adds matches to `ga`.
-void globpath(char *path, char_u *file, garray_T *ga, int expand_options)
+void globpath(char *path, char *file, garray_T *ga, int expand_options)
 {
   expand_T xpc;
   ExpandInit(&xpc);
diff --git a/src/nvim/debugger.c b/src/nvim/debugger.c
index 9fdeebf68a..36df62b502 100644
--- a/src/nvim/debugger.c
+++ b/src/nvim/debugger.c
@@ -718,9 +718,9 @@ void ex_breaklist(exarg_T *eap)
 /// @param file  true for a file, false for a function
 /// @param fname  file or function name
 /// @param after  after this line number
-linenr_T dbg_find_breakpoint(bool file, char_u *fname, linenr_T after)
+linenr_T dbg_find_breakpoint(bool file, char *fname, linenr_T after)
 {
-  return debuggy_find(file, fname, after, &dbg_breakp, NULL);
+  return debuggy_find(file, (char_u *)fname, after, &dbg_breakp, NULL);
 }
 
 /// @param file     true for a file, false for a function
@@ -728,9 +728,9 @@ linenr_T dbg_find_breakpoint(bool file, char_u *fname, linenr_T after)
 /// @param fp[out]  forceit
 ///
 /// @returns true if profiling is on for a function or sourced file.
-bool has_profiling(bool file, char_u *fname, bool *fp)
+bool has_profiling(bool file, char *fname, bool *fp)
 {
-  return debuggy_find(file, fname, (linenr_T)0, &prof_ga, fp)
+  return debuggy_find(file, (char_u *)fname, (linenr_T)0, &prof_ga, fp)
          != (linenr_T)0;
 }
 
@@ -825,9 +825,9 @@ static linenr_T debuggy_find(bool file, char_u *fname, linenr_T after, garray_T
 }
 
 /// Called when a breakpoint was encountered.
-void dbg_breakpoint(char_u *name, linenr_T lnum)
+void dbg_breakpoint(char *name, linenr_T lnum)
 {
   // We need to check if this line is actually executed in do_one_cmd()
-  debug_breakpoint_name = name;
+  debug_breakpoint_name = (char_u *)name;
   debug_breakpoint_lnum = lnum;
 }
diff --git a/src/nvim/digraph.c b/src/nvim/digraph.c
index de2dd09d1c..e4528f9038 100644
--- a/src/nvim/digraph.c
+++ b/src/nvim/digraph.c
@@ -1695,7 +1695,7 @@ static void digraph_header(const char *msg)
   if (msg_col > 0) {
     msg_putchar('\n');
   }
-  msg_outtrans_attr((const char_u *)msg, HL_ATTR(HLF_CM));
+  msg_outtrans_attr(msg, HL_ATTR(HLF_CM));
   msg_putchar('\n');
 }
 
@@ -1856,7 +1856,7 @@ static void printdigraph(const digr_T *dp, result_T *previous)
     p += utf_char2bytes(dp->result, (char *)p);
 
     *p = NUL;
-    msg_outtrans_attr(buf, HL_ATTR(HLF_8));
+    msg_outtrans_attr((char *)buf, HL_ATTR(HLF_8));
     p = buf;
     if (char2cells(dp->result) == 1) {
       *p++ = ' ';
@@ -2096,10 +2096,10 @@ void ex_loadkeymap(exarg_T *eap)
 
     if ((*p != '"') && (*p != NUL)) {
       kmap_T *kp = GA_APPEND_VIA_PTR(kmap_T, &curbuf->b_kmap_ga);
-      s = skiptowhite(p);
+      s = (char_u *)skiptowhite((char *)p);
       kp->from = vim_strnsave(p, (size_t)(s - p));
       p = (char_u *)skipwhite((char *)s);
-      s = skiptowhite(p);
+      s = (char_u *)skiptowhite((char *)p);
       kp->to = vim_strnsave(p, (size_t)(s - p));
 
       if ((STRLEN(kp->from) + STRLEN(kp->to) >= KMAP_LLEN)
diff --git a/src/nvim/drawline.c b/src/nvim/drawline.c
index b6654699d8..b6c4400c60 100644
--- a/src/nvim/drawline.c
+++ b/src/nvim/drawline.c
@@ -870,7 +870,7 @@ int win_line(win_T *wp, linenr_T lnum, int startrow, int endrow, bool nochange,
   if (has_spell && !number_only) {
     // For checking first word with a capital skip white space.
     if (cap_col == 0) {
-      cap_col = (int)getwhitecols(line);
+      cap_col = (int)getwhitecols((char *)line);
     }
 
     // To be able to spell-check over line boundaries copy the end of the
@@ -1171,7 +1171,7 @@ int win_line(win_T *wp, linenr_T lnum, int startrow, int endrow, bool nochange,
               if (wp->w_p_rl) {                       // reverse line numbers
                 // like rl_mirror(), but keep the space at the end
                 char_u *p2 = (char_u *)skipwhite((char *)extra);
-                p2 = skiptowhite(p2) - 1;
+                p2 = (char_u *)skiptowhite((char *)p2) - 1;
                 for (char_u *p1 = (char_u *)skipwhite((char *)extra); p1 < p2; p1++, p2--) {
                   const char_u t = *p1;
                   *p1 = *p2;
diff --git a/src/nvim/edit.c b/src/nvim/edit.c
index b0174de01f..aee8389900 100644
--- a/src/nvim/edit.c
+++ b/src/nvim/edit.c
@@ -2698,12 +2698,12 @@ int cursor_down(long n, int upd_topline)
 /// @param no_esc  Don't add an ESC at the end
 int stuff_inserted(int c, long count, int no_esc)
 {
-  char_u *esc_ptr;
-  char_u *ptr;
-  char_u *last_ptr;
-  char_u last = NUL;
+  char *esc_ptr;
+  char *ptr;
+  char *last_ptr;
+  char last = NUL;
 
-  ptr = get_last_insert();
+  ptr = (char *)get_last_insert();
   if (ptr == NULL) {
     emsg(_(e_noinstext));
     return FAIL;
@@ -2713,7 +2713,7 @@ int stuff_inserted(int c, long count, int no_esc)
   if (c != NUL) {
     stuffcharReadbuff(c);
   }
-  if ((esc_ptr = STRRCHR(ptr, ESC)) != NULL) {
+  if ((esc_ptr = strrchr(ptr, ESC)) != NULL) {
     // remove the ESC.
     *esc_ptr = NUL;
   }
diff --git a/src/nvim/eval.c b/src/nvim/eval.c
index f89b06843a..508d7cf491 100644
--- a/src/nvim/eval.c
+++ b/src/nvim/eval.c
@@ -2042,7 +2042,7 @@ void set_context_for_expression(expand_T *xp, char *arg, cmdidx_T cmdidx)
        || cmdidx == CMD_echomsg)
       && xp->xp_context == EXPAND_EXPRESSION) {
     for (;;) {
-      char *const n = (char *)skiptowhite((char_u *)arg);
+      char *const n = skiptowhite(arg);
 
       if (n == arg || ascii_iswhite_or_nul(*skipwhite(n))) {
         break;
@@ -2658,7 +2658,7 @@ static int eval5(char **arg, typval_T *rettv, int evaluate)
           tv_clear(&var2);
           return FAIL;
         }
-        p = (char *)concat_str((const char_u *)s1, (const char_u *)s2);
+        p = concat_str(s1, s2);
         tv_clear(rettv);
         rettv->v_type = VAR_STRING;
         rettv->vval.v_string = p;
@@ -7400,7 +7400,7 @@ hashtab_T *find_var_ht_dict(const char *name, const size_t name_len, const char
         bool should_free;
         // should_free is ignored as script_sctx will be resolved to a fnmae
         // & new_script_item will consume it.
-        char *sc_name = (char *)get_scriptname(last_set, &should_free);
+        char *sc_name = get_scriptname(last_set, &should_free);
         new_script_item(sc_name, &current_sctx.sc_sid);
       }
     }
@@ -7527,9 +7527,9 @@ int var_item_copy(const vimconv_T *const conv, typval_T *const from, typval_T *c
     } else {
       to->v_type = VAR_STRING;
       to->v_lock = VAR_UNLOCKED;
-      if ((to->vval.v_string = (char *)string_convert((vimconv_T *)conv,
-                                                      (char_u *)from->vval.v_string,
-                                                      NULL))
+      if ((to->vval.v_string = string_convert((vimconv_T *)conv,
+                                              from->vval.v_string,
+                                              NULL))
           == NULL) {
         to->vval.v_string = xstrdup(from->vval.v_string);
       }
@@ -7980,7 +7980,7 @@ void option_last_set_msg(LastSet last_set)
 {
   if (last_set.script_ctx.sc_sid != 0) {
     bool should_free;
-    char *p = (char *)get_scriptname(last_set, &should_free);
+    char *p = get_scriptname(last_set, &should_free);
     verbose_enter();
     msg_puts(_("\n\tLast set from "));
     msg_puts(p);
@@ -8077,7 +8077,7 @@ repeat:
     }
 
     // Append a path separator to a directory.
-    if (os_isdir((char_u *)(*fnamep))) {
+    if (os_isdir(*fnamep)) {
       // Make room for one or two extra characters.
       *fnamep = xstrnsave(*fnamep, STRLEN(*fnamep) + 2);
       xfree(*bufp);          // free any allocated file name
diff --git a/src/nvim/eval/executor.c b/src/nvim/eval/executor.c
index b461456a3a..0e0d0fe696 100644
--- a/src/nvim/eval/executor.c
+++ b/src/nvim/eval/executor.c
@@ -108,8 +108,7 @@ int eexe_mod_op(typval_T *const tv1, const typval_T *const tv2, const char *cons
         const char *tvs = tv_get_string(tv1);
         char numbuf[NUMBUFLEN];
         char *const s =
-          (char *)concat_str((const char_u *)tvs, (const char_u *)tv_get_string_buf(tv2,
-                                                                                    numbuf));
+          concat_str(tvs, tv_get_string_buf(tv2, numbuf));
         tv_clear(tv1);
         tv1->v_type = VAR_STRING;
         tv1->vval.v_string = s;
diff --git a/src/nvim/eval/funcs.c b/src/nvim/eval/funcs.c
index c442f5c465..f21011d22b 100644
--- a/src/nvim/eval/funcs.c
+++ b/src/nvim/eval/funcs.c
@@ -2210,7 +2210,7 @@ static void f_filereadable(typval_T *argvars, typval_T *rettv, EvalFuncData fptr
 {
   const char *const p = tv_get_string(&argvars[0]);
   rettv->vval.v_number =
-    (*p && !os_isdir((const char_u *)p) && os_file_is_readable(p));
+    (*p && !os_isdir(p) && os_file_is_readable(p));
 }
 
 /// @return  0 for not writable
@@ -2888,7 +2888,7 @@ static void f_getfsize(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
   FileInfo file_info;
   if (os_fileinfo(fname, &file_info)) {
     uint64_t filesize = os_fileinfo_size(&file_info);
-    if (os_isdir((const char_u *)fname)) {
+    if (os_isdir(fname)) {
       rettv->vval.v_number = 0;
     } else {
       rettv->vval.v_number = (varnumber_T)filesize;
@@ -3491,7 +3491,7 @@ static void f_globpath(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
   if (file != NULL && !error) {
     garray_T ga;
     ga_init(&ga, (int)sizeof(char_u *), 10);
-    globpath((char *)tv_get_string(&argvars[0]), (char_u *)file, &ga, flags);
+    globpath((char *)tv_get_string(&argvars[0]), (char *)file, &ga, flags);
 
     if (rettv->v_type == VAR_STRING) {
       rettv->vval.v_string = ga_concat_strings_sep(&ga, "\n");
@@ -3874,7 +3874,7 @@ static void f_iconv(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
   if (vimconv.vc_type == CONV_NONE) {
     rettv->vval.v_string = xstrdup(str);
   } else {
-    rettv->vval.v_string = (char *)string_convert(&vimconv, (char_u *)str, NULL);
+    rettv->vval.v_string = string_convert(&vimconv, (char *)str, NULL);
   }
 
   convert_setup(&vimconv, NULL, NULL);
@@ -4131,7 +4131,7 @@ static void f_invert(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
 /// "isdirectory()" function
 static void f_isdirectory(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
 {
-  rettv->vval.v_number = os_isdir((const char_u *)tv_get_string(&argvars[0]));
+  rettv->vval.v_number = os_isdir(tv_get_string(&argvars[0]));
 }
 
 /// "islocked()" function
@@ -4458,7 +4458,7 @@ static void f_jobstart(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
     if (new_cwd && *new_cwd != NUL) {
       cwd = new_cwd;
       // The new cwd must be a directory.
-      if (!os_isdir((const char_u *)cwd)) {
+      if (!os_isdir(cwd)) {
         semsg(_(e_invarg2), "expected valid directory");
         shell_free_argv(argv);
         return;
@@ -5891,7 +5891,7 @@ static void f_readfile(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
   // their own about CR-LF conversion.
   const char *const fname = tv_get_string(&argvars[0]);
 
-  if (os_isdir((const char_u *)fname)) {
+  if (os_isdir(fname)) {
     semsg(_(e_isadir2), fname);
     return;
   }
@@ -6343,7 +6343,7 @@ static void f_resolve(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
         if (*q != NUL) {
           cpy = remain;
           remain = (remain
-                    ? (char *)concat_str((char_u *)q - 1, (char_u *)remain)
+                    ? concat_str(q - 1, remain)
                     : xstrdup(q - 1));
           xfree(cpy);
           q[-1] = NUL;
@@ -6402,7 +6402,7 @@ static void f_resolve(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
                        && (p[2] == NUL
                            || vim_ispathsep(p[2])))))) {
         // Prepend "./".
-        cpy = (char *)concat_str((const char_u *)"./", (const char_u *)p);
+        cpy = concat_str("./", p);
         xfree(p);
         p = cpy;
       } else if (!is_relative_to_current) {
@@ -8339,7 +8339,7 @@ static void f_strftime(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
     char *enc = (char *)enc_locale();
     convert_setup(&conv, p_enc, enc);
     if (conv.vc_type != CONV_NONE) {
-      p = (char *)string_convert(&conv, (char_u *)p, NULL);
+      p = string_convert(&conv, p, NULL);
     }
     char result_buf[256];
     if (p != NULL) {
@@ -8353,7 +8353,7 @@ static void f_strftime(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
     }
     convert_setup(&conv, enc, p_enc);
     if (conv.vc_type != CONV_NONE) {
-      rettv->vval.v_string = (char *)string_convert(&conv, (char_u *)result_buf, NULL);
+      rettv->vval.v_string = string_convert(&conv, result_buf, NULL);
     } else {
       rettv->vval.v_string = xstrdup(result_buf);
     }
@@ -8599,7 +8599,7 @@ static void f_strptime(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
   char *enc = (char *)enc_locale();
   convert_setup(&conv, p_enc, enc);
   if (conv.vc_type != CONV_NONE) {
-    fmt = (char *)string_convert(&conv, (char_u *)fmt, NULL);
+    fmt = string_convert(&conv, fmt, NULL);
   }
   if (fmt == NULL
       || os_strptime(str, fmt, &tmval) == NULL
@@ -9070,7 +9070,7 @@ static void f_tagfiles(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
 
   bool first = true;
   tagname_T tn;
-  while (get_tagfname(&tn, first, (char_u *)fname) == OK) {
+  while (get_tagfname(&tn, first, fname) == OK) {
     tv_list_append_string(rettv->vval.v_list, fname, -1);
     first = false;
   }
@@ -9148,7 +9148,7 @@ static void f_termopen(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
     if (new_cwd && *new_cwd != NUL) {
       cwd = new_cwd;
       // The new cwd must be a directory.
-      if (!os_isdir((const char_u *)cwd)) {
+      if (!os_isdir(cwd)) {
         semsg(_(e_invarg2), "expected valid directory");
         shell_free_argv(argv);
         return;
diff --git a/src/nvim/eval/typval.c b/src/nvim/eval/typval.c
index 152c2eff8f..d5b2b1f2ae 100644
--- a/src/nvim/eval/typval.c
+++ b/src/nvim/eval/typval.c
@@ -2533,7 +2533,7 @@ dict_T *tv_dict_copy(const vimconv_T *const conv, dict_T *const orig, const bool
       new_di = tv_dict_item_alloc((const char *)di->di_key);
     } else {
       size_t len = STRLEN(di->di_key);
-      char *const key = (char *)string_convert(conv, di->di_key, &len);
+      char *const key = (char *)string_convert(conv, (char *)di->di_key, &len);
       if (key == NULL) {
         new_di = tv_dict_item_alloc_len((const char *)di->di_key, len);
       } else {
diff --git a/src/nvim/eval/userfunc.c b/src/nvim/eval/userfunc.c
index 2a48de5e41..b9a94a971b 100644
--- a/src/nvim/eval/userfunc.c
+++ b/src/nvim/eval/userfunc.c
@@ -409,7 +409,7 @@ void emsg_funcname(char *ermsg, const char_u *name)
   char_u *p;
 
   if (*name == K_SPECIAL) {
-    p = concat_str((char_u *)"<SNR>", name + 3);
+    p = (char_u *)concat_str("<SNR>", (char *)name + 3);
   } else {
     p = (char_u *)name;
   }
@@ -863,7 +863,7 @@ void call_user_func(ufunc_T *fp, int argcount, typval_T *argvars, typval_T *rett
   fc->rettv = rettv;
   fc->level = ex_nesting_level;
   // Check if this function has a breakpoint.
-  fc->breakpoint = dbg_find_breakpoint(false, fp->uf_name, (linenr_T)0);
+  fc->breakpoint = dbg_find_breakpoint(false, (char *)fp->uf_name, (linenr_T)0);
   fc->dbg_tick = debug_tick;
 
   // Set up fields for closure.
@@ -1058,7 +1058,7 @@ void call_user_func(ufunc_T *fp, int argcount, typval_T *argvars, typval_T *rett
 
   bool func_not_yet_profiling_but_should =
     do_profiling_yes
-    && !fp->uf_profiling && has_profiling(false, fp->uf_name, NULL);
+    && !fp->uf_profiling && has_profiling(false, (char *)fp->uf_name, NULL);
 
   if (func_not_yet_profiling_but_should) {
     started_profiling = true;
@@ -2332,7 +2332,7 @@ void ex_function(exarg_T *eap)
       }
 
       // heredoc: Check for ":python <<EOF", ":lua <<EOF", etc.
-      arg = (char_u *)skipwhite((char *)skiptowhite(p));
+      arg = (char_u *)skipwhite(skiptowhite((char *)p));
       if (arg[0] == '<' && arg[1] == '<'
           && ((p[0] == 'p' && p[1] == 'y'
                && (!ASCII_ISALNUM(p[2]) || p[2] == 't'
@@ -2359,12 +2359,12 @@ void ex_function(exarg_T *eap)
 
       // Check for ":let v =<< [trim] EOF"
       //       and ":let [a, b] =<< [trim] EOF"
-      arg = (char_u *)skipwhite((char *)skiptowhite(p));
+      arg = (char_u *)skipwhite(skiptowhite((char *)p));
       if (*arg == '[') {
         arg = (char_u *)vim_strchr((char *)arg, ']');
       }
       if (arg != NULL) {
-        arg = (char_u *)skipwhite((char *)skiptowhite(arg));
+        arg = (char_u *)skipwhite(skiptowhite((char *)arg));
         if (arg[0] == '='
             && arg[1] == '<'
             && arg[2] == '<'
@@ -2379,7 +2379,7 @@ void ex_function(exarg_T *eap)
             heredoc_trimmed =
               vim_strnsave(theline, (size_t)((char_u *)skipwhite((char *)theline) - theline));
           }
-          skip_until = vim_strnsave(p, (size_t)(skiptowhite(p) - p));
+          skip_until = vim_strnsave(p, (size_t)((char_u *)skiptowhite((char *)p) - p));
           do_concat = false;
           is_heredoc = true;
         }
@@ -3105,16 +3105,17 @@ int do_return(exarg_T *eap, int reanimate, int is_cmd, void *rettv)
 
 /// Generate a return command for producing the value of "rettv".  The result
 /// is an allocated string.  Used by report_pending() for verbose messages.
-char_u *get_return_cmd(void *rettv)
+char *get_return_cmd(void *rettv)
 {
-  char_u *s = NULL;
-  char_u *tofree = NULL;
+  char *s = NULL;
+  char *tofree = NULL;
 
   if (rettv != NULL) {
-    tofree = s = (char_u *)encode_tv2echo((typval_T *)rettv, NULL);
+    tofree = encode_tv2echo((typval_T *)rettv, NULL);
+    s = encode_tv2echo((typval_T *)rettv, NULL);
   }
   if (s == NULL) {
-    s = (char_u *)"";
+    s = "";
   }
 
   STRCPY(IObuff, ":return ");
@@ -3123,7 +3124,7 @@ char_u *get_return_cmd(void *rettv)
     STRCPY(IObuff + IOSIZE - 4, "...");
   }
   xfree(tofree);
-  return vim_strsave(IObuff);
+  return (char *)vim_strsave(IObuff);
 }
 
 /// Get next function line.
@@ -3134,12 +3135,12 @@ char *get_func_line(int c, void *cookie, int indent, bool do_concat)
 {
   funccall_T *fcp = (funccall_T *)cookie;
   ufunc_T *fp = fcp->func;
-  char_u *retval;
+  char *retval;
   garray_T *gap;    // growarray with function lines
 
   // If breakpoints have been added/deleted need to check for it.
   if (fcp->dbg_tick != debug_tick) {
-    fcp->breakpoint = dbg_find_breakpoint(false, fp->uf_name, SOURCING_LNUM);
+    fcp->breakpoint = dbg_find_breakpoint(false, (char *)fp->uf_name, SOURCING_LNUM);
     fcp->dbg_tick = debug_tick;
   }
   if (do_profiling == PROF_YES) {
@@ -3159,7 +3160,7 @@ char *get_func_line(int c, void *cookie, int indent, bool do_concat)
     if (fcp->linenr >= gap->ga_len) {
       retval = NULL;
     } else {
-      retval = (char_u *)xstrdup(((char **)(gap->ga_data))[fcp->linenr++]);
+      retval = xstrdup(((char **)(gap->ga_data))[fcp->linenr++]);
       SOURCING_LNUM = fcp->linenr;
       if (do_profiling == PROF_YES) {
         func_line_start(cookie);
@@ -3169,13 +3170,13 @@ char *get_func_line(int c, void *cookie, int indent, bool do_concat)
 
   // Did we encounter a breakpoint?
   if (fcp->breakpoint != 0 && fcp->breakpoint <= SOURCING_LNUM) {
-    dbg_breakpoint(fp->uf_name, SOURCING_LNUM);
+    dbg_breakpoint((char *)fp->uf_name, SOURCING_LNUM);
     // Find next breakpoint.
-    fcp->breakpoint = dbg_find_breakpoint(false, fp->uf_name, SOURCING_LNUM);
+    fcp->breakpoint = dbg_find_breakpoint(false, (char *)fp->uf_name, SOURCING_LNUM);
     fcp->dbg_tick = debug_tick;
   }
 
-  return (char *)retval;
+  return retval;
 }
 
 /// @return  true if the currently active function should be ended, because a
diff --git a/src/nvim/eval/vars.c b/src/nvim/eval/vars.c
index e73bba16e2..75410d40d8 100644
--- a/src/nvim/eval/vars.c
+++ b/src/nvim/eval/vars.c
@@ -81,7 +81,7 @@ static list_T *heredoc_get(exarg_T *eap, char *cmd)
   // The marker is the next word.
   if (*cmd != NUL && *cmd != '"') {
     marker = skipwhite(cmd);
-    p = (char *)skiptowhite((char_u *)marker);
+    p = skiptowhite(marker);
     if (*skipwhite(p) != NUL && *skipwhite(p) != '"') {
       semsg(_(e_trailing_arg), p);
       return NULL;
@@ -587,7 +587,7 @@ static char *ex_let_one(char *arg, typval_T *const tv, const bool copy, const bo
           char *s = vim_getenv(name);
 
           if (s != NULL) {
-            tofree = (char *)concat_str((const char_u *)s, (const char_u *)p);
+            tofree = concat_str(s, p);
             p = (const char *)tofree;
             xfree(s);
           }
@@ -663,8 +663,7 @@ static char *ex_let_one(char *arg, typval_T *const tv, const bool copy, const bo
           } else if (opt_type == gov_string && stringval != NULL && s != NULL) {
             // string
             char *const oldstringval = stringval;
-            stringval = (char *)concat_str((const char_u *)stringval,
-                                           (const char_u *)s);
+            stringval = concat_str(stringval, s);
             xfree(oldstringval);
             s = stringval;
           }
@@ -705,7 +704,7 @@ static char *ex_let_one(char *arg, typval_T *const tv, const bool copy, const bo
       if (p != NULL && op != NULL && *op == '.') {
         s = get_reg_contents(*arg == '@' ? '"' : *arg, kGRegExprSrc);
         if (s != NULL) {
-          ptofree = (char *)concat_str((char_u *)s, (const char_u *)p);
+          ptofree = concat_str(s, p);
           p = (const char *)ptofree;
           xfree(s);
         }
diff --git a/src/nvim/ex_cmds.c b/src/nvim/ex_cmds.c
index ba6594fd7a..fc753cf65c 100644
--- a/src/nvim/ex_cmds.c
+++ b/src/nvim/ex_cmds.c
@@ -586,11 +586,11 @@ void ex_sort(exarg_T *eap)
       p = s + start_col;
       if (sort_nr) {
         if (sort_what & STR2NR_HEX) {
-          s = (char *)skiptohex((char_u *)p);
+          s = skiptohex(p);
         } else if (sort_what & STR2NR_BIN) {
           s = (char *)skiptobin(p);
         } else {
-          s = (char *)skiptodigit((char_u *)p);
+          s = skiptodigit(p);
         }
         if (s > p && s[-1] == '-') {
           s--;  // include preceding negative sign
@@ -2006,7 +2006,7 @@ int check_overwrite(exarg_T *eap, buf_T *buf, char *fname, char *ffname, int oth
     if (!eap->forceit && !eap->append) {
 #ifdef UNIX
       // It is possible to open a directory on Unix.
-      if (os_isdir((char_u *)ffname)) {
+      if (os_isdir(ffname)) {
         semsg(_(e_isadir2), ffname);
         return FAIL;
       }
@@ -3940,8 +3940,7 @@ static int do_sub(exarg_T *eap, proftime_T timeout, long cmdpreview_ns, handle_T
                 // what matches.  Temporarily replace the line
                 // and change it back afterwards.
                 orig_line = (char *)vim_strsave(ml_get(lnum));
-                char *new_line = (char *)concat_str((char_u *)new_start,
-                                                    (char_u *)sub_firstline + copycol);
+                char *new_line = concat_str(new_start, sub_firstline + copycol);
 
                 // Position the cursor relative to the end of the line, the
                 // previous substitute may have inserted or deleted characters
@@ -4939,7 +4938,7 @@ char *skip_vimgrep_pat(char *p, char **s, int *flags)
     if (s != NULL) {
       *s = p;
     }
-    p = (char *)skiptowhite((char_u *)p);
+    p = skiptowhite(p);
     if (s != NULL && *p != NUL) {
       *p++ = NUL;
     }
diff --git a/src/nvim/ex_docmd.c b/src/nvim/ex_docmd.c
index 08709ec228..1fa14f4e4f 100644
--- a/src/nvim/ex_docmd.c
+++ b/src/nvim/ex_docmd.c
@@ -462,7 +462,7 @@ int do_cmdline(char *cmdline, LineGetter fgetline, void *cookie, int flags)
       if (breakpoint != NULL && dbg_tick != NULL
           && *dbg_tick != debug_tick) {
         *breakpoint = dbg_find_breakpoint(getline_equal(fgetline, cookie, getsourceline),
-                                          (char_u *)fname, SOURCING_LNUM);
+                                          fname, SOURCING_LNUM);
         *dbg_tick = debug_tick;
       }
 
@@ -471,10 +471,10 @@ int do_cmdline(char *cmdline, LineGetter fgetline, void *cookie, int flags)
 
       // Did we encounter a breakpoint?
       if (breakpoint != NULL && *breakpoint != 0 && *breakpoint <= SOURCING_LNUM) {
-        dbg_breakpoint((char_u *)fname, SOURCING_LNUM);
+        dbg_breakpoint(fname, SOURCING_LNUM);
         // Find next breakpoint.
         *breakpoint = dbg_find_breakpoint(getline_equal(fgetline, cookie, getsourceline),
-                                          (char_u *)fname, SOURCING_LNUM);
+                                          fname, SOURCING_LNUM);
         *dbg_tick = debug_tick;
       }
       if (do_profiling == PROF_YES) {
@@ -639,8 +639,7 @@ int do_cmdline(char *cmdline, LineGetter fgetline, void *cookie, int flags)
           // Check for the next breakpoint at or after the ":while"
           // or ":for".
           if (breakpoint != NULL) {
-            *breakpoint = dbg_find_breakpoint(getline_equal(fgetline, cookie, getsourceline),
-                                              (char_u *)fname,
+            *breakpoint = dbg_find_breakpoint(getline_equal(fgetline, cookie, getsourceline), fname,
                                               ((wcmd_T *)lines_ga.ga_data)[current_line].lnum - 1);
             *dbg_tick = debug_tick;
           }
@@ -3665,7 +3664,7 @@ char *replace_makeprg(exarg_T *eap, char *arg, char **cmdlinep)
       STRCAT(new_cmdline, arg);
     }
 
-    msg_make((char_u *)arg);
+    msg_make(arg);
 
     // 'eap->cmd' is not set here, because it is not used at CMD_make
     xfree(*cmdlinep);
@@ -3807,7 +3806,7 @@ int expand_filename(exarg_T *eap, char **cmdlinep, char **errormsgp)
     // done by ExpandOne() below.
 #ifdef UNIX
     if (!has_wildcards) {
-      backslash_halve((char_u *)eap->arg);
+      backslash_halve(eap->arg);
     }
 #else
     backslash_halve((char_u *)eap->arg);
@@ -5032,7 +5031,7 @@ static void ex_tabs(exarg_T *eap)
 
     msg_putchar('\n');
     vim_snprintf((char *)IObuff, IOSIZE, _("Tab page %d"), tabcount++);
-    msg_outtrans_attr(IObuff, HL_ATTR(HLF_T));
+    msg_outtrans_attr((char *)IObuff, HL_ATTR(HLF_T));
     ui_flush();            // output one line at a time
     os_breakcheck();
 
@@ -6154,7 +6153,7 @@ FILE *open_exfile(char_u *fname, int forceit, char *mode)
 {
 #ifdef UNIX
   // with Unix it is possible to open a directory
-  if (os_isdir(fname)) {
+  if (os_isdir((char *)fname)) {
     semsg(_(e_isadir2), fname);
     return NULL;
   }
@@ -6881,7 +6880,7 @@ char_u *eval_vars(char_u *src, char_u *srcstart, size_t *usedlen, linenr_T *lnum
     if (src[*usedlen] == '<') {
       (*usedlen)++;
       char *s;
-      if ((s = (char *)STRRCHR(result, '.')) != NULL
+      if ((s = strrchr(result, '.')) != NULL
           && s >= path_tail(result)) {
         resultlen = (size_t)(s - result);
       }
diff --git a/src/nvim/ex_eval.c b/src/nvim/ex_eval.c
index e2b02929d2..11795684cf 100644
--- a/src/nvim/ex_eval.c
+++ b/src/nvim/ex_eval.c
@@ -726,14 +726,14 @@ static void report_pending(int action, int pending, void *value)
     break;
   case CSTP_RETURN:
     // ":return" command producing value, allocated
-    s = (char *)get_return_cmd(value);
+    s = get_return_cmd(value);
     break;
 
   default:
     if (pending & CSTP_THROW) {
       vim_snprintf((char *)IObuff, IOSIZE,
                    mesg, _("Exception"));
-      mesg = (char *)concat_str(IObuff, (char_u *)": %s");
+      mesg = concat_str((char *)IObuff, ": %s");
       s = ((except_T *)value)->value;
     } else if ((pending & CSTP_ERROR) && (pending & CSTP_INTERRUPT)) {
       s = _("Error and interrupt");
diff --git a/src/nvim/ex_getln.c b/src/nvim/ex_getln.c
index 66c3327ce3..0998bdd867 100644
--- a/src/nvim/ex_getln.c
+++ b/src/nvim/ex_getln.c
@@ -3198,7 +3198,7 @@ static void draw_cmdline(int start, int len)
       }
     }
 
-    msg_outtrans_len((char_u *)arshape_buf, newlen);
+    msg_outtrans_len(arshape_buf, newlen);
   } else {
 draw_cmdline_no_arabicshape:
     if (kv_size(ccline.last_colors.colors)) {
@@ -3213,7 +3213,7 @@ draw_cmdline_no_arabicshape:
                               chunk.attr);
       }
     } else {
-      msg_outtrans_len(ccline.cmdbuff + start, len);
+      msg_outtrans_len((char *)ccline.cmdbuff + start, len);
     }
   }
 }
diff --git a/src/nvim/ex_session.c b/src/nvim/ex_session.c
index 453de89aea..e907c45e79 100644
--- a/src/nvim/ex_session.c
+++ b/src/nvim/ex_session.c
@@ -956,7 +956,7 @@ void ex_mkrc(exarg_T *eap)
   }
 
   // When using 'viewdir' may have to create the directory.
-  if (using_vdir && !os_isdir(p_vdir)) {
+  if (using_vdir && !os_isdir((char *)p_vdir)) {
     vim_mkdir_emsg((const char *)p_vdir, 0755);
   }
 
diff --git a/src/nvim/file_search.c b/src/nvim/file_search.c
index a990043017..bbc6e53aa8 100644
--- a/src/nvim/file_search.c
+++ b/src/nvim/file_search.c
@@ -471,7 +471,7 @@ void *vim_findfile_init(char_u *path, char_u *filename, char_u *stopdirs, int le
 
     STRCPY(buf, ff_expand_buffer);
     STRCPY(buf + eb_len, search_ctx->ffsc_fix_path);
-    if (os_isdir(buf)) {
+    if (os_isdir((char *)buf)) {
       STRCAT(ff_expand_buffer, search_ctx->ffsc_fix_path);
       add_pathsep((char *)ff_expand_buffer);
     } else {
@@ -796,7 +796,7 @@ char_u *vim_findfile(void *search_ctx_arg)
            */
           for (int i = stackp->ffs_filearray_cur; i < stackp->ffs_filearray_size; i++) {
             if (!path_with_url(stackp->ffs_filearray[i])
-                && !os_isdir((char_u *)stackp->ffs_filearray[i])) {
+                && !os_isdir(stackp->ffs_filearray[i])) {
               continue;                 // not a directory
             }
             // prepare the filename to be checked for existence below
@@ -828,7 +828,7 @@ char_u *vim_findfile(void *search_ctx_arg)
                    || (os_path_exists(file_path)
                        && (search_ctx->ffsc_find_what == FINDFILE_BOTH
                            || ((search_ctx->ffsc_find_what == FINDFILE_DIR)
-                               == os_isdir(file_path)))))
+                               == os_isdir((char *)file_path)))))
 #ifndef FF_VERBOSE
                   && (ff_check_visited(&search_ctx->ffsc_visited_list->ffvl_visited_list,
                                        file_path, (char_u *)"") == OK)
@@ -885,7 +885,7 @@ char_u *vim_findfile(void *search_ctx_arg)
         } else {
           // still wildcards left, push the directories for further search
           for (int i = stackp->ffs_filearray_cur; i < stackp->ffs_filearray_size; i++) {
-            if (!os_isdir((char_u *)stackp->ffs_filearray[i])) {
+            if (!os_isdir(stackp->ffs_filearray[i])) {
               continue;                 // not a directory
             }
             ff_push(search_ctx,
@@ -909,7 +909,7 @@ char_u *vim_findfile(void *search_ctx_arg)
                        stackp->ffs_fix_path) == 0) {
             continue;             // don't repush same directory
           }
-          if (!os_isdir((char_u *)stackp->ffs_filearray[i])) {
+          if (!os_isdir(stackp->ffs_filearray[i])) {
             continue;               // not a directory
           }
           ff_push(search_ctx,
@@ -1476,7 +1476,7 @@ char_u *find_file_in_path_option(char_u *ptr, size_t len, int options, int first
               (os_path_exists((char_u *)NameBuff)
                && (find_what == FINDFILE_BOTH
                    || ((find_what == FINDFILE_DIR)
-                       == os_isdir((char_u *)NameBuff))))) {
+                       == os_isdir(NameBuff))))) {
             file_name = vim_strsave((char_u *)NameBuff);
             goto theend;
           }
diff --git a/src/nvim/fileio.c b/src/nvim/fileio.c
index 450c608fad..d67cd36a85 100644
--- a/src/nvim/fileio.c
+++ b/src/nvim/fileio.c
@@ -143,7 +143,7 @@ void filemess(buf_T *buf, char_u *name, char_u *s, int attr)
   msg_scroll = msg_scroll_save;
   msg_scrolled_ign = true;
   // may truncate the message to avoid a hit-return prompt
-  msg_outtrans_attr(msg_may_trunc(false, IObuff), attr);
+  msg_outtrans_attr((char *)msg_may_trunc(false, IObuff), attr);
   msg_clr_eos();
   ui_flush();
   msg_scrolled_ign = false;
@@ -2775,7 +2775,7 @@ int buf_write(buf_T *buf, char *fname, char *sfname, linenr_T start, linenr_T en
         if (trailing_pathseps) {
           IObuff[dir_len - 2] = NUL;
         }
-        if (*dirp == NUL && !os_isdir(IObuff)) {
+        if (*dirp == NUL && !os_isdir((char *)IObuff)) {
           int ret;
           char *failed_dir;
           if ((ret = os_mkdir_recurse((char *)IObuff, 0755, &failed_dir)) != 0) {
@@ -2936,7 +2936,7 @@ nobackup:
         if (trailing_pathseps) {
           IObuff[dir_len - 2] = NUL;
         }
-        if (*dirp == NUL && !os_isdir(IObuff)) {
+        if (*dirp == NUL && !os_isdir((char *)IObuff)) {
           int ret;
           char *failed_dir;
           if ((ret = os_mkdir_recurse((char *)IObuff, 0755, &failed_dir)) != 0) {
@@ -4948,7 +4948,7 @@ int buf_check_timestamp(buf_T *buf)
       buf_store_file_info(buf, &file_info);
     }
 
-    if (os_isdir((char_u *)buf->b_fname)) {
+    if (os_isdir(buf->b_fname)) {
       // Don't do anything for a directory.  Might contain the file explorer.
     } else if ((buf->b_p_ar >= 0 ? buf->b_p_ar : p_ar)
                && !bufIsChanged(buf) && file_info_ok) {
@@ -5318,7 +5318,7 @@ static void vim_mktempdir(void)
   for (size_t i = 0; i < ARRAY_SIZE(temp_dirs); i++) {
     // Expand environment variables, leave room for "/tmp/nvim.<user>/XXXXXX/999999999".
     expand_env((char *)temp_dirs[i], tmp, TEMP_FILE_PATH_MAXLEN - 64);
-    if (!os_isdir((char_u *)tmp)) {
+    if (!os_isdir(tmp)) {
       continue;
     }
 
@@ -5328,7 +5328,7 @@ static void vim_mktempdir(void)
     xstrlcat(tmp, user, sizeof(tmp));
     (void)os_mkdir(tmp, 0700);  // Always create, to avoid a race.
     bool owned = os_file_owned(tmp);
-    bool isdir = os_isdir((char_u *)tmp);
+    bool isdir = os_isdir(tmp);
 #ifdef UNIX
     int perm = os_getperm(tmp);  // XDG_RUNTIME_DIR must be owned by the user, mode 0700.
     bool valid = isdir && owned && 0700 == (perm & 0777);
diff --git a/src/nvim/getchar.c b/src/nvim/getchar.c
index bb8cd5a1eb..0a9457ef35 100644
--- a/src/nvim/getchar.c
+++ b/src/nvim/getchar.c
@@ -1280,7 +1280,7 @@ void restore_typeahead(tasave_T *tp)
 /// Open a new script file for the ":source!" command.
 ///
 /// @param directly  when true execute directly
-void openscript(char_u *name, bool directly)
+void openscript(char *name, bool directly)
 {
   if (curscript + 1 == NSCRIPT) {
     emsg(_(e_nesting));
@@ -1302,7 +1302,7 @@ void openscript(char_u *name, bool directly)
     curscript++;
   }
   // use NameBuff for expanded name
-  expand_env((char *)name, NameBuff, MAXPATHL);
+  expand_env(name, NameBuff, MAXPATHL);
   int error;
   if ((scriptin[curscript] = file_open_new(&error, (char *)NameBuff,
                                            kFileReadOnly, 0)) == NULL) {
diff --git a/src/nvim/globals.h b/src/nvim/globals.h
index 77784defd1..ddbe727db9 100644
--- a/src/nvim/globals.h
+++ b/src/nvim/globals.h
@@ -177,7 +177,7 @@ EXTERN bool msg_scrolled_ign INIT(= false);
 // is reset before the screen is redrawn, so we need to keep track of this.
 EXTERN bool msg_did_scroll INIT(= false);
 
-EXTERN char_u *keep_msg INIT(= NULL);       // msg to be shown after redraw
+EXTERN char *keep_msg INIT(= NULL);         // msg to be shown after redraw
 EXTERN int keep_msg_attr INIT(= 0);         // highlight attr for keep_msg
 EXTERN bool need_fileinfo INIT(= false);    // do fileinfo() after redraw
 EXTERN int msg_scroll INIT(= false);        // msg_start() will scroll
diff --git a/src/nvim/hardcopy.c b/src/nvim/hardcopy.c
index 6e424f2fd6..602fa8b71d 100644
--- a/src/nvim/hardcopy.c
+++ b/src/nvim/hardcopy.c
@@ -3062,7 +3062,8 @@ int mch_print_text_out(char_u *const textp, size_t len)
 
   if (prt_do_conv) {
     // Convert from multi-byte to 8-bit encoding
-    tofree = p = string_convert(&prt_conv, p, &len);
+    p = (char_u *)string_convert(&prt_conv, (char *)p, &len);
+    tofree = p;
     if (p == NULL) {
       p = (char_u *)"";
       len = 0;
diff --git a/src/nvim/help.c b/src/nvim/help.c
index b25fabca48..245d80489f 100644
--- a/src/nvim/help.c
+++ b/src/nvim/help.c
@@ -741,8 +741,8 @@ void fix_help_buffer(void)
                 const char *const f2 = fnames[i2];
                 const char *const t1 = path_tail(f1);
                 const char *const t2 = path_tail(f2);
-                const char *const e1 = (char *)STRRCHR(t1, '.');
-                const char *const e2 = (char *)STRRCHR(t2, '.');
+                const char *const e1 = strrchr(t1, '.');
+                const char *const e2 = strrchr(t2, '.');
                 if (e1 == NULL || e2 == NULL) {
                   continue;
                 }
@@ -811,7 +811,7 @@ void fix_help_buffer(void)
                 } else {
                   // Do the conversion.  If it fails
                   // use the unconverted text.
-                  cp = (char *)string_convert(&vc, IObuff, NULL);
+                  cp = string_convert(&vc, (char *)IObuff, NULL);
                   if (cp == NULL) {
                     cp = (char *)IObuff;
                   }
@@ -1163,13 +1163,13 @@ void ex_helptags(exarg_T *eap)
   }
 
   if (STRCMP(eap->arg, "ALL") == 0) {
-    do_in_path((char_u *)p_rtp, "doc", DIP_ALL + DIP_DIR, helptags_cb, &add_help_tags);
+    do_in_path(p_rtp, "doc", DIP_ALL + DIP_DIR, helptags_cb, &add_help_tags);
   } else {
     ExpandInit(&xpc);
     xpc.xp_context = EXPAND_DIRECTORIES;
     dirname = (char *)ExpandOne(&xpc, (char_u *)eap->arg, NULL,
                                 WILD_LIST_NOTFOUND|WILD_SILENT, WILD_EXPAND_FREE);
-    if (dirname == NULL || !os_isdir((char_u *)dirname)) {
+    if (dirname == NULL || !os_isdir(dirname)) {
       semsg(_("E150: Not a directory: %s"), eap->arg);
     } else {
       do_helptags(dirname, add_help_tags, false);
diff --git a/src/nvim/highlight_group.c b/src/nvim/highlight_group.c
index e2d4a81345..ed1f0185b7 100644
--- a/src/nvim/highlight_group.c
+++ b/src/nvim/highlight_group.c
@@ -852,14 +852,14 @@ void do_highlight(const char *line, const bool forceit, const bool init)
   }
 
   // Isolate the name.
-  name_end = (const char *)skiptowhite((const char_u *)line);
+  name_end = (const char *)skiptowhite(line);
   linep = (const char *)skipwhite(name_end);
 
   // Check for "default" argument.
   if (strncmp(line, "default", (size_t)(name_end - line)) == 0) {
     dodefault = true;
     line = linep;
-    name_end = (const char *)skiptowhite((const char_u *)line);
+    name_end = (const char *)skiptowhite(line);
     linep = (const char *)skipwhite(name_end);
   }
 
@@ -891,9 +891,9 @@ void do_highlight(const char *line, const bool forceit, const bool init)
     int to_id;
     HlGroup *hlgroup = NULL;
 
-    from_end = (const char *)skiptowhite((const char_u *)from_start);
+    from_end = (const char *)skiptowhite(from_start);
     to_start = (const char *)skipwhite(from_end);
-    to_end   = (const char *)skiptowhite((const char_u *)to_start);
+    to_end   = (const char *)skiptowhite(to_start);
 
     if (ends_excmd((uint8_t)(*from_start))
         || ends_excmd((uint8_t)(*to_start))) {
@@ -969,7 +969,7 @@ void do_highlight(const char *line, const bool forceit, const bool init)
       redraw_all_later(UPD_NOT_VALID);
       return;
     }
-    name_end = (const char *)skiptowhite((const char_u *)line);
+    name_end = (const char *)skiptowhite(line);
     linep = (const char *)skipwhite(name_end);
   }
 
@@ -1054,7 +1054,7 @@ void do_highlight(const char *line, const bool forceit, const bool init)
         }
       } else {
         arg_start = linep;
-        linep = (const char *)skiptowhite((const char_u *)linep);
+        linep = (const char *)skiptowhite(linep);
       }
       if (linep == arg_start) {
         semsg(_("E417: missing argument: %s"), key_start);
@@ -2074,13 +2074,13 @@ void set_context_in_highlight_cmd(expand_T *xp, const char *arg)
 
   // (part of) subcommand already typed
   if (*arg != NUL) {
-    const char *p = (const char *)skiptowhite((const char_u *)arg);
+    const char *p = (const char *)skiptowhite(arg);
     if (*p != NUL) {  // Past "default" or group name.
       include_default = 0;
       if (strncmp("default", arg, (unsigned)(p - arg)) == 0) {
         arg = (const char *)skipwhite(p);
         xp->xp_pattern = (char *)arg;
-        p = (const char *)skiptowhite((const char_u *)arg);
+        p = (const char *)skiptowhite(arg);
       }
       if (*p != NUL) {                          // past group name
         include_link = 0;
@@ -2090,10 +2090,10 @@ void set_context_in_highlight_cmd(expand_T *xp, const char *arg)
         if (strncmp("link", arg, (unsigned)(p - arg)) == 0
             || strncmp("clear", arg, (unsigned)(p - arg)) == 0) {
           xp->xp_pattern = skipwhite(p);
-          p = (const char *)skiptowhite((char_u *)xp->xp_pattern);
+          p = (const char *)skiptowhite(xp->xp_pattern);
           if (*p != NUL) {  // Past first group name.
             xp->xp_pattern = skipwhite(p);
-            p = (const char *)skiptowhite((char_u *)xp->xp_pattern);
+            p = (const char *)skiptowhite(xp->xp_pattern);
           }
         }
         if (*p != NUL) {  // Past group name(s).
diff --git a/src/nvim/if_cscope.c b/src/nvim/if_cscope.c
index 2a9d2c357e..9413abb2e1 100644
--- a/src/nvim/if_cscope.c
+++ b/src/nvim/if_cscope.c
@@ -153,10 +153,10 @@ void set_context_in_cscope_cmd(expand_T *xp, const char *arg, cmdidx_T cmdidx)
 
   // (part of) subcommand already typed
   if (*arg != NUL) {
-    const char *p = (const char *)skiptowhite((const char_u *)arg);
+    const char *p = (const char *)skiptowhite(arg);
     if (*p != NUL) {  // Past first word.
       xp->xp_pattern = skipwhite(p);
-      if (*skiptowhite((char_u *)xp->xp_pattern) != NUL) {
+      if (*skiptowhite(xp->xp_pattern) != NUL) {
         xp->xp_context = EXPAND_NOTHING;
       } else if (STRNICMP(arg, "add", p - arg) == 0) {
         xp->xp_context = EXPAND_FILES;
diff --git a/src/nvim/indent_c.c b/src/nvim/indent_c.c
index 8ef6667374..166695ef5b 100644
--- a/src/nvim/indent_c.c
+++ b/src/nvim/indent_c.c
@@ -676,10 +676,10 @@ static int cin_first_id_amount(void)
 
   line = get_cursor_line_ptr();
   p = (char_u *)skipwhite((char *)line);
-  len = (int)(skiptowhite(p) - p);
+  len = (int)((char_u *)skiptowhite((char *)p) - p);
   if (len == 6 && STRNCMP(p, "static", 6) == 0) {
     p = (char_u *)skipwhite((char *)p + 6);
-    len = (int)(skiptowhite(p) - p);
+    len = (int)((char_u *)skiptowhite((char *)p) - p);
   }
   if (len == 6 && STRNCMP(p, "struct", 6) == 0) {
     p = (char_u *)skipwhite((char *)p + 6);
diff --git a/src/nvim/insexpand.c b/src/nvim/insexpand.c
index 3c32d0755e..ba0a36cafe 100644
--- a/src/nvim/insexpand.c
+++ b/src/nvim/insexpand.c
@@ -3767,7 +3767,7 @@ static int get_normal_compl_info(char_u *line, int startcol, colnr_T curs_col)
 /// Sets the global variables: compl_col, compl_length and compl_pattern.
 static int get_wholeline_compl_info(char_u *line, colnr_T curs_col)
 {
-  compl_col = (colnr_T)getwhitecols(line);
+  compl_col = (colnr_T)getwhitecols((char *)line);
   compl_length = (int)curs_col - (int)compl_col;
   if (compl_length < 0) {  // cursor in indent: empty pattern
     compl_length = 0;
@@ -3985,7 +3985,7 @@ static void ins_compl_continue_search(char_u *line)
       // first non_blank in the line, if it is not a wordchar
       // include it to get a better pattern, but then we don't
       // want the "\\<" prefix, check it below.
-      compl_col = (colnr_T)getwhitecols(line);
+      compl_col = (colnr_T)getwhitecols((char *)line);
       compl_startpos.col = compl_col;
       compl_startpos.lnum = curwin->w_cursor.lnum;
       compl_cont_status &= ~CONT_SOL;  // clear SOL if present
diff --git a/src/nvim/locale.c b/src/nvim/locale.c
index ba0566011c..3e0774c096 100644
--- a/src/nvim/locale.c
+++ b/src/nvim/locale.c
@@ -188,7 +188,7 @@ void ex_language(exarg_T *eap)
   // Check for "messages {name}", "ctype {name}" or "time {name}" argument.
   // Allow abbreviation, but require at least 3 characters to avoid
   // confusion with a two letter language name "me" or "ct".
-  p = (char *)skiptowhite((char_u *)eap->arg);
+  p = skiptowhite(eap->arg);
   if ((*p == NUL || ascii_iswhite(*p)) && p - eap->arg >= 3) {
     if (STRNICMP(eap->arg, "messages", p - eap->arg) == 0) {
       what = VIM_LC_MESSAGES;
diff --git a/src/nvim/log.c b/src/nvim/log.c
index 9f25543be7..9bdf327430 100644
--- a/src/nvim/log.c
+++ b/src/nvim/log.c
@@ -63,13 +63,13 @@ static void log_path_init(void)
   expand_env("$" ENV_LOGFILE, log_file_path, (int)size - 1);
   if (strequal("$" ENV_LOGFILE, log_file_path)
       || log_file_path[0] == '\0'
-      || os_isdir((char_u *)log_file_path)
+      || os_isdir(log_file_path)
       || !log_try_create(log_file_path)) {
     // Make $XDG_STATE_HOME if it does not exist.
     char *loghome = get_xdg_home(kXDGStateHome);
     char *failed_dir = NULL;
     bool log_dir_failure = false;
-    if (!os_isdir((char_u *)loghome)) {
+    if (!os_isdir(loghome)) {
       log_dir_failure = (os_mkdir_recurse(loghome, 0700, &failed_dir) != 0);
     }
     XFREE_CLEAR(loghome);
diff --git a/src/nvim/lua/stdlib.c b/src/nvim/lua/stdlib.c
index 7e8dda6ca1..1b874e673a 100644
--- a/src/nvim/lua/stdlib.c
+++ b/src/nvim/lua/stdlib.c
@@ -501,7 +501,7 @@ static int nlua_iconv(lua_State *lstate)
   vimconv.vc_type = CONV_NONE;
   convert_setup_ext(&vimconv, from, false, to, false);
 
-  char_u *ret = string_convert(&vimconv, (char_u *)str, &str_len);
+  char_u *ret = (char_u *)string_convert(&vimconv, (char *)str, &str_len);
 
   convert_setup(&vimconv, NULL, NULL);
 
diff --git a/src/nvim/main.c b/src/nvim/main.c
index 09a387262c..883f946cad 100644
--- a/src/nvim/main.c
+++ b/src/nvim/main.c
@@ -1342,8 +1342,8 @@ scripterror:
       ga_grow(&global_alist.al_ga, 1);
       char *p = xstrdup(argv[0]);
 
-      if (parmp->diff_mode && os_isdir((char_u *)p) && GARGCOUNT > 0
-          && !os_isdir((char_u *)alist_name(&GARGLIST[0]))) {
+      if (parmp->diff_mode && os_isdir(p) && GARGCOUNT > 0
+          && !os_isdir(alist_name(&GARGLIST[0]))) {
         char *r = concat_fnames(p, path_tail(alist_name(&GARGLIST[0])), true);
         xfree(p);
         p = r;
diff --git a/src/nvim/mark.c b/src/nvim/mark.c
index 92a7c7c4b0..9df4d416ff 100644
--- a/src/nvim/mark.c
+++ b/src/nvim/mark.c
@@ -922,7 +922,7 @@ static void show_one_mark(int c, char_u *arg, pos_T *p, char_u *name_arg, int cu
         snprintf((char *)IObuff, IOSIZE, " %c %6" PRIdLINENR " %4d ", c, p->lnum, p->col);
         msg_outtrans((char *)IObuff);
         if (name != NULL) {
-          msg_outtrans_attr(name, current ? HL_ATTR(HLF_D) : 0);
+          msg_outtrans_attr((char *)name, current ? HL_ATTR(HLF_D) : 0);
         }
       }
       ui_flush();  // show one line at a time
@@ -1052,7 +1052,7 @@ void ex_jumps(exarg_T *eap)
                i > curwin->w_jumplistidx ? i - curwin->w_jumplistidx : curwin->w_jumplistidx - i,
                curwin->w_jumplist[i].fmark.mark.lnum, curwin->w_jumplist[i].fmark.mark.col);
       msg_outtrans((char *)IObuff);
-      msg_outtrans_attr(name,
+      msg_outtrans_attr((char *)name,
                         curwin->w_jumplist[i].fmark.fnum == curbuf->b_fnum
                         ? HL_ATTR(HLF_D) : 0);
       xfree(name);
@@ -1097,7 +1097,7 @@ void ex_changes(exarg_T *eap)
               curbuf->b_changelist[i].mark.col);
       msg_outtrans((char *)IObuff);
       name = mark_line(&curbuf->b_changelist[i].mark, 17);
-      msg_outtrans_attr(name, HL_ATTR(HLF_D));
+      msg_outtrans_attr((char *)name, HL_ATTR(HLF_D));
       xfree(name);
       os_breakcheck();
     }
diff --git a/src/nvim/match.c b/src/nvim/match.c
index cabd008591..48f0d0fc05 100644
--- a/src/nvim/match.c
+++ b/src/nvim/match.c
@@ -1183,7 +1183,7 @@ void ex_match(exarg_T *eap)
               && (ascii_iswhite(eap->arg[4]) || ends_excmd(eap->arg[4])))) {
     end = (char_u *)eap->arg + 4;
   } else {
-    p = skiptowhite((char_u *)eap->arg);
+    p = (char_u *)skiptowhite(eap->arg);
     if (!eap->skip) {
       g = vim_strnsave((char_u *)eap->arg, (size_t)(p - (char_u *)eap->arg));
     }
diff --git a/src/nvim/mbyte.c b/src/nvim/mbyte.c
index e703280032..b874f0dc94 100644
--- a/src/nvim/mbyte.c
+++ b/src/nvim/mbyte.c
@@ -1942,7 +1942,7 @@ void utf_find_illegal(void)
     p = get_cursor_pos_ptr();
     if (vimconv.vc_type != CONV_NONE) {
       xfree(tofree);
-      tofree = string_convert(&vimconv, p, NULL);
+      tofree = (char_u *)string_convert(&vimconv, (char *)p, NULL);
       if (tofree == NULL) {
         break;
       }
@@ -2521,16 +2521,14 @@ int convert_setup_ext(vimconv_T *vcp, char_u *from, bool from_unicode_is_utf8, c
   return OK;
 }
 
-/*
- * Convert text "ptr[*lenp]" according to "vcp".
- * Returns the result in allocated memory and sets "*lenp".
- * When "lenp" is NULL, use NUL terminated strings.
- * Illegal chars are often changed to "?", unless vcp->vc_fail is set.
- * When something goes wrong, NULL is returned and "*lenp" is unchanged.
- */
-char_u *string_convert(const vimconv_T *const vcp, char_u *ptr, size_t *lenp)
+/// Convert text "ptr[*lenp]" according to "vcp".
+/// Returns the result in allocated memory and sets "*lenp".
+/// When "lenp" is NULL, use NUL terminated strings.
+/// Illegal chars are often changed to "?", unless vcp->vc_fail is set.
+/// When something goes wrong, NULL is returned and "*lenp" is unchanged.
+char *string_convert(const vimconv_T *const vcp, char *ptr, size_t *lenp)
 {
-  return string_convert_ext(vcp, ptr, lenp, NULL);
+  return (char *)string_convert_ext(vcp, (char_u *)ptr, lenp, NULL);
 }
 
 /*
diff --git a/src/nvim/memline.c b/src/nvim/memline.c
index 044655ef2b..b0b6b675cb 100644
--- a/src/nvim/memline.c
+++ b/src/nvim/memline.c
@@ -857,7 +857,7 @@ void ml_recover(bool checkext)
   if ((hp = mf_get(mfp, 0, 1)) == NULL) {
     msg_start();
     msg_puts_attr(_("Unable to read block 0 from "), attr | MSG_HIST);
-    msg_outtrans_attr(mfp->mf_fname, attr | MSG_HIST);
+    msg_outtrans_attr((char *)mfp->mf_fname, attr | MSG_HIST);
     msg_puts_attr(_("\nMaybe no changes were made or Vim did not update the swap file."),
                   attr | MSG_HIST);
     msg_end();
@@ -866,7 +866,7 @@ void ml_recover(bool checkext)
   b0p = hp->bh_data;
   if (STRNCMP(b0p->b0_version, "VIM 3.0", 7) == 0) {
     msg_start();
-    msg_outtrans_attr(mfp->mf_fname, MSG_HIST);
+    msg_outtrans_attr((char *)mfp->mf_fname, MSG_HIST);
     msg_puts_attr(_(" cannot be used with this version of Vim.\n"),
                   MSG_HIST);
     msg_puts_attr(_("Use Vim version 3.0.\n"), MSG_HIST);
@@ -879,7 +879,7 @@ void ml_recover(bool checkext)
   }
   if (b0_magic_wrong(b0p)) {
     msg_start();
-    msg_outtrans_attr(mfp->mf_fname, attr | MSG_HIST);
+    msg_outtrans_attr((char *)mfp->mf_fname, attr | MSG_HIST);
     msg_puts_attr(_(" cannot be used on this computer.\n"),
                   attr | MSG_HIST);
     msg_puts_attr(_("The file was created on "), attr | MSG_HIST);
@@ -901,7 +901,7 @@ void ml_recover(bool checkext)
     mf_new_page_size(mfp, (unsigned)char_to_long(b0p->b0_page_size));
     if (mfp->mf_page_size < previous_page_size) {
       msg_start();
-      msg_outtrans_attr(mfp->mf_fname, attr | MSG_HIST);
+      msg_outtrans_attr((char *)mfp->mf_fname, attr | MSG_HIST);
       msg_puts_attr(_(" has been damaged (page size is smaller than minimum value).\n"),
                     attr | MSG_HIST);
       msg_end();
@@ -3614,7 +3614,7 @@ static char *findswapname(buf_T *buf, char **dirp, char *old_fname, bool *found_
     fname[n - 1]--;                     // ".swo", ".swn", etc.
   }
 
-  if (os_isdir((char_u *)dir_name)) {
+  if (os_isdir(dir_name)) {
     *found_existing_dir = true;
   } else if (!*found_existing_dir && **dirp == NUL) {
     int ret;
diff --git a/src/nvim/menu.c b/src/nvim/menu.c
index b1d729f71d..cb6918cd27 100644
--- a/src/nvim/menu.c
+++ b/src/nvim/menu.c
@@ -853,7 +853,7 @@ static void show_menus_recursive(vimmenu_T *menu, int modes, int depth)
       msg_puts(" ");
     }
     // Same highlighting as for directories!?
-    msg_outtrans_attr((char_u *)menu->name, HL_ATTR(HLF_D));
+    msg_outtrans_attr(menu->name, HL_ATTR(HLF_D));
   }
 
   if (menu != NULL && menu->children == NULL) {
diff --git a/src/nvim/message.c b/src/nvim/message.c
index 4fba78feca..80b5f53f4e 100644
--- a/src/nvim/message.c
+++ b/src/nvim/message.c
@@ -265,7 +265,7 @@ void msg_multiline_attr(const char *s, int attr, bool check_int, bool *need_clea
   // Print the rest of the message. We know there is no special
   // character because strpbrk returned NULL
   if (*s != NUL) {
-    msg_outtrans_attr((char_u *)s, attr);
+    msg_outtrans_attr(s, attr);
   }
 }
 
@@ -325,7 +325,7 @@ bool msg_attr_keep(const char *s, int attr, bool keep, bool multiline)
 
   // Add message to history (unless it's a repeated kept message or a
   // truncated message)
-  if ((const char_u *)s != keep_msg
+  if (s != keep_msg
       || (*s != '<'
           && last_msg_hist != NULL
           && last_msg_hist->msg != NULL
@@ -344,7 +344,7 @@ bool msg_attr_keep(const char *s, int attr, bool keep, bool multiline)
   if (multiline) {
     msg_multiline_attr(s, attr, false, &need_clear);
   } else {
-    msg_outtrans_attr((char_u *)s, attr);
+    msg_outtrans_attr(s, attr);
   }
   if (need_clear) {
     msg_clr_eos();
@@ -1307,7 +1307,7 @@ void wait_return(int redraw)
   emsg_on_display = false;      // can delete error message now
   lines_left = -1;              // reset lines_left at next msg_start()
   reset_last_sourcing();
-  if (keep_msg != NULL && vim_strsize((char *)keep_msg) >=
+  if (keep_msg != NULL && vim_strsize(keep_msg) >=
       (Rows - cmdline_row - 1) * Columns + sc_col) {
     XFREE_CLEAR(keep_msg);          // don't redisplay message, it's too long
   }
@@ -1350,7 +1350,7 @@ void set_keep_msg(char *s, int attr)
 {
   xfree(keep_msg);
   if (s != NULL && msg_silent == 0) {
-    keep_msg = vim_strsave((char_u *)s);
+    keep_msg = xstrdup(s);
   } else {
     keep_msg = NULL;
   }
@@ -1510,7 +1510,7 @@ void msg_home_replace_hl(char_u *fname)
 static void msg_home_replace_attr(char_u *fname, int attr)
 {
   char *name = home_replace_save(NULL, (char *)fname);
-  msg_outtrans_attr((char_u *)name, attr);
+  msg_outtrans_attr(name, attr);
   xfree(name);
 }
 
@@ -1521,29 +1521,29 @@ static void msg_home_replace_attr(char_u *fname, int attr)
 /// @return  the number of characters it takes on the screen.
 int msg_outtrans(char *str)
 {
-  return msg_outtrans_attr((char_u *)str, 0);
+  return msg_outtrans_attr(str, 0);
 }
 
-int msg_outtrans_attr(const char_u *str, int attr)
+int msg_outtrans_attr(const char *str, int attr)
 {
-  return msg_outtrans_len_attr(str, (int)STRLEN(str), attr);
+  return msg_outtrans_len_attr((char_u *)str, (int)STRLEN(str), attr);
 }
 
-int msg_outtrans_len(const char_u *str, int len)
+int msg_outtrans_len(const char *str, int len)
 {
-  return msg_outtrans_len_attr(str, len, 0);
+  return msg_outtrans_len_attr((char_u *)str, len, 0);
 }
 
 /// Output one character at "p".
 /// Handles multi-byte characters.
 ///
 /// @return  pointer to the next character.
-char_u *msg_outtrans_one(char_u *p, int attr)
+char *msg_outtrans_one(char *p, int attr)
 {
   int l;
 
-  if ((l = utfc_ptr2len((char *)p)) > 1) {
-    msg_outtrans_len_attr(p, l, attr);
+  if ((l = utfc_ptr2len(p)) > 1) {
+    msg_outtrans_len_attr((char_u *)p, l, attr);
     return p + l;
   }
   msg_puts_attr((const char *)transchar_byte(*p), attr);
@@ -1628,12 +1628,13 @@ int msg_outtrans_len_attr(const char_u *msgstr, int len, int attr)
   return retval;
 }
 
-void msg_make(char_u *arg)
+void msg_make(char *arg)
 {
   int i;
-  static char_u *str = (char_u *)"eeffoc", *rs = (char_u *)"Plon#dqg#vxjduB";
+  static char *str = "eeffoc";
+  static char *rs = "Plon#dqg#vxjduB";
 
-  arg = (char_u *)skipwhite((char *)arg);
+  arg = skipwhite(arg);
   for (i = 5; *arg && i >= 0; i--) {
     if (*arg++ != str[i]) {
       break;
@@ -1976,13 +1977,13 @@ void msg_prt_line(char_u *s, int list)
 /// Use grid_puts() to output one multi-byte character.
 ///
 /// @return  the pointer "s" advanced to the next character.
-static char_u *screen_puts_mbyte(char_u *s, int l, int attr)
+static char *screen_puts_mbyte(char *s, int l, int attr)
 {
   int cw;
   attr = hl_combine_attr(HL_ATTR(HLF_MSG), attr);
 
   msg_didout = true;            // remember that line is not empty
-  cw = utf_ptr2cells((char *)s);
+  cw = utf_ptr2cells(s);
   if (cw > 1
       && (cmdmsg_rl ? msg_col <= 1 : msg_col == Columns - 1)) {
     // Doesn't fit, print a highlighted '>' to fill it up.
@@ -1990,7 +1991,7 @@ static char_u *screen_puts_mbyte(char_u *s, int l, int attr)
     return s;
   }
 
-  grid_puts_len(&msg_grid_adj, (char *)s, l, msg_row, msg_col, attr);
+  grid_puts_len(&msg_grid_adj, s, l, msg_row, msg_col, attr);
   if (cmdmsg_rl) {
     msg_col -= cw;
     if (msg_col == 0) {
@@ -2197,7 +2198,7 @@ static void msg_puts_display(const char_u *str, int maxlen, int attr, int recurs
       // ourselves).
       if (t_col > 0) {
         // output postponed text
-        t_puts(&t_col, t_s, s, attr);
+        t_puts(&t_col, (char *)t_s, (char *)s, attr);
       }
 
       // When no more prompt and no more room, truncate here
@@ -2222,7 +2223,7 @@ static void msg_puts_display(const char_u *str, int maxlen, int attr, int recurs
         } else {
           l = utfc_ptr2len((char *)s);
         }
-        s = screen_puts_mbyte((char_u *)s, l, attr);
+        s = (char_u *)screen_puts_mbyte((char *)s, l, attr);
         did_last_char = true;
       } else {
         did_last_char = false;
@@ -2281,7 +2282,7 @@ static void msg_puts_display(const char_u *str, int maxlen, int attr, int recurs
     if (t_col > 0 && (wrap || *s == '\r' || *s == '\b'
                       || *s == '\t' || *s == BELL)) {
       // Output any postponed text.
-      t_puts(&t_col, t_s, s, attr);
+      t_puts(&t_col, (char *)t_s, (char *)s, attr);
     }
 
     if (wrap && p_more && !recurse) {
@@ -2324,7 +2325,7 @@ static void msg_puts_display(const char_u *str, int maxlen, int attr, int recurs
       // characters and draw them all at once later.
       if (cmdmsg_rl || (cw > 1 && msg_col + t_col >= Columns - 1)) {
         if (l > 1) {
-          s = screen_puts_mbyte((char_u *)s, l, attr) - 1;
+          s = (char_u *)screen_puts_mbyte((char *)s, l, attr) - 1;
         } else {
           msg_screen_putchar(*s, attr);
         }
@@ -2342,7 +2343,7 @@ static void msg_puts_display(const char_u *str, int maxlen, int attr, int recurs
 
   // Output any postponed text.
   if (t_col > 0) {
-    t_puts(&t_col, t_s, s, attr);
+    t_puts(&t_col, (char *)t_s, (char *)s, attr);
   }
   if (p_more && !recurse) {
     store_sb_text((char **)&sb_str, (char *)s, attr, &sb_col, false);
@@ -2698,7 +2699,7 @@ static msgchunk_T *disp_sb_line(int row, msgchunk_T *smp)
 }
 
 /// Output any postponed text for msg_puts_attr_len().
-static void t_puts(int *t_col, const char_u *t_s, const char_u *s, int attr)
+static void t_puts(int *t_col, const char *t_s, const char *s, int attr)
 {
   attr = hl_combine_attr(HL_ATTR(HLF_MSG), attr);
   // Output postponed text.
@@ -2708,7 +2709,7 @@ static void t_puts(int *t_col, const char_u *t_s, const char_u *s, int attr)
   *t_col = 0;
   // If the string starts with a composing character don't increment the
   // column position for it.
-  if (utf_iscomposing(utf_ptr2char((char *)t_s))) {
+  if (utf_iscomposing(utf_ptr2char(t_s))) {
     msg_col--;
   }
   if (msg_col >= Columns) {
diff --git a/src/nvim/normal.c b/src/nvim/normal.c
index 6430070f1b..47ad000385 100644
--- a/src/nvim/normal.c
+++ b/src/nvim/normal.c
@@ -631,16 +631,16 @@ static void normal_redraw_mode_message(NormalState *s)
   if (must_redraw && keep_msg != NULL && !emsg_on_display) {
     char_u *kmsg;
 
-    kmsg = keep_msg;
+    kmsg = (char_u *)keep_msg;
     keep_msg = NULL;
     // Showmode() will clear keep_msg, but we want to use it anyway.
     // First update w_topline.
     setcursor();
     update_screen(0);
     // now reset it, otherwise it's put in the history again
-    keep_msg = kmsg;
+    keep_msg = (char *)kmsg;
 
-    kmsg = vim_strsave(keep_msg);
+    kmsg = vim_strsave((char_u *)keep_msg);
     msg_attr((const char *)kmsg, keep_msg_attr);
     xfree(kmsg);
   }
@@ -1302,7 +1302,7 @@ static void normal_redraw(NormalState *s)
   // Display message after redraw. If an external message is still visible,
   // it contains the kept message already.
   if (keep_msg != NULL && !msg_ext_is_visible()) {
-    char_u *const p = vim_strsave(keep_msg);
+    char *const p = xstrdup(keep_msg);
 
     // msg_start() will set keep_msg to NULL, make a copy
     // first.  Don't reset keep_msg, msg_attr_keep() uses it to
diff --git a/src/nvim/ops.c b/src/nvim/ops.c
index 7b6f9e6370..4f2b84d20f 100644
--- a/src/nvim/ops.c
+++ b/src/nvim/ops.c
@@ -2500,7 +2500,7 @@ int op_change(oparg_T *oap)
     }
     firstline = ml_get(oap->start.lnum);
     pre_textlen = (long)STRLEN(firstline);
-    pre_indent = (long)getwhitecols(firstline);
+    pre_indent = (long)getwhitecols((char *)firstline);
     bd.textcol = curwin->w_cursor.col;
   }
 
@@ -2521,7 +2521,7 @@ int op_change(oparg_T *oap)
     // the indent, exclude that indent change from the inserted text.
     firstline = ml_get(oap->start.lnum);
     if (bd.textcol > (colnr_T)pre_indent) {
-      long new_indent = (long)getwhitecols(firstline);
+      long new_indent = (long)getwhitecols((char *)firstline);
 
       pre_textlen += new_indent - pre_indent;
       bd.textcol += (colnr_T)(new_indent - pre_indent);
@@ -3860,7 +3860,7 @@ void ex_display(exarg_T *eap)
           for (p = (char_u *)yb->y_array[j];
                *p != NUL && (n -= ptr2cells((char *)p)) >= 0; p++) {  // -V1019
             clen = utfc_ptr2len((char *)p);
-            msg_outtrans_len(p, clen);
+            msg_outtrans_len((char *)p, clen);
             p += clen - 1;
           }
         }
@@ -3938,10 +3938,10 @@ static void dis_msg(const char_u *p, bool skip_esc)
          && !(*p == ESC && skip_esc && *(p + 1) == NUL)
          && (n -= ptr2cells((char *)p)) >= 0) {
     if ((l = utfc_ptr2len((char *)p)) > 1) {
-      msg_outtrans_len(p, l);
+      msg_outtrans_len((char *)p, l);
       p += l;
     } else {
-      msg_outtrans_len(p++, 1);
+      msg_outtrans_len((char *)p++, 1);
     }
   }
   os_breakcheck();
diff --git a/src/nvim/os/env.c b/src/nvim/os/env.c
index 274e13e3c6..c940c86675 100644
--- a/src/nvim/os/env.c
+++ b/src/nvim/os/env.c
@@ -765,12 +765,12 @@ static char *vim_version_dir(const char *vimdir)
     return NULL;
   }
   char *p = concat_fnames(vimdir, VIM_VERSION_NODOT, true);
-  if (os_isdir((char_u *)p)) {
+  if (os_isdir(p)) {
     return p;
   }
   xfree(p);
   p = concat_fnames(vimdir, RUNTIME_DIRNAME, true);
-  if (os_isdir((char_u *)p)) {
+  if (os_isdir(p)) {
     return p;
   }
   xfree(p);
@@ -976,7 +976,7 @@ char *vim_getenv(const char *name)
       assert(vim_path_end >= vim_path);
       vim_path = xstrndup(vim_path, (size_t)(vim_path_end - vim_path));
 
-      if (!os_isdir((char_u *)vim_path)) {
+      if (!os_isdir(vim_path)) {
         xfree(vim_path);
         vim_path = NULL;
       }
diff --git a/src/nvim/os/fs.c b/src/nvim/os/fs.c
index dc96c39d25..c0d5616666 100644
--- a/src/nvim/os/fs.c
+++ b/src/nvim/os/fs.c
@@ -129,10 +129,10 @@ bool os_isrealdir(const char *name)
 /// Check if the given path exists and is a directory.
 ///
 /// @return `true` if `name` is a directory.
-bool os_isdir(const char_u *name)
+bool os_isdir(const char *name)
   FUNC_ATTR_NONNULL_ALL
 {
-  int32_t mode = os_getperm((const char *)name);
+  int32_t mode = os_getperm(name);
   if (mode < 0) {
     return false;
   }
@@ -865,7 +865,7 @@ int os_file_is_writable(const char *name)
   int r;
   RUN_UV_FS_FUNC(r, uv_fs_access, name, W_OK, NULL);
   if (r == 0) {
-    return os_isdir((char_u *)name) ? 2 : 1;
+    return os_isdir(name) ? 2 : 1;
   }
   return 0;
 }
@@ -915,7 +915,7 @@ int os_mkdir_recurse(const char *const dir, int32_t mode, char **const failed_di
   char *e = curdir + dirlen;
   const char *const real_end = e;
   const char past_head_save = *past_head;
-  while (!os_isdir((char_u *)curdir)) {
+  while (!os_isdir(curdir)) {
     e = path_tail_with_sep(curdir);
     if (e <= past_head) {
       *past_head = NUL;
diff --git a/src/nvim/os/shell.c b/src/nvim/os/shell.c
index c8267ede14..461a79c37b 100644
--- a/src/nvim/os/shell.c
+++ b/src/nvim/os/shell.c
@@ -55,7 +55,7 @@ static void save_patterns(int num_pat, char **pat, int *num_file, char ***file)
     char_u *s = vim_strsave((char_u *)pat[i]);
     // Be compatible with expand_filename(): halve the number of
     // backslashes.
-    backslash_halve(s);
+    backslash_halve((char *)s);
     (*file)[i] = (char *)s;
   }
   *num_file = num_pat;
@@ -508,7 +508,7 @@ int os_expand_wildcards(int num_pat, char **pat, int *num_file, char ***file, in
     }
 
     // check if this entry should be included
-    dir = (os_isdir((char_u *)(*file)[i]));
+    dir = (os_isdir((*file)[i]));
     if ((dir && !(flags & EW_DIR)) || (!dir && !(flags & EW_FILE))) {
       continue;
     }
diff --git a/src/nvim/path.c b/src/nvim/path.c
index e40729b114..a5cec6772f 100644
--- a/src/nvim/path.c
+++ b/src/nvim/path.c
@@ -326,7 +326,7 @@ bool dir_of_file_exists(char_u *fname)
   }
   char c = *p;
   *p = NUL;
-  bool retval = os_isdir(fname);
+  bool retval = os_isdir((char *)fname);
   *p = c;
   return retval;
 }
@@ -752,7 +752,7 @@ static size_t do_path_expand(garray_T *gap, const char_u *path, size_t wildoff,
           // no more wildcards, check if there is a match
           // remove backslashes for the remaining components only
           if (*path_end != NUL) {
-            backslash_halve(buf + len + 1);
+            backslash_halve((char *)buf + len + 1);
           }
           // add existing file or symbolic link
           if ((flags & EW_ALLLINKS) ? os_fileinfo_link((char *)buf, &file_info)
@@ -1135,7 +1135,7 @@ static int expand_in_path(garray_T *const gap, char_u *const pattern, const int
   if (flags & EW_ADDSLASH) {
     glob_flags |= WILD_ADD_SLASH;
   }
-  globpath((char *)paths, pattern, gap, glob_flags);
+  globpath((char *)paths, (char *)pattern, gap, glob_flags);
   xfree(paths);
 
   return gap->ga_len;
@@ -1312,7 +1312,7 @@ int gen_expand_wildcards(int num_pat, char **pat, int *num_file, char ***file, i
     }
 
     if (add_pat == -1 || (add_pat == 0 && (flags & EW_NOTFOUND))) {
-      char_u *t = backslash_halve_save(p);
+      char_u *t = (char_u *)backslash_halve_save((char *)p);
 
       /* When EW_NOTFOUND is used, always add files and dirs.  Makes
        * "vim c:/" work. */
@@ -1472,7 +1472,7 @@ void addfile(garray_T *gap, char_u *f, int flags)
   }
 #endif
 
-  isdir = os_isdir(f);
+  isdir = os_isdir((char *)f);
   if ((isdir && !(flags & EW_DIR)) || (!isdir && !(flags & EW_FILE))) {
     return;
   }
@@ -1845,7 +1845,7 @@ int vim_FullName(const char *fname, char *buf, size_t len, bool force)
     return OK;
   }
 
-  int rv = path_to_absolute((char_u *)fname, (char_u *)buf, len, force);
+  int rv = path_to_absolute(fname, buf, len, force);
   if (rv == FAIL) {
     xstrlcpy(buf, fname, len);  // something failed; use the filename
   }
@@ -1904,7 +1904,7 @@ void path_fix_case(char *name)
   }
 
   // Open the directory where the file is located.
-  char *slash = (char *)STRRCHR(name, '/');
+  char *slash = strrchr(name, '/');
   char *tail;
   Directory dir;
   bool ok;
@@ -2139,7 +2139,7 @@ int expand_wildcards_eval(char_u **pat, int *num_file, char ***file, int flags)
                          true);
     emsg_off--;
     if (eval_pat != NULL) {
-      exp_pat = (char *)concat_str(eval_pat, (char_u *)exp_pat + usedlen);
+      exp_pat = concat_str((char *)eval_pat, exp_pat + usedlen);
     }
   }
 
@@ -2353,20 +2353,20 @@ int append_path(char *path, const char *to_append, size_t max_len)
 /// @param  force  also expand when "fname" is already absolute.
 ///
 /// @return FAIL for failure, OK for success.
-static int path_to_absolute(const char_u *fname, char_u *buf, size_t len, int force)
+static int path_to_absolute(const char *fname, char *buf, size_t len, int force)
 {
-  char_u *p;
+  char *p;
   *buf = NUL;
 
   char *relative_directory = xmalloc(len);
   char *end_of_path = (char *)fname;
 
   // expand it if forced or not an absolute path
-  if (force || !path_is_absolute(fname)) {
-    p = STRRCHR(fname, '/');
+  if (force || !path_is_absolute((char_u *)fname)) {
+    p = strrchr(fname, '/');
 #ifdef WIN32
     if (p == NULL) {
-      p = STRRCHR(fname, '\\');
+      p = strrchr(fname, '\\');
     }
 #endif
     if (p != NULL) {
@@ -2380,19 +2380,19 @@ static int path_to_absolute(const char_u *fname, char_u *buf, size_t len, int fo
         memcpy(relative_directory, fname, (size_t)(p - fname));
         relative_directory[p - fname] = NUL;
       }
-      end_of_path = (char *)(p + 1);
+      end_of_path = p + 1;
     } else {
       relative_directory[0] = NUL;
       end_of_path = (char *)fname;
     }
 
-    if (FAIL == path_full_dir_name(relative_directory, (char *)buf, len)) {
+    if (FAIL == path_full_dir_name(relative_directory, buf, len)) {
       xfree(relative_directory);
       return FAIL;
     }
   }
   xfree(relative_directory);
-  return append_path((char *)buf, end_of_path, len);
+  return append_path(buf, end_of_path, len);
 }
 
 /// Check if file `fname` is a full (absolute) path.
diff --git a/src/nvim/plines.c b/src/nvim/plines.c
index 11b6951edd..cc730ba307 100644
--- a/src/nvim/plines.c
+++ b/src/nvim/plines.c
@@ -262,7 +262,7 @@ int linetabsize_col(int startcol, char *s)
     cts.cts_vcol += lbr_chartabsize_adv(&cts);
   }
   clear_chartabsize_arg(&cts);
-  return (int)cts.cts_vcol;
+  return cts.cts_vcol;
 }
 
 /// Like linetabsize(), but for a given window instead of the current one.
@@ -530,7 +530,7 @@ static int win_nolbr_chartabsize(chartabsize_T *cts, int *headp)
                            wp->w_buffer->b_p_ts,
                            wp->w_buffer->b_p_vts_array);
   }
-  n = ptr2cells((char *)s);
+  n = ptr2cells(s);
 
   // Add one cell for a double-width character in the last column of the
   // window, displayed with a ">".
diff --git a/src/nvim/popupmenu.c b/src/nvim/popupmenu.c
index b144348188..0d9080ceb7 100644
--- a/src/nvim/popupmenu.c
+++ b/src/nvim/popupmenu.c
@@ -524,7 +524,7 @@ void pum_redraw(void)
             }
 
             if (pum_rl) {
-              char *rt = (char *)reverse_text(st);
+              char *rt = reverse_text((char *)st);
               char *rt_start = rt;
               int size = vim_strsize(rt);
 
diff --git a/src/nvim/profile.c b/src/nvim/profile.c
index d4f3756f4d..cded231c85 100644
--- a/src/nvim/profile.c
+++ b/src/nvim/profile.c
@@ -279,7 +279,7 @@ void ex_profile(exarg_T *eap)
   char *e;
   int len;
 
-  e = (char *)skiptowhite((char_u *)eap->arg);
+  e = skiptowhite(eap->arg);
   len = (int)(e - eap->arg);
   e = skipwhite(e);
 
@@ -354,7 +354,7 @@ void set_context_in_profile_cmd(expand_T *xp, const char *arg)
   pexpand_what = PEXP_SUBCMD;
   xp->xp_pattern = (char *)arg;
 
-  char_u *const end_subcmd = skiptowhite((const char_u *)arg);
+  char_u *const end_subcmd = (char_u *)skiptowhite(arg);
   if (*end_subcmd == NUL) {
     return;
   }
@@ -612,7 +612,7 @@ static void func_dump_profile(FILE *fd)
             .script_ctx = fp->uf_script_ctx,
             .channel_id = 0,
           };
-          char *p = (char *)get_scriptname(last_set, &should_free);
+          char *p = get_scriptname(last_set, &should_free);
           fprintf(fd, "    Defined: %s:%" PRIdLINENR "\n",
                   p, fp->uf_script_ctx.sc_lnum);
           if (should_free) {
@@ -721,7 +721,7 @@ static void script_dump_profile(FILE *fd)
       fprintf(fd, "\n");
       fprintf(fd, "count  total (s)   self (s)\n");
 
-      sfd = os_fopen((char *)si->sn_name, "r");
+      sfd = os_fopen(si->sn_name, "r");
       if (sfd == NULL) {
         fprintf(fd, "Cannot open file!\n");
       } else {
diff --git a/src/nvim/quickfix.c b/src/nvim/quickfix.c
index 20e6893ea5..f9c4892b91 100644
--- a/src/nvim/quickfix.c
+++ b/src/nvim/quickfix.c
@@ -799,7 +799,7 @@ retry:
 
   // Convert a line if it contains a non-ASCII character
   if (state->vc.vc_type != CONV_NONE && has_non_ascii((char_u *)state->linebuf)) {
-    char *line = (char *)string_convert(&state->vc, (char_u *)state->linebuf, &state->linelen);
+    char *line = string_convert(&state->vc, state->linebuf, &state->linelen);
     if (line != NULL) {
       if (state->linelen < IOSIZE) {
         STRLCPY(state->linebuf, line, state->linelen + 1);
@@ -2129,7 +2129,7 @@ static char *qf_push_dir(char *dirbuf, struct dir_stack_T **stackptr, bool is_fi
     while (ds_new) {
       xfree((*stackptr)->dirname);
       (*stackptr)->dirname = concat_fnames(ds_new->dirname, dirbuf, true);
-      if (os_isdir((char_u *)(*stackptr)->dirname)) {
+      if (os_isdir((*stackptr)->dirname)) {
         break;
       }
 
@@ -3054,7 +3054,7 @@ static void qf_list_entry(qfline_T *qfp, int qf_idx, bool cursel)
   }
 
   msg_putchar('\n');
-  msg_outtrans_attr(IObuff, cursel ? HL_ATTR(HLF_QFL) : qfFileAttr);
+  msg_outtrans_attr((char *)IObuff, cursel ? HL_ATTR(HLF_QFL) : qfFileAttr);
 
   if (qfp->qf_lnum != 0) {
     msg_puts_attr(":", qfSepAttr);
diff --git a/src/nvim/runtime.c b/src/nvim/runtime.c
index 41056a2773..e85167f8fd 100644
--- a/src/nvim/runtime.c
+++ b/src/nvim/runtime.c
@@ -123,7 +123,7 @@ char *estack_sfile(estack_arg_T which)
                                        ? &entry->es_info.ufunc->uf_script_ctx
                                        : &entry->es_info.aucmd->script_ctx);
         return def_ctx->sc_sid > 0
-                ? xstrdup((char *)(SCRIPT_ITEM(def_ctx->sc_sid).sn_name))
+                ? xstrdup((SCRIPT_ITEM(def_ctx->sc_sid).sn_name))
                 : NULL;
       } else if (entry->es_type == ETYPE_SCRIPT) {
         return xstrdup(entry->es_name);
@@ -192,7 +192,7 @@ void runtime_init(void)
 void ex_runtime(exarg_T *eap)
 {
   char *arg = eap->arg;
-  char *p = (char *)skiptowhite((char_u *)arg);
+  char *p = skiptowhite(arg);
   ptrdiff_t len = p - arg;
   int flags = eap->forceit ? DIP_ALL : 0;
 
@@ -226,9 +226,9 @@ static void source_callback(char *fname, void *cookie)
 /// When "flags" has DIP_ERR: give an error message if there is no match.
 ///
 /// return FAIL when no file could be sourced, OK otherwise.
-int do_in_path(char_u *path, char *name, int flags, DoInRuntimepathCB callback, void *cookie)
+int do_in_path(char *path, char *name, int flags, DoInRuntimepathCB callback, void *cookie)
 {
-  char_u *tail;
+  char *tail;
   int num_files;
   char **files;
   int i;
@@ -236,17 +236,17 @@ int do_in_path(char_u *path, char *name, int flags, DoInRuntimepathCB callback,
 
   // Make a copy of 'runtimepath'.  Invoking the callback may change the
   // value.
-  char_u *rtp_copy = vim_strsave(path);
+  char *rtp_copy = xstrdup(path);
   char *buf = xmallocz(MAXPATHL);
   {
     if (p_verbose > 10 && name != NULL) {
       verbose_enter();
-      smsg(_("Searching for \"%s\" in \"%s\""), name, (char *)path);
+      smsg(_("Searching for \"%s\" in \"%s\""), name, path);
       verbose_leave();
     }
 
     // Loop over all entries in 'runtimepath'.
-    char *rtp = (char *)rtp_copy;
+    char *rtp = rtp_copy;
     while (*rtp != NUL && ((flags & DIP_ALL) || !did_one)) {
       // Copy the path from 'runtimepath' to buf[].
       copy_option_part(&rtp, buf, MAXPATHL, ",");
@@ -267,14 +267,14 @@ int do_in_path(char_u *path, char *name, int flags, DoInRuntimepathCB callback,
         did_one = true;
       } else if (buflen + STRLEN(name) + 2 < MAXPATHL) {
         add_pathsep(buf);
-        tail = (char_u *)buf + STRLEN(buf);
+        tail = buf + STRLEN(buf);
 
         // Loop over all patterns in "name"
         char *np = name;
         while (*np != NUL && ((flags & DIP_ALL) || !did_one)) {
           // Append the pattern from "name" to buf[].
-          assert(MAXPATHL >= (tail - (char_u *)buf));
-          copy_option_part(&np, (char *)tail, (size_t)(MAXPATHL - (tail - (char_u *)buf)), "\t ");
+          assert(MAXPATHL >= (tail - buf));
+          copy_option_part(&np, tail, (size_t)(MAXPATHL - (tail - buf)), "\t ");
 
           if (p_verbose > 10) {
             verbose_enter();
@@ -303,7 +303,7 @@ int do_in_path(char_u *path, char *name, int flags, DoInRuntimepathCB callback,
   xfree(buf);
   xfree(rtp_copy);
   if (!did_one && name != NULL) {
-    char *basepath = path == (char_u *)p_rtp ? "runtimepath" : "packpath";
+    char *basepath = path == p_rtp ? "runtimepath" : "packpath";
 
     if (flags & DIP_ERR) {
       semsg(_(e_dirnotf), basepath, name);
@@ -363,19 +363,19 @@ void runtime_search_path_unref(RuntimeSearchPath path, int *ref)
 /// When "flags" has DIP_ERR: give an error message if there is no match.
 ///
 /// return FAIL when no file could be sourced, OK otherwise.
-int do_in_cached_path(char_u *name, int flags, DoInRuntimepathCB callback, void *cookie)
+int do_in_cached_path(char *name, int flags, DoInRuntimepathCB callback, void *cookie)
 {
-  char_u *tail;
+  char *tail;
   int num_files;
   char **files;
   int i;
   bool did_one = false;
 
-  char_u buf[MAXPATHL];
+  char buf[MAXPATHL];
 
   if (p_verbose > 10 && name != NULL) {
     verbose_enter();
-    smsg(_("Searching for \"%s\" in runtime path"), (char *)name);
+    smsg(_("Searching for \"%s\" in runtime path"), name);
     verbose_leave();
   }
 
@@ -399,15 +399,15 @@ int do_in_cached_path(char_u *name, int flags, DoInRuntimepathCB callback, void
       (*callback)(item.path, cookie);
     } else if (buflen + STRLEN(name) + 2 < MAXPATHL) {
       STRCPY(buf, item.path);
-      add_pathsep((char *)buf);
+      add_pathsep(buf);
       tail = buf + STRLEN(buf);
 
       // Loop over all patterns in "name"
-      char *np = (char *)name;
+      char *np = name;
       while (*np != NUL && ((flags & DIP_ALL) || !did_one)) {
         // Append the pattern from "name" to buf[].
         assert(MAXPATHL >= (tail - buf));
-        copy_option_part(&np, (char *)tail, (size_t)(MAXPATHL - (tail - buf)), "\t ");
+        copy_option_part(&np, tail, (size_t)(MAXPATHL - (tail - buf)), "\t ");
 
         if (p_verbose > 10) {
           verbose_enter();
@@ -419,7 +419,7 @@ int do_in_cached_path(char_u *name, int flags, DoInRuntimepathCB callback, void
                        | (flags & DIP_DIRFILE) ? (EW_DIR|EW_FILE) : 0;
 
         // Expand wildcards, invoke the callback for each match.
-        char *(pat[]) = { (char *)buf };
+        char *(pat[]) = { buf };
         if (gen_expand_wildcards(1, pat, &num_files, &files, ew_flags) == OK) {
           for (i = 0; i < num_files; i++) {
             (*callback)(files[i], cookie);
@@ -499,7 +499,7 @@ ArrayOf(String) runtime_get_named_common(bool lua, Array pat, bool all,
     if (lua) {
       if (item->has_lua == kNone) {
         size_t size = (size_t)snprintf(buf, buf_len, "%s/lua/", item->path);
-        item->has_lua = (size < buf_len && os_isdir((char_u *)buf));
+        item->has_lua = (size < buf_len && os_isdir(buf));
       }
       if (item->has_lua == kFalse) {
         continue;
@@ -534,13 +534,13 @@ done:
 /// If "name" is NULL calls callback for each entry in "path". Cookie is
 /// passed by reference in this case, setting it to NULL indicates that callback
 /// has done its job.
-int do_in_path_and_pp(char_u *path, char_u *name, int flags, DoInRuntimepathCB callback,
-                      void *cookie)
+int do_in_path_and_pp(char *path, char *name, int flags, DoInRuntimepathCB callback, void *cookie)
 {
   int done = FAIL;
 
   if ((flags & DIP_NORTP) == 0) {
-    done |= do_in_path(path, (char *)((name && !*name) ? NULL : name), flags, callback, cookie);
+    done |= do_in_path(path, (name && !*name) ? NULL : name, flags, callback,
+                       cookie);
   }
 
   if ((done == FAIL || (flags & DIP_ALL)) && (flags & DIP_START)) {
@@ -550,7 +550,7 @@ int do_in_path_and_pp(char_u *path, char_u *name, int flags, DoInRuntimepathCB c
     char *suffix = (flags & DIP_AFTER) ? "after/" : "";
 
     vim_snprintf(s, len, start_dir, suffix, name);
-    done |= do_in_path((char_u *)p_pp, s, flags & ~DIP_AFTER, callback, cookie);
+    done |= do_in_path(p_pp, s, flags & ~DIP_AFTER, callback, cookie);
 
     xfree(s);
 
@@ -560,7 +560,7 @@ int do_in_path_and_pp(char_u *path, char_u *name, int flags, DoInRuntimepathCB c
       s = xmallocz(len);
 
       vim_snprintf(s, len, start_dir, suffix, name);
-      done |= do_in_path((char_u *)p_pp, s, flags & ~DIP_AFTER, callback, cookie);
+      done |= do_in_path(p_pp, s, flags & ~DIP_AFTER, callback, cookie);
 
       xfree(s);
     }
@@ -572,7 +572,7 @@ int do_in_path_and_pp(char_u *path, char_u *name, int flags, DoInRuntimepathCB c
     char *s = xmallocz(len);
 
     vim_snprintf(s, len, opt_dir, name);
-    done |= do_in_path((char_u *)p_pp, s, flags, callback, cookie);
+    done |= do_in_path(p_pp, s, flags, callback, cookie);
 
     xfree(s);
 
@@ -582,7 +582,7 @@ int do_in_path_and_pp(char_u *path, char_u *name, int flags, DoInRuntimepathCB c
       s = xmallocz(len);
 
       vim_snprintf(s, len, opt_dir, name);
-      done |= do_in_path((char_u *)p_pp, s, flags, callback, cookie);
+      done |= do_in_path(p_pp, s, flags, callback, cookie);
 
       xfree(s);
     }
@@ -625,7 +625,7 @@ static void expand_rtp_entry(RuntimeSearchPath *search_path, Map(String, handle_
 }
 
 static void expand_pack_entry(RuntimeSearchPath *search_path, Map(String, handle_T) *rtp_used,
-                              CharVec *after_path, char_u *pack_entry, size_t pack_entry_len)
+                              CharVec *after_path, char *pack_entry, size_t pack_entry_len)
 {
   static char buf[MAXPATHL];
   char *(start_pat[]) = { "/pack/*/start/*", "/start/*" };  // NOLINT
@@ -664,10 +664,10 @@ RuntimeSearchPath runtime_search_path_build(void)
   RuntimeSearchPath search_path = KV_INITIAL_VALUE;
   CharVec after_path = KV_INITIAL_VALUE;
 
-  static char_u buf[MAXPATHL];
+  static char buf[MAXPATHL];
   for (char *entry = p_pp; *entry != NUL;) {
     char *cur_entry = entry;
-    copy_option_part(&entry, (char *)buf, MAXPATHL, ",");
+    copy_option_part(&entry, buf, MAXPATHL, ",");
 
     String the_entry = { .data = cur_entry, .size = STRLEN(buf) };
 
@@ -678,18 +678,18 @@ RuntimeSearchPath runtime_search_path_build(void)
   char *rtp_entry;
   for (rtp_entry = p_rtp; *rtp_entry != NUL;) {
     char *cur_entry = rtp_entry;
-    copy_option_part(&rtp_entry, (char *)buf, MAXPATHL, ",");
+    copy_option_part(&rtp_entry, buf, MAXPATHL, ",");
     size_t buflen = STRLEN(buf);
 
-    if (path_is_after((char *)buf, buflen)) {
+    if (path_is_after(buf, buflen)) {
       rtp_entry = cur_entry;
       break;
     }
 
     // fact: &rtp entries can contain wild chars
-    expand_rtp_entry(&search_path, &rtp_used, (char *)buf, false);
+    expand_rtp_entry(&search_path, &rtp_used, buf, false);
 
-    handle_T *h = map_ref(String, handle_T)(&pack_used, cstr_as_string((char *)buf), false);
+    handle_T *h = map_ref(String, handle_T)(&pack_used, cstr_as_string(buf), false);
     if (h) {
       (*h)++;
       expand_pack_entry(&search_path, &rtp_used, &after_path, buf, buflen);
@@ -700,7 +700,7 @@ RuntimeSearchPath runtime_search_path_build(void)
     String item = kv_A(pack_entries, i);
     handle_T h = map_get(String, handle_T)(&pack_used, item);
     if (h == 0) {
-      expand_pack_entry(&search_path, &rtp_used, &after_path, (char_u *)item.data, item.size);
+      expand_pack_entry(&search_path, &rtp_used, &after_path, item.data, item.size);
     }
   }
 
@@ -712,8 +712,8 @@ RuntimeSearchPath runtime_search_path_build(void)
 
   // "after" dirs in rtp
   for (; *rtp_entry != NUL;) {
-    copy_option_part(&rtp_entry, (char *)buf, MAXPATHL, ",");
-    expand_rtp_entry(&search_path, &rtp_used, (char *)buf, path_is_after((char *)buf, STRLEN(buf)));
+    copy_option_part(&rtp_entry, buf, MAXPATHL, ",");
+    expand_rtp_entry(&search_path, &rtp_used, buf, path_is_after(buf, STRLEN(buf)));
   }
 
   // strings are not owned
@@ -767,13 +767,13 @@ int do_in_runtimepath(char *name, int flags, DoInRuntimepathCB callback, void *c
 {
   int success = FAIL;
   if (!(flags & DIP_NORTP)) {
-    success |= do_in_cached_path((name && !*name) ? NULL : (char_u *)name, flags, callback, cookie);
+    success |= do_in_cached_path((name && !*name) ? NULL : name, flags, callback, cookie);
     flags = (flags & ~DIP_START) | DIP_NORTP;
   }
   // TODO(bfredl): we could integrate disabled OPT dirs into the cached path
   // which would effectivize ":packadd myoptpack" as well
   if ((flags & (DIP_START|DIP_OPT)) && (success == FAIL || (flags & DIP_ALL))) {
-    success |= do_in_path_and_pp((char_u *)p_rtp, (char_u *)name, flags, callback, cookie);
+    success |= do_in_path_and_pp(p_rtp, name, flags, callback, cookie);
   }
   return success;
 }
@@ -789,7 +789,7 @@ int source_runtime(char *name, int flags)
 }
 
 /// Just like source_runtime(), but use "path" instead of 'runtimepath'.
-int source_in_path(char_u *path, char_u *name, int flags)
+int source_in_path(char *path, char *name, int flags)
 {
   return do_in_path_and_pp(path, name, flags, source_callback, NULL);
 }
@@ -813,14 +813,14 @@ static void source_all_matches(char *pat)
 ///
 /// @param fname the package path
 /// @param is_pack whether the added dir is a "pack/*/start/*/" style package
-static int add_pack_dir_to_rtp(char_u *fname, bool is_pack)
+static int add_pack_dir_to_rtp(char *fname, bool is_pack)
 {
   char *p;
   char *buf = NULL;
   char *afterdir = NULL;
   int retval = FAIL;
 
-  char *p1 = get_past_head((char *)fname);
+  char *p1 = get_past_head(fname);
   char *p2 = p1;
   char *p3 = p1;
   char *p4 = p1;
@@ -841,7 +841,7 @@ static int add_pack_dir_to_rtp(char_u *fname, bool is_pack)
   p4++;  // append pathsep in order to expand symlink
   char c = *p4;
   *p4 = NUL;
-  char *const ffname = fix_fname((char *)fname);
+  char *const ffname = fix_fname(fname);
   *p4 = c;
 
   if (ffname == NULL) {
@@ -895,9 +895,9 @@ static int add_pack_dir_to_rtp(char_u *fname, bool is_pack)
   }
 
   // check if rtp/pack/name/start/name/after exists
-  afterdir = concat_fnames((char *)fname, "after", true);
+  afterdir = concat_fnames(fname, "after", true);
   size_t afterlen = 0;
-  if (is_pack ? pack_has_entries((char_u *)afterdir) : os_isdir((char_u *)afterdir)) {
+  if (is_pack ? pack_has_entries(afterdir) : os_isdir(afterdir)) {
     afterlen = strlen(afterdir) + 1;  // add one for comma
   }
 
@@ -964,29 +964,29 @@ theend:
 /// Load scripts in "plugin" directory of the package.
 /// For opt packages, also load scripts in "ftdetect" (start packages already
 /// load these from filetype.vim)
-static int load_pack_plugin(bool opt, char_u *fname)
+static int load_pack_plugin(bool opt, char *fname)
 {
   static const char *ftpat = "%s/ftdetect/*.vim";  // NOLINT
 
-  char *const ffname = fix_fname((char *)fname);
+  char *const ffname = fix_fname(fname);
   size_t len = strlen(ffname) + STRLEN(ftpat);
-  char_u *pat = xmallocz(len);
+  char *pat = xmallocz(len);
 
-  vim_snprintf((char *)pat, len, "%s/plugin/**/*.vim", ffname);  // NOLINT
-  source_all_matches((char *)pat);
-  vim_snprintf((char *)pat, len, "%s/plugin/**/*.lua", ffname);  // NOLINT
-  source_all_matches((char *)pat);
+  vim_snprintf(pat, len, "%s/plugin/**/*.vim", ffname);  // NOLINT
+  source_all_matches(pat);
+  vim_snprintf(pat, len, "%s/plugin/**/*.lua", ffname);  // NOLINT
+  source_all_matches(pat);
 
-  char_u *cmd = vim_strsave((char_u *)"g:did_load_filetypes");
+  char *cmd = xstrdup("g:did_load_filetypes");
 
   // If runtime/filetype.vim wasn't loaded yet, the scripts will be
   // found when it loads.
-  if (opt && eval_to_number((char *)cmd) > 0) {
+  if (opt && eval_to_number(cmd) > 0) {
     do_cmdline_cmd("augroup filetypedetect");
-    vim_snprintf((char *)pat, len, ftpat, ffname);
-    source_all_matches((char *)pat);
+    vim_snprintf(pat, len, ftpat, ffname);
+    source_all_matches(pat);
     vim_snprintf((char *)pat, len, "%s/ftdetect/*.lua", ffname);  // NOLINT
-    source_all_matches((char *)pat);
+    source_all_matches(pat);
     do_cmdline_cmd("augroup END");
   }
   xfree(cmd);
@@ -1001,7 +1001,7 @@ static int APP_ADD_DIR;
 static int APP_LOAD;
 static int APP_BOTH;
 
-static void add_pack_plugin(bool opt, char_u *fname, void *cookie)
+static void add_pack_plugin(bool opt, char *fname, void *cookie)
 {
   if (cookie != &APP_LOAD) {
     char *buf = xmalloc(MAXPATHL);
@@ -1010,7 +1010,7 @@ static void add_pack_plugin(bool opt, char_u *fname, void *cookie)
     const char *p = (const char *)p_rtp;
     while (*p != NUL) {
       copy_option_part((char **)&p, buf, MAXPATHL, ",");
-      if (path_fnamecmp(buf, (char *)fname) == 0) {
+      if (path_fnamecmp(buf, fname) == 0) {
         found = true;
         break;
       }
@@ -1031,25 +1031,25 @@ static void add_pack_plugin(bool opt, char_u *fname, void *cookie)
 
 static void add_start_pack_plugin(char *fname, void *cookie)
 {
-  add_pack_plugin(false, (char_u *)fname, cookie);
+  add_pack_plugin(false, fname, cookie);
 }
 
 static void add_opt_pack_plugin(char *fname, void *cookie)
 {
-  add_pack_plugin(true, (char_u *)fname, cookie);
+  add_pack_plugin(true, fname, cookie);
 }
 
 /// Add all packages in the "start" directory to 'runtimepath'.
 void add_pack_start_dirs(void)
 {
-  do_in_path((char_u *)p_pp, NULL, DIP_ALL + DIP_DIR, add_pack_start_dir, NULL);
+  do_in_path(p_pp, NULL, DIP_ALL + DIP_DIR, add_pack_start_dir, NULL);
 }
 
-static bool pack_has_entries(char_u *buf)
+static bool pack_has_entries(char *buf)
 {
   int num_files;
   char **files;
-  char *(pat[]) = { (char *)buf };
+  char *(pat[]) = { buf };
   if (gen_expand_wildcards(1, pat, &num_files, &files, EW_DIR) == OK) {
     FreeWild(num_files, files);
   }
@@ -1058,7 +1058,7 @@ static bool pack_has_entries(char_u *buf)
 
 static void add_pack_start_dir(char *fname, void *cookie)
 {
-  static char_u buf[MAXPATHL];
+  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) {
@@ -1076,9 +1076,9 @@ static void add_pack_start_dir(char *fname, void *cookie)
 void load_start_packages(void)
 {
   did_source_packages = true;
-  do_in_path((char_u *)p_pp, "pack/*/start/*", DIP_ALL + DIP_DIR,  // NOLINT
+  do_in_path(p_pp, "pack/*/start/*", DIP_ALL + DIP_DIR,  // NOLINT
              add_start_pack_plugin, &APP_LOAD);
-  do_in_path((char_u *)p_pp, "start/*", DIP_ALL + DIP_DIR,  // NOLINT
+  do_in_path(p_pp, "start/*", DIP_ALL + DIP_DIR,  // NOLINT
              add_start_pack_plugin, &APP_LOAD);
 }
 
@@ -1099,12 +1099,12 @@ void ex_packloadall(exarg_T *eap)
 void load_plugins(void)
 {
   if (p_lpl) {
-    char_u *rtp_copy = (char_u *)p_rtp;
-    char_u *const plugin_pattern_vim = (char_u *)"plugin/**/*.vim";  // NOLINT
-    char_u *const plugin_pattern_lua = (char_u *)"plugin/**/*.lua";  // NOLINT
+    char *rtp_copy = p_rtp;
+    char *const plugin_pattern_vim = "plugin/**/*.vim";  // NOLINT
+    char *const plugin_pattern_lua = "plugin/**/*.lua";  // NOLINT
 
     if (!did_source_packages) {
-      rtp_copy = vim_strsave((char_u *)p_rtp);
+      rtp_copy = xstrdup(p_rtp);
       add_pack_start_dirs();
     }
 
@@ -1121,8 +1121,8 @@ void load_plugins(void)
     }
     TIME_MSG("loading packages");
 
-    source_runtime((char *)plugin_pattern_vim, DIP_ALL | DIP_AFTER);
-    source_runtime((char *)plugin_pattern_lua, DIP_ALL | DIP_AFTER);
+    source_runtime(plugin_pattern_vim, DIP_ALL | DIP_AFTER);
+    source_runtime(plugin_pattern_lua, DIP_ALL | DIP_AFTER);
     TIME_MSG("loading after plugins");
   }
 }
@@ -1146,7 +1146,7 @@ void ex_packadd(exarg_T *eap)
     // The first round don't give a "not found" error, in the second round
     // only when nothing was found in the first round.
     res =
-      do_in_path((char_u *)p_pp, pat, DIP_ALL + DIP_DIR + (round == 2 && res == FAIL ? DIP_ERR : 0),
+      do_in_path(p_pp, pat, DIP_ALL + DIP_DIR + (round == 2 && res == FAIL ? DIP_ERR : 0),
                  round == 1 ? add_start_pack_plugin : add_opt_pack_plugin,
                  eap->forceit ? &APP_ADD_DIR : &APP_BOTH);
     xfree(pat);
@@ -1162,7 +1162,7 @@ void ex_packadd(exarg_T *eap)
 ///   'packpath'/pack/ * /opt/ * /{dirnames}/{pat}.vim
 /// When "flags" has DIP_LUA: search also performed for .lua files
 /// "dirnames" is an array with one or more directory names.
-int ExpandRTDir(char_u *pat, int flags, int *num_file, char ***file, char *dirnames[])
+int ExpandRTDir(char *pat, int flags, int *num_file, char ***file, char *dirnames[])
 {
   *num_file = 0;
   *file = NULL;
@@ -1174,11 +1174,11 @@ int ExpandRTDir(char_u *pat, int flags, int *num_file, char ***file, char *dirna
   // 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;
-    char_u *s = xmalloc(size);
-    snprintf((char *)s, size, "%s/%s*.vim", dirnames[i], pat);
+    char *s = xmalloc(size);
+    snprintf(s, size, "%s/%s*.vim", dirnames[i], pat);
     globpath(p_rtp, s, &ga, 0);
     if (flags & DIP_LUA) {
-      snprintf((char *)s, size, "%s/%s*.lua", dirnames[i], pat);
+      snprintf(s, size, "%s/%s*.lua", dirnames[i], pat);
       globpath(p_rtp, s, &ga, 0);
     }
     xfree(s);
@@ -1187,11 +1187,11 @@ int ExpandRTDir(char_u *pat, int flags, int *num_file, char ***file, char *dirna
   if (flags & DIP_START) {
     for (int i = 0; dirnames[i] != NULL; i++) {
       size_t size = STRLEN(dirnames[i]) + pat_len + 22;
-      char_u *s = xmalloc(size);
-      snprintf((char *)s, size, "pack/*/start/*/%s/%s*.vim", dirnames[i], pat);  // NOLINT
+      char *s = xmalloc(size);
+      snprintf(s, size, "pack/*/start/*/%s/%s*.vim", dirnames[i], pat);  // NOLINT
       globpath(p_pp, s, &ga, 0);
       if (flags & DIP_LUA) {
-        snprintf((char *)s, size, "pack/*/start/*/%s/%s*.lua", dirnames[i], pat);  // NOLINT
+        snprintf(s, size, "pack/*/start/*/%s/%s*.lua", dirnames[i], pat);  // NOLINT
         globpath(p_pp, s, &ga, 0);
       }
       xfree(s);
@@ -1199,11 +1199,11 @@ int ExpandRTDir(char_u *pat, int flags, int *num_file, char ***file, char *dirna
 
     for (int i = 0; dirnames[i] != NULL; i++) {
       size_t size = STRLEN(dirnames[i]) + pat_len + 22;
-      char_u *s = xmalloc(size);
-      snprintf((char *)s, size, "start/*/%s/%s*.vim", dirnames[i], pat);  // NOLINT
+      char *s = xmalloc(size);
+      snprintf(s, size, "start/*/%s/%s*.vim", dirnames[i], pat);  // NOLINT
       globpath(p_pp, s, &ga, 0);
       if (flags & DIP_LUA) {
-        snprintf((char *)s, size, "start/*/%s/%s*.lua", dirnames[i], pat);  // NOLINT
+        snprintf(s, size, "start/*/%s/%s*.lua", dirnames[i], pat);  // NOLINT
         globpath(p_pp, s, &ga, 0);
       }
       xfree(s);
@@ -1213,11 +1213,11 @@ int ExpandRTDir(char_u *pat, int flags, int *num_file, char ***file, char *dirna
   if (flags & DIP_OPT) {
     for (int i = 0; dirnames[i] != NULL; i++) {
       size_t size = STRLEN(dirnames[i]) + pat_len + 20;
-      char_u *s = xmalloc(size);
-      snprintf((char *)s, size, "pack/*/opt/*/%s/%s*.vim", dirnames[i], pat);  // NOLINT
+      char *s = xmalloc(size);
+      snprintf(s, size, "pack/*/opt/*/%s/%s*.vim", dirnames[i], pat);  // NOLINT
       globpath(p_pp, s, &ga, 0);
       if (flags & DIP_LUA) {
-        snprintf((char *)s, size, "pack/*/opt/*/%s/%s*.lua", dirnames[i], pat);  // NOLINT
+        snprintf(s, size, "pack/*/opt/*/%s/%s*.lua", dirnames[i], pat);  // NOLINT
         globpath(p_pp, s, &ga, 0);
       }
       xfree(s);
@@ -1225,11 +1225,11 @@ int ExpandRTDir(char_u *pat, int flags, int *num_file, char ***file, char *dirna
 
     for (int i = 0; dirnames[i] != NULL; i++) {
       size_t size = STRLEN(dirnames[i]) + pat_len + 20;
-      char_u *s = xmalloc(size);
-      snprintf((char *)s, size, "opt/*/%s/%s*.vim", dirnames[i], pat);  // NOLINT
+      char *s = xmalloc(size);
+      snprintf(s, size, "opt/*/%s/%s*.vim", dirnames[i], pat);  // NOLINT
       globpath(p_pp, s, &ga, 0);
       if (flags & DIP_LUA) {
-        snprintf((char *)s, size, "opt/*/%s/%s*.lua", dirnames[i], pat);  // NOLINT
+        snprintf(s, size, "opt/*/%s/%s*.lua", dirnames[i], pat);  // NOLINT
         globpath(p_pp, s, &ga, 0);
       }
       xfree(s);
@@ -1237,9 +1237,9 @@ int ExpandRTDir(char_u *pat, int flags, int *num_file, char ***file, char *dirna
   }
 
   for (int i = 0; i < ga.ga_len; i++) {
-    char_u *match = ((char_u **)ga.ga_data)[i];
-    char_u *s = match;
-    char_u *e = s + STRLEN(s);
+    char *match = ((char **)ga.ga_data)[i];
+    char *s = match;
+    char *e = s + STRLEN(s);
     if (e - s > 4 && (STRNICMP(e - 4, ".vim", 4) == 0
                       || ((flags & DIP_LUA)
                           && STRNICMP(e - 4, ".lua", 4) == 0))) {
@@ -1271,7 +1271,7 @@ int ExpandRTDir(char_u *pat, int flags, int *num_file, char ***file, char *dirna
 
 /// Expand loadplugin names:
 /// 'packpath'/pack/ * /opt/{pat}
-int ExpandPackAddDir(char_u *pat, int *num_file, char ***file)
+int ExpandPackAddDir(char *pat, int *num_file, char ***file)
 {
   garray_T ga;
 
@@ -1281,16 +1281,16 @@ int ExpandPackAddDir(char_u *pat, int *num_file, char ***file)
   ga_init(&ga, (int)sizeof(char *), 10);
 
   size_t buflen = pat_len + 26;
-  char_u *s = xmalloc(buflen);
-  snprintf((char *)s, buflen, "pack/*/opt/%s*", pat);  // NOLINT
+  char *s = xmalloc(buflen);
+  snprintf(s, buflen, "pack/*/opt/%s*", pat);  // NOLINT
   globpath(p_pp, s, &ga, 0);
-  snprintf((char *)s, buflen, "opt/%s*", pat);  // NOLINT
+  snprintf(s, buflen, "opt/%s*", pat);  // NOLINT
   globpath(p_pp, s, &ga, 0);
   xfree(s);
 
   for (int i = 0; i < ga.ga_len; i++) {
-    char_u *match = ((char_u **)ga.ga_data)[i];
-    s = (char_u *)path_tail((char *)match);
+    char *match = ((char **)ga.ga_data)[i];
+    s = path_tail(match);
     memmove(match, s, STRLEN(s) + 1);
   }
 
@@ -1479,7 +1479,7 @@ char *get_lib_dir(void)
   // TODO(bfredl): too fragile? Ideally default_lib_dir would be made empty
   // in an appimage build
   if (strlen(default_lib_dir) != 0
-      && os_isdir((const char_u *)default_lib_dir)) {
+      && os_isdir(default_lib_dir)) {
     return xstrdup(default_lib_dir);
   }
 
@@ -1611,7 +1611,7 @@ static void cmd_source(char *fname, exarg_T *eap)
     // - after ":argdo", ":windo" or ":bufdo"
     // - another command follows
     // - inside a loop
-    openscript((char_u *)fname, global_busy || listcmd_busy || eap->nextcmd != NULL
+    openscript(fname, global_busy || listcmd_busy || eap->nextcmd != NULL
                || eap->cstack->cs_idx >= 0);
 
     // ":source" read ex commands
@@ -1691,12 +1691,12 @@ static FILE *fopen_noinh_readbin(char *filename)
 ///
 /// @return true if this line did begin with a continuation (the next line
 ///         should also be considered, if it exists); false otherwise
-static bool concat_continued_line(garray_T *const ga, const int init_growsize,
-                                  const char_u *const p, size_t len)
+static bool concat_continued_line(garray_T *const ga, const int init_growsize, const char *const p,
+                                  size_t len)
   FUNC_ATTR_NONNULL_ALL
 {
-  const char *const line = (char *)skipwhite_len(p, len);
-  len -= (size_t)((char_u *)line - p);
+  const char *const line = skipwhite_len((char *)p, len);
+  len -= (size_t)(line - p);
   // Skip lines starting with '\" ', concat lines starting with '\'
   if (len >= 3 && STRNCMP(line, "\"\\ ", 3) == 0) {
     return true;
@@ -1732,15 +1732,15 @@ static char *get_str_line(int c, void *cookie, int indent, bool do_concat)
     return NULL;
   }
   const char *line = p->buf + p->offset;
-  const char *eol = (char *)skip_to_newline((char_u *)line);
+  const char *eol = skip_to_newline(line);
   garray_T ga;
-  ga_init(&ga, sizeof(char_u), 400);
+  ga_init(&ga, sizeof(char), 400);
   ga_concat_len(&ga, line, (size_t)(eol - line));
   if (do_concat && vim_strchr(p_cpo, CPO_CONCAT) == NULL) {
     while (eol[0] != NUL) {
       line = eol + 1;
-      const char_u *const next_eol = skip_to_newline((char_u *)line);
-      if (!concat_continued_line(&ga, 400, (char_u *)line, (size_t)(next_eol - (char_u *)line))) {
+      const char *const next_eol = skip_to_newline(line);
+      if (!concat_continued_line(&ga, 400, line, (size_t)(next_eol - line))) {
         break;
       }
       eol = (char *)next_eol;
@@ -1770,7 +1770,7 @@ scriptitem_T *new_script_item(char *const name, scid_T *const sid_out)
     SCRIPT_ITEM(script_items.ga_len).sn_name = NULL;
     SCRIPT_ITEM(script_items.ga_len).sn_prof_on = false;
   }
-  SCRIPT_ITEM(sid).sn_name = (char_u *)name;
+  SCRIPT_ITEM(sid).sn_name = name;
   new_script_vars(sid);  // Allocate the local script variables to use for this script.
   return &SCRIPT_ITEM(sid);
 }
@@ -1814,7 +1814,7 @@ static void cmd_source_buffer(const exarg_T *const eap)
     return;
   }
   garray_T ga;
-  ga_init(&ga, sizeof(char_u), 400);
+  ga_init(&ga, sizeof(char), 400);
   const linenr_T final_lnum = eap->line2;
   // Copy the contents to be executed.
   for (linenr_T curr_lnum = eap->line1; curr_lnum <= final_lnum; curr_lnum++) {
@@ -1825,7 +1825,7 @@ static void cmd_source_buffer(const exarg_T *const eap)
     ga_concat(&ga, (char *)ml_get(curr_lnum));
     ga_append(&ga, NL);
   }
-  ((char_u *)ga.ga_data)[ga.ga_len - 1] = NUL;
+  ((char *)ga.ga_data)[ga.ga_len - 1] = NUL;
   const GetStrLineCookie cookie = {
     .buf = ga.ga_data,
     .offset = 0,
@@ -1886,7 +1886,7 @@ int do_source(char *fname, int check_other, int is_vimrc)
   if (fname_exp == NULL) {
     return retval;
   }
-  if (os_isdir((char_u *)fname_exp)) {
+  if (os_isdir(fname_exp)) {
     smsg(_("Cannot source a directory: \"%s\""), fname);
     goto theend;
   }
@@ -1963,7 +1963,7 @@ int do_source(char *fname, int check_other, int is_vimrc)
   cookie.finished = false;
 
   // Check if this script has a breakpoint.
-  cookie.breakpoint = dbg_find_breakpoint(true, (char_u *)fname_exp, (linenr_T)0);
+  cookie.breakpoint = dbg_find_breakpoint(true, fname_exp, (linenr_T)0);
   cookie.fname = fname_exp;
   cookie.dbg_tick = debug_tick;
 
@@ -1992,7 +1992,7 @@ int do_source(char *fname, int check_other, int is_vimrc)
   si = get_current_script_id(&fname_exp, &current_sctx);
 
   // Keep the sourcing name/lnum, for recursive calls.
-  estack_push(ETYPE_SCRIPT, (char *)si->sn_name, 0);
+  estack_push(ETYPE_SCRIPT, si->sn_name, 0);
 
   if (l_do_profiling == PROF_YES) {
     bool forceit = false;
@@ -2025,7 +2025,7 @@ int do_source(char *fname, int check_other, int is_vimrc)
         && firstline[1] == 0xbb && firstline[2] == 0xbf) {
       // Found BOM; setup conversion, skip over BOM and recode the line.
       convert_setup(&cookie.conv, "utf-8", p_enc);
-      p = (char *)string_convert(&cookie.conv, (char_u *)firstline + 3, NULL);
+      p = string_convert(&cookie.conv, (char *)firstline + 3, NULL);
       if (p == NULL) {
         p = xstrdup((char *)firstline + 3);
       }
@@ -2128,7 +2128,7 @@ scriptitem_T *get_current_script_id(char **fnamep, sctx_T *ret_sctx)
   }
   if (script_sctx.sc_sid == 0) {
     si = new_script_item(*fnamep, &script_sctx.sc_sid);
-    *fnamep = xstrdup((char *)si->sn_name);
+    *fnamep = xstrdup(si->sn_name);
   }
   if (ret_sctx != NULL) {
     *ret_sctx = script_sctx;
@@ -2145,7 +2145,7 @@ void ex_scriptnames(exarg_T *eap)
     if (eap->line2 < 1 || eap->line2 > script_items.ga_len) {
       emsg(_(e_invarg));
     } else {
-      eap->arg = (char *)SCRIPT_ITEM(eap->line2).sn_name;
+      eap->arg = SCRIPT_ITEM(eap->line2).sn_name;
       do_exedit(eap, NULL);
     }
     return;
@@ -2153,7 +2153,7 @@ void ex_scriptnames(exarg_T *eap)
 
   for (int i = 1; i <= script_items.ga_len && !got_int; i++) {
     if (SCRIPT_ITEM(i).sn_name != NULL) {
-      home_replace(NULL, (char *)SCRIPT_ITEM(i).sn_name, (char *)NameBuff, MAXPATHL, true);
+      home_replace(NULL, SCRIPT_ITEM(i).sn_name, (char *)NameBuff, MAXPATHL, true);
       vim_snprintf((char *)IObuff, IOSIZE, "%3d: %s", i, NameBuff);
       if (!message_filtered((char *)IObuff)) {
         msg_putchar('\n');
@@ -2179,40 +2179,40 @@ void scriptnames_slash_adjust(void)
 
 /// Get a pointer to a script name.  Used for ":verbose set".
 /// Message appended to "Last set from "
-char_u *get_scriptname(LastSet last_set, bool *should_free)
+char *get_scriptname(LastSet last_set, bool *should_free)
 {
   *should_free = false;
 
   switch (last_set.script_ctx.sc_sid) {
   case SID_MODELINE:
-    return (char_u *)_("modeline");
+    return _("modeline");
   case SID_CMDARG:
-    return (char_u *)_("--cmd argument");
+    return _("--cmd argument");
   case SID_CARG:
-    return (char_u *)_("-c argument");
+    return _("-c argument");
   case SID_ENV:
-    return (char_u *)_("environment variable");
+    return _("environment variable");
   case SID_ERROR:
-    return (char_u *)_("error handler");
+    return _("error handler");
   case SID_WINLAYOUT:
-    return (char_u *)_("changed window size");
+    return _("changed window size");
   case SID_LUA:
-    return (char_u *)_("Lua");
+    return _("Lua");
   case SID_API_CLIENT:
     snprintf((char *)IObuff, IOSIZE, _("API client (channel id %" PRIu64 ")"), last_set.channel_id);
-    return IObuff;
+    return (char *)IObuff;
   case SID_STR:
-    return (char_u *)_("anonymous :source");
+    return _("anonymous :source");
   default: {
-    char *const sname = (char *)SCRIPT_ITEM(last_set.script_ctx.sc_sid).sn_name;
+    char *const sname = SCRIPT_ITEM(last_set.script_ctx.sc_sid).sn_name;
     if (sname == NULL) {
       snprintf((char *)IObuff, IOSIZE, _("anonymous :source (script id %d)"),
                last_set.script_ctx.sc_sid);
-      return IObuff;
+      return (char *)IObuff;
     }
 
     *should_free = true;
-    return (char_u *)home_replace_save(NULL, sname);
+    return home_replace_save(NULL, sname);
   }
   }
 }
@@ -2248,7 +2248,7 @@ char *getsourceline(int c, void *cookie, int indent, bool do_concat)
 
   // If breakpoints have been added/deleted need to check for it.
   if (sp->dbg_tick < debug_tick) {
-    sp->breakpoint = dbg_find_breakpoint(true, (char_u *)sp->fname, SOURCING_LNUM);
+    sp->breakpoint = dbg_find_breakpoint(true, sp->fname, SOURCING_LNUM);
     sp->dbg_tick = debug_tick;
   }
   if (do_profiling == PROF_YES) {
@@ -2287,11 +2287,10 @@ char *getsourceline(int c, void *cookie, int indent, bool do_concat)
             || (p[0] == '"' && p[1] == '\\' && p[2] == ' '))) {
       garray_T ga;
 
-      ga_init(&ga, (int)sizeof(char_u), 400);
+      ga_init(&ga, (int)sizeof(char), 400);
       ga_concat(&ga, line);
       while (sp->nextline != NULL
-             && concat_continued_line(&ga, 400, (char_u *)sp->nextline,
-                                      STRLEN(sp->nextline))) {
+             && concat_continued_line(&ga, 400, sp->nextline, STRLEN(sp->nextline))) {
         xfree(sp->nextline);
         sp->nextline = get_one_sourceline(sp);
       }
@@ -2305,7 +2304,7 @@ char *getsourceline(int c, void *cookie, int indent, bool do_concat)
     char *s;
 
     // Convert the encoding of the script line.
-    s = (char *)string_convert(&sp->conv, (char_u *)line, NULL);
+    s = string_convert(&sp->conv, line, NULL);
     if (s != NULL) {
       xfree(line);
       line = s;
@@ -2314,9 +2313,9 @@ char *getsourceline(int c, void *cookie, int indent, bool do_concat)
 
   // Did we encounter a breakpoint?
   if (sp->breakpoint != 0 && sp->breakpoint <= SOURCING_LNUM) {
-    dbg_breakpoint((char_u *)sp->fname, SOURCING_LNUM);
+    dbg_breakpoint(sp->fname, SOURCING_LNUM);
     // Find next breakpoint.
-    sp->breakpoint = dbg_find_breakpoint(true, (char_u *)sp->fname, SOURCING_LNUM);
+    sp->breakpoint = dbg_find_breakpoint(true, sp->fname, SOURCING_LNUM);
     sp->dbg_tick = debug_tick;
   }
 
diff --git a/src/nvim/runtime.h b/src/nvim/runtime.h
index 03c426c79b..053c71212e 100644
--- a/src/nvim/runtime.h
+++ b/src/nvim/runtime.h
@@ -51,7 +51,7 @@ typedef enum {
 } estack_arg_T;
 
 typedef struct scriptitem_S {
-  char_u *sn_name;
+  char *sn_name;
   bool sn_prof_on;              ///< true when script is/was profiled
   bool sn_pr_force;             ///< forceit: profile functions in this script
   proftime_T sn_pr_child;       ///< time set when going into first child
diff --git a/src/nvim/screen.c b/src/nvim/screen.c
index 6efaae3725..d268dde845 100644
--- a/src/nvim/screen.c
+++ b/src/nvim/screen.c
@@ -1270,7 +1270,7 @@ static int get_encoded_char_adv(const char_u **p)
     int64_t num = 0;
     for (int bytes = s[1] == 'x' ? 1 : s[1] == 'u' ? 2 : 4; bytes > 0; bytes--) {
       *p += 2;
-      int n = hexhex2nr(*p);
+      int n = hexhex2nr((char *)(*p));
       if (n < 0) {
         return 0;
       }
diff --git a/src/nvim/search.c b/src/nvim/search.c
index c1c2f0dbe9..e995081df8 100644
--- a/src/nvim/search.c
+++ b/src/nvim/search.c
@@ -170,7 +170,7 @@ int search_regcomp(char_u *pat, int pat_save, int pat_use, int options, regmmatc
   }
 
   if (curwin->w_p_rl && *curwin->w_p_rlc == 's') {
-    mr_pattern = reverse_text(pat);
+    mr_pattern = (char_u *)reverse_text((char *)pat);
     mr_pattern_alloced = true;
   } else {
     mr_pattern = pat;
@@ -1261,7 +1261,7 @@ int do_search(oparg_T *oap, int dirc, int search_delim, char_u *pat, long count,
         // it would be blanked out again very soon.  Show it on the
         // left, but do reverse the text.
         if (curwin->w_p_rl && *curwin->w_p_rlc == 's') {
-          char_u *r = reverse_text(trunc != NULL ? trunc : msgbuf);
+          char_u *r = (char_u *)reverse_text(trunc != NULL ? (char *)trunc : (char *)msgbuf);
           xfree(msgbuf);
           msgbuf = r;
           // move reversed text to beginning of buffer
@@ -3666,7 +3666,7 @@ void find_pattern_in_path(char_u *ptr, Direction dir, size_t len, bool whole, bo
           if (new_fname != NULL) {
             // using "new_fname" is more reliable, e.g., when
             // 'includeexpr' is set.
-            msg_outtrans_attr(new_fname, HL_ATTR(HLF_D));
+            msg_outtrans_attr((char *)new_fname, HL_ATTR(HLF_D));
           } else {
             /*
              * Isolate the file name.
@@ -3702,7 +3702,7 @@ void find_pattern_in_path(char_u *ptr, Direction dir, size_t len, bool whole, bo
             }
             save_char = p[i];
             p[i] = NUL;
-            msg_outtrans_attr(p, HL_ATTR(HLF_D));
+            msg_outtrans_attr((char *)p, HL_ATTR(HLF_D));
             p[i] = save_char;
           }
 
diff --git a/src/nvim/shada.c b/src/nvim/shada.c
index 88ad7d519a..d2f1b39ca4 100644
--- a/src/nvim/shada.c
+++ b/src/nvim/shada.c
@@ -3023,7 +3023,7 @@ shada_write_file_nomerge: {}
     if (tail != fname) {
       const char tail_save = *tail;
       *tail = NUL;
-      if (!os_isdir((char_u *)fname)) {
+      if (!os_isdir(fname)) {
         int ret;
         char *failed_dir;
         if ((ret = os_mkdir_recurse(fname, 0700, &failed_dir)) != 0) {
diff --git a/src/nvim/sign.c b/src/nvim/sign.c
index a9640eacda..ed7f53d3ba 100644
--- a/src/nvim/sign.c
+++ b/src/nvim/sign.c
@@ -858,7 +858,7 @@ static void sign_define_init_icon(sign_T *sp, char_u *icon)
 {
   xfree(sp->sn_icon);
   sp->sn_icon = vim_strsave(icon);
-  backslash_halve(sp->sn_icon);
+  backslash_halve((char *)sp->sn_icon);
 }
 
 /// Initialize the text for a new sign
@@ -1353,7 +1353,7 @@ static int parse_sign_cmd_args(int cmd, char_u *arg, char_u **sign_name, int *si
     if (STRNCMP(arg, "line=", 5) == 0) {
       arg += 5;
       *lnum = atoi((char *)arg);
-      arg = skiptowhite(arg);
+      arg = (char_u *)skiptowhite((char *)arg);
       lnum_arg = true;
     } else if (STRNCMP(arg, "*", 1) == 0 && cmd == SIGNCMD_UNPLACE) {
       if (*signid != -1) {
@@ -1361,11 +1361,11 @@ static int parse_sign_cmd_args(int cmd, char_u *arg, char_u **sign_name, int *si
         return FAIL;
       }
       *signid = -2;
-      arg = skiptowhite(arg + 1);
+      arg = (char_u *)skiptowhite((char *)arg + 1);
     } else if (STRNCMP(arg, "name=", 5) == 0) {
       arg += 5;
       name = arg;
-      arg = skiptowhite(arg);
+      arg = (char_u *)skiptowhite((char *)arg);
       if (*arg != NUL) {
         *arg++ = NUL;
       }
@@ -1376,14 +1376,14 @@ static int parse_sign_cmd_args(int cmd, char_u *arg, char_u **sign_name, int *si
     } else if (STRNCMP(arg, "group=", 6) == 0) {
       arg += 6;
       *group = arg;
-      arg = skiptowhite(arg);
+      arg = (char_u *)skiptowhite((char *)arg);
       if (*arg != NUL) {
         *arg++ = NUL;
       }
     } else if (STRNCMP(arg, "priority=", 9) == 0) {
       arg += 9;
       *prio = atoi((char *)arg);
-      arg = skiptowhite(arg);
+      arg = (char_u *)skiptowhite((char *)arg);
     } else if (STRNCMP(arg, "file=", 5) == 0) {
       arg += 5;
       filename = arg;
@@ -1427,7 +1427,7 @@ void ex_sign(exarg_T *eap)
   sign_T *sp;
 
   // Parse the subcommand.
-  p = skiptowhite(arg);
+  p = (char_u *)skiptowhite((char *)arg);
   idx = sign_cmd_idx(arg, p);
   if (idx == SIGNCMD_LAST) {
     semsg(_("E160: Unknown sign command: %s"), arg);
@@ -1449,7 +1449,7 @@ void ex_sign(exarg_T *eap)
 
       // Isolate the sign name.  If it's a number skip leading zeroes,
       // so that "099" and "99" are the same sign.  But keep "0".
-      p = skiptowhite(arg);
+      p = (char_u *)skiptowhite((char *)arg);
       if (*p != NUL) {
         *p++ = NUL;
       }
@@ -1789,7 +1789,7 @@ void set_context_in_sign_cmd(expand_T *xp, char_u *arg)
   expand_what = EXP_SUBCMD;
   xp->xp_pattern = (char *)arg;
 
-  end_subcmd = skiptowhite(arg);
+  end_subcmd = (char_u *)skiptowhite((char *)arg);
   if (*end_subcmd == NUL) {
     // expand subcmd name
     // :sign {subcmd}<CTRL-D>
@@ -1814,7 +1814,7 @@ void set_context_in_sign_cmd(expand_T *xp, char_u *arg)
   do {
     p = (char_u *)skipwhite((char *)p);
     last = p;
-    p = skiptowhite(p);
+    p = (char_u *)skiptowhite((char *)p);
   } while (*p != NUL);
 
   p = (char_u *)vim_strchr((char *)last, '=');
diff --git a/src/nvim/spell.c b/src/nvim/spell.c
index 10923829c3..1259736e0e 100644
--- a/src/nvim/spell.c
+++ b/src/nvim/spell.c
@@ -243,7 +243,7 @@ size_t spell_check(win_T *wp, char_u *ptr, hlf_T *attrp, int *capcol, bool docou
     if (*ptr == '0' && (ptr[1] == 'b' || ptr[1] == 'B')) {
       mi.mi_end = (char_u *)skipbin((char *)ptr + 2);
     } else if (*ptr == '0' && (ptr[1] == 'x' || ptr[1] == 'X')) {
-      mi.mi_end = skiphex(ptr + 2);
+      mi.mi_end = (char_u *)skiphex((char *)ptr + 2);
     } else {
       mi.mi_end = (char_u *)skipdigits((char *)ptr);
     }
@@ -1258,10 +1258,10 @@ size_t spell_move_to(win_T *wp, int dir, bool allwords, bool curline, hlf_T *att
 
     // For checking first word with a capital skip white space.
     if (capcol == 0) {
-      capcol = (int)getwhitecols(line);
+      capcol = (int)getwhitecols((char *)line);
     } else if (curline && wp == curwin) {
       // For spellbadword(): check if first word needs a capital.
-      col = (int)getwhitecols(line);
+      col = (int)getwhitecols((char *)line);
       if (check_need_cap(lnum, col)) {
         capcol = col;
       }
@@ -1876,7 +1876,7 @@ char *did_set_spelllang(win_T *wp)
 
       // Check if we loaded this language before.
       for (slang = first_lang; slang != NULL; slang = slang->sl_next) {
-        if (path_full_compare((char *)lang, (char *)slang->sl_fname, false, true)
+        if (path_full_compare((char *)lang, slang->sl_fname, false, true)
             == kEqualFiles) {
           break;
         }
@@ -1925,7 +1925,7 @@ char *did_set_spelllang(win_T *wp)
     // Loop over the languages, there can be several files for "lang".
     for (slang = first_lang; slang != NULL; slang = slang->sl_next) {
       if (filename
-          ? path_full_compare((char *)lang, (char *)slang->sl_fname, false, true) == kEqualFiles
+          ? path_full_compare((char *)lang, slang->sl_fname, false, true) == kEqualFiles
           : STRICMP(lang, slang->sl_name) == 0) {
         region_mask = REGION_ALL;
         if (!filename && region != NULL) {
@@ -1981,7 +1981,7 @@ char *did_set_spelllang(win_T *wp)
 
       // If it was already found above then skip it.
       for (c = 0; c < ga.ga_len; c++) {
-        p = LANGP_ENTRY(ga, c)->lp_slang->sl_fname;
+        p = (char_u *)LANGP_ENTRY(ga, c)->lp_slang->sl_fname;
         if (p != NULL
             && path_full_compare((char *)spf_name, (char *)p, false, true) == kEqualFiles) {
           break;
@@ -1994,7 +1994,7 @@ char *did_set_spelllang(win_T *wp)
 
     // Check if it was loaded already.
     for (slang = first_lang; slang != NULL; slang = slang->sl_next) {
-      if (path_full_compare((char *)spf_name, (char *)slang->sl_fname, false, true)
+      if (path_full_compare((char *)spf_name, slang->sl_fname, false, true)
           == kEqualFiles) {
         break;
       }
@@ -2473,7 +2473,7 @@ bool check_need_cap(linenr_T lnum, colnr_T col)
   char_u *line = get_cursor_line_ptr();
   char_u *line_copy = NULL;
   colnr_T endcol = 0;
-  if (getwhitecols(line) >= (int)col) {
+  if (getwhitecols((char *)line) >= (int)col) {
     // At start of line, check if previous line is empty or sentence
     // ends there.
     if (lnum == 1) {
@@ -2484,7 +2484,7 @@ bool check_need_cap(linenr_T lnum, colnr_T col)
         need_cap = true;
       } else {
         // Append a space in place of the line break.
-        line_copy = concat_str(line, (char_u *)" ");
+        line_copy = (char_u *)concat_str((char *)line, " ");
         line = line_copy;
         endcol = (colnr_T)STRLEN(line);
       }
@@ -3599,8 +3599,8 @@ char *compile_cap_prog(synblock_T *synblock)
     synblock->b_cap_prog = NULL;
   } else {
     // Prepend a ^ so that we only match at one column
-    char_u *re = concat_str((char_u *)"^", (char_u *)synblock->b_p_spc);
-    synblock->b_cap_prog = vim_regcomp((char *)re, RE_MAGIC);
+    char *re = concat_str("^", synblock->b_p_spc);
+    synblock->b_cap_prog = vim_regcomp(re, RE_MAGIC);
     xfree(re);
     if (synblock->b_cap_prog == NULL) {
       synblock->b_cap_prog = rp;         // restore the previous program
diff --git a/src/nvim/spell_defs.h b/src/nvim/spell_defs.h
index 61f722b9ee..27b9777dc2 100644
--- a/src/nvim/spell_defs.h
+++ b/src/nvim/spell_defs.h
@@ -115,9 +115,9 @@ typedef struct slang_S slang_T;
 
 struct slang_S {
   slang_T *sl_next;         // next language
-  char_u *sl_name;         // language name "en", "en.rare", "nl", etc.
-  char_u *sl_fname;        // name of .spl file
-  bool sl_add;                  // true if it's a .add file.
+  char_u *sl_name;          // language name "en", "en.rare", "nl", etc.
+  char *sl_fname;           // name of .spl file
+  bool sl_add;              // true if it's a .add file.
 
   char_u *sl_fbyts;        // case-folded word bytes
   long sl_fbyts_len;     // length of sl_fbyts
diff --git a/src/nvim/spellfile.c b/src/nvim/spellfile.c
index 33e8c5c099..0f8034312e 100644
--- a/src/nvim/spellfile.c
+++ b/src/nvim/spellfile.c
@@ -604,7 +604,7 @@ slang_T *spell_load_file(char_u *fname, char_u *lang, slang_T *old_lp, bool sile
     lp = slang_alloc(lang);
 
     // Remember the file name, used to reload the file when it's updated.
-    lp->sl_fname = vim_strsave(fname);
+    lp->sl_fname = (char *)vim_strsave(fname);
 
     // Check for .add.spl.
     lp->sl_add = strstr(path_tail((char *)fname), SPL_FNAME_ADD) != NULL;
@@ -869,12 +869,12 @@ static void tree_count_words(char_u *byts, idx_T *idxs)
   }
 }
 
-// Load the .sug files for languages that have one and weren't loaded yet.
+/// Load the .sug files for languages that have one and weren't loaded yet.
 void suggest_load_files(void)
 {
   langp_T *lp;
   slang_T *slang;
-  char_u *dotp;
+  char *dotp;
   FILE *fd;
   char_u buf[MAXWLEN];
   int i;
@@ -894,12 +894,12 @@ void suggest_load_files(void)
       // don't try again and again.
       slang->sl_sugloaded = true;
 
-      dotp = STRRCHR(slang->sl_fname, '.');
+      dotp = strrchr(slang->sl_fname, '.');
       if (dotp == NULL || FNAMECMP(dotp, ".spl") != 0) {
         continue;
       }
       STRCPY(dotp, ".sug");
-      fd = os_fopen((char *)slang->sl_fname, "r");
+      fd = os_fopen(slang->sl_fname, "r");
       if (fd == NULL) {
         goto nextone;
       }
@@ -1822,7 +1822,7 @@ static void spell_reload_one(char_u *fname, bool added_word)
   bool didit = false;
 
   for (slang = first_lang; slang != NULL; slang = slang->sl_next) {
-    if (path_full_compare((char *)fname, (char *)slang->sl_fname, false, true) == kEqualFiles) {
+    if (path_full_compare((char *)fname, slang->sl_fname, false, true) == kEqualFiles) {
       slang_clear(slang);
       if (spell_load_file(fname, NULL, slang, false) == NULL) {
         // reloading failed, clear the language
@@ -2075,7 +2075,7 @@ static afffile_T *spell_read_aff(spellinfo_T *spin, char_u *fname)
     // Convert from "SET" to 'encoding' when needed.
     xfree(pc);
     if (spin->si_conv.vc_type != CONV_NONE) {
-      pc = string_convert(&spin->si_conv, rline, NULL);
+      pc = (char_u *)string_convert(&spin->si_conv, (char *)rline, NULL);
       if (pc == NULL) {
         smsg(_("Conversion failure for word in %s line %d: %s"),
              fname, lnum, rline);
@@ -3155,7 +3155,7 @@ static int spell_read_dic(spellinfo_T *spin, char_u *fname, afffile_T *affile)
 
     // Convert from "SET" to 'encoding' when needed.
     if (spin->si_conv.vc_type != CONV_NONE) {
-      pc = string_convert(&spin->si_conv, line, NULL);
+      pc = (char_u *)string_convert(&spin->si_conv, (char *)line, NULL);
       if (pc == NULL) {
         smsg(_("Conversion failure for word in %s line %d: %s"),
              fname, lnum, line);
@@ -3701,7 +3701,7 @@ static int spell_read_wordfile(spellinfo_T *spin, char_u *fname)
     // Convert from "/encoding={encoding}" to 'encoding' when needed.
     xfree(pc);
     if (spin->si_conv.vc_type != CONV_NONE) {
-      pc = string_convert(&spin->si_conv, rline, NULL);
+      pc = (char_u *)string_convert(&spin->si_conv, (char *)rline, NULL);
       if (pc == NULL) {
         smsg(_("Conversion failure for word in %s line %ld: %s"),
              fname, lnum, rline);
@@ -4907,7 +4907,7 @@ static void spell_make_sugfile(spellinfo_T *spin, char *wfname)
   // of the code for the soundfolding stuff.
   // It might have been done already by spell_reload_one().
   for (slang = first_lang; slang != NULL; slang = slang->sl_next) {
-    if (path_full_compare(wfname, (char *)slang->sl_fname, false, true)
+    if (path_full_compare(wfname, slang->sl_fname, false, true)
         == kEqualFiles) {
       break;
     }
@@ -5343,7 +5343,7 @@ static void mkspell(int fcount, char **fnames, bool ascii, bool over_write, bool
       emsg(_(e_exists));
       goto theend;
     }
-    if (os_isdir((char_u *)wfname)) {
+    if (os_isdir(wfname)) {
       semsg(_(e_isadir2), wfname);
       goto theend;
     }
@@ -5723,7 +5723,7 @@ static void init_spellfile(void)
                        "/%.*s", (int)(lend - lstart), lstart);
         }
         l = (int)STRLEN(buf);
-        fname = LANGP_ENTRY(curwin->w_s->b_langp, 0)
+        fname = (char_u *)LANGP_ENTRY(curwin->w_s->b_langp, 0)
                 ->lp_slang->sl_fname;
         vim_snprintf((char *)buf + l, MAXPATHL - (size_t)l, ".%s.add",
                      ((fname != NULL
diff --git a/src/nvim/spellsuggest.c b/src/nvim/spellsuggest.c
index fa46d94342..23c8c621b5 100644
--- a/src/nvim/spellsuggest.c
+++ b/src/nvim/spellsuggest.c
@@ -972,7 +972,7 @@ static void suggest_try_special(suginfo_T *su)
   char_u word[MAXWLEN];
 
   // Recognize a word that is repeated: "the the".
-  char_u *p = skiptowhite(su->su_fbadword);
+  char_u *p = (char_u *)skiptowhite((char *)su->su_fbadword);
   size_t len = (size_t)(p - su->su_fbadword);
   p = (char_u *)skipwhite((char *)p);
   if (STRLEN(p) == len && STRNCMP(su->su_fbadword, p, len) == 0) {
@@ -1369,8 +1369,8 @@ static void suggest_trie_walk(suginfo_T *su, langp_T *lp, char_u *fword, bool so
 
           if (compound_ok) {
             p = preword;
-            while (*skiptowhite(p) != NUL) {
-              p = (char_u *)skipwhite((char *)skiptowhite(p));
+            while (*skiptowhite((char *)p) != NUL) {
+              p = (char_u *)skipwhite(skiptowhite((char *)p));
             }
             if (fword_ends && !can_compound(slang, p,
                                             compflags + sp->ts_compsplit)) {
@@ -1590,8 +1590,8 @@ static void suggest_trie_walk(suginfo_T *su, langp_T *lp, char_u *fword, bool so
               break;
             }
             p = preword;
-            while (*skiptowhite(p) != NUL) {
-              p = (char_u *)skipwhite((char *)skiptowhite(p));
+            while (*skiptowhite((char *)p) != NUL) {
+              p = (char_u *)skipwhite(skiptowhite((char *)p));
             }
             if (sp->ts_complen > sp->ts_compsplit
                 && !can_compound(slang, p,
@@ -2636,8 +2636,8 @@ static int stp_sal_score(suggest_T *stp, suginfo_T *su, slang_T *slang, char_u *
     // removing the space.  Don't do it when the good word also contains a
     // space.
     if (ascii_iswhite(su->su_badptr[su->su_badlen])
-        && *skiptowhite(stp->st_word) == NUL) {
-      for (p = fword; *(p = skiptowhite(p)) != NUL;) {
+        && *skiptowhite((char *)stp->st_word) == NUL) {
+      for (p = fword; *(p = (char_u *)skiptowhite((char *)p)) != NUL;) {
         STRMOVE(p, p + 1);
       }
     }
diff --git a/src/nvim/strings.c b/src/nvim/strings.c
index bd0f122f99..16691d0ded 100644
--- a/src/nvim/strings.c
+++ b/src/nvim/strings.c
@@ -503,7 +503,7 @@ static int sort_compare(const void *s1, const void *s2)
 
 void sort_strings(char **files, int count)
 {
-  qsort((void *)files, (size_t)count, sizeof(char_u *), sort_compare);
+  qsort((void *)files, (size_t)count, sizeof(char *), sort_compare);
 }
 
 /*
@@ -540,14 +540,12 @@ bool has_non_ascii_len(const char *const s, const size_t len)
   return false;
 }
 
-/*
- * Concatenate two strings and return the result in allocated memory.
- */
-char_u *concat_str(const char_u *restrict str1, const char_u *restrict str2)
+/// Concatenate two strings and return the result in allocated memory.
+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_u *dest = xmalloc(l + STRLEN(str2) + 1);
+  char *dest = xmalloc(l + STRLEN(str2) + 1);
   STRCPY(dest, str1);
   STRCPY(dest + l, str2);
   return dest;
@@ -1511,15 +1509,15 @@ int kv_do_printf(StringBuilder *str, const char *fmt, ...)
 /// Reverse text into allocated memory.
 ///
 /// @return  the allocated string.
-char_u *reverse_text(char_u *s)
+char *reverse_text(char *s)
   FUNC_ATTR_NONNULL_RET
 {
   // Reverse the pattern.
   size_t len = STRLEN(s);
-  char_u *rev = xmalloc(len + 1);
+  char *rev = xmalloc(len + 1);
   size_t rev_i = len;
   for (size_t s_i = 0; s_i < len; s_i++) {
-    const int mb_len = utfc_ptr2len((char *)s + s_i);
+    const int mb_len = utfc_ptr2len(s + s_i);
     rev_i -= (size_t)mb_len;
     memmove(rev + rev_i, s + s_i, (size_t)mb_len);
     s_i += (size_t)mb_len - 1;
diff --git a/src/nvim/syntax.c b/src/nvim/syntax.c
index e88b1b17f6..f055cc9b0e 100644
--- a/src/nvim/syntax.c
+++ b/src/nvim/syntax.c
@@ -3013,7 +3013,7 @@ static void syn_cmd_conceal(exarg_T *eap, int syncing)
     return;
   }
 
-  next = skiptowhite(arg);
+  next = (char_u *)skiptowhite((char *)arg);
   if (*arg == NUL) {
     if (curwin->w_s->b_syn_conceal) {
       msg("syntax conceal on");
@@ -3042,7 +3042,7 @@ static void syn_cmd_case(exarg_T *eap, int syncing)
     return;
   }
 
-  next = skiptowhite(arg);
+  next = (char_u *)skiptowhite((char *)arg);
   if (*arg == NUL) {
     if (curwin->w_s->b_syn_ic) {
       msg("syntax case ignore");
@@ -3081,7 +3081,7 @@ static void syn_cmd_foldlevel(exarg_T *eap, int syncing)
     return;
   }
 
-  arg_end = skiptowhite(arg);
+  arg_end = (char_u *)skiptowhite((char *)arg);
   if (STRNICMP(arg, "start", 5) == 0 && arg_end - arg == 5) {
     curwin->w_s->b_syn_foldlevel = SYNFLD_START;
   } else if (STRNICMP(arg, "minimum", 7) == 0 && arg_end - arg == 7) {
@@ -3110,7 +3110,7 @@ static void syn_cmd_spell(exarg_T *eap, int syncing)
     return;
   }
 
-  next = skiptowhite(arg);
+  next = (char_u *)skiptowhite((char *)arg);
   if (*arg == NUL) {
     if (curwin->w_s->b_syn_spell == SYNSPL_TOP) {
       msg("syntax spell toplevel");
@@ -3345,7 +3345,7 @@ static void syn_cmd_clear(exarg_T *eap, int syncing)
      * Clear the group IDs that are in the argument.
      */
     while (!ends_excmd(*arg)) {
-      arg_end = skiptowhite(arg);
+      arg_end = (char_u *)skiptowhite((char *)arg);
       if (*arg == '@') {
         id = syn_scl_namen2id(arg + 1, (int)(arg_end - arg - 1));
         if (id == 0) {
@@ -3522,7 +3522,7 @@ static void syn_cmd_list(exarg_T *eap, int syncing)
      * List the group IDs and syntax clusters that are in the argument.
      */
     while (!ends_excmd(*arg) && !got_int) {
-      arg_end = skiptowhite(arg);
+      arg_end = (char_u *)skiptowhite((char *)arg);
       if (*arg == '@') {
         int id = syn_scl_namen2id(arg + 1, (int)(arg_end - arg - 1));
         if (id == 0) {
@@ -4029,7 +4029,7 @@ static void add_keyword(char_u *const name, const int id, const int flags,
 ///                  Return NULL if the end of the command was found instead of further args.
 static char *get_group_name(char *arg, char **name_end)
 {
-  *name_end = (char *)skiptowhite((char_u *)arg);
+  *name_end = skiptowhite(arg);
   char *rest = skipwhite(*name_end);
 
   // Check if there are enough arguments.  The first argument may be a
@@ -4163,7 +4163,7 @@ static char *get_syn_options(char *arg, syn_opt_arg_T *opt, int *conceal_char, i
           return NULL;
         }
         gname_start = (char_u *)arg;
-        arg = (char *)skiptowhite((char_u *)arg);
+        arg = skiptowhite(arg);
         if (gname_start == (char_u *)arg) {
           return NULL;
         }
@@ -4600,7 +4600,7 @@ static void syn_cmd_region(exarg_T *eap, int syncing)
     }
 
     if (item == ITEM_MATCHGROUP) {
-      p = (char *)skiptowhite((char_u *)rest);
+      p = skiptowhite(rest);
       if ((p - rest == 4 && STRNCMP(rest, "NONE", 4) == 0) || eap->skip) {
         matchgroup_id = 0;
       } else {
@@ -5141,7 +5141,7 @@ static void syn_cmd_sync(exarg_T *eap, int syncing)
   }
 
   while (!ends_excmd(*arg_start)) {
-    arg_end = (char *)skiptowhite(arg_start);
+    arg_end = skiptowhite((char *)arg_start);
     next_arg = (char_u *)skipwhite(arg_end);
     xfree(key);
     key = vim_strnsave_up(arg_start, (size_t)(arg_end - (char *)arg_start));
@@ -5150,7 +5150,7 @@ static void syn_cmd_sync(exarg_T *eap, int syncing)
         curwin->w_s->b_syn_sync_flags |= SF_CCOMMENT;
       }
       if (!ends_excmd(*next_arg)) {
-        arg_end = (char *)skiptowhite(next_arg);
+        arg_end = skiptowhite((char *)next_arg);
         if (!eap->skip) {
           curwin->w_s->b_syn_sync_id =
             (int16_t)syn_check_group((char *)next_arg, (size_t)(arg_end - (char *)next_arg));
@@ -5693,10 +5693,10 @@ void set_context_in_syntax_cmd(expand_T *xp, const char *arg)
 
   // (part of) subcommand already typed
   if (*arg != NUL) {
-    const char *p = (const char *)skiptowhite((const char_u *)arg);
+    const char *p = (const char *)skiptowhite(arg);
     if (*p != NUL) {  // Past first word.
       xp->xp_pattern = skipwhite(p);
-      if (*skiptowhite((char_u *)xp->xp_pattern) != NUL) {
+      if (*skiptowhite(xp->xp_pattern) != NUL) {
         xp->xp_context = EXPAND_NOTHING;
       } else if (STRNICMP(arg, "case", p - arg) == 0) {
         expand_what = EXP_CASE;
@@ -6028,7 +6028,7 @@ static void syntime_report(void)
     if (len > (int)STRLEN(p->pattern)) {
       len = (int)STRLEN(p->pattern);
     }
-    msg_outtrans_len(p->pattern, len);
+    msg_outtrans_len((char *)p->pattern, len);
     msg_puts("\n");
   }
   ga_clear(&ga);
diff --git a/src/nvim/tag.c b/src/nvim/tag.c
index 11825ce1c4..5270412382 100644
--- a/src/nvim/tag.c
+++ b/src/nvim/tag.c
@@ -738,7 +738,7 @@ static void print_tag_list(int new_tag, int use_tagstack, int num_matches, char
                  mt_names[matches[i][0] & MT_MASK]);
     msg_puts((char *)IObuff);
     if (tagp.tagkind != NULL) {
-      msg_outtrans_len(tagp.tagkind,
+      msg_outtrans_len((char *)tagp.tagkind,
                        (int)(tagp.tagkind_end - tagp.tagkind));
     }
     msg_advance(13);
@@ -752,7 +752,7 @@ static void print_tag_list(int new_tag, int use_tagstack, int num_matches, char
     // it and put "..." in the middle
     p = tag_full_fname(&tagp);
     if (p != NULL) {
-      msg_outtrans_attr(p, HL_ATTR(HLF_D));
+      msg_outtrans_attr((char *)p, HL_ATTR(HLF_D));
       XFREE_CLEAR(p);
     }
     if (msg_col > 0) {
@@ -794,7 +794,7 @@ static void print_tag_list(int new_tag, int use_tagstack, int num_matches, char
             }
             msg_advance(15);
           }
-          p = msg_outtrans_one(p, attr);
+          p = (char_u *)msg_outtrans_one((char *)p, attr);
           if (*p == TAB) {
             msg_puts_attr(" ", attr);
             break;
@@ -852,7 +852,7 @@ static void print_tag_list(int new_tag, int use_tagstack, int num_matches, char
         msg_putchar(' ');
         p++;
       } else {
-        p = msg_outtrans_one(p, 0);
+        p = (char_u *)msg_outtrans_one((char *)p, 0);
       }
 
       // don't display the "$/;\"" and "$?;\""
@@ -1052,7 +1052,7 @@ void do_tags(exarg_T *eap)
                    tagstack[i].tagname,
                    tagstack[i].fmark.mark.lnum);
       msg_outtrans((char *)IObuff);
-      msg_outtrans_attr(name, tagstack[i].fmark.fnum == curbuf->b_fnum
+      msg_outtrans_attr((char *)name, tagstack[i].fmark.fnum == curbuf->b_fnum
                         ? HL_ATTR(HLF_D) : 0);
       xfree(name);
     }
@@ -1561,7 +1561,7 @@ int find_tags(char *pat, int *num_matches, char ***matchesp, int flags, int minc
 
     // Try tag file names from tags option one by one.
     for (first_file = true;
-         use_cscope || get_tagfname(&tn, first_file, tag_fname) == OK;
+         use_cscope || get_tagfname(&tn, first_file, (char *)tag_fname) == OK;
          first_file = false) {
       // A file that doesn't exist is silently ignored.  Only when not a
       // single file is found, an error message is given (further on).
@@ -1705,7 +1705,7 @@ int find_tags(char *pat, int *num_matches, char ***matchesp, int flags, int minc
             eof = vim_fgets(lbuf, lbuf_size, fp);
           }
           // skip empty and blank lines
-          while (!eof && vim_isblankline(lbuf)) {
+          while (!eof && vim_isblankline((char *)lbuf)) {
             search_info.curr_offset = vim_ftell(fp);
             eof = vim_fgets(lbuf, lbuf_size, fp);
           }
@@ -1726,7 +1726,7 @@ int find_tags(char *pat, int *num_matches, char ***matchesp, int flags, int minc
             eof = use_cscope
               ? cs_fgets(lbuf, lbuf_size)
               : vim_fgets(lbuf, lbuf_size, fp);
-          } while (!eof && vim_isblankline(lbuf));
+          } while (!eof && vim_isblankline((char *)lbuf));
 
           if (eof) {
             break;                                  // end of file
@@ -1741,7 +1741,7 @@ line_read_in:
           // Convert every line.  Converting the pattern from 'enc' to
           // the tags file encoding doesn't work, because characters are
           // not recognized.
-          conv_line = string_convert(&vimconv, lbuf, NULL);
+          conv_line = (char_u *)string_convert(&vimconv, (char *)lbuf, NULL);
           if (conv_line != NULL) {
             // Copy or swap lbuf and conv_line.
             len = (int)STRLEN(conv_line) + 1;
@@ -2340,10 +2340,10 @@ void free_tag_stuff(void)
 /// @param buf  pointer to buffer of MAXPATHL chars
 ///
 /// @return  FAIL if no more tag file names, OK otherwise.
-int get_tagfname(tagname_T *tnp, int first, char_u *buf)
+int get_tagfname(tagname_T *tnp, int first, char *buf)
 {
-  char_u *fname = NULL;
-  char_u *r_ptr;
+  char *fname = NULL;
+  char *r_ptr;
 
   if (first) {
     CLEAR_POINTER(tnp);
@@ -2374,7 +2374,7 @@ int get_tagfname(tagname_T *tnp, int first, char_u *buf)
 #ifdef BACKSLASH_IN_FILENAME
       slash_adjust(buf);
 #endif
-      simplify_filename(buf);
+      simplify_filename((char_u *)buf);
 
       for (int i = 0; i < tag_fnames.ga_len; i++) {
         if (STRCMP(buf, ((char **)(tag_fnames.ga_data))[i]) == 0) {
@@ -2402,7 +2402,7 @@ int get_tagfname(tagname_T *tnp, int first, char_u *buf)
    */
   for (;;) {
     if (tnp->tn_did_filefind_init) {
-      fname = vim_findfile(tnp->tn_search_ctx);
+      fname = (char *)vim_findfile(tnp->tn_search_ctx);
       if (fname != NULL) {
         break;
       }
@@ -2422,17 +2422,17 @@ int get_tagfname(tagname_T *tnp, int first, char_u *buf)
        * Copy next file name into buf.
        */
       buf[0] = NUL;
-      (void)copy_option_part(&tnp->tn_np, (char *)buf, MAXPATHL - 1, " ,");
+      (void)copy_option_part(&tnp->tn_np, buf, MAXPATHL - 1, " ,");
 
-      r_ptr = vim_findfile_stopdir(buf);
+      r_ptr = (char *)vim_findfile_stopdir((char_u *)buf);
       // move the filename one char forward and truncate the
       // filepath with a NUL
-      filename = (char_u *)path_tail((char *)buf);
+      filename = (char_u *)path_tail(buf);
       STRMOVE(filename + 1, filename);
       *filename++ = NUL;
 
-      tnp->tn_search_ctx = vim_findfile_init(buf, filename,
-                                             r_ptr, 100,
+      tnp->tn_search_ctx = vim_findfile_init((char_u *)buf, filename,
+                                             (char_u *)r_ptr, 100,
                                              false,                   // don't free visited list
                                              FINDFILE_FILE,           // we search for a file
                                              tnp->tn_search_ctx, true, (char_u *)curbuf->b_ffname);
diff --git a/src/nvim/undo.c b/src/nvim/undo.c
index ac52bce2f9..97a925f3ad 100644
--- a/src/nvim/undo.c
+++ b/src/nvim/undo.c
@@ -685,7 +685,7 @@ char *u_get_undo_file_name(const char *const buf_ffname, const bool reading)
         *p-- = NUL;
       }
 
-      bool has_directory = os_isdir((char_u *)dir_name);
+      bool has_directory = os_isdir(dir_name);
       if (!has_directory && *dirp == NUL && !reading) {
         // Last directory in the list does not exist, create it.
         int ret;
diff --git a/src/nvim/usercmd.c b/src/nvim/usercmd.c
index ae312de61a..5b2101587f 100644
--- a/src/nvim/usercmd.c
+++ b/src/nvim/usercmd.c
@@ -216,7 +216,7 @@ const char *set_context_in_user_cmd(expand_T *xp, const char *arg_in)
   // Check for attributes
   while (*arg == '-') {
     arg++;  // Skip "-".
-    p = (const char *)skiptowhite((const char_u *)arg);
+    p = (const char *)skiptowhite(arg);
     if (*p == NUL) {
       // Cursor is still in the attribute.
       p = strchr(arg, '=');
@@ -248,7 +248,7 @@ const char *set_context_in_user_cmd(expand_T *xp, const char *arg_in)
   }
 
   // After the attributes comes the new command name.
-  p = (const char *)skiptowhite((const char_u *)arg);
+  p = (const char *)skiptowhite(arg);
   if (*p == NUL) {
     xp->xp_context = EXPAND_USER_COMMANDS;
     xp->xp_pattern = (char *)arg;
@@ -434,7 +434,7 @@ static void uc_list(char *name, size_t name_len)
         msg_putchar(' ');
       }
 
-      msg_outtrans_attr((char_u *)cmd->uc_name, HL_ATTR(HLF_D));
+      msg_outtrans_attr(cmd->uc_name, HL_ATTR(HLF_D));
       len = (int)STRLEN(cmd->uc_name) + 4;
 
       do {
@@ -930,7 +930,7 @@ void ex_command(exarg_T *eap)
   // Check for attributes
   while (*p == '-') {
     p++;
-    end = (char *)skiptowhite((char_u *)p);
+    end = skiptowhite(p);
     if (uc_scan_attr(p, (size_t)(end - p), &argt, &def, &flags, &compl, (char_u **)&compl_arg,
                      &addr_type_arg) == FAIL) {
       return;
diff --git a/src/nvim/vim.h b/src/nvim/vim.h
index 3e12d8b0b4..ec8d6ab153 100644
--- a/src/nvim/vim.h
+++ b/src/nvim/vim.h
@@ -230,10 +230,7 @@ enum { FOLD_TEXT_LEN = 51, };  //!< buffer size for get_foldtext()
 # endif
 #endif
 
-#define STRRCHR(s, c)       (char_u *)strrchr((const char *)(s), (c))
-
-#define STRCAT(d, s)        strcat((char *)(d), (char *)(s))
-#define STRNCAT(d, s, n)    strncat((char *)(d), (char *)(s), (size_t)(n))
+#define STRCAT(d, s)        strcat((char *)(d), (char *)(s))  // NOLINT(runtime/printf)
 #define STRLCAT(d, s, n)    xstrlcat((char *)(d), (char *)(s), (size_t)(n))
 
 // Character used as separated in autoload function/variable names.
diff --git a/src/nvim/viml/parser/parser.h b/src/nvim/viml/parser/parser.h
index b8835127e7..55f54cedbe 100644
--- a/src/nvim/viml/parser/parser.h
+++ b/src/nvim/viml/parser/parser.h
@@ -142,9 +142,7 @@ static inline void viml_preader_get_line(ParserInputReader *const preader,
       .allocated = true,
       .size = pline.size,
     };
-    cpline.data = (char *)string_convert(&preader->conv,
-                                         (char_u *)pline.data,
-                                         &cpline.size);
+    cpline.data = string_convert(&preader->conv, (char *)pline.data, &cpline.size);
     if (pline.allocated) {
       xfree((void *)pline.data);
     }
diff --git a/src/nvim/window.c b/src/nvim/window.c
index 832cb82bda..5adc8db088 100644
--- a/src/nvim/window.c
+++ b/src/nvim/window.c
@@ -730,7 +730,7 @@ void win_set_minimal_style(win_T *wp)
     char_u *old = (char_u *)wp->w_p_fcs;
     wp->w_p_fcs = ((*old == NUL)
                    ? xstrdup("eob: ")
-                   : (char *)concat_str(old, (char_u *)",eob: "));
+                   : concat_str((char *)old, ",eob: "));
     free_string_option((char *)old);
   }
 
@@ -739,7 +739,7 @@ void win_set_minimal_style(win_T *wp)
   char_u *old = (char_u *)wp->w_p_winhl;
   wp->w_p_winhl = ((*old == NUL)
                    ? xstrdup("EndOfBuffer:")
-                   : (char *)concat_str(old, (char_u *)",EndOfBuffer:"));
+                   : concat_str((char *)old, ",EndOfBuffer:"));
   free_string_option((char *)old);
   parse_winhl_opt(wp);