refactor: replace char_u with char 22 (#21786)

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

54 files changed, 532 insertions, 535 deletions

diff --git a/src/nvim/buffer.c b/src/nvim/buffer.c
index 3f93d85624..bc0bd9e004 100644
--- a/src/nvim/buffer.c
+++ b/src/nvim/buffer.c
@@ -3829,7 +3829,7 @@ static int chk_modeline(linenr_T lnum, int flags)
             && (s[0] != 'V'
                 || strncmp(skipwhite(e + 1), "set", 3) == 0)
             && (s[3] == ':'
-                || (VIM_VERSION_100 >= vers && isdigit(s[3]))
+                || (VIM_VERSION_100 >= vers && isdigit((uint8_t)s[3]))
                 || (VIM_VERSION_100 < vers && s[3] == '<')
                 || (VIM_VERSION_100 > vers && s[3] == '>')
                 || (VIM_VERSION_100 == vers && s[3] == '='))) {
diff --git a/src/nvim/charset.c b/src/nvim/charset.c
index aa2d845728..fa9aa27774 100644
--- a/src/nvim/charset.c
+++ b/src/nvim/charset.c
@@ -146,19 +146,19 @@ int buf_init_chartab(buf_T *buf, int global)
   // options Each option is a list of characters, character numbers or
   // ranges, separated by commas, e.g.: "200-210,x,#-178,-"
   for (i = global ? 0 : 3; i <= 3; i++) {
-    const char_u *p;
+    const char *p;
     if (i == 0) {
       // first round: 'isident'
-      p = (char_u *)p_isi;
+      p = p_isi;
     } else if (i == 1) {
       // second round: 'isprint'
-      p = (char_u *)p_isp;
+      p = p_isp;
     } else if (i == 2) {
       // third round: 'isfname'
-      p = (char_u *)p_isf;
+      p = p_isf;
     } else {  // i == 3
       // fourth round: 'iskeyword'
-      p = (char_u *)buf->b_p_isk;
+      p = buf->b_p_isk;
     }
 
     while (*p) {
@@ -254,8 +254,8 @@ int buf_init_chartab(buf_T *buf, int global)
         c++;
       }
 
-      c = *p;
-      p = (char_u *)skip_to_option_part((char *)p);
+      c = (uint8_t)(*p);
+      p = skip_to_option_part(p);
 
       if ((c == ',') && (*p == NUL)) {
         // Trailing comma is not allowed.
diff --git a/src/nvim/cmdexpand.c b/src/nvim/cmdexpand.c
index b5956d75ab..59891e9899 100644
--- a/src/nvim/cmdexpand.c
+++ b/src/nvim/cmdexpand.c
@@ -1174,7 +1174,7 @@ static bool expand_showtail(expand_T *xp)
     // separator, on DOS the '*' "path\*\file" must not be skipped.
     if (rem_backslash(s)) {
       s++;
-    } else if (vim_strchr("*?[", *s) != NULL) {
+    } else if (vim_strchr("*?[", (uint8_t)(*s)) != NULL) {
       return false;
     }
   }
@@ -1405,7 +1405,7 @@ static const char *set_cmd_index(const char *cmd, exarg_T *eap, expand_T *xp, in
       }
     }
     // check for non-alpha command
-    if (p == cmd && vim_strchr("@*!=><&~#", *p) != NULL) {
+    if (p == cmd && vim_strchr("@*!=><&~#", (uint8_t)(*p)) != NULL) {
       p++;
     }
     len = (size_t)(p - cmd);
@@ -1435,7 +1435,7 @@ static const char *set_cmd_index(const char *cmd, exarg_T *eap, expand_T *xp, in
   }
 
   if (eap->cmdidx == CMD_SIZE) {
-    if (*cmd == 's' && vim_strchr("cgriI", cmd[1]) != NULL) {
+    if (*cmd == 's' && vim_strchr("cgriI", (uint8_t)cmd[1]) != NULL) {
       eap->cmdidx = CMD_substitute;
       p = cmd + 1;
     } else if (cmd[0] >= 'A' && cmd[0] <= 'Z') {
@@ -2171,7 +2171,7 @@ static const char *set_one_cmd_context(expand_T *xp, const char *buff)
 
   // 1. skip comment lines and leading space, colons or bars
   const char *cmd;
-  for (cmd = buff; vim_strchr(" \t:|", *cmd) != NULL; cmd++) {}
+  for (cmd = buff; vim_strchr(" \t:|", (uint8_t)(*cmd)) != NULL; cmd++) {}
   xp->xp_pattern = (char *)cmd;
 
   if (*cmd == NUL) {
@@ -2967,7 +2967,7 @@ static void expand_shellcmd(char *filepat, char ***matches, int *numMatches, int
     path = ".";
   } else {
     // For an absolute name we don't use $PATH.
-    if (!path_is_absolute((char_u *)pat)) {
+    if (!path_is_absolute(pat)) {
       path = vim_getenv("PATH");
     }
     if (path == NULL) {
diff --git a/src/nvim/cmdhist.c b/src/nvim/cmdhist.c
index d12ac87bbb..2df82d9355 100644
--- a/src/nvim/cmdhist.c
+++ b/src/nvim/cmdhist.c
@@ -280,7 +280,7 @@ static HistoryType get_histtype(const char *const name, const size_t len, const
     }
   }
 
-  if (vim_strchr(":=@>?/", name[0]) != NULL && len == 1) {
+  if (vim_strchr(":=@>?/", (uint8_t)name[0]) != NULL && len == 1) {
     return hist_char2type(name[0]);
   }
 
@@ -437,7 +437,7 @@ int clr_history(const int histype)
 /// Remove all entries matching {str} from a history.
 ///
 /// @param histype  may be one of the HIST_ values.
-static int del_history_entry(int histype, char_u *str)
+static int del_history_entry(int histype, char *str)
 {
   if (hislen == 0 || histype < 0 || histype >= HIST_COUNT || *str == NUL
       || hisidx[histype] < 0) {
@@ -446,7 +446,7 @@ static int del_history_entry(int histype, char_u *str)
 
   const int idx = hisidx[histype];
   regmatch_T regmatch;
-  regmatch.regprog = vim_regcomp((char *)str, RE_MAGIC + RE_STRING);
+  regmatch.regprog = vim_regcomp(str, RE_MAGIC + RE_STRING);
   if (regmatch.regprog == NULL) {
     return false;
   }
@@ -560,7 +560,7 @@ void f_histdel(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
     // string given: remove all matching entries
     char buf[NUMBUFLEN];
     n = del_history_entry(get_histtype(str, strlen(str), false),
-                          (char_u *)tv_get_string_buf(&argvars[1], buf));
+                          (char *)tv_get_string_buf(&argvars[1], buf));
   }
   rettv->vval.v_number = n;
 }
@@ -611,7 +611,7 @@ void ex_history(exarg_T *eap)
   int idx;
   int i, j, k;
   char *end;
-  char_u *arg = (char_u *)eap->arg;
+  char *arg = eap->arg;
 
   if (hislen == 0) {
     msg(_("'history' option is zero"));
@@ -619,12 +619,12 @@ void ex_history(exarg_T *eap)
   }
 
   if (!(ascii_isdigit(*arg) || *arg == '-' || *arg == ',')) {
-    end = (char *)arg;
+    end = arg;
     while (ASCII_ISALPHA(*end)
-           || vim_strchr(":=@>/?", *end) != NULL) {
+           || vim_strchr(":=@>/?", (uint8_t)(*end)) != NULL) {
       end++;
     }
-    histype1 = get_histtype((const char *)arg, (size_t)(end - (char *)arg), false);
+    histype1 = get_histtype(arg, (size_t)(end - arg), false);
     if (histype1 == HIST_INVALID) {
       if (STRNICMP(arg, "all", end - (char *)arg) == 0) {
         histype1 = 0;
@@ -637,7 +637,7 @@ void ex_history(exarg_T *eap)
       histype2 = histype1;
     }
   } else {
-    end = (char *)arg;
+    end = arg;
   }
   if (!get_list_range(&end, &hisidx1, &hisidx2) || *end != NUL) {
     semsg(_(e_trailing_arg), end);
diff --git a/src/nvim/diff.c b/src/nvim/diff.c
index 45f00cb41e..40be6b1abc 100644
--- a/src/nvim/diff.c
+++ b/src/nvim/diff.c
@@ -1575,7 +1575,7 @@ static bool extract_hunk(FILE *fd, diffhunk_T *hunk, diffstyle_T *diffstyle)
       // --- file1       2018-03-20 13:23:35.783153140 +0100
       // +++ file2       2018-03-20 13:23:41.183156066 +0100
       // @@ -1,3 +1,5 @@
-      if (isdigit(*line)) {
+      if (isdigit((uint8_t)(*line))) {
         *diffstyle = DIFF_ED;
       } else if ((strncmp(line, "@@ ", 3) == 0)) {
         *diffstyle = DIFF_UNIFIED;
@@ -1593,7 +1593,7 @@ static bool extract_hunk(FILE *fd, diffhunk_T *hunk, diffstyle_T *diffstyle)
     }
 
     if (*diffstyle == DIFF_ED) {
-      if (!isdigit(*line)) {
+      if (!isdigit((uint8_t)(*line))) {
         continue;   // not the start of a diff block
       }
       if (parse_diff_ed(line, hunk) == FAIL) {
diff --git a/src/nvim/digraph.c b/src/nvim/digraph.c
index 33038dfb9f..144817fe2b 100644
--- a/src/nvim/digraph.c
+++ b/src/nvim/digraph.c
@@ -1885,7 +1885,7 @@ static int get_digraph_chars(const typval_T *arg, int *char1, int *char2)
 {
   char buf_chars[NUMBUFLEN];
   const char *chars = tv_get_string_buf_chk(arg, buf_chars);
-  const char_u *p = (const char_u *)chars;
+  const char *p = chars;
 
   if (p != NULL) {
     if (*p != NUL) {
@@ -1917,7 +1917,7 @@ static bool digraph_set_common(const typval_T *argchars, const typval_T *argdigr
   if (digraph == NULL) {
     return false;
   }
-  const char_u *p = (const char_u *)digraph;
+  const char *p = digraph;
   int n = mb_cptr2char_adv(&p);
   if (*p != NUL) {
     semsg(_(e_digraph_argument_must_be_one_character_str), digraph);
diff --git a/src/nvim/drawline.c b/src/nvim/drawline.c
index ae3e5698b2..9287fdb460 100644
--- a/src/nvim/drawline.c
+++ b/src/nvim/drawline.c
@@ -513,7 +513,7 @@ static bool use_cursor_line_nr(win_T *wp, linenr_T lnum, int row, int startrow,
                  && (wp->w_p_culopt_flags & CULOPT_LINE)));
 }
 
-static inline void get_line_number_str(win_T *wp, linenr_T lnum, char_u *buf, size_t buf_len)
+static inline void get_line_number_str(win_T *wp, linenr_T lnum, char *buf, size_t buf_len)
 {
   long num;
   char *fmt = "%*ld ";
@@ -531,7 +531,7 @@ static inline void get_line_number_str(win_T *wp, linenr_T lnum, char_u *buf, si
     }
   }
 
-  snprintf((char *)buf, buf_len, fmt, number_width(wp), num);
+  snprintf(buf, buf_len, fmt, number_width(wp), num);
 }
 
 static int get_line_number_attr(win_T *wp, linenr_T lnum, int row, int startrow, int filler_lines)
@@ -612,7 +612,7 @@ int win_line(win_T *wp, linenr_T lnum, int startrow, int endrow, bool nochange,
   int row;                            // row in the window, excl w_winrow
   ScreenGrid *grid = &wp->w_grid;     // grid specific to the window
 
-  char_u extra[57];                   // sign, line number and 'fdc' must
+  char extra[57];                     // sign, line number and 'fdc' must
                                       // fit in here
   int n_extra = 0;                    // number of extra chars
   char *p_extra = NULL;               // string of extra chars, plus NUL
@@ -806,7 +806,7 @@ int win_line(win_T *wp, linenr_T lnum, int startrow, int endrow, bool nochange,
       nextline[SPWORDLEN] = NUL;
       if (lnum < wp->w_buffer->b_ml.ml_line_count) {
         line = ml_get_buf(wp->w_buffer, lnum + 1, false);
-        spell_cat_line(nextline + SPWORDLEN, (char_u *)line, SPWORDLEN);
+        spell_cat_line(nextline + SPWORDLEN, line, SPWORDLEN);
       }
 
       // When a word wrapped from the previous line the start of the current
@@ -1132,7 +1132,7 @@ int win_line(win_T *wp, linenr_T lnum, int startrow, int endrow, bool nochange,
         // no bad word found at line start, don't check until end of a
         // word
         spell_hlf = HLF_COUNT;
-        word_end = (int)(spell_to_word_end((char_u *)ptr, wp) - (char_u *)line + 1);
+        word_end = (int)(spell_to_word_end(ptr, wp) - line + 1);
       } else {
         // bad word found, use attributes until end of word
         assert(len <= INT_MAX);
@@ -1278,7 +1278,7 @@ int win_line(win_T *wp, linenr_T lnum, int startrow, int endrow, bool nochange,
         if (wp->w_scwidth > 0) {
           get_sign_display_info(false, wp, lnum, sattrs, row,
                                 startrow, filler_lines, filler_todo,
-                                &c_extra, &c_final, (char *)extra, sizeof(extra),
+                                &c_extra, &c_final, extra, sizeof(extra),
                                 &p_extra, &n_extra, &char_attr, sign_idx,
                                 sign_cul_attr);
           sign_idx++;
@@ -1303,29 +1303,29 @@ int win_line(win_T *wp, linenr_T lnum, int startrow, int endrow, bool nochange,
           if (*wp->w_p_scl == 'n' && *(wp->w_p_scl + 1) == 'u' && num_signs > 0) {
             get_sign_display_info(true, wp, lnum, sattrs, row,
                                   startrow, filler_lines, filler_todo,
-                                  &c_extra, &c_final, (char *)extra, sizeof(extra),
+                                  &c_extra, &c_final, extra, sizeof(extra),
                                   &p_extra, &n_extra, &char_attr, sign_idx,
                                   sign_cul_attr);
           } else {
             // Draw the line number (empty space after wrapping).
             if (row == startrow + filler_lines) {
-              get_line_number_str(wp, lnum, (char_u *)extra, sizeof(extra));
+              get_line_number_str(wp, lnum, extra, sizeof(extra));
               if (wp->w_skipcol > 0) {
-                for (p_extra = (char *)extra; *p_extra == ' '; p_extra++) {
+                for (p_extra = extra; *p_extra == ' '; p_extra++) {
                   *p_extra = '-';
                 }
               }
               if (wp->w_p_rl) {                       // reverse line numbers
                 // like rl_mirror(), but keep the space at the end
-                char *p2 = skipwhite((char *)extra);
+                char *p2 = skipwhite(extra);
                 p2 = skiptowhite(p2) - 1;
-                for (char *p1 = skipwhite((char *)extra); p1 < p2; p1++, p2--) {
+                for (char *p1 = skipwhite(extra); p1 < p2; p1++, p2--) {
                   const char t = *p1;
                   *p1 = *p2;
                   *p2 = t;
                 }
               }
-              p_extra = (char *)extra;
+              p_extra = extra;
               c_extra = NUL;
             } else {
               c_extra = ' ';
@@ -1729,14 +1729,14 @@ int win_line(win_T *wp, linenr_T lnum, int startrow, int endrow, bool nochange,
           || (mb_l > 1 && (!vim_isprintc(mb_c)))) {
         // Illegal UTF-8 byte: display as <xx>.
         // Non-BMP character : display as ? or fullwidth ?.
-        transchar_hex((char *)extra, mb_c);
+        transchar_hex(extra, mb_c);
         if (wp->w_p_rl) {  // reverse
-          rl_mirror((char *)extra);
+          rl_mirror(extra);
         }
 
-        p_extra = (char *)extra;
+        p_extra = extra;
         c = (uint8_t)(*p_extra);
-        mb_c = mb_ptr2char_adv((const char_u **)&p_extra);
+        mb_c = mb_ptr2char_adv((const char **)&p_extra);
         mb_utf8 = (c >= 0x80);
         n_extra = (int)strlen(p_extra);
         c_extra = NUL;
@@ -1909,7 +1909,7 @@ int win_line(win_T *wp, linenr_T lnum, int startrow, int endrow, bool nochange,
               p = prev_ptr;
             }
             cap_col -= (int)(prev_ptr - line);
-            size_t tmplen = spell_check(wp, (char_u *)p, &spell_hlf, &cap_col, nochange);
+            size_t tmplen = spell_check(wp, p, &spell_hlf, &cap_col, nochange);
             assert(tmplen <= INT_MAX);
             len = (int)tmplen;
             word_end = (int)v + len;
@@ -2075,12 +2075,12 @@ int win_line(win_T *wp, linenr_T lnum, int startrow, int endrow, bool nochange,
         if (c == TAB && (!wp->w_p_list || wp->w_p_lcs_chars.tab1)) {
           int tab_len = 0;
           long vcol_adjusted = vcol;  // removed showbreak length
-          char_u *const sbr = get_showbreak_value(wp);
+          char *const sbr = (char *)get_showbreak_value(wp);
 
           // Only adjust the tab_len, when at the first column after the
           // showbreak value was drawn.
           if (*sbr != NUL && vcol == vcol_sbr && wp->w_p_wrap) {
-            vcol_adjusted = vcol - mb_charlen((char *)sbr);
+            vcol_adjusted = vcol - mb_charlen(sbr);
           }
           // tab amount depends on current column
           tab_len = tabstop_padding((colnr_T)vcol_adjusted,
diff --git a/src/nvim/edit.c b/src/nvim/edit.c
index 6102f05abd..9b82d50012 100644
--- a/src/nvim/edit.c
+++ b/src/nvim/edit.c
@@ -3127,7 +3127,7 @@ bool in_cinkeys(int keytyped, int when, bool line_is_empty)
         // make up some named keys <o>, <O>, <e>, <0>, <>>, <<>, <*>,
         // <:> and <!> so that people can re-indent on o, O, e, 0, <,
         // >, *, : and ! keys if they really really want to.
-        if (vim_strchr("<>!*oOe0:", look[1]) != NULL
+        if (vim_strchr("<>!*oOe0:", (uint8_t)look[1]) != NULL
             && keytyped == look[1]) {
           return true;
         }
@@ -3182,7 +3182,7 @@ bool in_cinkeys(int keytyped, int when, bool line_is_empty)
           // TODO(@brammool): multi-byte
           if (keytyped == (int)(uint8_t)p[-1]
               || (icase && keytyped < 256
-                  && TOLOWER_LOC(keytyped) == TOLOWER_LOC((int)p[-1]))) {
+                  && TOLOWER_LOC(keytyped) == TOLOWER_LOC((uint8_t)p[-1]))) {
             line = get_cursor_pos_ptr();
             assert(p >= look && (uintmax_t)(p - look) <= SIZE_MAX);
             if ((curwin->w_cursor.col == (colnr_T)(p - look)
diff --git a/src/nvim/eval.c b/src/nvim/eval.c
index 6d32b71016..b0805aecff 100644
--- a/src/nvim/eval.c
+++ b/src/nvim/eval.c
@@ -2185,7 +2185,7 @@ int pattern_match(const char *pat, const char *text, bool ic)
   regmatch.regprog = vim_regcomp((char *)pat, RE_MAGIC + RE_STRING);
   if (regmatch.regprog != NULL) {
     regmatch.rm_ic = ic;
-    matches = vim_regexec_nl(&regmatch, (char_u *)text, (colnr_T)0);
+    matches = vim_regexec_nl(&regmatch, (char *)text, (colnr_T)0);
     vim_regfree(regmatch.regprog);
   }
   p_cpo = save_cpo;
@@ -2543,7 +2543,7 @@ static int eval4(char **arg, typval_T *rettv, int evaluate)
       if (p[2] == 'n' && p[3] == 'o' && p[4] == 't') {
         len = 5;
       }
-      if (!isalnum(p[len]) && p[len] != '_') {
+      if (!isalnum((uint8_t)p[len]) && p[len] != '_') {
         type = len == 2 ? EXPR_IS : EXPR_ISNOT;
       }
     }
@@ -3777,7 +3777,7 @@ static int get_string_tv(char **arg, typval_T *rettv, int evaluate)
       case 'U':
         if (ascii_isxdigit(p[1])) {
           int n, nr;
-          int c = toupper(*p);
+          int c = toupper((uint8_t)(*p));
 
           if (c == 'X') {
             n = 2;
@@ -6302,7 +6302,7 @@ int get_id_len(const char **const arg)
       // slice "[n:]". Also "xx:" is not a namespace.
       len = (int)(p - *arg);
       if (len > 1
-          || (len == 1 && vim_strchr(namespace_char, **arg) == NULL)) {
+          || (len == 1 && vim_strchr(namespace_char, (uint8_t)(**arg)) == NULL)) {
         break;
       }
     }
@@ -6430,7 +6430,7 @@ const char *find_name_end(const char *arg, const char **expr_start, const char *
       // slice "[n:]".  Also "xx:" is not a namespace. But {ns}: is.
       len = (int)(p - arg);
       if ((len > 1 && p[-1] != '}')
-          || (len == 1 && vim_strchr(namespace_char, *arg) == NULL)) {
+          || (len == 1 && vim_strchr(namespace_char, (uint8_t)(*arg)) == NULL)) {
         break;
       }
     }
@@ -8081,7 +8081,7 @@ char *do_string_sub(char *str, char *pat, char *sub, typval_T *expr, const char
   if (regmatch.regprog != NULL) {
     char *tail = str;
     char *end = str + strlen(str);
-    while (vim_regexec_nl(&regmatch, (char_u *)str, (colnr_T)(tail - str))) {
+    while (vim_regexec_nl(&regmatch, str, (colnr_T)(tail - str))) {
       // Skip empty match except for first match.
       if (regmatch.startp[0] == regmatch.endp[0]) {
         if (zero_width == regmatch.startp[0]) {
diff --git a/src/nvim/eval/executor.c b/src/nvim/eval/executor.c
index 86d6063b01..831c468288 100644
--- a/src/nvim/eval/executor.c
+++ b/src/nvim/eval/executor.c
@@ -69,7 +69,7 @@ int eexe_mod_op(typval_T *const tv1, const typval_T *const tv2, const char *cons
       if (tv2->v_type == VAR_LIST) {
         break;
       }
-      if (vim_strchr("+-*/%", *op) != NULL) {
+      if (vim_strchr("+-*/%", (uint8_t)(*op)) != NULL) {
         // nr += nr  or  nr -= nr, nr *= nr, nr /= nr, nr %= nr
         varnumber_T n = tv_get_number(tv1);
         if (tv2->v_type == VAR_FLOAT) {
diff --git a/src/nvim/eval/funcs.c b/src/nvim/eval/funcs.c
index d6b9ca20fc..25e026706c 100644
--- a/src/nvim/eval/funcs.c
+++ b/src/nvim/eval/funcs.c
@@ -1770,7 +1770,7 @@ static void f_expand(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
     }
     size_t len;
     char *errormsg = NULL;
-    char *result = (char *)eval_vars((char_u *)s, (char_u *)s, &len, NULL, &errormsg, NULL, false);
+    char *result = (char *)eval_vars((char *)s, (char_u *)s, &len, NULL, &errormsg, NULL, false);
     if (p_verbose == 0) {
       emsg_off--;
     } else if (errormsg != NULL) {
@@ -4488,7 +4488,7 @@ static void find_some_match(typval_T *const argvars, typval_T *const rettv,
         }
       }
 
-      match = vim_regexec_nl(&regmatch, (char_u *)str, startcol);
+      match = vim_regexec_nl(&regmatch, str, startcol);
 
       if (match && --nth <= 0) {
         break;
@@ -5885,7 +5885,7 @@ static void f_resolve(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
           q[-1] = NUL;
           q = path_tail(p);
         }
-        if (q > p && !path_is_absolute((const char_u *)buf)) {
+        if (q > p && !path_is_absolute(buf)) {
           // Symlink is relative to directory of argument. Replace the
           // symlink with the resolved name in the same directory.
           const size_t p_len = strlen(p);
@@ -6228,7 +6228,7 @@ static int search_cmn(typval_T *argvars, pos_T *match_pos, int *flagsp)
   // Repeat until {skip} returns false.
   for (;;) {
     subpatnum
-      = searchit(curwin, curbuf, &pos, NULL, dir, (char_u *)pat, 1, options, RE_SEARCH, &sia);
+      = searchit(curwin, curbuf, &pos, NULL, dir, (char *)pat, 1, options, RE_SEARCH, &sia);
     // finding the first match again means there is no match where {skip}
     // evaluates to zero.
     if (firstpos.lnum != 0 && equalpos(pos, firstpos)) {
@@ -6810,7 +6810,7 @@ long do_searchpair(const char *spat, const char *mpat, const char *epat, int dir
       .sa_tm = &tm,
     };
 
-    int n = searchit(curwin, curbuf, &pos, NULL, dir, (char_u *)pat, 1L,
+    int n = searchit(curwin, curbuf, &pos, NULL, dir, pat, 1L,
                      options, RE_SEARCH, &sia);
     if (n == FAIL || (firstpos.lnum != 0 && equalpos(pos, firstpos))) {
       // didn't find it or found the first match again: FAIL
@@ -7073,7 +7073,7 @@ static void f_setcharsearch(typval_T *argvars, typval_T *rettv, EvalFuncData fpt
   if (csearch != NULL) {
     int pcc[MAX_MCO];
     const int c = utfc_ptr2char((char *)csearch, pcc);
-    set_last_csearch(c, csearch, utfc_ptr2len((char *)csearch));
+    set_last_csearch(c, (char *)csearch, utfc_ptr2len((char *)csearch));
   }
 
   dictitem_T *di = tv_dict_find(d, S_LEN("forward"));
@@ -7553,7 +7553,7 @@ static void f_spellbadword(typval_T *argvars, typval_T *rettv, EvalFuncData fptr
     if (str != NULL) {
       // Check the argument for spelling.
       while (*str != NUL) {
-        len = spell_check(curwin, (char_u *)str, &attr, &capcol, false);
+        len = spell_check(curwin, (char *)str, &attr, &capcol, false);
         if (attr != HLF_COUNT) {
           word = str;
           break;
@@ -7668,7 +7668,7 @@ static void f_split(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
       if (*str == NUL) {
         match = false;  // Empty item at the end.
       } else {
-        match = vim_regexec_nl(&regmatch, (char_u *)str, col);
+        match = vim_regexec_nl(&regmatch, (char *)str, col);
       }
       const char *end;
       if (match) {
@@ -7930,11 +7930,11 @@ static void strchar_common(typval_T *argvars, typval_T *rettv, bool skipcc)
 {
   const char *s = tv_get_string(&argvars[0]);
   varnumber_T len = 0;
-  int (*func_mb_ptr2char_adv)(const char_u **pp);
+  int (*func_mb_ptr2char_adv)(const char **pp);
 
   func_mb_ptr2char_adv = skipcc ? mb_ptr2char_adv : mb_cptr2char_adv;
   while (*s != NUL) {
-    func_mb_ptr2char_adv((const char_u **)&s);
+    func_mb_ptr2char_adv(&s);
     len++;
   }
   rettv->vval.v_number = len;
diff --git a/src/nvim/eval/userfunc.c b/src/nvim/eval/userfunc.c
index 1a3fd13fe3..5d3b70b414 100644
--- a/src/nvim/eval/userfunc.c
+++ b/src/nvim/eval/userfunc.c
@@ -118,7 +118,7 @@ static int get_function_args(char **argp, char_u endchar, garray_T *newargs, int
       while (ASCII_ISALNUM(*p) || *p == '_') {
         p++;
       }
-      if (arg == p || isdigit(*arg)
+      if (arg == p || isdigit((uint8_t)(*arg))
           || (p - arg == 9 && strncmp(arg, "firstline", 9) == 0)
           || (p - arg == 8 && strncmp(arg, "lastline", 8) == 0)) {
         if (!skip) {
@@ -1228,7 +1228,7 @@ void call_user_func(ufunc_T *fp, int argcount, typval_T *argvars, typval_T *rett
 /// looked up by name.
 static bool func_name_refcount(const char_u *name)
 {
-  return isdigit(*name) || *name == '<';
+  return isdigit((uint8_t)(*name)) || *name == '<';
 }
 
 /// Call a user function after checking the arguments.
@@ -2002,7 +2002,7 @@ static void list_functions(regmatch_T *regmatch)
           && (regmatch == NULL
               ? (!message_filtered((char *)fp->uf_name)
                  && !func_name_refcount((char_u *)fp->uf_name))
-              : (!isdigit(*fp->uf_name)
+              : (!isdigit((uint8_t)(*fp->uf_name))
                  && vim_regexec(regmatch, (char *)fp->uf_name, 0)))) {
         list_func_head(fp, false, false);
         if (changed != func_hashtab.ht_changed) {
@@ -2792,7 +2792,7 @@ void ex_delfunction(exarg_T *eap)
     *p = NUL;
   }
 
-  if (isdigit(*name) && fudi.fd_dict == NULL) {
+  if (isdigit((uint8_t)(*name)) && fudi.fd_dict == NULL) {
     if (!eap->skip) {
       semsg(_(e_invarg2), eap->arg);
     }
@@ -2858,7 +2858,7 @@ void func_unref(char_u *name)
   }
 
   fp = find_func(name);
-  if (fp == NULL && isdigit(*name)) {
+  if (fp == NULL && isdigit((uint8_t)(*name))) {
 #ifdef EXITFREE
     if (!entered_free_all_mem) {
       internal_error("func_unref()");
@@ -2901,7 +2901,7 @@ void func_ref(char_u *name)
   fp = find_func(name);
   if (fp != NULL) {
     (fp->uf_refcount)++;
-  } else if (isdigit(*name)) {
+  } else if (isdigit((uint8_t)(*name))) {
     // Only give an error for a numbered function.
     // Fail silently, when named or lambda function isn't found.
     internal_error("func_ref()");
diff --git a/src/nvim/eval/vars.c b/src/nvim/eval/vars.c
index 206df03381..75af99fbd5 100644
--- a/src/nvim/eval/vars.c
+++ b/src/nvim/eval/vars.c
@@ -106,7 +106,7 @@ static list_T *heredoc_get(exarg_T *eap, char *cmd)
       return NULL;
     }
     *p = NUL;
-    if (islower(*marker)) {
+    if (islower((uint8_t)(*marker))) {
       emsg(_("E221: Marker cannot start with lower case letter"));
       return NULL;
     }
@@ -208,7 +208,7 @@ static void ex_let_const(exarg_T *eap, const bool is_const)
     argend--;
   }
   expr = skipwhite(argend);
-  if (*expr != '=' && !((vim_strchr("+-*/%.", *expr) != NULL
+  if (*expr != '=' && !((vim_strchr("+-*/%.", (uint8_t)(*expr)) != NULL
                          && expr[1] == '=') || strncmp(expr, "..=", 3) == 0)) {
     // ":let" without "=": list variables
     if (*arg == '[') {
@@ -244,7 +244,7 @@ static void ex_let_const(exarg_T *eap, const bool is_const)
     op[0] = '=';
     op[1] = NUL;
     if (*expr != '=') {
-      if (vim_strchr("+-*/%.", *expr) != NULL) {
+      if (vim_strchr("+-*/%.", (uint8_t)(*expr)) != NULL) {
         op[0] = *expr;  // +=, -=, *=, /=, %= or .=
         if (expr[0] == '.' && expr[1] == '.') {  // ..=
           expr++;
@@ -590,10 +590,10 @@ static char *ex_let_one(char *arg, typval_T *const tv, const bool copy, const bo
     if (len == 0) {
       semsg(_(e_invarg2), name - 1);
     } else {
-      if (op != NULL && vim_strchr("+-*/%", *op) != NULL) {
+      if (op != NULL && vim_strchr("+-*/%", (uint8_t)(*op)) != NULL) {
         semsg(_(e_letwrong), op);
       } else if (endchars != NULL
-                 && vim_strchr(endchars, *skipwhite(arg)) == NULL) {
+                 && vim_strchr(endchars, (uint8_t)(*skipwhite(arg))) == NULL) {
         emsg(_(e_letunexp));
       } else if (!check_secure()) {
         char *tofree = NULL;
@@ -629,7 +629,7 @@ static char *ex_let_one(char *arg, typval_T *const tv, const bool copy, const bo
     char *const p = (char *)find_option_end((const char **)&arg, &scope);
     if (p == NULL
         || (endchars != NULL
-            && vim_strchr(endchars, *skipwhite(p)) == NULL)) {
+            && vim_strchr(endchars, (uint8_t)(*skipwhite(p))) == NULL)) {
       emsg(_(e_letunexp));
     } else {
       varnumber_T n = 0;
@@ -716,10 +716,10 @@ static char *ex_let_one(char *arg, typval_T *const tv, const bool copy, const bo
       return NULL;
     }
     arg++;
-    if (op != NULL && vim_strchr("+-*/%", *op) != NULL) {
+    if (op != NULL && vim_strchr("+-*/%", (uint8_t)(*op)) != NULL) {
       semsg(_(e_letwrong), op);
     } else if (endchars != NULL
-               && vim_strchr(endchars, *skipwhite(arg + 1)) == NULL) {
+               && vim_strchr(endchars, (uint8_t)(*skipwhite(arg + 1))) == NULL) {
       emsg(_(e_letunexp));
     } else {
       char *s;
@@ -747,7 +747,7 @@ static char *ex_let_one(char *arg, typval_T *const tv, const bool copy, const bo
 
     char *const p = get_lval(arg, tv, &lv, false, false, 0, FNE_CHECK_START);
     if (p != NULL && lv.ll_name != NULL) {
-      if (endchars != NULL && vim_strchr(endchars, *skipwhite(p)) == NULL) {
+      if (endchars != NULL && vim_strchr(endchars, (uint8_t)(*skipwhite(p))) == NULL) {
         emsg(_(e_letunexp));
       } else {
         set_var_lval(&lv, p, tv, copy, is_const, op);
@@ -1464,7 +1464,7 @@ bool var_wrong_func_name(const char *const name, const bool new_var)
 {
   // Allow for w: b: s: and t:.
   // Allow autoload variable.
-  if (!(vim_strchr("wbst", name[0]) != NULL && name[1] == ':')
+  if (!(vim_strchr("wbst", (uint8_t)name[0]) != NULL && name[1] == ':')
       && !ASCII_ISUPPER((name[0] != NUL && name[1] == ':') ? name[2] : name[0])
       && vim_strchr(name, '#') == NULL) {
     semsg(_("E704: Funcref variable name must start with a capital: %s"), name);
diff --git a/src/nvim/ex_cmds.c b/src/nvim/ex_cmds.c
index c2af0e6986..4ea11dd32a 100644
--- a/src/nvim/ex_cmds.c
+++ b/src/nvim/ex_cmds.c
@@ -528,7 +528,7 @@ void ex_sort(exarg_T *eap)
           emsg(_(e_noprevre));
           goto sortend;
         }
-        regmatch.regprog = vim_regcomp((char *)last_search_pat(), RE_MAGIC);
+        regmatch.regprog = vim_regcomp(last_search_pat(), RE_MAGIC);
       } else {
         regmatch.regprog = vim_regcomp(p + 1, RE_MAGIC);
       }
@@ -3332,7 +3332,7 @@ static int do_sub(exarg_T *eap, proftime_T timeout, long cmdpreview_ns, handle_T
   }
   // new pattern and substitution
   if (eap->cmd[0] == 's' && *cmd != NUL && !ascii_iswhite(*cmd)
-      && vim_strchr("0123456789cegriIp|\"", *cmd) == NULL) {
+      && vim_strchr("0123456789cegriIp|\"", (uint8_t)(*cmd)) == NULL) {
     // don't accept alphanumeric for separator
     if (check_regexp_delim(*cmd) == FAIL) {
       return 0;
@@ -3343,7 +3343,7 @@ static int do_sub(exarg_T *eap, proftime_T timeout, long cmdpreview_ns, handle_T
     //  //sub/r).  "\&sub&" use last substitute pattern (like //sub/).
     if (*cmd == '\\') {
       cmd++;
-      if (vim_strchr("/?&", *cmd) == NULL) {
+      if (vim_strchr("/?&", (uint8_t)(*cmd)) == NULL) {
         emsg(_(e_backslash));
         return 0;
       }
@@ -3443,7 +3443,7 @@ static int do_sub(exarg_T *eap, proftime_T timeout, long cmdpreview_ns, handle_T
     return 0;
   }
 
-  if (search_regcomp((char_u *)pat, NULL, RE_SUBST, which_pat,
+  if (search_regcomp(pat, NULL, RE_SUBST, which_pat,
                      (cmdpreview ? 0 : SEARCH_HIS), &regmatch) == FAIL) {
     if (subflags.do_error) {
       emsg(_(e_invcmd));
@@ -4372,7 +4372,7 @@ void ex_global(exarg_T *eap)
   //             "\&": use previous substitute pattern.
   if (*cmd == '\\') {
     cmd++;
-    if (vim_strchr("/?&", *cmd) == NULL) {
+    if (vim_strchr("/?&", (uint8_t)(*cmd)) == NULL) {
       emsg(_(e_backslash));
       return;
     }
@@ -4398,8 +4398,8 @@ void ex_global(exarg_T *eap)
     }
   }
 
-  char_u *used_pat;
-  if (search_regcomp((char_u *)pat, &used_pat, RE_BOTH, which_pat,
+  char *used_pat;
+  if (search_regcomp(pat, &used_pat, RE_BOTH, which_pat,
                      SEARCH_HIS, &regmatch) == FAIL) {
     emsg(_(e_invcmd));
     return;
diff --git a/src/nvim/ex_docmd.c b/src/nvim/ex_docmd.c
index 511251f0b5..896130debf 100644
--- a/src/nvim/ex_docmd.c
+++ b/src/nvim/ex_docmd.c
@@ -2852,7 +2852,7 @@ bool checkforcmd(char **pp, const char *cmd, int len)
       break;
     }
   }
-  if (i >= len && !isalpha((*pp)[i])) {
+  if (i >= len && !isalpha((uint8_t)(*pp)[i])) {
     *pp = skipwhite(*pp + i);
     return true;
   }
@@ -2877,7 +2877,7 @@ static void append_command(char *cmd)
   STRCAT(IObuff, ": ");
   d = IObuff + strlen(IObuff);
   while (*s != NUL && d - IObuff + 5 < IOSIZE) {
-    if ((char_u)s[0] == 0xc2 && (char_u)s[1] == 0xa0) {
+    if ((uint8_t)s[0] == 0xc2 && (uint8_t)s[1] == 0xa0) {
       s += 2;
       STRCPY(d, "<a0>");
       d += 4;
@@ -2942,7 +2942,7 @@ char *find_ex_command(exarg_T *eap, int *full)
     }
 
     // check for non-alpha command
-    if (p == eap->cmd && vim_strchr("@!=><&~#", *p) != NULL) {
+    if (p == eap->cmd && vim_strchr("@!=><&~#", (uint8_t)(*p)) != NULL) {
       p++;
     }
     int len = (int)(p - eap->cmd);
@@ -2967,7 +2967,7 @@ char *find_ex_command(exarg_T *eap, int *full)
     }
 
     if (ASCII_ISLOWER(eap->cmd[0])) {
-      const int c1 = (char_u)eap->cmd[0];
+      const int c1 = (uint8_t)eap->cmd[0];
       const int c2 = len == 1 ? NUL : eap->cmd[1];
 
       if (command_count != CMD_SIZE) {
@@ -3172,7 +3172,7 @@ uint32_t excmd_get_argt(cmdidx_T idx)
 /// @return the "cmd" pointer advanced to beyond the range.
 char *skip_range(const char *cmd, int *ctx)
 {
-  while (vim_strchr(" \t0123456789.$%'/?-+,;\\", *cmd) != NULL) {
+  while (vim_strchr(" \t0123456789.$%'/?-+,;\\", (uint8_t)(*cmd)) != NULL) {
     if (*cmd == '\\') {
       if (cmd[1] == '?' || cmd[1] == '/' || cmd[1] == '&') {
         cmd++;
@@ -3361,7 +3361,7 @@ static linenr_T get_address(exarg_T *eap, char **ptr, cmd_addr_T addr_type, int
 
     case '/':
     case '?':                           // '/' or '?' - search
-      c = (char_u)(*cmd++);
+      c = (uint8_t)(*cmd++);
       if (addr_type != ADDR_LINES) {
         addr_error(addr_type);
         cmd = NULL;
@@ -3434,7 +3434,7 @@ static linenr_T get_address(exarg_T *eap, char **ptr, cmd_addr_T addr_type, int
         pos.coladd = 0;
         if (searchit(curwin, curbuf, &pos, NULL,
                      *cmd == '?' ? BACKWARD : FORWARD,
-                     (char_u *)"", 1L, SEARCH_MSG, i, NULL) != FAIL) {
+                     "", 1L, SEARCH_MSG, i, NULL) != FAIL) {
           lnum = pos.lnum;
         } else {
           cmd = NULL;
@@ -3495,7 +3495,7 @@ static linenr_T get_address(exarg_T *eap, char **ptr, cmd_addr_T addr_type, int
       if (ascii_isdigit(*cmd)) {
         i = '+';                        // "number" is same as "+number"
       } else {
-        i = (char_u)(*cmd++);
+        i = (uint8_t)(*cmd++);
       }
       if (!ascii_isdigit(*cmd)) {       // '+' is '+1'
         n = 1;
@@ -3542,7 +3542,7 @@ error:
 /// Get flags from an Ex command argument.
 static void get_flags(exarg_T *eap)
 {
-  while (vim_strchr("lp#", *eap->arg) != NULL) {
+  while (vim_strchr("lp#", (uint8_t)(*eap->arg)) != NULL) {
     if (*eap->arg == 'l') {
       eap->flags |= EXFLAG_LIST;
     } else if (*eap->arg == 'p') {
@@ -3759,7 +3759,7 @@ int expand_filename(exarg_T *eap, char **cmdlinep, char **errormsgp)
     }
     // Quick check if this cannot be the start of a special string.
     // Also removes backslash before '%', '#' and '<'.
-    if (vim_strchr("%#<", *p) == NULL) {
+    if (vim_strchr("%#<", (uint8_t)(*p)) == NULL) {
       p++;
       continue;
     }
@@ -3767,7 +3767,7 @@ int expand_filename(exarg_T *eap, char **cmdlinep, char **errormsgp)
     // Try to find a match at this position.
     size_t srclen;
     int escaped;
-    char *repl = (char *)eval_vars((char_u *)p, (char_u *)eap->arg, &srclen, &(eap->do_ecmd_lnum),
+    char *repl = (char *)eval_vars(p, (char_u *)eap->arg, &srclen, &(eap->do_ecmd_lnum),
                                    errormsgp, &escaped, true);
     if (*errormsgp != NULL) {           // error detected
       return FAIL;
@@ -3812,7 +3812,7 @@ int expand_filename(exarg_T *eap, char **cmdlinep, char **errormsgp)
 #endif
 
       for (l = repl; *l; l++) {
-        if (vim_strchr((char *)ESCAPE_CHARS, *l) != NULL) {
+        if (vim_strchr((char *)ESCAPE_CHARS, (uint8_t)(*l)) != NULL) {
           l = vim_strsave_escaped(repl, (char *)ESCAPE_CHARS);
           xfree(repl);
           repl = l;
@@ -4044,15 +4044,15 @@ char *skip_cmd_arg(char *p, int rembs)
   return p;
 }
 
-int get_bad_opt(const char_u *p, exarg_T *eap)
+int get_bad_opt(const char *p, exarg_T *eap)
   FUNC_ATTR_NONNULL_ALL
 {
   if (STRICMP(p, "keep") == 0) {
     eap->bad_char = BAD_KEEP;
   } else if (STRICMP(p, "drop") == 0) {
     eap->bad_char = BAD_DROP;
-  } else if (MB_BYTE2LEN(*p) == 1 && p[1] == NUL) {
-    eap->bad_char = *p;
+  } else if (MB_BYTE2LEN((uint8_t)(*p)) == 1 && p[1] == NUL) {
+    eap->bad_char = (uint8_t)(*p);
   } else {
     return FAIL;
   }
@@ -4129,7 +4129,7 @@ static int getargopt(exarg_T *eap)
     if (check_ff_value(eap->cmd + eap->force_ff) == FAIL) {
       return FAIL;
     }
-    eap->force_ff = (char_u)eap->cmd[eap->force_ff];
+    eap->force_ff = (uint8_t)eap->cmd[eap->force_ff];
   } else if (pp == &eap->force_enc) {
     // Make 'fileencoding' lower case.
     for (char *p = eap->cmd + eap->force_enc; *p != NUL; p++) {
@@ -4138,7 +4138,7 @@ static int getargopt(exarg_T *eap)
   } else {
     // Check ++bad= argument.  Must be a single-byte character, "keep" or
     // "drop".
-    if (get_bad_opt((char_u *)eap->cmd + bad_char_idx, eap) == FAIL) {
+    if (get_bad_opt(eap->cmd + bad_char_idx, eap) == FAIL) {
       return FAIL;
     }
   }
@@ -6002,7 +6002,7 @@ static void ex_later(exarg_T *eap)
 
   if (*p == NUL) {
     count = 1;
-  } else if (isdigit(*p)) {
+  } else if (isdigit((uint8_t)(*p))) {
     count = getdigits_long(&p, false, 0);
     switch (*p) {
     case 's':
@@ -6060,7 +6060,7 @@ static void ex_redir(exarg_T *eap)
       close_redir();
       arg++;
       if (valid_yank_reg(*arg, true) && *arg != '_') {
-        redir_reg = (char_u)(*arg++);
+        redir_reg = (uint8_t)(*arg++);
         if (*arg == '>' && arg[1] == '>') {        // append
           arg += 2;
         } else {
@@ -6725,7 +6725,7 @@ ssize_t find_cmdline_var(const char *src, size_t *usedlen)
 /// @return          an allocated string if a valid match was found.
 ///                  Returns NULL if no match was found.  "usedlen" then still contains the
 ///                  number of characters to skip.
-char_u *eval_vars(char_u *src, const char_u *srcstart, size_t *usedlen, linenr_T *lnump,
+char_u *eval_vars(char *src, const char_u *srcstart, size_t *usedlen, linenr_T *lnump,
                   char **errormsg, int *escaped, bool empty_is_error)
 {
   char *result;
@@ -6742,7 +6742,7 @@ char_u *eval_vars(char_u *src, const char_u *srcstart, size_t *usedlen, linenr_T
   }
 
   // Check if there is something to do.
-  ssize_t spec_idx = find_cmdline_var((char *)src, usedlen);
+  ssize_t spec_idx = find_cmdline_var(src, usedlen);
   if (spec_idx < 0) {   // no match
     *usedlen = 1;
     return NULL;
@@ -6750,7 +6750,7 @@ char_u *eval_vars(char_u *src, const char_u *srcstart, size_t *usedlen, linenr_T
 
   // Skip when preceded with a backslash "\%" and "\#".
   // Note: In "\\%" the % is also not recognized!
-  if (src > srcstart && src[-1] == '\\') {
+  if ((char_u *)src > srcstart && src[-1] == '\\') {
     *usedlen = 0;
     STRMOVE(src - 1, (char *)src);      // remove backslash
     return NULL;
@@ -6800,16 +6800,16 @@ char_u *eval_vars(char_u *src, const char_u *srcstart, size_t *usedlen, linenr_T
         skip_mod = true;
         break;
       }
-      char *s = (char *)src + 1;
+      char *s = src + 1;
       if (*s == '<') {                  // "#<99" uses v:oldfiles.
         s++;
       }
       int i = getdigits_int(&s, false, 0);
-      if ((char_u *)s == src + 2 && src[1] == '-') {
+      if (s == src + 2 && src[1] == '-') {
         // just a minus sign, don't skip over it
         s--;
       }
-      *usedlen = (size_t)((char_u *)s - src);           // length of what we expand
+      *usedlen = (size_t)(s - src);           // length of what we expand
 
       if (src[1] == '<' && i != 0) {
         if (*usedlen < 2) {
@@ -6855,7 +6855,7 @@ char_u *eval_vars(char_u *src, const char_u *srcstart, size_t *usedlen, linenr_T
 
     case SPEC_AFILE:  // file name for autocommand
       if (autocmd_fname != NULL
-          && !path_is_absolute((char_u *)autocmd_fname)
+          && !path_is_absolute(autocmd_fname)
           // For CmdlineEnter and related events, <afile> is not a path! #9348
           && !strequal("/", autocmd_fname)) {
         // Still need to turn the fname into a full path.  It was
@@ -6962,7 +6962,7 @@ char_u *eval_vars(char_u *src, const char_u *srcstart, size_t *usedlen, linenr_T
         resultlen = (size_t)(s - result);
       }
     } else if (!skip_mod) {
-      valid |= modify_fname((char *)src, tilde_file, usedlen, &result,
+      valid |= modify_fname(src, tilde_file, usedlen, &result,
                             &resultbuf, &resultlen);
       if (result == NULL) {
         *errormsg = "";
@@ -7002,7 +7002,7 @@ char *expand_sfile(char *arg)
       // replace "<sfile>" with the sourced file name, and do ":" stuff
       size_t srclen;
       char *errormsg;
-      char *repl = (char *)eval_vars((char_u *)p, (char_u *)result, &srclen, NULL, &errormsg, NULL,
+      char *repl = (char *)eval_vars(p, (char_u *)result, &srclen, NULL, &errormsg, NULL,
                                      true);
       if (errormsg != NULL) {
         if (*errormsg) {
diff --git a/src/nvim/ex_eval.c b/src/nvim/ex_eval.c
index 6450892e39..bfbb6f89b5 100644
--- a/src/nvim/ex_eval.c
+++ b/src/nvim/ex_eval.c
@@ -449,8 +449,8 @@ static int throw_exception(void *value, except_type_T type, char *cmdname)
   // when no active try block is found, see do_cmdline().
   if (type == ET_USER) {
     if (strncmp(value, "Vim", 3) == 0
-        && (((char_u *)value)[3] == NUL || ((char_u *)value)[3] == ':'
-            || ((char_u *)value)[3] == '(')) {
+        && (((char *)value)[3] == NUL || ((char *)value)[3] == ':'
+            || ((char *)value)[3] == '(')) {
       emsg(_("E608: Cannot :throw exceptions with 'Vim' prefix"));
       goto fail;
     }
@@ -1372,8 +1372,7 @@ void ex_catch(exarg_T *eap)
           //
           prev_got_int = got_int;
           got_int = false;
-          caught = vim_regexec_nl(&regmatch, (char_u *)current_exception->value,
-                                  (colnr_T)0);
+          caught = vim_regexec_nl(&regmatch, current_exception->value, (colnr_T)0);
           got_int |= prev_got_int;
           vim_regfree(regmatch.regprog);
         }
diff --git a/src/nvim/ex_getln.c b/src/nvim/ex_getln.c
index 47ee1c00ce..0a1d6b2857 100644
--- a/src/nvim/ex_getln.c
+++ b/src/nvim/ex_getln.c
@@ -274,7 +274,7 @@ static bool do_incsearch_highlighting(int firstc, int *search_delim, incsearch_s
   parse_command_modifiers(&ea, &dummy, &dummy_cmdmod, true);
 
   cmd = skip_range(ea.cmd, NULL);
-  if (vim_strchr("sgvl", *cmd) == NULL) {
+  if (vim_strchr("sgvl", (uint8_t)(*cmd)) == NULL) {
     goto theend;
   }
 
@@ -558,7 +558,7 @@ static int may_add_char_to_search(int firstc, int *c, incsearch_state_T *s)
       // command line has no uppercase characters, convert
       // the character to lowercase
       if (p_ic && p_scs
-          && !pat_has_uppercase((char_u *)ccline.cmdbuff + skiplen)) {
+          && !pat_has_uppercase(ccline.cmdbuff + skiplen)) {
         *c = mb_tolower(*c);
       }
       if (*c == search_delim
@@ -1379,7 +1379,7 @@ static int may_do_command_line_next_incsearch(int firstc, long count, incsearch_
   char save;
 
   if (search_delim == ccline.cmdbuff[skiplen]) {
-    pat = (char *)last_search_pattern();
+    pat = last_search_pattern();
     if (pat == NULL) {
       restore_last_search_pattern();
       return FAIL;
@@ -1409,7 +1409,7 @@ static int may_do_command_line_next_incsearch(int firstc, long count, incsearch_
   pat[patlen] = NUL;
   int found = searchit(curwin, curbuf, &t, NULL,
                        next_match ? FORWARD : BACKWARD,
-                       (char_u *)pat, count, search_flags,
+                       pat, count, search_flags,
                        RE_SEARCH, NULL);
   emsg_off--;
   pat[patlen] = save;
@@ -2165,7 +2165,7 @@ static bool empty_pattern_magic(char *p, size_t len, magic_T magic_val)
 {
   // remove trailing \v and the like
   while (len >= 2 && p[len - 2] == '\\'
-         && vim_strchr("mMvVcCZ", p[len - 1]) != NULL) {
+         && vim_strchr("mMvVcCZ", (uint8_t)p[len - 1]) != NULL) {
     len -= 2;
   }
 
@@ -3733,7 +3733,7 @@ static bool cmdline_paste(int regname, bool literally, bool remcr)
       }
     }
 
-    cmdline_paste_str(p, literally);
+    cmdline_paste_str((char *)p, literally);
     if (allocated) {
       xfree(arg);
     }
@@ -3747,19 +3747,19 @@ static bool cmdline_paste(int regname, bool literally, bool remcr)
 // When "literally" is true, insert literally.
 // When "literally" is false, insert as typed, but don't leave the command
 // line.
-void cmdline_paste_str(char_u *s, int literally)
+void cmdline_paste_str(char *s, int literally)
 {
   int c, cv;
 
   if (literally) {
-    put_on_cmdline((char *)s, -1, true);
+    put_on_cmdline(s, -1, true);
   } else {
     while (*s != NUL) {
-      cv = *s;
+      cv = (uint8_t)(*s);
       if (cv == Ctrl_V && s[1]) {
         s++;
       }
-      c = mb_cptr2char_adv((const char_u **)&s);
+      c = mb_cptr2char_adv((const char **)&s);
       if (cv == Ctrl_V || c == ESC || c == Ctrl_C
           || c == CAR || c == NL || c == Ctrl_L
           || (c == Ctrl_BSL && *s == Ctrl_N)) {
diff --git a/src/nvim/fileio.c b/src/nvim/fileio.c
index 0ee547d124..3a7db22d2f 100644
--- a/src/nvim/fileio.c
+++ b/src/nvim/fileio.c
@@ -278,7 +278,7 @@ int readfile(char *fname, char *sfname, linenr_T from, linenr_T lines_to_skip,
       && fname != NULL
       && vim_strchr(p_cpo, CPO_FNAMER) != NULL
       && !(flags & READ_DUMMY)) {
-    if (set_rw_fname((char_u *)fname, (char_u *)sfname) == FAIL) {
+    if (set_rw_fname(fname, sfname) == FAIL) {
       return FAIL;
     }
   }
@@ -860,7 +860,7 @@ retry:
       // Skip conversion when it's already done (retry for wrong
       // "fileformat").
       if (tmpname == NULL) {
-        tmpname = (char *)readfile_charconvert((char_u *)fname, (char_u *)fenc, &fd);
+        tmpname = readfile_charconvert(fname, fenc, &fd);
         if (tmpname == NULL) {
           // Conversion failed.  Try another one.
           advance_fenc = true;
@@ -1175,7 +1175,7 @@ retry:
             goto rewind_retry;
           }
           if (conv_error == 0) {
-            conv_error = readfile_linenr(linecnt, (char_u *)ptr, (char_u *)top);
+            conv_error = readfile_linenr(linecnt, ptr, top);
           }
 
           // Deal with a bad byte and continue with the next.
@@ -1287,7 +1287,7 @@ retry:
                   goto rewind_retry;
                 }
                 if (conv_error == 0) {
-                  conv_error = readfile_linenr(linecnt, (char_u *)ptr, p);
+                  conv_error = readfile_linenr(linecnt, ptr, (char *)p);
                 }
                 if (bad_char_behavior == BAD_DROP) {
                   continue;
@@ -1315,7 +1315,7 @@ retry:
                   goto rewind_retry;
                 }
                 if (conv_error == 0) {
-                  conv_error = readfile_linenr(linecnt, (char_u *)ptr, p);
+                  conv_error = readfile_linenr(linecnt, ptr, (char *)p);
                 }
                 if (bad_char_behavior == BAD_DROP) {
                   continue;
@@ -1356,7 +1356,7 @@ retry:
                   goto rewind_retry;
                 }
                 if (conv_error == 0) {
-                  conv_error = readfile_linenr(linecnt, (char_u *)ptr, p);
+                  conv_error = readfile_linenr(linecnt, ptr, (char *)p);
                 }
                 if (bad_char_behavior == BAD_DROP) {
                   continue;
@@ -1423,12 +1423,12 @@ retry:
 #ifdef HAVE_ICONV
               // When we did a conversion report an error.
               if (iconv_fd != (iconv_t)-1 && conv_error == 0) {
-                conv_error = readfile_linenr(linecnt, (char_u *)ptr, p);
+                conv_error = readfile_linenr(linecnt, ptr, (char *)p);
               }
 #endif
               // Remember the first linenr with an illegal byte
               if (conv_error == 0 && illegal_byte == 0) {
-                illegal_byte = readfile_linenr(linecnt, (char_u *)ptr, p);
+                illegal_byte = readfile_linenr(linecnt, ptr, (char *)p);
               }
 
               // Drop, keep or replace the bad byte.
@@ -1887,7 +1887,7 @@ failed:
     char_u hash[UNDO_HASH_SIZE];
 
     sha256_finish(&sha_ctx, hash);
-    u_read_undo(NULL, hash, (char_u *)fname);
+    u_read_undo(NULL, hash, fname);
   }
 
   if (!read_stdin && !read_fifo && (!read_buffer || sfname != NULL)) {
@@ -1958,9 +1958,9 @@ bool is_dev_fd_file(char *fname)
 /// @param linecnt  line count before reading more bytes
 /// @param p        start of more bytes read
 /// @param endp     end of more bytes read
-static linenr_T readfile_linenr(linenr_T linecnt, char_u *p, const char_u *endp)
+static linenr_T readfile_linenr(linenr_T linecnt, char *p, const char *endp)
 {
-  char_u *s;
+  char *s;
   linenr_T lnum;
 
   lnum = curbuf->b_ml.ml_line_count - linecnt + 1;
@@ -2040,7 +2040,7 @@ static char *next_fenc(char **pp, bool *alloced)
     *pp = NULL;
     return "";
   }
-  p = vim_strchr((*pp), ',');
+  p = vim_strchr(*pp, ',');
   if (p == NULL) {
     r = enc_canonize(*pp);
     *pp += strlen(*pp);
@@ -2065,22 +2065,22 @@ static char *next_fenc(char **pp, bool *alloced)
 ///
 /// @return       name of the resulting converted file (the caller should delete it after reading it).
 ///               Returns NULL if the conversion failed ("*fdp" is not set) .
-static char_u *readfile_charconvert(char_u *fname, char_u *fenc, int *fdp)
+static char *readfile_charconvert(char *fname, char *fenc, int *fdp)
 {
-  char_u *tmpname;
+  char *tmpname;
   char *errmsg = NULL;
 
-  tmpname = (char_u *)vim_tempname();
+  tmpname = vim_tempname();
   if (tmpname == NULL) {
     errmsg = _("Can't find temp file for conversion");
   } else {
     close(*fdp);                // close the input file, ignore errors
     *fdp = -1;
-    if (eval_charconvert((char *)fenc, "utf-8",
-                         (char *)fname, (char *)tmpname) == FAIL) {
+    if (eval_charconvert(fenc, "utf-8",
+                         fname, tmpname) == FAIL) {
       errmsg = _("Conversion with 'charconvert' failed");
     }
-    if (errmsg == NULL && (*fdp = os_open((char *)tmpname, O_RDONLY, 0)) < 0) {
+    if (errmsg == NULL && (*fdp = os_open(tmpname, O_RDONLY, 0)) < 0) {
       errmsg = _("can't read output of 'charconvert'");
     }
   }
@@ -2090,14 +2090,14 @@ static char_u *readfile_charconvert(char_u *fname, char_u *fenc, int *fdp)
     // another type of conversion might still work.
     msg(errmsg);
     if (tmpname != NULL) {
-      os_remove((char *)tmpname);  // delete converted file
+      os_remove(tmpname);  // delete converted file
       XFREE_CLEAR(tmpname);
     }
   }
 
   // If the input file is closed, open it (caller should check for error).
   if (*fdp < 0) {
-    *fdp = os_open((char *)fname, O_RDONLY, 0);
+    *fdp = os_open(fname, O_RDONLY, 0);
   }
 
   return tmpname;
@@ -2254,7 +2254,7 @@ int buf_write(buf_T *buf, char *fname, char *sfname, linenr_T start, linenr_T en
       && !filtering
       && (!append || vim_strchr(p_cpo, CPO_FNAMEAPP) != NULL)
       && vim_strchr(p_cpo, CPO_FNAMEW) != NULL) {
-    if (set_rw_fname((char_u *)fname, (char_u *)sfname) == FAIL) {
+    if (set_rw_fname(fname, sfname) == FAIL) {
       return FAIL;
     }
     buf = curbuf;           // just in case autocmds made "buf" invalid
@@ -2572,7 +2572,7 @@ int buf_write(buf_T *buf, char *fname, char *sfname, linenr_T start, linenr_T en
 
   // If 'backupskip' is not empty, don't make a backup for some files.
   dobackup = (p_wb || p_bk || *p_pm != NUL);
-  if (dobackup && *p_bsk != NUL && match_file_list(p_bsk, (char_u *)sfname, (char_u *)ffname)) {
+  if (dobackup && *p_bsk != NUL && match_file_list((char *)p_bsk, sfname, ffname)) {
     dobackup = false;
   }
 
@@ -3652,7 +3652,7 @@ nofail:
 
 /// Set the name of the current buffer.  Use when the buffer doesn't have a
 /// name and a ":r" or ":w" command with a file name is used.
-static int set_rw_fname(char_u *fname, char_u *sfname)
+static int set_rw_fname(char *fname, char *sfname)
 {
   buf_T *buf = curbuf;
 
@@ -3670,7 +3670,7 @@ static int set_rw_fname(char_u *fname, char_u *sfname)
     return FAIL;
   }
 
-  if (setfname(curbuf, (char *)fname, (char *)sfname, false) == OK) {
+  if (setfname(curbuf, fname, sfname, false) == OK) {
     curbuf->b_flags |= BF_NOTEDITED;
   }
 
@@ -4205,7 +4205,7 @@ static int make_bom(char_u *buf, char_u *name)
 ///
 /// For buffers that have buftype "nofile" or "scratch": never change the file
 /// name.
-void shorten_buf_fname(buf_T *buf, char_u *dirname, int force)
+void shorten_buf_fname(buf_T *buf, char *dirname, int force)
 {
   char *p;
 
@@ -4214,11 +4214,11 @@ void shorten_buf_fname(buf_T *buf, char_u *dirname, int force)
       && !path_with_url(buf->b_fname)
       && (force
           || buf->b_sfname == NULL
-          || path_is_absolute((char_u *)buf->b_sfname))) {
+          || path_is_absolute(buf->b_sfname))) {
     if (buf->b_sfname != buf->b_ffname) {
       XFREE_CLEAR(buf->b_sfname);
     }
-    p = path_shorten_fname(buf->b_ffname, (char *)dirname);
+    p = path_shorten_fname(buf->b_ffname, dirname);
     if (p != NULL) {
       buf->b_sfname = xstrdup(p);
       buf->b_fname = buf->b_sfname;
@@ -4236,7 +4236,7 @@ void shorten_fnames(int force)
 
   os_dirname((char *)dirname, MAXPATHL);
   FOR_ALL_BUFFERS(buf) {
-    shorten_buf_fname(buf, dirname, force);
+    shorten_buf_fname(buf, (char *)dirname, force);
 
     // Always make the swap file name a full path, a "nofile" buffer may
     // also have a swap file.
@@ -4552,7 +4552,7 @@ int vim_rename(const char *from, const char *to)
   }
 
   if (use_tmp_file) {
-    char_u tempname[MAXPATHL + 1];
+    char tempname[MAXPATHL + 1];
 
     // Find a name that doesn't exist and is in the same directory.
     // Rename "from" to "tempname" and then rename "tempname" to "to".
@@ -4561,17 +4561,17 @@ int vim_rename(const char *from, const char *to)
     }
     STRCPY(tempname, from);
     for (n = 123; n < 99999; n++) {
-      char *tail = path_tail((char *)tempname);
-      snprintf(tail, (size_t)((MAXPATHL + 1) - (tail - (char *)tempname - 1)), "%d", n);
+      char *tail = path_tail(tempname);
+      snprintf(tail, (size_t)((MAXPATHL + 1) - (tail - tempname - 1)), "%d", n);
 
-      if (!os_path_exists((char *)tempname)) {
-        if (os_rename((char_u *)from, tempname) == OK) {
-          if (os_rename(tempname, (char_u *)to) == OK) {
+      if (!os_path_exists(tempname)) {
+        if (os_rename(from, tempname) == OK) {
+          if (os_rename(tempname, to) == OK) {
             return 0;
           }
           // Strange, the second step failed.  Try moving the
           // file back and return failure.
-          (void)os_rename(tempname, (char_u *)from);
+          (void)os_rename(tempname, from);
           return -1;
         }
         // If it fails for one temp name it will most likely fail
@@ -4589,7 +4589,7 @@ int vim_rename(const char *from, const char *to)
   os_remove((char *)to);
 
   // First try a normal rename, return if it works.
-  if (os_rename((char_u *)from, (char_u *)to) == OK) {
+  if (os_rename(from, to) == OK) {
     return 0;
   }
 
@@ -5317,7 +5317,7 @@ int delete_recursive(const char *name)
     garray_T ga;
     if (readdir_core(&ga, exp, NULL, NULL) == OK) {
       for (int i = 0; i < ga.ga_len; i++) {
-        vim_snprintf(NameBuff, MAXPATHL, "%s/%s", exp, ((char_u **)ga.ga_data)[i]);
+        vim_snprintf(NameBuff, MAXPATHL, "%s/%s", exp, ((char **)ga.ga_data)[i]);
         if (delete_recursive((const char *)NameBuff) != 0) {
           // Remember the failure but continue deleting any further
           // entries.
@@ -5505,28 +5505,27 @@ bool match_file_pat(char *pattern, regprog_T **prog, char *fname, char *sfname,
 /// @param ffname full file name
 ///
 /// @return true if there was a match
-bool match_file_list(char_u *list, char_u *sfname, char_u *ffname)
+bool match_file_list(char *list, char *sfname, char *ffname)
   FUNC_ATTR_WARN_UNUSED_RESULT FUNC_ATTR_NONNULL_ARG(1, 3)
 {
-  char_u buf[100];
-  char_u *tail;
-  char_u *regpat;
+  char buf[100];
+  char *tail;
+  char *regpat;
   char allow_dirs;
   bool match;
   char *p;
 
-  tail = (char_u *)path_tail((char *)sfname);
+  tail = path_tail(sfname);
 
   // try all patterns in 'wildignore'
-  p = (char *)list;
+  p = list;
   while (*p) {
-    copy_option_part(&p, (char *)buf, ARRAY_SIZE(buf), ",");
-    regpat = (char_u *)file_pat_to_reg_pat((char *)buf, NULL, &allow_dirs, false);
+    copy_option_part(&p, buf, ARRAY_SIZE(buf), ",");
+    regpat = file_pat_to_reg_pat(buf, NULL, &allow_dirs, false);
     if (regpat == NULL) {
       break;
     }
-    match = match_file_pat((char *)regpat, NULL, (char *)ffname, (char *)sfname, (char *)tail,
-                           (int)allow_dirs);
+    match = match_file_pat(regpat, NULL, ffname, sfname, tail, (int)allow_dirs);
     xfree(regpat);
     if (match) {
       return true;
diff --git a/src/nvim/fold.c b/src/nvim/fold.c
index 6cb9e5c38d..7306131574 100644
--- a/src/nvim/fold.c
+++ b/src/nvim/fold.c
@@ -2873,7 +2873,7 @@ static void foldlevelIndent(fline_T *flp)
 
   // empty line or lines starting with a character in 'foldignore': level
   // depends on surrounding lines
-  if (*s == NUL || vim_strchr(flp->wp->w_p_fdi, *s) != NULL) {
+  if (*s == NUL || vim_strchr(flp->wp->w_p_fdi, (uint8_t)(*s)) != NULL) {
     // first and last line can't be undefined, use level 0
     if (lnum == 1 || lnum == buf->b_ml.ml_line_count) {
       flp->lvl = 0;
diff --git a/src/nvim/garray.c b/src/nvim/garray.c
index 0f11868031..f75210bacb 100644
--- a/src/nvim/garray.c
+++ b/src/nvim/garray.c
@@ -173,9 +173,9 @@ char *ga_concat_strings_sep(const garray_T *gap, const char *sep)
 /// @param gap
 ///
 /// @returns the concatenated strings
-char_u *ga_concat_strings(const garray_T *gap) FUNC_ATTR_NONNULL_RET
+char *ga_concat_strings(const garray_T *gap) FUNC_ATTR_NONNULL_RET
 {
-  return (char_u *)ga_concat_strings_sep(gap, ",");
+  return ga_concat_strings_sep(gap, ",");
 }
 
 /// Concatenate a string to a growarray which contains characters.
diff --git a/src/nvim/getchar.c b/src/nvim/getchar.c
index b9e3b6b902..842b0b10b6 100644
--- a/src/nvim/getchar.c
+++ b/src/nvim/getchar.c
@@ -538,7 +538,7 @@ void AppendToRedobuffLit(const char *str, int len)
 
     // Handle a special or multibyte character.
     // Composing chars separately are handled separately.
-    const int c = mb_cptr2char_adv((const char_u **)&s);
+    const int c = mb_cptr2char_adv(&s);
     if (c < ' ' || c == DEL || (*s == NUL && (c == '0' || c == '^'))) {
       add_char_buff(&redobuff, Ctrl_V);
     }
@@ -599,7 +599,7 @@ void stuffReadbuffSpec(const char *s)
       stuffReadbuffLen(s, 3);
       s += 3;
     } else {
-      int c = mb_cptr2char_adv((const char_u **)&s);
+      int c = mb_cptr2char_adv(&s);
       if (c == CAR || c == NL || c == ESC) {
         c = ' ';
       }
@@ -640,7 +640,7 @@ void stuffescaped(const char *arg, bool literally)
 
     // stuff a single special character
     if (*arg != NUL) {
-      const int c = mb_cptr2char_adv((const char_u **)&arg);
+      const int c = mb_cptr2char_adv(&arg);
       if (literally && ((c < ' ' && c != TAB) || c == DEL)) {
         stuffcharReadbuff(Ctrl_V);
       }
diff --git a/src/nvim/help.c b/src/nvim/help.c
index 0a695a0aa7..91fda60859 100644
--- a/src/nvim/help.c
+++ b/src/nvim/help.c
@@ -412,7 +412,7 @@ int find_help_tags(const char *arg, int *num_matches, char ***matches, bool keep
     // And also "\_$" and "\_^".
     if (arg[0] == '\\'
         && ((arg[1] != NUL && arg[2] == NUL)
-            || (vim_strchr("%_z@", arg[1]) != NULL
+            || (vim_strchr("%_z@", (uint8_t)arg[1]) != NULL
                 && arg[2] != NUL))) {
       vim_snprintf(d, IOSIZE, "/\\\\%s", arg + 1);
       // Check for "/\\_$", should be "/\\_\$"
@@ -471,7 +471,7 @@ int find_help_tags(const char *arg, int *num_matches, char ***matches, bool keep
         // Insert '-' before and after "CTRL-X" when applicable.
         if (*s < ' '
             || (*s == '^' && s[1]
-                && (ASCII_ISALPHA(s[1]) || vim_strchr("?@[\\]^", s[1]) != NULL))) {
+                && (ASCII_ISALPHA(s[1]) || vim_strchr("?@[\\]^", (uint8_t)s[1]) != NULL))) {
           if (d > IObuff && d[-1] != '_' && d[-1] != '\\') {
             *d++ = '_';                 // prepend a '_' to make x_CTRL-x
           }
@@ -974,12 +974,12 @@ static void helptags_one(char *dir, const char *ext, const char *tagfname, bool
       }
       if (in_example) {
         // skip over example; a non-white in the first column ends it
-        if (vim_strchr(" \t\n\r", IObuff[0])) {
+        if (vim_strchr(" \t\n\r", (uint8_t)IObuff[0])) {
           continue;
         }
         in_example = false;
       }
-      p1 = vim_strchr((char *)IObuff, '*');       // find first '*'
+      p1 = vim_strchr(IObuff, '*');       // find first '*'
       while (p1 != NULL) {
         p2 = strchr((const char *)p1 + 1, '*');  // Find second '*'.
         if (p2 != NULL && p2 > p1 + 1) {         // Skip "*" and "**".
@@ -994,7 +994,7 @@ static void helptags_one(char *dir, const char *ext, const char *tagfname, bool
           // followed by a white character or end-of-line.
           if (s == p2
               && (p1 == IObuff || p1[-1] == ' ' || p1[-1] == '\t')
-              && (vim_strchr(" \t\n\r", s[1]) != NULL
+              && (vim_strchr(" \t\n\r", (uint8_t)s[1]) != NULL
                   || s[1] == '\0')) {
             *p2 = '\0';
             p1++;
diff --git a/src/nvim/highlight_group.c b/src/nvim/highlight_group.c
index 404835c4a9..2a81b4deb0 100644
--- a/src/nvim/highlight_group.c
+++ b/src/nvim/highlight_group.c
@@ -2921,9 +2921,9 @@ color_name_table_T color_name_table[] = {
 /// return the hex value or -1 if could not find a correct value
 RgbValue name_to_color(const char *name, int *idx)
 {
-  if (name[0] == '#' && isxdigit(name[1]) && isxdigit(name[2])
-      && isxdigit(name[3]) && isxdigit(name[4]) && isxdigit(name[5])
-      && isxdigit(name[6]) && name[7] == NUL) {
+  if (name[0] == '#' && isxdigit((uint8_t)name[1]) && isxdigit((uint8_t)name[2])
+      && isxdigit((uint8_t)name[3]) && isxdigit((uint8_t)name[4]) && isxdigit((uint8_t)name[5])
+      && isxdigit((uint8_t)name[6]) && name[7] == NUL) {
     // rgb hex string
     *idx = kColorIdxHex;
     return (RgbValue)strtol((char *)(name + 1), NULL, 16);
diff --git a/src/nvim/indent_c.c b/src/nvim/indent_c.c
index c2293add76..1c771073b2 100644
--- a/src/nvim/indent_c.c
+++ b/src/nvim/indent_c.c
@@ -704,7 +704,7 @@ static int cin_get_equal_amount(linenr_T lnum)
 
   s = ml_get(lnum);
   line = s;
-  while (*s != NUL && vim_strchr("=;{}\"'", *s) == NULL) {
+  while (*s != NUL && vim_strchr("=;{}\"'", (uint8_t)(*s)) == NULL) {
     if (cin_iscomment(s)) {     // ignore comments
       s = cin_skipcomment(s);
     } else {
diff --git a/src/nvim/insexpand.c b/src/nvim/insexpand.c
index ba948ff924..38fb7a2873 100644
--- a/src/nvim/insexpand.c
+++ b/src/nvim/insexpand.c
@@ -598,7 +598,7 @@ static char *ins_compl_infercase_gettext(const char *str, int char_len, int comp
   // Allocate wide character array for the completion and fill it.
   int *const wca = xmalloc((size_t)char_len * sizeof(*wca));
   {
-    const char_u *p = (char_u *)str;
+    const char *p = str;
     for (int i = 0; i < char_len; i++) {
       wca[i] = mb_ptr2char_adv(&p);
     }
@@ -606,7 +606,7 @@ static char *ins_compl_infercase_gettext(const char *str, int char_len, int comp
 
   // Rule 1: Were any chars converted to lower?
   {
-    const char_u *p = (char_u *)compl_orig_text;
+    const char *p = compl_orig_text;
     for (int i = 0; i < min_len; i++) {
       const int c = mb_ptr2char_adv(&p);
       if (mb_islower(c)) {
@@ -625,7 +625,7 @@ static char *ins_compl_infercase_gettext(const char *str, int char_len, int comp
   // Rule 2: No lower case, 2nd consecutive letter converted to
   // upper case.
   if (!has_lower) {
-    const char_u *p = (char_u *)compl_orig_text;
+    const char *p = compl_orig_text;
     for (int i = 0; i < min_len; i++) {
       const int c = mb_ptr2char_adv(&p);
       if (was_letter && mb_isupper(c) && mb_islower(wca[i])) {
@@ -641,7 +641,7 @@ static char *ins_compl_infercase_gettext(const char *str, int char_len, int comp
 
   // Copy the original case of the part we typed.
   {
-    const char_u *p = (char_u *)compl_orig_text;
+    const char *p = compl_orig_text;
     for (int i = 0; i < min_len; i++) {
       const int c = mb_ptr2char_adv(&p);
       if (mb_islower(c)) {
@@ -2857,7 +2857,7 @@ static int process_next_cpt_value(ins_compl_next_state_T *st, int *compl_type_ar
     // Remember the first match so that the loop stops when we
     // wrap and come back there a second time.
     st->set_match_pos = true;
-  } else if (vim_strchr("buwU", *st->e_cpt) != NULL
+  } else if (vim_strchr("buwU", (uint8_t)(*st->e_cpt)) != NULL
              && (st->ins_buf = ins_compl_next_buf(st->ins_buf, *st->e_cpt)) != curbuf) {
     // Scan a buffer, but not the current one.
     if (st->ins_buf->b_ml.ml_mfp != NULL) {  // loaded buffer
@@ -3161,7 +3161,7 @@ static int get_next_default_completion(ins_compl_next_state_T *st, pos_T *start_
                                               compl_direction, compl_pattern);
     } else {
       found_new_match = searchit(NULL, st->ins_buf, st->cur_match_pos,
-                                 NULL, compl_direction, (char_u *)compl_pattern, 1L,
+                                 NULL, compl_direction, compl_pattern, 1L,
                                  SEARCH_KEEP + SEARCH_NFMSG, RE_LAST, NULL);
     }
     msg_silent--;
diff --git a/src/nvim/lua/spell.c b/src/nvim/lua/spell.c
index 0a566b2f86..d510d25e90 100644
--- a/src/nvim/lua/spell.c
+++ b/src/nvim/lua/spell.c
@@ -61,7 +61,7 @@ int nlua_spell_check(lua_State *lstate)
 
   while (*str != NUL) {
     attr = HLF_COUNT;
-    len = spell_check(curwin, (char_u *)str, &attr, &capcol, false);
+    len = spell_check(curwin, (char *)str, &attr, &capcol, false);
     assert(len <= INT_MAX);
 
     if (attr != HLF_COUNT) {
diff --git a/src/nvim/mbyte.c b/src/nvim/mbyte.c
index 93ac0fccfa..b5274b9695 100644
--- a/src/nvim/mbyte.c
+++ b/src/nvim/mbyte.c
@@ -699,23 +699,23 @@ static int utf_safe_read_char_adv(const char_u **s, size_t *n)
 
 // Get character at **pp and advance *pp to the next character.
 // Note: composing characters are skipped!
-int mb_ptr2char_adv(const char_u **const pp)
+int mb_ptr2char_adv(const char **const pp)
 {
   int c;
 
-  c = utf_ptr2char((char *)(*pp));
-  *pp += utfc_ptr2len((char *)(*pp));
+  c = utf_ptr2char(*pp);
+  *pp += utfc_ptr2len(*pp);
   return c;
 }
 
 // Get character at **pp and advance *pp to the next character.
 // Note: composing characters are returned as separate characters.
-int mb_cptr2char_adv(const char_u **pp)
+int mb_cptr2char_adv(const char **pp)
 {
   int c;
 
-  c = utf_ptr2char((char *)(*pp));
-  *pp += utf_ptr2len((char *)(*pp));
+  c = utf_ptr2char(*pp);
+  *pp += utf_ptr2len(*pp);
   return c;
 }
 
@@ -2232,7 +2232,7 @@ char_u *enc_locale(void)
   const char *p = vim_strchr(s, '.');
   if (p != NULL) {
     if (p > s + 2 && !STRNICMP(p + 1, "EUC", 3)
-        && !isalnum((int)p[4]) && p[4] != '-' && p[-3] == '_') {
+        && !isalnum((uint8_t)p[4]) && p[4] != '-' && p[-3] == '_') {
       // Copy "XY.EUC" to "euc-XY" to buf[10].
       memmove(buf, "euc-", 4);
       buf[4] = (char)(ASCII_ISALNUM(p[-2]) ? TOLOWER_ASC(p[-2]) : 0);
diff --git a/src/nvim/memline.c b/src/nvim/memline.c
index eee3b9d517..759920c4ec 100644
--- a/src/nvim/memline.c
+++ b/src/nvim/memline.c
@@ -749,7 +749,7 @@ void ml_recover(bool checkext)
   int len = (int)strlen(fname);
   if (checkext && len >= 4
       && STRNICMP(fname + len - 4, ".s", 2) == 0
-      && vim_strchr("abcdefghijklmnopqrstuvw", TOLOWER_ASC(fname[len - 2])) != NULL
+      && vim_strchr("abcdefghijklmnopqrstuvw", TOLOWER_ASC((uint8_t)fname[len - 2])) != NULL
       && ASCII_ISALPHA(fname[len - 1])) {
     directly = true;
     fname_used = xstrdup(fname);     // make a copy for mf_open()
@@ -3000,7 +3000,7 @@ int resolve_symlink(const char *fname, char *buf)
     // If it's relative, build a new path based on the directory
     // portion of the filename (if any) and the path the symlink
     // points to.
-    if (path_is_absolute((char_u *)buf)) {
+    if (path_is_absolute(buf)) {
       STRCPY(tmp, buf);
     } else {
       char *tail = path_tail(tmp);
diff --git a/src/nvim/mouse.c b/src/nvim/mouse.c
index 258f596ecc..950b025e53 100644
--- a/src/nvim/mouse.c
+++ b/src/nvim/mouse.c
@@ -86,17 +86,17 @@ static int get_mouse_class(char *p)
 /// Move "pos" back to the start of the word it's in.
 static void find_start_of_word(pos_T *pos)
 {
-  char_u *line;
+  char *line;
   int cclass;
   int col;
 
-  line = (char_u *)ml_get(pos->lnum);
-  cclass = get_mouse_class((char *)line + pos->col);
+  line = ml_get(pos->lnum);
+  cclass = get_mouse_class(line + pos->col);
 
   while (pos->col > 0) {
     col = pos->col - 1;
-    col -= utf_head_off((char *)line, (char *)line + col);
-    if (get_mouse_class((char *)line + col) != cclass) {
+    col -= utf_head_off(line, line + col);
+    if (get_mouse_class(line + col) != cclass) {
       break;
     }
     pos->col = col;
@@ -107,19 +107,19 @@ static void find_start_of_word(pos_T *pos)
 /// When 'selection' is "exclusive", the position is just after the word.
 static void find_end_of_word(pos_T *pos)
 {
-  char_u *line;
+  char *line;
   int cclass;
   int col;
 
-  line = (char_u *)ml_get(pos->lnum);
+  line = ml_get(pos->lnum);
   if (*p_sel == 'e' && pos->col > 0) {
     pos->col--;
-    pos->col -= utf_head_off((char *)line, (char *)line + pos->col);
+    pos->col -= utf_head_off(line, line + pos->col);
   }
-  cclass = get_mouse_class((char *)line + pos->col);
+  cclass = get_mouse_class(line + pos->col);
   while (line[pos->col] != NUL) {
-    col = pos->col + utfc_ptr2len((char *)line + pos->col);
-    if (get_mouse_class((char *)line + col) != cclass) {
+    col = pos->col + utfc_ptr2len(line + pos->col);
+    if (get_mouse_class(line + col) != cclass) {
       if (*p_sel == 'e') {
         pos->col = col;
       }
@@ -1540,16 +1540,16 @@ colnr_T vcol2col(win_T *const wp, const linenr_T lnum, const colnr_T vcol)
   FUNC_ATTR_NONNULL_ALL FUNC_ATTR_WARN_UNUSED_RESULT
 {
   // try to advance to the specified column
-  char_u *line = (char_u *)ml_get_buf(wp->w_buffer, lnum, false);
+  char *line = ml_get_buf(wp->w_buffer, lnum, false);
   chartabsize_T cts;
-  init_chartabsize_arg(&cts, wp, lnum, 0, (char *)line, (char *)line);
+  init_chartabsize_arg(&cts, wp, lnum, 0, line, line);
   while (cts.cts_vcol < vcol && *cts.cts_ptr != NUL) {
     cts.cts_vcol += win_lbr_chartabsize(&cts, NULL);
     MB_PTR_ADV(cts.cts_ptr);
   }
   clear_chartabsize_arg(&cts);
 
-  return (colnr_T)((char_u *)cts.cts_ptr - line);
+  return (colnr_T)(cts.cts_ptr - line);
 }
 
 /// Set UI mouse depending on current mode and 'mouse'.
@@ -1575,10 +1575,10 @@ static void set_mouse_topline(win_T *wp)
 static colnr_T scroll_line_len(linenr_T lnum)
 {
   colnr_T col = 0;
-  char_u *line = (char_u *)ml_get(lnum);
+  char *line = ml_get(lnum);
   if (*line != NUL) {
     for (;;) {
-      int numchar = win_chartabsize(curwin, (char *)line, col);
+      int numchar = win_chartabsize(curwin, line, col);
       MB_PTR_ADV(line);
       if (*line == NUL) {    // don't count the last character
         break;
@@ -1680,10 +1680,10 @@ static int mouse_adjust_click(win_T *wp, int row, int col)
   // highlighting the second byte, not the ninth.
 
   linenr_T lnum = wp->w_cursor.lnum;
-  char_u *line = (char_u *)ml_get(lnum);
-  char_u *ptr = line;
-  char_u *ptr_end;
-  char_u *ptr_row_offset = line;  // Where we begin adjusting `ptr_end`
+  char *line = ml_get(lnum);
+  char *ptr = line;
+  char *ptr_end;
+  char *ptr_row_offset = line;  // Where we begin adjusting `ptr_end`
 
   // Find the offset where scanning should begin.
   int offset = wp->w_leftcol;
@@ -1701,8 +1701,8 @@ static int mouse_adjust_click(win_T *wp, int row, int col)
     // checked for concealed characters.
     vcol = 0;
     while (vcol < offset && *ptr != NUL) {
-      vcol += win_chartabsize(curwin, (char *)ptr, vcol);
-      ptr += utfc_ptr2len((char *)ptr);
+      vcol += win_chartabsize(curwin, ptr, vcol);
+      ptr += utfc_ptr2len(ptr);
     }
 
     ptr_row_offset = ptr;
@@ -1712,8 +1712,8 @@ static int mouse_adjust_click(win_T *wp, int row, int col)
   vcol = offset;
   ptr_end = ptr_row_offset;
   while (vcol < col && *ptr_end != NUL) {
-    vcol += win_chartabsize(curwin, (char *)ptr_end, vcol);
-    ptr_end += utfc_ptr2len((char *)ptr_end);
+    vcol += win_chartabsize(curwin, ptr_end, vcol);
+    ptr_end += utfc_ptr2len(ptr_end);
   }
 
   int matchid;
@@ -1727,7 +1727,7 @@ static int mouse_adjust_click(win_T *wp, int row, int col)
 #define DECR() nudge--; ptr_end -= utfc_ptr2len((char *)ptr_end)
 
   while (ptr < ptr_end && *ptr != NUL) {
-    cwidth = win_chartabsize(curwin, (char *)ptr, vcol);
+    cwidth = win_chartabsize(curwin, ptr, vcol);
     vcol += cwidth;
     if (cwidth > 1 && *ptr == '\t' && nudge > 0) {
       // A tab will "absorb" any previous adjustments.
@@ -1755,7 +1755,7 @@ static int mouse_adjust_click(win_T *wp, int row, int col)
 
         while (prev_matchid == matchid && *ptr != NUL) {
           INCR();
-          ptr += utfc_ptr2len((char *)ptr);
+          ptr += utfc_ptr2len(ptr);
           matchid = syn_get_concealed_id(wp, lnum, (colnr_T)(ptr - line));
         }
 
@@ -1763,7 +1763,7 @@ static int mouse_adjust_click(win_T *wp, int row, int col)
       }
     }
 
-    ptr += utfc_ptr2len((char *)ptr);
+    ptr += utfc_ptr2len(ptr);
   }
 
   return col + nudge;
diff --git a/src/nvim/normal.c b/src/nvim/normal.c
index 8c499b28fc..6fb00ca6b5 100644
--- a/src/nvim/normal.c
+++ b/src/nvim/normal.c
@@ -2337,7 +2337,7 @@ bool find_decl(char_u *ptr, size_t len, bool locally, bool thisblock, int flags_
   clearpos(&found_pos);
   for (;;) {
     t = searchit(curwin, curbuf, &curwin->w_cursor, NULL, FORWARD,
-                 (char_u *)pat, 1L, searchflags, RE_LAST, NULL);
+                 pat, 1L, searchflags, RE_LAST, NULL);
     if (curwin->w_cursor.lnum >= old_pos.lnum) {
       t = false;         // match after start is failure too
     }
@@ -3561,7 +3561,7 @@ static void nv_ident(cmdarg_T *cap)
     p = buf + strlen(buf);
     while (n-- > 0) {
       // put a backslash before \ and some others
-      if (vim_strchr(aux_ptr, *ptr) != NULL) {
+      if (vim_strchr(aux_ptr, (uint8_t)(*ptr)) != NULL) {
         *p++ = '\\';
       }
       // When current byte is a part of multibyte character, copy all
diff --git a/src/nvim/ops.c b/src/nvim/ops.c
index 73707e4122..42ff2b15ed 100644
--- a/src/nvim/ops.c
+++ b/src/nvim/ops.c
@@ -1006,7 +1006,7 @@ static int stuff_yank(int regname, char *p)
   } else {
     free_register(reg);
     set_yreg_additional_data(reg, NULL);
-    reg->y_array = xmalloc(sizeof(char_u *));
+    reg->y_array = xmalloc(sizeof(char *));
     reg->y_array[0] = p;
     reg->y_size = 1;
     reg->y_type = kMTCharWise;
@@ -1028,14 +1028,14 @@ static int execreg_lastc = NUL;
 ///              with a \. Lines that start with a comment "\ character are ignored.
 /// @returns the concatenated line. The index of the line that should be
 ///          processed next is returned in idx.
-static char_u *execreg_line_continuation(char **lines, size_t *idx)
+static char *execreg_line_continuation(char **lines, size_t *idx)
 {
   size_t i = *idx;
   assert(i > 0);
   const size_t cmd_end = i;
 
   garray_T ga;
-  ga_init(&ga, (int)sizeof(char_u), 400);
+  ga_init(&ga, (int)sizeof(char), 400);
 
   char *p;
 
@@ -1068,7 +1068,7 @@ static char_u *execreg_line_continuation(char **lines, size_t *idx)
   ga_clear(&ga);
 
   *idx = i;
-  return (char_u *)str;
+  return str;
 }
 
 /// Execute a yank register: copy it into the stuff buffer
@@ -1118,9 +1118,9 @@ int do_execreg(int regname, int colon, int addcr, int silent)
     // When in Visual mode "'<,'>" will be prepended to the command.
     // Remove it when it's already there.
     if (VIsual_active && strncmp(p, "'<,'>", 5) == 0) {
-      retval = put_in_typebuf((char_u *)p + 5, true, true, silent);
+      retval = put_in_typebuf(p + 5, true, true, silent);
     } else {
-      retval = put_in_typebuf((char_u *)p, true, true, silent);
+      retval = put_in_typebuf(p, true, true, silent);
     }
     xfree(p);
   } else if (regname == '=') {
@@ -1128,7 +1128,7 @@ int do_execreg(int regname, int colon, int addcr, int silent)
     if (p == NULL) {
       return FAIL;
     }
-    retval = put_in_typebuf((char_u *)p, true, colon, silent);
+    retval = put_in_typebuf(p, true, colon, silent);
     xfree(p);
   } else if (regname == '.') {        // use last inserted text
     p = (char *)get_last_insert_save();
@@ -1136,7 +1136,7 @@ int do_execreg(int regname, int colon, int addcr, int silent)
       emsg(_(e_noinstext));
       return FAIL;
     }
-    retval = put_in_typebuf((char_u *)p, false, colon, silent);
+    retval = put_in_typebuf(p, false, colon, silent);
     xfree(p);
   } else {
     yankreg_T *reg = get_yank_register(regname, YREG_PASTE);
@@ -1164,7 +1164,7 @@ int do_execreg(int regname, int colon, int addcr, int silent)
       if (colon && i > 0) {
         p = skipwhite(str);
         if (*p == '\\' || (p[0] == '"' && p[1] == '\\' && p[2] == ' ')) {
-          str = (char *)execreg_line_continuation(reg->y_array, &i);
+          str = execreg_line_continuation(reg->y_array, &i);
           free_str = true;
         }
       }
@@ -1214,7 +1214,7 @@ static void put_reedit_in_typebuf(int silent)
 /// @param esc    when true then it is to be taken literally: Escape K_SPECIAL
 ///               characters and no remapping.
 /// @param colon  add ':' before the line
-static int put_in_typebuf(char_u *s, bool esc, bool colon, int silent)
+static int put_in_typebuf(char *s, bool esc, bool colon, int silent)
 {
   int retval = OK;
 
@@ -1226,9 +1226,9 @@ static int put_in_typebuf(char_u *s, bool esc, bool colon, int silent)
     char *p;
 
     if (esc) {
-      p = vim_strsave_escape_ks((char *)s);
+      p = vim_strsave_escape_ks(s);
     } else {
-      p = (char *)s;
+      p = s;
     }
     if (p == NULL) {
       retval = FAIL;
@@ -1347,7 +1347,7 @@ bool get_spec_reg(int regname, char **argp, bool *allocated, bool errmsg)
     if (last_search_pat() == NULL && errmsg) {
       emsg(_(e_noprevre));
     }
-    *argp = (char *)last_search_pat();
+    *argp = last_search_pat();
     return true;
 
   case '.':                     // last inserted text
@@ -1418,11 +1418,11 @@ bool cmdline_paste_reg(int regname, bool literally_arg, bool remcr)
   }
 
   for (size_t i = 0; i < reg->y_size; i++) {
-    cmdline_paste_str((char_u *)reg->y_array[i], literally);
+    cmdline_paste_str(reg->y_array[i], literally);
 
     // Insert ^M between lines, unless `remcr` is true.
     if (i < reg->y_size - 1 && !remcr) {
-      cmdline_paste_str((char_u *)"\r", literally);
+      cmdline_paste_str("\r", literally);
     }
 
     // Check for CTRL-C, in case someone tries to paste a few thousand
@@ -1455,7 +1455,7 @@ int op_delete(oparg_T *oap)
 {
   int n;
   linenr_T lnum;
-  char_u *ptr;
+  char *ptr;
   char *newp, *oldp;
   struct block_def bd = { 0 };
   linenr_T old_lcount = curbuf->b_ml.ml_line_count;
@@ -1489,11 +1489,11 @@ int op_delete(oparg_T *oap)
       && oap->line_count > 1
       && oap->motion_force == NUL
       && oap->op_type == OP_DELETE) {
-    ptr = (char_u *)ml_get(oap->end.lnum) + oap->end.col;
+    ptr = ml_get(oap->end.lnum) + oap->end.col;
     if (*ptr != NUL) {
       ptr += oap->inclusive;
     }
-    ptr = (char_u *)skipwhite((char *)ptr);
+    ptr = skipwhite(ptr);
     if (*ptr == NUL && inindent(0)) {
       oap->motion_type = kMTLineWise;
     }
@@ -2740,7 +2740,7 @@ static void op_yank_reg(oparg_T *oap, bool message, yankreg_T *reg, bool append)
   }
 
   if (curr != reg) {      // append the new block to the old block
-    new_ptr = xmalloc(sizeof(char_u *) * (curr->y_size + reg->y_size));
+    new_ptr = xmalloc(sizeof(char *) * (curr->y_size + reg->y_size));
     for (j = 0; j < curr->y_size; j++) {
       new_ptr[j] = curr->y_array[j];
     }
@@ -3083,7 +3083,7 @@ void do_put(int regname, yankreg_T *reg, int dir, long count, int flags)
         if (y_array != NULL) {
           break;
         }
-        y_array = xmalloc(y_size * sizeof(char_u *));
+        y_array = xmalloc(y_size * sizeof(char *));
       }
     } else {
       y_size = 1;               // use fake one-line yank register
@@ -3889,9 +3889,9 @@ void ex_display(exarg_T *eap)
   // display last search pattern
   if (last_search_pat() != NULL
       && (arg == NULL || vim_strchr(arg, '/') != NULL) && !got_int
-      && !message_filtered((char *)last_search_pat())) {
+      && !message_filtered(last_search_pat())) {
     msg_puts("\n  c  \"/   ");
-    dis_msg((char *)last_search_pat(), false);
+    dis_msg(last_search_pat(), false);
   }
 
   // display last used expression
@@ -4475,7 +4475,7 @@ void op_addsub(oparg_T *oap, linenr_T Prenum1, bool g_cmd)
 int do_addsub(int op_type, pos_T *pos, int length, linenr_T Prenum1)
 {
   int col;
-  char_u *buf1 = NULL;
+  char *buf1 = NULL;
   char buf2[NUMBUFLEN];
   int pre;  // 'X' or 'x': hex; '0': octal; 'B' or 'b': bin
   static bool hexupper = false;  // 0xABC
@@ -4747,7 +4747,7 @@ int do_addsub(int op_type, pos_T *pos, int length, linenr_T Prenum1)
     // When there are many leading zeros it could be very long.
     // Allocate a bit too much.
     buf1 = xmalloc((size_t)length + NUMBUFLEN);
-    ptr = (char *)buf1;
+    ptr = buf1;
     if (negative && (!visual || was_positive)) {
       *ptr++ = '-';
     }
@@ -4799,7 +4799,7 @@ int do_addsub(int op_type, pos_T *pos, int length, linenr_T Prenum1)
     }
     *ptr = NUL;
     STRCAT(buf1, buf2);
-    ins_str((char *)buf1);              // insert the new number
+    ins_str(buf1);              // insert the new number
     endpos = curwin->w_cursor;
     if (curwin->w_cursor.col) {
       curwin->w_cursor.col--;
@@ -5088,7 +5088,7 @@ void write_reg_contents_ex(int name, const char *str, ssize_t len, bool must_app
 
   // Special case: '/' search pattern
   if (name == '/') {
-    set_last_search_pat((char_u *)str, RE_SEARCH, true, true);
+    set_last_search_pat(str, RE_SEARCH, true, true);
     return;
   }
 
@@ -5200,7 +5200,7 @@ static void str_to_reg(yankreg_T *y_ptr, MotionType yank_type, const char *str,
   }
 
   // Grow the register array to hold the pointers to the new lines.
-  char **pp = xrealloc(y_ptr->y_array, (y_ptr->y_size + newlines) * sizeof(char_u *));
+  char **pp = xrealloc(y_ptr->y_array, (y_ptr->y_size + newlines) * sizeof(char *));
   y_ptr->y_array = pp;
 
   size_t lnum = y_ptr->y_size;  // The current line number.
@@ -5276,8 +5276,8 @@ void clear_oparg(oparg_T *oap)
 ///  line, stopping if it encounters an end-of-line (NUL byte).  In that
 ///  case, eol_size will be added to the character count to account for
 ///  the size of the EOL character.
-static varnumber_T line_count_info(char_u *line, varnumber_T *wc, varnumber_T *cc,
-                                   varnumber_T limit, int eol_size)
+static varnumber_T line_count_info(char *line, varnumber_T *wc, varnumber_T *cc, varnumber_T limit,
+                                   int eol_size)
 {
   varnumber_T i;
   varnumber_T words = 0;
@@ -5294,7 +5294,7 @@ static varnumber_T line_count_info(char_u *line, varnumber_T *wc, varnumber_T *c
       is_word = 1;
     }
     chars++;
-    i += utfc_ptr2len((char *)line + i);
+    i += utfc_ptr2len(line + i);
   }
 
   if (is_word) {
@@ -5319,8 +5319,8 @@ static varnumber_T line_count_info(char_u *line, varnumber_T *wc, varnumber_T *c
 void cursor_pos_info(dict_T *dict)
 {
   char *p;
-  char_u buf1[50];
-  char_u buf2[40];
+  char buf1[50];
+  char buf2[40];
   linenr_T lnum;
   varnumber_T byte_count = 0;
   varnumber_T bom_count = 0;
@@ -5429,7 +5429,7 @@ void cursor_pos_info(dict_T *dict)
         break;
         }
         if (s != NULL) {
-          byte_count_cursor += line_count_info((char_u *)s, &word_count_cursor,
+          byte_count_cursor += line_count_info(s, &word_count_cursor,
                                                &char_count_cursor, len, eol_size);
           if (lnum == curbuf->b_ml.ml_line_count
               && !curbuf->b_p_eol
@@ -5444,14 +5444,14 @@ void cursor_pos_info(dict_T *dict)
           word_count_cursor += word_count;
           char_count_cursor += char_count;
           byte_count_cursor = byte_count
-                              + line_count_info((char_u *)ml_get(lnum), &word_count_cursor,
+                              + line_count_info(ml_get(lnum), &word_count_cursor,
                                                 &char_count_cursor,
                                                 (varnumber_T)curwin->w_cursor.col + 1,
                                                 eol_size);
         }
       }
       // Add to the running totals
-      byte_count += line_count_info((char_u *)ml_get(lnum), &word_count, &char_count,
+      byte_count += line_count_info(ml_get(lnum), &word_count, &char_count,
                                     (varnumber_T)MAXCOL, eol_size);
     }
 
@@ -5466,7 +5466,7 @@ void cursor_pos_info(dict_T *dict)
           getvcols(curwin, &min_pos, &max_pos, &min_pos.col, &max_pos.col);
           int64_t cols;
           STRICT_SUB(oparg.end_vcol + 1, oparg.start_vcol, &cols, int64_t);
-          vim_snprintf((char *)buf1, sizeof(buf1), _("%" PRId64 " Cols; "),
+          vim_snprintf(buf1, sizeof(buf1), _("%" PRId64 " Cols; "),
                        cols);
         } else {
           buf1[0] = NUL;
@@ -5497,7 +5497,7 @@ void cursor_pos_info(dict_T *dict)
       } else {
         p = get_cursor_line_ptr();
         validate_virtcol();
-        col_print((char *)buf1, sizeof(buf1), (int)curwin->w_cursor.col + 1,
+        col_print(buf1, sizeof(buf1), (int)curwin->w_cursor.col + 1,
                   (int)curwin->w_virtcol + 1);
         col_print((char *)buf2, sizeof(buf2), (int)strlen(p), linetabsize(p));
 
@@ -5507,7 +5507,7 @@ void cursor_pos_info(dict_T *dict)
                        _("Col %s of %s; Line %" PRId64 " of %" PRId64 ";"
                          " Word %" PRId64 " of %" PRId64 ";"
                          " Byte %" PRId64 " of %" PRId64 ""),
-                       (char *)buf1, (char *)buf2,
+                       buf1, buf2,
                        (int64_t)curwin->w_cursor.lnum,
                        (int64_t)curbuf->b_ml.ml_line_count,
                        (int64_t)word_count_cursor, (int64_t)word_count,
@@ -5518,7 +5518,7 @@ void cursor_pos_info(dict_T *dict)
                          " Word %" PRId64 " of %" PRId64 ";"
                          " Char %" PRId64 " of %" PRId64 ";"
                          " Byte %" PRId64 " of %" PRId64 ""),
-                       (char *)buf1, (char *)buf2,
+                       buf1, buf2,
                        (int64_t)curwin->w_cursor.lnum,
                        (int64_t)curbuf->b_ml.ml_line_count,
                        (int64_t)word_count_cursor, (int64_t)word_count,
diff --git a/src/nvim/option.c b/src/nvim/option.c
index 024bf3af09..0c2a2f7060 100644
--- a/src/nvim/option.c
+++ b/src/nvim/option.c
@@ -999,14 +999,14 @@ static int do_set_string(int opt_idx, int opt_flags, char **argp, int nextchar,
         // 'whichwrap'
         if (flags & P_ONECOMMA) {
           if (*s != ',' && *(s + 1) == ','
-              && vim_strchr(s + 2, *s) != NULL) {
+              && vim_strchr(s + 2, (uint8_t)(*s)) != NULL) {
             // Remove the duplicated value and the next comma.
             STRMOVE(s, s + 2);
             continue;
           }
         } else {
           if ((!(flags & P_COMMA) || *s != ',')
-              && vim_strchr(s + 1, *s) != NULL) {
+              && vim_strchr(s + 1, (uint8_t)(*s)) != NULL) {
             STRMOVE(s, s + 1);
             continue;
           }
@@ -1106,7 +1106,7 @@ int do_set(char *arg, int opt_flags)
     char *errmsg = NULL;
     char *startarg = arg;             // remember for error message
 
-    if (strncmp(arg, "all", 3) == 0 && !isalpha(arg[3])
+    if (strncmp(arg, "all", 3) == 0 && !isalpha((uint8_t)arg[3])
         && !(opt_flags & OPT_MODELINE)) {
       // ":set all"  show all options.
       // ":set all&" set all options to their default value.
@@ -1210,7 +1210,7 @@ int do_set(char *arg, int opt_flags)
         if (options[opt_idx].var == NULL) {         // hidden option: skip
           // Only give an error message when requesting the value of
           // a hidden option, ignore setting it.
-          if (vim_strchr("=:!&<", nextchar) == NULL
+          if (vim_strchr("=:!&<", (uint8_t)nextchar) == NULL
               && (!(options[opt_idx].flags & P_BOOL)
                   || nextchar == '?')) {
             errmsg = e_unsupportedoption;
@@ -1264,7 +1264,7 @@ int do_set(char *arg, int opt_flags)
         goto skip;
       }
 
-      if (vim_strchr("?=:!&<", nextchar) != NULL) {
+      if (vim_strchr("?=:!&<", (uint8_t)nextchar) != NULL) {
         arg += len;
         if (nextchar == '&' && arg[1] == 'v' && arg[2] == 'i') {
           if (arg[3] == 'm') {  // "opt&vim": set to Vim default
@@ -1273,7 +1273,7 @@ int do_set(char *arg, int opt_flags)
             arg += 2;
           }
         }
-        if (vim_strchr("?!&<", nextchar) != NULL
+        if (vim_strchr("?!&<", (uint8_t)nextchar) != NULL
             && arg[1] != NUL && !ascii_iswhite(arg[1])) {
           errmsg = e_trailing;
           goto skip;
@@ -1286,7 +1286,7 @@ int do_set(char *arg, int opt_flags)
       //
       if (nextchar == '?'
           || (prefix == 1
-              && vim_strchr("=:&<", nextchar) == NULL
+              && vim_strchr("=:&<", (uint8_t)nextchar) == NULL
               && !(flags & P_BOOL))) {
         // print value
         if (did_show) {
@@ -1359,7 +1359,7 @@ int do_set(char *arg, int opt_flags)
 
           errmsg = set_bool_option(opt_idx, (char_u *)varp, (int)value, opt_flags);
         } else {  // Numeric or string.
-          if (vim_strchr("=:&<", nextchar) == NULL
+          if (vim_strchr("=:&<", (uint8_t)nextchar) == NULL
               || prefix != 1) {
             errmsg = e_invarg;
             goto skip;
@@ -1775,7 +1775,7 @@ bool valid_name(const char *val, const char *allowed)
 {
   for (const char_u *s = (char_u *)val; *s != NUL; s++) {
     if (!ASCII_ISALNUM(*s)
-        && vim_strchr(allowed, *s) == NULL) {
+        && vim_strchr(allowed, (uint8_t)(*s)) == NULL) {
       return false;
     }
   }
@@ -1974,7 +1974,7 @@ static char *set_bool_option(const int opt_idx, char_u *const varp, const int va
              || (opt_flags & OPT_GLOBAL) || opt_flags == 0)
             && !bufIsChanged(bp) && bp->b_ml.ml_mfp != NULL) {
           u_compute_hash(bp, hash);
-          u_read_undo(NULL, hash, (char_u *)bp->b_fname);
+          u_read_undo(NULL, hash, bp->b_fname);
         }
       }
     }
@@ -5388,9 +5388,9 @@ size_t copy_option_part(char **option, char *buf, size_t maxlen, char *sep_chars
   if (*p == '.') {
     buf[len++] = *p++;
   }
-  while (*p != NUL && vim_strchr(sep_chars, *p) == NULL) {
+  while (*p != NUL && vim_strchr(sep_chars, (uint8_t)(*p)) == NULL) {
     // Skip backslash before a separator character and space.
-    if (p[0] == '\\' && vim_strchr(sep_chars, p[1]) != NULL) {
+    if (p[0] == '\\' && vim_strchr(sep_chars, (uint8_t)p[1]) != NULL) {
       p++;
     }
     if (len < maxlen - 1) {
diff --git a/src/nvim/optionstr.c b/src/nvim/optionstr.c
index a1a5cadd8d..ab58888482 100644
--- a/src/nvim/optionstr.c
+++ b/src/nvim/optionstr.c
@@ -614,7 +614,7 @@ char *check_stl_option(char *s)
       groupdepth++;
       continue;
     }
-    if (vim_strchr(STL_ALL, *s) == NULL) {
+    if (vim_strchr(STL_ALL, (uint8_t)(*s)) == NULL) {
       return illegal_char(errbuf, sizeof(errbuf), *s);
     }
     if (*s == '{') {
@@ -946,7 +946,7 @@ char *did_set_string_option(int opt_idx, char **varp, char *oldval, char *errbuf
   } else if (gvarp == &p_com) {  // 'comments'
     for (s = *varp; *s;) {
       while (*s && *s != ':') {
-        if (vim_strchr(COM_ALL, *s) == NULL
+        if (vim_strchr(COM_ALL, (uint8_t)(*s)) == NULL
             && !ascii_isdigit(*s) && *s != '-') {
           errmsg = illegal_char(errbuf, errbuflen, *s);
           break;
@@ -1016,7 +1016,7 @@ char *did_set_string_option(int opt_idx, char **varp, char *oldval, char *errbuf
     free_oldval = (opt->flags & P_ALLOCED);
     for (s = p_shada; *s;) {
       // Check it's a valid character
-      if (vim_strchr("!\"%'/:<@cfhnrs", *s) == NULL) {
+      if (vim_strchr("!\"%'/:<@cfhnrs", (uint8_t)(*s)) == NULL) {
         errmsg = illegal_char(errbuf, errbuflen, *s);
         break;
       }
@@ -1221,7 +1221,7 @@ char *did_set_string_option(int opt_idx, char **varp, char *oldval, char *errbuf
       if (!*s) {
         break;
       }
-      if (vim_strchr(".wbuksid]tU", *s) == NULL) {
+      if (vim_strchr(".wbuksid]tU", (uint8_t)(*s)) == NULL) {
         errmsg = illegal_char(errbuf, errbuflen, *s);
         break;
       }
@@ -1569,7 +1569,7 @@ char *did_set_string_option(int opt_idx, char **varp, char *oldval, char *errbuf
     }
     if (p != NULL) {
       for (s = *varp; *s; s++) {
-        if (vim_strchr(p, *s) == NULL) {
+        if (vim_strchr(p, (uint8_t)(*s)) == NULL) {
           errmsg = illegal_char(errbuf, errbuflen, *s);
           break;
         }
diff --git a/src/nvim/os/env.c b/src/nvim/os/env.c
index e1db7a8ef7..ae34a79365 100644
--- a/src/nvim/os/env.c
+++ b/src/nvim/os/env.c
@@ -656,7 +656,7 @@ void expand_env_esc(char *restrict srcp, char *restrict dst, int dstlen, bool es
 #endif
       } else if (src[1] == NUL  // home directory
                  || vim_ispathsep(src[1])
-                 || vim_strchr(" ,\t\n", src[1]) != NULL) {
+                 || vim_strchr(" ,\t\n", (uint8_t)src[1]) != NULL) {
         var = homedir;
         tail = src + 1;
       } else {  // user directory
@@ -1198,7 +1198,7 @@ bool os_setenv_append_path(const char *fname)
 // No prescribed maximum on unix.
 # define MAX_ENVPATHLEN INT_MAX
 #endif
-  if (!path_is_absolute((char_u *)fname)) {
+  if (!path_is_absolute(fname)) {
     internal_error("os_setenv_append_path()");
     return false;
   }
diff --git a/src/nvim/os/fs.c b/src/nvim/os/fs.c
index 98ec9aa826..ce1b2d1cf5 100644
--- a/src/nvim/os/fs.c
+++ b/src/nvim/os/fs.c
@@ -914,12 +914,11 @@ int os_file_is_writable(const char *name)
 /// Rename a file or directory.
 ///
 /// @return `OK` for success, `FAIL` for failure.
-int os_rename(const char_u *path, const char_u *new_path)
+int os_rename(const char *path, const char *new_path)
   FUNC_ATTR_NONNULL_ALL
 {
   int r;
-  RUN_UV_FS_FUNC(r, uv_fs_rename, (const char *)path, (const char *)new_path,
-                 NULL);
+  RUN_UV_FS_FUNC(r, uv_fs_rename, path, new_path, NULL);
   return (r == kLibuvSuccess ? OK : FAIL);
 }
 
@@ -1382,7 +1381,7 @@ bool os_is_reparse_point_include(const char *path)
   }
 
   p = utf16_path;
-  if (isalpha(p[0]) && p[1] == L':' && IS_PATH_SEP(p[2])) {
+  if (isalpha((uint8_t)p[0]) && p[1] == L':' && IS_PATH_SEP(p[2])) {
     p += 3;
   } else if (IS_PATH_SEP(p[0]) && IS_PATH_SEP(p[1])) {
     p += 2;
diff --git a/src/nvim/os/shell.c b/src/nvim/os/shell.c
index 8177f06c64..ac8a141bbe 100644
--- a/src/nvim/os/shell.c
+++ b/src/nvim/os/shell.c
@@ -221,7 +221,7 @@ int os_expand_wildcards(int num_pat, char **pat, int *num_file, char ***file, in
     // "command" below.
     len++;                              // add space
     for (j = 0; pat[i][j] != NUL; j++) {
-      if (vim_strchr(SHELL_SPECIAL, pat[i][j]) != NULL) {
+      if (vim_strchr(SHELL_SPECIAL, (uint8_t)pat[i][j]) != NULL) {
         len++;                  // may add a backslash
       }
       len++;
@@ -304,14 +304,14 @@ int os_expand_wildcards(int num_pat, char **pat, int *num_file, char ***file, in
           // backslash inside backticks, before a special character
           // and before a backtick.
           if (intick
-              || vim_strchr(SHELL_SPECIAL, pat[i][j + 1]) != NULL
+              || vim_strchr(SHELL_SPECIAL, (uint8_t)pat[i][j + 1]) != NULL
               || pat[i][j + 1] == '`') {
             *p++ = '\\';
           }
           j++;
         } else if (!intick
                    && ((flags & EW_KEEPDOLLAR) == 0 || pat[i][j] != '$')
-                   && vim_strchr(SHELL_SPECIAL, pat[i][j]) != NULL) {
+                   && vim_strchr(SHELL_SPECIAL, (uint8_t)pat[i][j]) != NULL) {
           // Put a backslash before a special character, but not
           // when inside ``. And not for $var when EW_KEEPDOLLAR is
           // set.
diff --git a/src/nvim/path.c b/src/nvim/path.c
index 6d14db7de1..afc0563498 100644
--- a/src/nvim/path.c
+++ b/src/nvim/path.c
@@ -155,7 +155,7 @@ char *path_tail_with_sep(char *fname)
 /// @post if `len` is not null, stores the length of the executable name.
 ///
 /// @return The position of the last path separator + 1.
-const char_u *invocation_path_tail(const char *invocation, size_t *len)
+const char *invocation_path_tail(const char *invocation, size_t *len)
     FUNC_ATTR_NONNULL_RET FUNC_ATTR_NONNULL_ARG(1)
 {
   const char *tail = get_past_head(invocation);
@@ -172,7 +172,7 @@ const char_u *invocation_path_tail(const char *invocation, size_t *len)
     *len = (size_t)(p - tail);
   }
 
-  return (char_u *)tail;
+  return tail;
 }
 
 /// Get the next path component of a path name.
@@ -211,10 +211,10 @@ int path_head_length(void)
 /// @return
 ///   - True if path begins with a path head
 ///   - False otherwise
-bool is_path_head(const char_u *path)
+bool is_path_head(const char *path)
 {
 #ifdef MSWIN
-  return isalpha(path[0]) && path[1] == ':';
+  return isalpha((uint8_t)path[0]) && path[1] == ':';
 #else
   return vim_ispathsep(*path);
 #endif
@@ -511,7 +511,7 @@ char *FullName_save(const char *fname, bool force)
 char *save_abs_path(const char *name)
   FUNC_ATTR_MALLOC FUNC_ATTR_NONNULL_ALL
 {
-  if (!path_is_absolute((char_u *)name)) {
+  if (!path_is_absolute(name)) {
     return FullName_save(name, true);
   }
   return xstrdup(name);
@@ -536,7 +536,7 @@ bool path_has_wildcard(const char *p)
     // Windows:
     const char *wildcards = "?*$[`";
 #endif
-    if (vim_strchr(wildcards, *p) != NULL
+    if (vim_strchr(wildcards, (uint8_t)(*p)) != NULL
         || (p[0] == '~' && p[1] != NUL)) {
       return true;
     }
@@ -649,7 +649,7 @@ static size_t do_path_expand(garray_T *gap, const char *path, size_t wildoff, in
       }
       s = p + 1;
     } else if (path_end >= path + wildoff
-               && (vim_strchr("*?[{~$", *path_end) != NULL
+               && (vim_strchr("*?[{~$", (uint8_t)(*path_end)) != NULL
 #ifndef MSWIN
                    || (!p_fic && (flags & EW_ICASE) && mb_isalpha(utf_ptr2char((char *)path_end)))
 #endif
@@ -783,8 +783,8 @@ static size_t do_path_expand(garray_T *gap, const char *path, size_t wildoff, in
   // slow, thus skip it.
   size_t matches = (size_t)(gap->ga_len - start_len);
   if (matches > 0 && !got_int) {
-    qsort(((char_u **)gap->ga_data) + start_len, matches,
-          sizeof(char_u *), pstrcmp);
+    qsort(((char **)gap->ga_data) + start_len, matches,
+          sizeof(char *), pstrcmp);
   }
   return matches;
 }
@@ -842,11 +842,11 @@ static bool is_unique(char *maybe_unique, garray_T *gap, int i)
 // expanding each into their equivalent path(s).
 static void expand_path_option(char *curdir, garray_T *gap)
 {
-  char_u *path_option = *curbuf->b_p_path == NUL ? p_path : (char_u *)curbuf->b_p_path;
+  char *path_option = *curbuf->b_p_path == NUL ? (char *)p_path : curbuf->b_p_path;
   char *buf = xmalloc(MAXPATHL);
 
   while (*path_option != NUL) {
-    copy_option_part((char **)&path_option, buf, MAXPATHL, " ,");
+    copy_option_part(&path_option, buf, MAXPATHL, " ,");
 
     if (buf[0] == '.' && (buf[1] == NUL || vim_ispathsep(buf[1]))) {
       // Relative to current buffer:
@@ -871,7 +871,7 @@ static void expand_path_option(char *curdir, garray_T *gap)
       STRCPY(buf, curdir);  // relative to current directory
     } else if (path_with_url(buf)) {
       continue;  // URL can't be used here
-    } else if (!path_is_absolute((char_u *)buf)) {
+    } else if (!path_is_absolute(buf)) {
       // Expand relative path to their full path equivalent
       size_t len = strlen(curdir);
       if (len + strlen(buf) + 3 > MAXPATHL) {
@@ -895,11 +895,11 @@ static void expand_path_option(char *curdir, garray_T *gap)
 //    path: /foo/bar/baz
 //   fname: /foo/bar/baz/quux.txt
 // returns:              ^this
-static char_u *get_path_cutoff(char_u *fname, garray_T *gap)
+static char *get_path_cutoff(char *fname, garray_T *gap)
 {
   int maxlen = 0;
-  char_u **path_part = (char_u **)gap->ga_data;
-  char_u *cutoff = NULL;
+  char **path_part = gap->ga_data;
+  char *cutoff = NULL;
 
   for (int i = 0; i < gap->ga_len; i++) {
     int j = 0;
@@ -985,7 +985,7 @@ static void uniquefy_paths(garray_T *gap, char *pattern)
     }
 
     // Shorten the filename while maintaining its uniqueness
-    path_cutoff = (char *)get_path_cutoff((char_u *)path, &path_ga);
+    path_cutoff = get_path_cutoff(path, &path_ga);
 
     // Don't assume all files can be reached without path when search
     // pattern starts with **/, so only remove path_cutoff
@@ -1012,7 +1012,7 @@ static void uniquefy_paths(garray_T *gap, char *pattern)
       }
     }
 
-    if (path_is_absolute((char_u *)path)) {
+    if (path_is_absolute(path)) {
       // Last resort: shorten relative to curdir if possible.
       // 'possible' means:
       // 1. It is under the current directory.
@@ -1128,7 +1128,7 @@ static int expand_in_path(garray_T *const gap, char *const pattern, const int fl
     return 0;
   }
 
-  char *const paths = (char *)ga_concat_strings(&path_ga);
+  char *const paths = ga_concat_strings(&path_ga);
   ga_clear_strings(&path_ga);
 
   int glob_flags = 0;
@@ -1146,12 +1146,12 @@ static int expand_in_path(garray_T *const gap, char *const pattern, const int fl
 
 /// Return true if "p" contains what looks like an environment variable.
 /// Allowing for escaping.
-static bool has_env_var(char_u *p)
+static bool has_env_var(char *p)
 {
   for (; *p; MB_PTR_ADV(p)) {
     if (*p == '\\' && p[1] != NUL) {
       p++;
-    } else if (vim_strchr("$", *p) != NULL) {
+    } else if (vim_strchr("$", (uint8_t)(*p)) != NULL) {
       return true;
     }
   }
@@ -1162,7 +1162,7 @@ static bool has_env_var(char_u *p)
 
 // Return true if "p" contains a special wildcard character, one that Vim
 // cannot expand, requires using a shell.
-static bool has_special_wildchar(char_u *p)
+static bool has_special_wildchar(char *p)
 {
   for (; *p; MB_PTR_ADV(p)) {
     // Disallow line break characters.
@@ -1172,13 +1172,13 @@ static bool has_special_wildchar(char_u *p)
     // Allow for escaping.
     if (*p == '\\' && p[1] != NUL && p[1] != '\r' && p[1] != '\n') {
       p++;
-    } else if (vim_strchr(SPECIAL_WILDCHAR, *p) != NULL) {
+    } else if (vim_strchr(SPECIAL_WILDCHAR, (uint8_t)(*p)) != NULL) {
       // A { must be followed by a matching }.
-      if (*p == '{' && vim_strchr((char *)p, '}') == NULL) {
+      if (*p == '{' && vim_strchr(p, '}') == NULL) {
         continue;
       }
       // A quote and backtick must be followed by another one.
-      if ((*p == '`' || *p == '\'') && vim_strchr((char *)p, *p) == NULL) {
+      if ((*p == '`' || *p == '\'') && vim_strchr(p, (uint8_t)(*p)) == NULL) {
         continue;
       }
       return true;
@@ -1232,7 +1232,7 @@ int gen_expand_wildcards(int num_pat, char **pat, int *num_file, char ***file, i
   // avoids starting the shell for each argument separately.
   // For `=expr` do use the internal function.
   for (int i = 0; i < num_pat; i++) {
-    if (has_special_wildchar((char_u *)pat[i])
+    if (has_special_wildchar(pat[i])
         && !(vim_backtick(pat[i]) && pat[i][1] == '=')) {
       return os_expand_wildcards(num_pat, pat, num_file, file, flags);
     }
@@ -1259,7 +1259,7 @@ int gen_expand_wildcards(int num_pat, char **pat, int *num_file, char ***file, i
       }
     } else {
       // First expand environment variables, "~/" and "~user/".
-      if ((has_env_var((char_u *)p) && !(flags & EW_NOTENV)) || *p == '~') {
+      if ((has_env_var(p) && !(flags & EW_NOTENV)) || *p == '~') {
         p = (char *)expand_env_save_opt(p, true);
         if (p == NULL) {
           p = pat[i];
@@ -1268,7 +1268,7 @@ int gen_expand_wildcards(int num_pat, char **pat, int *num_file, char ***file, i
           // On Unix, if expand_env() can't expand an environment
           // variable, use the shell to do that.  Discard previously
           // found file names and start all over again.
-          if (has_env_var((char_u *)p) || *p == '~') {
+          if (has_env_var(p) || *p == '~') {
             xfree(p);
             ga_clear_strings(&ga);
             i = os_expand_wildcards(num_pat, pat, num_file, file,
@@ -1287,7 +1287,7 @@ int gen_expand_wildcards(int num_pat, char **pat, int *num_file, char ***file, i
       // given.
       if (path_has_exp_wildcard(p) || (flags & EW_ICASE)) {
         if ((flags & EW_PATH)
-            && !path_is_absolute((char_u *)p)
+            && !path_is_absolute(p)
             && !(p[0] == '.'
                  && (vim_ispathsep(p[1])
                      || (p[1] == '.'
@@ -1478,7 +1478,7 @@ void addfile(garray_T *gap, char *f, int flags)
     return;
   }
 
-  char_u *p = xmalloc(strlen(f) + 1 + isdir);
+  char *p = xmalloc(strlen(f) + 1 + isdir);
 
   STRCPY(p, f);
 #ifdef BACKSLASH_IN_FILENAME
@@ -1486,9 +1486,9 @@ void addfile(garray_T *gap, char *f, int flags)
 #endif
   // Append a slash or backslash after directory names if none is present.
   if (isdir && (flags & EW_ADDSLASH)) {
-    add_pathsep((char *)p);
+    add_pathsep(p);
   }
-  GA_APPEND(char_u *, gap, p);
+  GA_APPEND(char *, gap, p);
 }
 
 // Converts a file name into a canonical form. It simplifies a file name into
@@ -1768,7 +1768,7 @@ int path_with_url(const char *fname)
   // non-URL text.
 
   // first character must be alpha
-  if (!isalpha(*fname)) {
+  if (!isalpha((uint8_t)(*fname))) {
     return 0;
   }
 
@@ -1777,7 +1777,7 @@ int path_with_url(const char *fname)
   }
 
   // check body: alpha or dash
-  for (p = fname + 1; (isalpha(*p) || (*p == '-')); p++) {}
+  for (p = fname + 1; (isalpha((uint8_t)(*p)) || (*p == '-')); p++) {}
 
   // check last char is not a dash
   if (p[-1] == '-') {
@@ -1800,7 +1800,7 @@ bool path_with_extension(const char *path, const char *extension)
 /// Return true if "name" is a full (absolute) path name or URL.
 bool vim_isAbsName(char *name)
 {
-  return path_with_url(name) != 0 || path_is_absolute((char_u *)name);
+  return path_with_url(name) != 0 || path_is_absolute(name);
 }
 
 /// Save absolute file name to "buf[len]".
@@ -2076,7 +2076,7 @@ char *path_shorten_fname(char *full_path, char *dir_name)
   size_t len = strlen(dir_name);
 
   // If dir_name is a path head, full_path can always be made relative.
-  if (len == (size_t)path_head_length() && is_path_head((char_u *)dir_name)) {
+  if (len == (size_t)path_head_length() && is_path_head(dir_name)) {
     return full_path + len;
   }
 
@@ -2124,7 +2124,7 @@ int expand_wildcards_eval(char **pat, int *num_file, char ***file, int flags)
 
   if (is_cur_alt_file || *exp_pat == '<') {
     emsg_off++;
-    eval_pat = (char *)eval_vars((char_u *)exp_pat, (char_u *)exp_pat, &usedlen, NULL, &ignored_msg,
+    eval_pat = (char *)eval_vars(exp_pat, (char_u *)exp_pat, &usedlen, NULL, &ignored_msg,
                                  NULL,
                                  true);
     emsg_off--;
@@ -2186,15 +2186,15 @@ int expand_wildcards(int num_pat, char **pat, int *num_files, char ***files, int
 
   // Remove names that match 'wildignore'.
   if (*p_wig) {
-    char_u *ffname;
+    char *ffname;
 
     // check all files in (*files)[]
     assert(*num_files == 0 || *files != NULL);
     for (i = 0; i < *num_files; i++) {
-      ffname = (char_u *)FullName_save((*files)[i], false);
+      ffname = FullName_save((*files)[i], false);
       assert((*files)[i] != NULL);
       assert(ffname != NULL);
-      if (match_file_list((char_u *)p_wig, (char_u *)(*files)[i], ffname)) {
+      if (match_file_list(p_wig, (*files)[i], ffname)) {
         // remove this matching file from the list
         xfree((*files)[i]);
         for (j = i; j + 1 < *num_files; j++) {
@@ -2291,7 +2291,7 @@ int path_full_dir_name(char *directory, char *buffer, size_t len)
     // Path does not exist (yet).  For a full path fail,
     // will use the path as-is.  For a relative path use
     // the current directory and append the file name.
-    if (path_is_absolute((const char_u *)directory)) {
+    if (path_is_absolute(directory)) {
       // Do not return immediately since we may be in the wrong directory.
       retval = FAIL;
     } else {
@@ -2361,7 +2361,7 @@ static int path_to_absolute(const char *fname, char *buf, size_t len, int force)
   char *end_of_path = (char *)fname;
 
   // expand it if forced or not an absolute path
-  if (force || !path_is_absolute((char_u *)fname)) {
+  if (force || !path_is_absolute(fname)) {
     p = strrchr(fname, '/');
 #ifdef MSWIN
     if (p == NULL) {
@@ -2390,14 +2390,14 @@ static int path_to_absolute(const char *fname, char *buf, size_t len, int force)
 /// Check if file `fname` is a full (absolute) path.
 ///
 /// @return `true` if "fname" is absolute.
-int path_is_absolute(const char_u *fname)
+int path_is_absolute(const char *fname)
 {
 #ifdef MSWIN
   if (*fname == NUL) {
     return false;
   }
   // A name like "d:/foo" and "//server/share" is absolute
-  return ((isalpha(fname[0]) && fname[1] == ':' && vim_ispathsep_nocolon(fname[2]))
+  return ((isalpha((uint8_t)fname[0]) && fname[1] == ':' && vim_ispathsep_nocolon(fname[2]))
           || (vim_ispathsep_nocolon(fname[0]) && fname[0] == fname[1]));
 #else
   // UNIX: This just checks if the file name starts with '/' or '~'.
@@ -2417,7 +2417,7 @@ void path_guess_exepath(const char *argv0, char *buf, size_t bufsize)
 {
   const char *path = os_getenv("PATH");
 
-  if (path == NULL || path_is_absolute((char_u *)argv0)) {
+  if (path == NULL || path_is_absolute(argv0)) {
     xstrlcpy(buf, argv0, bufsize);
   } else if (argv0[0] == '.' || strchr(argv0, PATHSEP)) {
     // Relative to CWD.
diff --git a/src/nvim/quickfix.c b/src/nvim/quickfix.c
index 3d09fa1030..32ae0fc276 100644
--- a/src/nvim/quickfix.c
+++ b/src/nvim/quickfix.c
@@ -384,9 +384,9 @@ static char *efmpat_to_regpat(const char *efmpat, char *regpat, efm_T *efminfo,
     return NULL;
   }
   if ((idx && idx < FMT_PATTERN_R
-       && vim_strchr("DXOPQ", efminfo->prefix) != NULL)
+       && vim_strchr("DXOPQ", (uint8_t)efminfo->prefix) != NULL)
       || (idx == FMT_PATTERN_R
-          && vim_strchr("OPQ", efminfo->prefix) == NULL)) {
+          && vim_strchr("OPQ", (uint8_t)efminfo->prefix) == NULL)) {
     semsg(_("E373: Unexpected %%%c in format string"), *efmpat);
     return NULL;
   }
@@ -468,10 +468,10 @@ static char *scanf_fmt_to_regpat(const char **pefmp, const char *efm, int len, c
 static const char *efm_analyze_prefix(const char *efmp, efm_T *efminfo)
   FUNC_ATTR_NONNULL_ALL
 {
-  if (vim_strchr("+-", *efmp) != NULL) {
+  if (vim_strchr("+-", (uint8_t)(*efmp)) != NULL) {
     efminfo->flags = *efmp++;
   }
-  if (vim_strchr("DXAEWINCZGOPQ", *efmp) != NULL) {
+  if (vim_strchr("DXAEWINCZGOPQ", (uint8_t)(*efmp)) != NULL) {
     efminfo->prefix = *efmp;
   } else {
     semsg(_("E376: Invalid %%%c in format string prefix"), *efmp);
@@ -510,7 +510,7 @@ static int efm_to_regpat(const char *efm, int len, efm_T *fmt_ptr, char *regpat)
         if (ptr == NULL) {
           return FAIL;
         }
-      } else if (vim_strchr("%\\.^$~[", *efmp) != NULL) {
+      } else if (vim_strchr("%\\.^$~[", (uint8_t)(*efmp)) != NULL) {
         *ptr++ = *efmp;  // regexp magic characters
       } else if (*efmp == '#') {
         *ptr++ = '*';
@@ -530,7 +530,7 @@ static int efm_to_regpat(const char *efm, int len, efm_T *fmt_ptr, char *regpat)
     } else {                    // copy normal character
       if (*efmp == '\\' && efmp + 1 < efm + len) {
         efmp++;
-      } else if (vim_strchr(".*^$~[", *efmp) != NULL) {
+      } else if (vim_strchr(".*^$~[", (uint8_t)(*efmp)) != NULL) {
         *ptr++ = '\\';  // escape regexp atoms
       }
       if (*efmp) {
@@ -1483,7 +1483,7 @@ static int qf_parse_match(char *linebuf, size_t linelen, efm_T *fmt_ptr, regmatc
   if ((idx == 'C' || idx == 'Z') && !qf_multiline) {
     return QF_FAIL;
   }
-  if (vim_strchr("EWIN", idx) != NULL) {
+  if (vim_strchr("EWIN", (uint8_t)idx) != NULL) {
     fields->type = idx;
   } else {
     fields->type = 0;
@@ -1524,7 +1524,7 @@ static int qf_parse_match(char *linebuf, size_t linelen, efm_T *fmt_ptr, regmatc
 static int qf_parse_get_fields(char *linebuf, size_t linelen, efm_T *fmt_ptr, qffields_T *fields,
                                int qf_multiline, int qf_multiscan, char **tail)
 {
-  if (qf_multiscan && vim_strchr("OPQ", fmt_ptr->prefix) == NULL) {
+  if (qf_multiscan && vim_strchr("OPQ", (uint8_t)fmt_ptr->prefix) == NULL) {
     return QF_FAIL;
   }
 
@@ -3959,11 +3959,11 @@ static int qf_buf_add_line(qf_list_T *qfl, buf_T *buf, linenr_T lnum, const qfli
         // buffer.
         if (first_bufline
             && (errbuf->b_sfname == NULL
-                || path_is_absolute((char_u *)errbuf->b_sfname))) {
+                || path_is_absolute(errbuf->b_sfname))) {
           if (*dirname == NUL) {
             os_dirname(dirname, MAXPATHL);
           }
-          shorten_buf_fname(errbuf, (char_u *)dirname, false);
+          shorten_buf_fname(errbuf, dirname, false);
         }
         xstrlcpy(IObuff, errbuf->b_fname, IOSIZE);
       }
@@ -5105,7 +5105,7 @@ static void vgr_init_regmatch(regmmatch_T *regmatch, char *s)
       emsg(_(e_noprevre));
       return;
     }
-    regmatch->regprog = vim_regcomp((char *)last_search_pat(), RE_MAGIC);
+    regmatch->regprog = vim_regcomp(last_search_pat(), RE_MAGIC);
   } else {
     regmatch->regprog = vim_regcomp(s, RE_MAGIC);
   }
diff --git a/src/nvim/regexp.c b/src/nvim/regexp.c
index e396e54ced..54461bfa07 100644
--- a/src/nvim/regexp.c
+++ b/src/nvim/regexp.c
@@ -456,9 +456,9 @@ static char_u *skip_anyof(char *p)
         MB_PTR_ADV(p);
       }
     } else if (*p == '\\'
-               && (vim_strchr(REGEXP_INRANGE, p[1]) != NULL
+               && (vim_strchr(REGEXP_INRANGE, (uint8_t)p[1]) != NULL
                    || (!reg_cpo_lit
-                       && vim_strchr(REGEXP_ABBR, p[1]) != NULL))) {
+                       && vim_strchr(REGEXP_ABBR, (uint8_t)p[1]) != NULL))) {
       p += 2;
     } else if (*p == '[') {
       if (get_char_class(&p) == CLASS_NONE
@@ -1399,8 +1399,8 @@ static int cstrncmp(char *s1, char *s2, int *n)
     str2 = s2;
     c1 = c2 = 0;
     while ((int)(str1 - s1) < *n) {
-      c1 = mb_ptr2char_adv((const char_u **)&str1);
-      c2 = mb_ptr2char_adv((const char_u **)&str2);
+      c1 = mb_ptr2char_adv((const char **)&str1);
+      c2 = mb_ptr2char_adv((const char **)&str2);
 
       // decompose the character if necessary, into 'base' characters
       // because I don't care about Arabic, I will hard-code the Hebrew
@@ -1860,7 +1860,7 @@ static int vim_regsub_both(char *source, typval_T *expr, char *dest, int destlen
           no = 0;
         } else if ('0' <= *src && *src <= '9') {
           no = *src++ - '0';
-        } else if (vim_strchr("uUlLeE", *src)) {
+        } else if (vim_strchr("uUlLeE", (uint8_t)(*src))) {
           switch (*src++) {
           case 'u':
             func_one = (fptr_T)do_upper;
@@ -2497,9 +2497,9 @@ bool vim_regexec(regmatch_T *rmp, char *line, colnr_T col)
 // Like vim_regexec(), but consider a "\n" in "line" to be a line break.
 // Note: "rmp->regprog" may be freed and changed.
 // Return true if there is a match, false if not.
-bool vim_regexec_nl(regmatch_T *rmp, char_u *line, colnr_T col)
+bool vim_regexec_nl(regmatch_T *rmp, char *line, colnr_T col)
 {
-  return vim_regexec_string(rmp, line, col, true);
+  return vim_regexec_string(rmp, (char_u *)line, col, true);
 }
 
 /// Match a regexp against multiple lines.
diff --git a/src/nvim/regexp_bt.c b/src/nvim/regexp_bt.c
index f930d872b6..a047c51145 100644
--- a/src/nvim/regexp_bt.c
+++ b/src/nvim/regexp_bt.c
@@ -2165,7 +2165,7 @@ collection:
                 endc = get_coll_element(&regparse);
               }
               if (endc == 0) {
-                endc = mb_ptr2char_adv((const char_u **)&regparse);
+                endc = mb_ptr2char_adv((const char **)&regparse);
               }
 
               // Handle \o40, \x20 and \u20AC style sequences
@@ -2197,10 +2197,10 @@ collection:
           // accepts "\t", "\e", etc., but only when the 'l' flag in
           // 'cpoptions' is not included.
           else if (*regparse == '\\'
-                   && (vim_strchr(REGEXP_INRANGE, regparse[1]) != NULL
+                   && (vim_strchr(REGEXP_INRANGE, (uint8_t)regparse[1]) != NULL
                        || (!reg_cpo_lit
                            && vim_strchr(REGEXP_ABBR,
-                                         regparse[1]) != NULL))) {
+                                         (uint8_t)regparse[1]) != NULL))) {
             regparse++;
             if (*regparse == 'n') {
               // '\n' in range: also match NL
diff --git a/src/nvim/regexp_nfa.c b/src/nvim/regexp_nfa.c
index 6e7ff31c03..66a31f0184 100644
--- a/src/nvim/regexp_nfa.c
+++ b/src/nvim/regexp_nfa.c
@@ -2363,9 +2363,9 @@ collection:
         // 'cpoptions' is not included.
         if (*regparse == '\\'
             && (char_u *)regparse + 1 <= endp
-            && (vim_strchr(REGEXP_INRANGE, regparse[1]) != NULL
+            && (vim_strchr(REGEXP_INRANGE, (uint8_t)regparse[1]) != NULL
                 || (!reg_cpo_lit
-                    && vim_strchr(REGEXP_ABBR, regparse[1])
+                    && vim_strchr(REGEXP_ABBR, (uint8_t)regparse[1])
                     != NULL))) {
           MB_PTR_ADV(regparse);
 
diff --git a/src/nvim/screen.c b/src/nvim/screen.c
index 6a3103123b..0b6b1d9e77 100644
--- a/src/nvim/screen.c
+++ b/src/nvim/screen.c
@@ -815,15 +815,15 @@ int number_width(win_T *wp)
 /// Calls mb_cptr2char_adv(p) and returns the character.
 /// If "p" starts with "\x", "\u" or "\U" the hex or unicode value is used.
 /// Returns 0 for invalid hex or invalid UTF-8 byte.
-static int get_encoded_char_adv(const char_u **p)
+static int get_encoded_char_adv(const char **p)
 {
-  const char *s = (const char *)(*p);
+  const char *s = *p;
 
   if (s[0] == '\\' && (s[1] == 'x' || s[1] == 'u' || s[1] == 'U')) {
     int64_t num = 0;
     for (int bytes = s[1] == 'x' ? 1 : s[1] == 'u' ? 2 : 4; bytes > 0; bytes--) {
       *p += 2;
-      int n = hexhex2nr((char *)(*p));
+      int n = hexhex2nr(*p);
       if (n < 0) {
         return 0;
       }
@@ -952,7 +952,7 @@ char *set_chars_option(win_T *wp, char **varp, bool apply)
         if (strncmp(p, tab[i].name, len) == 0
             && p[len] == ':'
             && p[len + 1] != NUL) {
-          const char_u *s = (char_u *)p + len + 1;
+          const char *s = p + len + 1;
           int c1 = get_encoded_char_adv(&s);
           if (c1 == 0 || char2cells(c1) > 1) {
             return e_invarg;
@@ -983,7 +983,7 @@ char *set_chars_option(win_T *wp, char **varp, bool apply)
                 *(tab[i].cp) = c1;
               }
             }
-            p = (char *)s;
+            p = s;
             break;
           }
         }
@@ -996,7 +996,7 @@ char *set_chars_option(win_T *wp, char **varp, bool apply)
             && strncmp(p, "multispace", len) == 0
             && p[len] == ':'
             && p[len + 1] != NUL) {
-          const char_u *s = (char_u *)p + len + 1;
+          const char *s = p + len + 1;
           if (round == 0) {
             // Get length of lcs-multispace string in the first round
             last_multispace = p;
@@ -1012,7 +1012,7 @@ char *set_chars_option(win_T *wp, char **varp, bool apply)
               // lcs-multispace cannot be an empty string
               return e_invarg;
             }
-            p = (char *)s;
+            p = s;
           } else {
             int multispace_pos = 0;
             while (*s != NUL && *s != ',') {
@@ -1021,13 +1021,13 @@ char *set_chars_option(win_T *wp, char **varp, bool apply)
                 wp->w_p_lcs_chars.multispace[multispace_pos++] = c1;
               }
             }
-            p = (char *)s;
+            p = s;
           }
         } else if (is_listchars
                    && strncmp(p, "leadmultispace", len2) == 0
                    && p[len2] == ':'
                    && p[len2 + 1] != NUL) {
-          const char_u *s = (char_u *)p + len2 + 1;
+          const char *s = p + len2 + 1;
           if (round == 0) {
             // get length of lcs-leadmultispace string in first round
             last_lmultispace = p;
@@ -1043,7 +1043,7 @@ char *set_chars_option(win_T *wp, char **varp, bool apply)
               // lcs-leadmultispace cannot be an empty string
               return e_invarg;
             }
-            p = (char *)s;
+            p = s;
           } else {
             int multispace_pos = 0;
             while (*s != NUL && *s != ',') {
@@ -1052,7 +1052,7 @@ char *set_chars_option(win_T *wp, char **varp, bool apply)
                 wp->w_p_lcs_chars.leadmultispace[multispace_pos++] = c1;
               }
             }
-            p = (char *)s;
+            p = s;
           }
         } else {
           return e_invarg;
diff --git a/src/nvim/search.c b/src/nvim/search.c
index 205eec8b35..ea62a94f28 100644
--- a/src/nvim/search.c
+++ b/src/nvim/search.c
@@ -133,7 +133,7 @@ typedef struct SearchedFile {
 /// @param regmatch  return: pattern and ignore-case flag
 ///
 /// @return          FAIL if failed, OK otherwise.
-int search_regcomp(char_u *pat, char_u **used_pat, int pat_save, int pat_use, int options,
+int search_regcomp(char *pat, char **used_pat, int pat_save, int pat_use, int options,
                    regmmatch_T *regmatch)
 {
   int magic;
@@ -158,11 +158,11 @@ int search_regcomp(char_u *pat, char_u **used_pat, int pat_save, int pat_use, in
       rc_did_emsg = true;
       return FAIL;
     }
-    pat = (char_u *)spats[i].pat;
+    pat = spats[i].pat;
     magic = spats[i].magic;
     no_smartcase = spats[i].no_scs;
   } else if (options & SEARCH_HIS) {      // put new pattern in history
-    add_to_history(HIST_SEARCH, (char *)pat, true, NUL);
+    add_to_history(HIST_SEARCH, pat, true, NUL);
   }
 
   if (used_pat) {
@@ -171,9 +171,9 @@ int search_regcomp(char_u *pat, char_u **used_pat, int pat_save, int pat_use, in
 
   xfree(mr_pattern);
   if (curwin->w_p_rl && *curwin->w_p_rlc == 's') {
-    mr_pattern = reverse_text((char *)pat);
+    mr_pattern = reverse_text(pat);
   } else {
-    mr_pattern = xstrdup((char *)pat);
+    mr_pattern = xstrdup(pat);
   }
 
   // Save the currently used pattern in the appropriate place,
@@ -181,17 +181,17 @@ int search_regcomp(char_u *pat, char_u **used_pat, int pat_save, int pat_use, in
   if (!(options & SEARCH_KEEP) && (cmdmod.cmod_flags & CMOD_KEEPPATTERNS) == 0) {
     // search or global command
     if (pat_save == RE_SEARCH || pat_save == RE_BOTH) {
-      save_re_pat(RE_SEARCH, (char *)pat, magic);
+      save_re_pat(RE_SEARCH, pat, magic);
     }
     // substitute or global command
     if (pat_save == RE_SUBST || pat_save == RE_BOTH) {
-      save_re_pat(RE_SUBST, (char *)pat, magic);
+      save_re_pat(RE_SUBST, pat, magic);
     }
   }
 
-  regmatch->rmm_ic = ignorecase((char *)pat);
+  regmatch->rmm_ic = ignorecase(pat);
   regmatch->rmm_maxcol = 0;
-  regmatch->regprog = vim_regcomp((char *)pat, magic ? RE_MAGIC : 0);
+  regmatch->regprog = vim_regcomp(pat, magic ? RE_MAGIC : 0);
   if (regmatch->regprog == NULL) {
     return FAIL;
   }
@@ -346,9 +346,9 @@ static void restore_incsearch_state(void)
   search_match_lines  = saved_search_match_lines;
 }
 
-char_u *last_search_pattern(void)
+char *last_search_pattern(void)
 {
-  return (char_u *)spats[RE_SEARCH].pat;
+  return spats[RE_SEARCH].pat;
 }
 
 /// Return true when case should be ignored for search pattern "pat".
@@ -365,7 +365,7 @@ int ignorecase_opt(char *pat, int ic_in, int scs)
   if (ic && !no_smartcase && scs
       && !(ctrl_x_mode_not_default()
            && curbuf->b_p_inf)) {
-    ic = !pat_has_uppercase((char_u *)pat);
+    ic = !pat_has_uppercase(pat);
   }
   no_smartcase = false;
 
@@ -373,14 +373,14 @@ int ignorecase_opt(char *pat, int ic_in, int scs)
 }
 
 /// Returns true if pattern `pat` has an uppercase character.
-bool pat_has_uppercase(char_u *pat)
+bool pat_has_uppercase(char *pat)
   FUNC_ATTR_NONNULL_ALL
 {
-  char *p = (char *)pat;
+  char *p = pat;
   magic_T magic_val = MAGIC_ON;
 
   // get the magicness of the pattern
-  (void)skip_regexp_ex((char *)pat, NUL, magic_isset(), NULL, NULL, &magic_val);
+  (void)skip_regexp_ex(pat, NUL, magic_isset(), NULL, NULL, &magic_val);
 
   while (*p != NUL) {
     const int l = utfc_ptr2len(p);
@@ -431,7 +431,7 @@ int last_csearch_until(void)
   return last_t_cmd == true;
 }
 
-void set_last_csearch(int c, char_u *s, int len)
+void set_last_csearch(int c, char *s, int len)
 {
   *lastc = (char_u)c;
   lastc_bytelen = len;
@@ -452,9 +452,9 @@ void set_csearch_until(int t_cmd)
   last_t_cmd = t_cmd;
 }
 
-char_u *last_search_pat(void)
+char *last_search_pat(void)
 {
-  return (char_u *)spats[last_idx].pat;
+  return spats[last_idx].pat;
 }
 
 // Reset search direction to forward.  For "gd" and "gD" commands.
@@ -466,14 +466,14 @@ void reset_search_dir(void)
 
 // Set the last search pattern.  For ":let @/ =" and ShaDa file.
 // Also set the saved search pattern, so that this works in an autocommand.
-void set_last_search_pat(const char_u *s, int idx, int magic, int setlast)
+void set_last_search_pat(const char *s, int idx, int magic, int setlast)
 {
   free_spat(&spats[idx]);
   // An empty string means that nothing should be matched.
   if (*s == NUL) {
     spats[idx].pat = NULL;
   } else {
-    spats[idx].pat = xstrdup((char *)s);
+    spats[idx].pat = xstrdup(s);
   }
   spats[idx].timestamp = os_time();
   spats[idx].additional_data = NULL;
@@ -513,7 +513,7 @@ void last_pat_prog(regmmatch_T *regmatch)
     return;
   }
   emsg_off++;           // So it doesn't beep if bad expr
-  (void)search_regcomp((char_u *)"", NULL, 0, last_idx, SEARCH_KEEP, regmatch);
+  (void)search_regcomp("", NULL, 0, last_idx, SEARCH_KEEP, regmatch);
   emsg_off--;
 }
 
@@ -540,7 +540,7 @@ void last_pat_prog(regmmatch_T *regmatch)
 /// @returns          FAIL (zero) for failure, non-zero for success.
 ///                   the index of the first matching
 ///                   subpattern plus one; one if there was none.
-int searchit(win_T *win, buf_T *buf, pos_T *pos, pos_T *end_pos, Direction dir, char_u *pat,
+int searchit(win_T *win, buf_T *buf, pos_T *pos, pos_T *end_pos, Direction dir, char *pat,
              long count, int options, int pat_use, searchit_arg_T *extra_arg)
 {
   int found;
@@ -1296,7 +1296,7 @@ int do_search(oparg_T *oap, int dirc, int search_delim, char *pat, long count, i
     }
 
     c = searchit(curwin, curbuf, &pos, NULL, dirc == '/' ? FORWARD : BACKWARD,
-                 (char_u *)searchstr, count,
+                 searchstr, count,
                  (spats[0].off.end * SEARCH_END
                   + (options
                      & (SEARCH_KEEP + SEARCH_PEEK + SEARCH_HIS + SEARCH_MSG
@@ -2440,7 +2440,7 @@ int current_search(long count, bool forward)
 
     result = searchit(curwin, curbuf, &pos, &end_pos,
                       (dir ? FORWARD : BACKWARD),
-                      (char_u *)spats[last_idx].pat, i ? count : 1,
+                      spats[last_idx].pat, i ? count : 1,
                       SEARCH_KEEP | flags, RE_SEARCH, NULL);
 
     p_ws = old_p_ws;
@@ -2527,7 +2527,7 @@ static int is_zero_width(char *pattern, int move, pos_T *cur, Direction directio
     pattern = spats[last_idx].pat;
   }
 
-  if (search_regcomp((char_u *)pattern, NULL, RE_SEARCH, RE_SEARCH,
+  if (search_regcomp(pattern, NULL, RE_SEARCH, RE_SEARCH,
                      SEARCH_KEEP, &regmatch) == FAIL) {
     return -1;
   }
@@ -2542,7 +2542,7 @@ static int is_zero_width(char *pattern, int move, pos_T *cur, Direction directio
     // accept a match at the cursor position
     flag = SEARCH_START;
   }
-  if (searchit(curwin, curbuf, &pos, NULL, direction, (char_u *)pattern, 1,
+  if (searchit(curwin, curbuf, &pos, NULL, direction, pattern, 1,
                SEARCH_KEEP + flag, RE_SEARCH, NULL) != FAIL) {
     // Zero-width pattern should match somewhere, then we can check if
     // start and end are in the same position.
@@ -3637,8 +3637,8 @@ void find_pattern_in_path(char *ptr, Direction dir, size_t len, bool whole, bool
                                            1L, p_fname);
       } else {
         // Use text after match with 'include'.
-        new_fname = (char *)file_name_in_line((char_u *)incl_regmatch.endp[0], 0,
-                                              FNAME_EXP|FNAME_INCL|FNAME_REL, 1L, (char_u *)p_fname,
+        new_fname = (char *)file_name_in_line(incl_regmatch.endp[0], 0,
+                                              FNAME_EXP|FNAME_INCL|FNAME_REL, 1L, p_fname,
                                               NULL);
       }
       already_searched = false;
diff --git a/src/nvim/spell.c b/src/nvim/spell.c
index 48aed9c6de..c17fafd3d7 100644
--- a/src/nvim/spell.c
+++ b/src/nvim/spell.c
@@ -214,7 +214,7 @@ char *repl_to = NULL;
 ///
 /// @return  the length of the word in bytes, also when it's OK, so that the
 /// caller can skip over the word.
-size_t spell_check(win_T *wp, char_u *ptr, hlf_T *attrp, int *capcol, bool docount)
+size_t spell_check(win_T *wp, char *ptr, hlf_T *attrp, int *capcol, bool docount)
 {
   matchinf_T mi;              // Most things are put in "mi" so that it can
                               // be passed to functions quickly.
@@ -226,7 +226,7 @@ size_t spell_check(win_T *wp, char_u *ptr, hlf_T *attrp, int *capcol, bool docou
 
   // A word never starts at a space or a control character. Return quickly
   // then, skipping over the character.
-  if (*ptr <= ' ') {
+  if ((uint8_t)(*ptr) <= ' ') {
     return 1;
   }
 
@@ -242,18 +242,18 @@ size_t spell_check(win_T *wp, char_u *ptr, hlf_T *attrp, int *capcol, bool docou
   // julifeest".
   if (*ptr >= '0' && *ptr <= '9') {
     if (*ptr == '0' && (ptr[1] == 'b' || ptr[1] == 'B')) {
-      mi.mi_end = (char_u *)skipbin((char *)ptr + 2);
+      mi.mi_end = (char_u *)skipbin(ptr + 2);
     } else if (*ptr == '0' && (ptr[1] == 'x' || ptr[1] == 'X')) {
-      mi.mi_end = (char_u *)skiphex((char *)ptr + 2);
+      mi.mi_end = (char_u *)skiphex(ptr + 2);
     } else {
-      mi.mi_end = (char_u *)skipdigits((char *)ptr);
+      mi.mi_end = (char_u *)skipdigits(ptr);
     }
-    nrlen = (size_t)(mi.mi_end - ptr);
+    nrlen = (size_t)(mi.mi_end - (char_u *)ptr);
   }
 
   // Find the normal end of the word (until the next non-word character).
-  mi.mi_word = (char *)ptr;
-  mi.mi_fend = ptr;
+  mi.mi_word = ptr;
+  mi.mi_fend = (char_u *)ptr;
   if (spell_iswordp(mi.mi_fend, wp)) {
     bool this_upper = false;  // init for gcc
 
@@ -275,9 +275,9 @@ size_t spell_check(win_T *wp, char_u *ptr, hlf_T *attrp, int *capcol, bool docou
 
     if (capcol != NULL && *capcol == 0 && wp->w_s->b_cap_prog != NULL) {
       // Check word starting with capital letter.
-      int c = utf_ptr2char((char *)ptr);
+      int c = utf_ptr2char(ptr);
       if (!SPELL_ISUPPER(c)) {
-        wrongcaplen = (size_t)(mi.mi_fend - ptr);
+        wrongcaplen = (size_t)(mi.mi_fend - (char_u *)ptr);
       }
     }
   }
@@ -300,7 +300,7 @@ size_t spell_check(win_T *wp, char_u *ptr, hlf_T *attrp, int *capcol, bool docou
     MB_PTR_ADV(mi.mi_fend);
   }
 
-  (void)spell_casefold(wp, ptr, (int)(mi.mi_fend - ptr), (char_u *)mi.mi_fword,
+  (void)spell_casefold(wp, (char_u *)ptr, (int)(mi.mi_fend - (char_u *)ptr), (char_u *)mi.mi_fword,
                        MAXWLEN + 1);
   mi.mi_fwordlen = (int)strlen(mi.mi_fword);
 
@@ -344,8 +344,8 @@ size_t spell_check(win_T *wp, char_u *ptr, hlf_T *attrp, int *capcol, bool docou
 
     // Count the word in the first language where it's found to be OK.
     if (count_word && mi.mi_result == SP_OK) {
-      count_common_word(mi.mi_lp->lp_slang, (char *)ptr,
-                        (int)(mi.mi_end - ptr), 1);
+      count_common_word(mi.mi_lp->lp_slang, ptr,
+                        (int)(mi.mi_end - (char_u *)ptr), 1);
       count_word = false;
     }
   }
@@ -357,7 +357,7 @@ size_t spell_check(win_T *wp, char_u *ptr, hlf_T *attrp, int *capcol, bool docou
       if (mi.mi_result == SP_BAD || mi.mi_result == SP_BANNED) {
         return nrlen;
       }
-    } else if (!spell_iswordp_nmw(ptr, wp)) {
+    } else if (!spell_iswordp_nmw((char_u *)ptr, wp)) {
       // When we are at a non-word character there is no error, just
       // skip over the character (try looking for a word after it).
       if (capcol != NULL && wp->w_s->b_cap_prog != NULL) {
@@ -366,15 +366,15 @@ size_t spell_check(win_T *wp, char_u *ptr, hlf_T *attrp, int *capcol, bool docou
         // Check for end of sentence.
         regmatch.regprog = wp->w_s->b_cap_prog;
         regmatch.rm_ic = false;
-        int r = vim_regexec(&regmatch, (char *)ptr, 0);
+        int r = vim_regexec(&regmatch, ptr, 0);
         wp->w_s->b_cap_prog = regmatch.regprog;
         if (r) {
-          *capcol = (int)(regmatch.endp[0] - (char *)ptr);
+          *capcol = (int)(regmatch.endp[0] - ptr);
         }
       }
 
-      return (size_t)(utfc_ptr2len((char *)ptr));
-    } else if (mi.mi_end == ptr) {
+      return (size_t)(utfc_ptr2len(ptr));
+    } else if (mi.mi_end == (char_u *)ptr) {
       // Always include at least one character.  Required for when there
       // is a mixup in "midword".
       MB_PTR_ADV(mi.mi_end);
@@ -421,7 +421,7 @@ size_t spell_check(win_T *wp, char_u *ptr, hlf_T *attrp, int *capcol, bool docou
     return wrongcaplen;
   }
 
-  return (size_t)(mi.mi_end - ptr);
+  return (size_t)(mi.mi_end - (char_u *)ptr);
 }
 
 // Check if the word at "mip->mi_word" is in the tree.
@@ -1319,7 +1319,7 @@ size_t spell_move_to(win_T *wp, int dir, bool allwords, bool curline, hlf_T *att
     STRCPY(buf, line);
     if (lnum < wp->w_buffer->b_ml.ml_line_count) {
       spell_cat_line(buf + strlen(buf),
-                     (char_u *)ml_get_buf(wp->w_buffer, lnum + 1, false),
+                     ml_get_buf(wp->w_buffer, lnum + 1, false),
                      MAXWLEN);
     }
     char *p = buf + skip;
@@ -1336,7 +1336,7 @@ size_t spell_move_to(win_T *wp, int dir, bool allwords, bool curline, hlf_T *att
 
       // start of word
       attr = HLF_COUNT;
-      len = spell_check(wp, (char_u *)p, &attr, &capcol, false);
+      len = spell_check(wp, p, &attr, &capcol, false);
 
       if (attr != HLF_COUNT) {
         // We found a bad word.  Check the attribute.
@@ -1480,17 +1480,17 @@ theend:
 // "buf", blanking-out special characters.  Copy less than "maxlen" bytes.
 // Keep the blanks at the start of the next line, this is used in win_line()
 // to skip those bytes if the word was OK.
-void spell_cat_line(char *buf, char_u *line, int maxlen)
+void spell_cat_line(char *buf, char *line, int maxlen)
 {
-  char_u *p = (char_u *)skipwhite((char *)line);
-  while (vim_strchr("*#/\"\t", *p) != NULL) {
+  char_u *p = (char_u *)skipwhite(line);
+  while (vim_strchr("*#/\"\t", (uint8_t)(*p)) != NULL) {
     p = (char_u *)skipwhite((char *)p + 1);
   }
 
   if (*p != NUL) {
     // Only worth concatenating if there is something else than spaces to
     // concatenate.
-    int n = (int)(p - line) + 1;
+    int n = (int)(p - (char_u *)line) + 1;
     if (n < maxlen - 1) {
       memset(buf, ' ', (size_t)n);
       xstrlcpy(buf + n, (char *)p, (size_t)(maxlen - n));
@@ -2213,24 +2213,24 @@ static int find_region(const char_u *rp, const char_u *region)
 int captype(char_u *word, const char_u *end)
   FUNC_ATTR_NONNULL_ARG(1)
 {
-  char_u *p;
+  char *p;
 
   // find first letter
-  for (p = word; !spell_iswordp_nmw(p, curwin); MB_PTR_ADV(p)) {
-    if (end == NULL ? *p == NUL : p >= end) {
+  for (p = (char *)word; !spell_iswordp_nmw((char_u *)p, curwin); MB_PTR_ADV(p)) {
+    if (end == NULL ? *p == NUL : (char_u *)p >= end) {
       return 0;             // only non-word characters, illegal word
     }
   }
-  int c = mb_ptr2char_adv((const char_u **)&p);
+  int c = mb_ptr2char_adv((const char **)&p);
   bool allcap;
   bool firstcap = allcap = SPELL_ISUPPER(c);
   bool past_second = false;              // past second word char
 
   // Need to check all letters to find a word with mixed upper/lower.
   // But a word with an upper char only at start is a ONECAP.
-  for (; end == NULL ? *p != NUL : p < end; MB_PTR_ADV(p)) {
-    if (spell_iswordp_nmw(p, curwin)) {
-      c = utf_ptr2char((char *)p);
+  for (; end == NULL ? *p != NUL : (char_u *)p < end; MB_PTR_ADV(p)) {
+    if (spell_iswordp_nmw((char_u *)p, curwin)) {
+      c = utf_ptr2char(p);
       if (!SPELL_ISUPPER(c)) {
         // UUl -> KEEPCAP
         if (past_second && allcap) {
@@ -2482,18 +2482,18 @@ int spell_casefold(const win_T *wp, char_u *str, int len, char_u *buf, int bufle
   int outi = 0;
 
   // Fold one character at a time.
-  for (char_u *p = str; p < str + len;) {
+  for (char *p = (char *)str; (char_u *)p < str + len;) {
     if (outi + MB_MAXBYTES > buflen) {
       buf[outi] = NUL;
       return FAIL;
     }
-    int c = mb_cptr2char_adv((const char_u **)&p);
+    int c = mb_cptr2char_adv((const char **)&p);
 
     // Exception: greek capital sigma 0x03A3 folds to 0x03C3, except
     // when it is the last character in a word, then it folds to
     // 0x03C2.
     if (c == 0x03a3 || c == 0x03c2) {
-      if (p == str + len || !spell_iswordp(p, wp)) {
+      if (p == (char *)str + len || !spell_iswordp((char_u *)p, wp)) {
         c = 0x03c2;
       } else {
         c = 0x03c3;
@@ -2636,15 +2636,15 @@ void ex_spellrepall(exarg_T *eap)
 /// @param[in]  upper  True to upper case, otherwise lower case
 void onecap_copy(char_u *word, char *wcopy, bool upper)
 {
-  char_u *p = word;
-  int c = mb_cptr2char_adv((const char_u **)&p);
+  char *p = (char *)word;
+  int c = mb_cptr2char_adv((const char **)&p);
   if (upper) {
     c = SPELL_TOUPPER(c);
   } else {
     c = SPELL_TOFOLD(c);
   }
   int l = utf_char2bytes(c, wcopy);
-  xstrlcpy(wcopy + l, (char *)p, (size_t)(MAXWLEN - l));
+  xstrlcpy(wcopy + l, p, (size_t)(MAXWLEN - l));
 }
 
 // Make a copy of "word" with all the letters upper cased into
@@ -2652,8 +2652,8 @@ void onecap_copy(char_u *word, char *wcopy, bool upper)
 void allcap_copy(char_u *word, char_u *wcopy)
 {
   char_u *d = wcopy;
-  for (char_u *s = word; *s != NUL;) {
-    int c = mb_cptr2char_adv((const char_u **)&s);
+  for (char *s = (char *)word; *s != NUL;) {
+    int c = mb_cptr2char_adv((const char **)&s);
 
     if (c == 0xdf) {
       c = 'S';
@@ -2776,8 +2776,8 @@ static void spell_soundfold_sofo(slang_T *slang, char_u *inword, char_u *res)
 
   // The sl_sal_first[] table contains the translation for chars up to
   // 255, sl_sal the rest.
-  for (char_u *s = inword; *s != NUL;) {
-    int c = mb_cptr2char_adv((const char_u **)&s);
+  for (char *s = (char *)inword; *s != NUL;) {
+    int c = mb_cptr2char_adv((const char **)&s);
     if (utf_class(c) == 0) {
       c = ' ';
     } else if (c < 256) {
@@ -2837,8 +2837,8 @@ static void spell_soundfold_wsal(slang_T *slang, const char_u *inword, char_u *r
   // Remove accents, if wanted.  We actually remove all non-word characters.
   // But keep white space.
   int wordlen = 0;
-  for (const char_u *s = inword; *s != NUL;) {
-    const char_u *t = s;
+  for (const char *s = (char *)inword; *s != NUL;) {
+    const char_u *t = (char_u *)s;
     int c = mb_cptr2char_adv(&s);
     if (slang->sl_rem_accents) {
       if (utf_class(c) == 0) {
@@ -3524,11 +3524,11 @@ static linenr_T dump_prefixes(slang_T *slang, char *word, char_u *pat, Direction
 
 // Move "p" to the end of word "start".
 // Uses the spell-checking word characters.
-char_u *spell_to_word_end(char_u *start, win_T *win)
+char *spell_to_word_end(char *start, win_T *win)
 {
-  char_u *p = start;
+  char *p = start;
 
-  while (*p != NUL && spell_iswordp(p, win)) {
+  while (*p != NUL && spell_iswordp((char_u *)p, win)) {
     MB_PTR_ADV(p);
   }
   return p;
diff --git a/src/nvim/spellfile.c b/src/nvim/spellfile.c
index e6257aeca1..6f5bd836b1 100644
--- a/src/nvim/spellfile.c
+++ b/src/nvim/spellfile.c
@@ -1064,12 +1064,12 @@ static int read_region_section(FILE *fd, slang_T *lp, int len)
 // Return SP_*ERROR flags.
 static int read_charflags_section(FILE *fd)
 {
-  char_u *flags;
+  char *flags;
   char_u *fol;
   int flagslen, follen;
 
   // <charflagslen> <charflags>
-  flags = read_cnt_string(fd, 1, &flagslen);
+  flags = (char *)read_cnt_string(fd, 1, &flagslen);
   if (flagslen < 0) {
     return flagslen;
   }
@@ -1083,7 +1083,7 @@ static int read_charflags_section(FILE *fd)
 
   // Set the word-char flags and fill SPELL_ISUPPER() table.
   if (flags != NULL && fol != NULL) {
-    set_spell_charflags(flags, flagslen, fol);
+    set_spell_charflags((char_u *)flags, flagslen, fol);
   }
 
   xfree(flags);
@@ -1430,7 +1430,7 @@ static int read_compound(FILE *fd, slang_T *slang, int len)
       return SP_TRUNCERROR;
     }
     todo -= 2;
-    ga_init(gap, sizeof(char_u *), c);
+    ga_init(gap, sizeof(char *), c);
     ga_grow(gap, c);
     while (--c >= 0) {
       ((char **)(gap->ga_data))[gap->ga_len++] = (char *)read_cnt_string(fd, 1, &cnt);
@@ -1551,8 +1551,8 @@ static int read_compound(FILE *fd, slang_T *slang, int len)
 // Returns SP_*ERROR flags when there is something wrong.
 static int set_sofo(slang_T *lp, char_u *from, char_u *to)
 {
-  char_u *s;
-  char_u *p;
+  char *s;
+  char *p;
 
   // Use "sl_sal" as an array with 256 pointers to a list of wide
   // characters.  The index is the low byte of the character.
@@ -1566,8 +1566,8 @@ static int set_sofo(slang_T *lp, char_u *from, char_u *to)
 
   // First count the number of items for each list.  Temporarily use
   // sl_sal_first[] for this.
-  for (p = from, s = to; *p != NUL && *s != NUL;) {
-    const int c = mb_cptr2char_adv((const char_u **)&p);
+  for (p = (char *)from, s = (char *)to; *p != NUL && *s != NUL;) {
+    const int c = mb_cptr2char_adv((const char **)&p);
     MB_CPTR_ADV(s);
     if (c >= 256) {
       lp->sl_sal_first[c & 0xff]++;
@@ -1589,9 +1589,9 @@ static int set_sofo(slang_T *lp, char_u *from, char_u *to)
   // Put the characters up to 255 in sl_sal_first[] the rest in a sl_sal
   // list.
   memset(lp->sl_sal_first, 0, sizeof(salfirst_T) * 256);
-  for (p = from, s = to; *p != NUL && *s != NUL;) {
-    const int c = mb_cptr2char_adv((const char_u **)&p);
-    const int i = mb_cptr2char_adv((const char_u **)&s);
+  for (p = (char *)from, s = (char *)to; *p != NUL && *s != NUL;) {
+    const int c = mb_cptr2char_adv((const char **)&p);
+    const int i = mb_cptr2char_adv((const char **)&s);
     if (c >= 256) {
       // Append the from-to chars at the end of the list with
       // the low byte.
@@ -1665,8 +1665,8 @@ static int *mb_str2wide(char_u *s)
   int i = 0;
 
   int *res = xmalloc(((size_t)mb_charlen((char *)s) + 1) * sizeof(int));
-  for (char_u *p = s; *p != NUL;) {
-    res[i++] = mb_ptr2char_adv((const char_u **)&p);
+  for (char *p = (char *)s; *p != NUL;) {
+    res[i++] = mb_ptr2char_adv((const char **)&p);
   }
   res[i] = NUL;
 
@@ -2608,7 +2608,7 @@ static afffile_T *spell_read_aff(spellinfo_T *spin, char_u *fname)
       } else if (is_aff_rule(items, itemcnt, "REP", 2)
                  || is_aff_rule(items, itemcnt, "REPSAL", 2)) {
         // Ignore REP/REPSAL count
-        if (!isdigit(*items[1])) {
+        if (!isdigit((uint8_t)(*items[1]))) {
           smsg(_("Expected REP(SAL) count in %s line %d"),
                fname, lnum);
         }
@@ -2643,7 +2643,7 @@ static afffile_T *spell_read_aff(spellinfo_T *spin, char_u *fname)
         if (!found_map) {
           // First line contains the count.
           found_map = true;
-          if (!isdigit(*items[1])) {
+          if (!isdigit((uint8_t)(*items[1]))) {
             smsg(_("Expected MAP count in %s line %d"),
                  fname, lnum);
           }
@@ -2652,7 +2652,7 @@ static afffile_T *spell_read_aff(spellinfo_T *spin, char_u *fname)
 
           // Check that every character appears only once.
           for (p = items[1]; *p != NUL;) {
-            c = mb_ptr2char_adv((const char_u **)&p);
+            c = mb_ptr2char_adv((const char **)&p);
             if ((!GA_EMPTY(&spin->si_map)
                  && vim_strchr(spin->si_map.ga_data, c)
                  != NULL)
@@ -2802,18 +2802,18 @@ static bool is_aff_rule(char **items, int itemcnt, char *rulename, int mincount)
 // ae_flags to ae_comppermit and ae_compforbid.
 static void aff_process_flags(afffile_T *affile, affentry_T *entry)
 {
-  char_u *p;
+  char *p;
   char_u *prevp;
   unsigned flag;
 
   if (entry->ae_flags != NULL
       && (affile->af_compforbid != 0 || affile->af_comppermit != 0)) {
-    for (p = entry->ae_flags; *p != NUL;) {
-      prevp = p;
+    for (p = (char *)entry->ae_flags; *p != NUL;) {
+      prevp = (char_u *)p;
       flag = get_affitem(affile->af_flagtype, &p);
       if (flag == affile->af_comppermit || flag == affile->af_compforbid) {
         STRMOVE(prevp, (char *)p);
-        p = prevp;
+        p = (char *)prevp;
         if (flag == affile->af_comppermit) {
           entry->ae_comppermit = true;
         } else {
@@ -2846,7 +2846,7 @@ static bool spell_info_item(char *s)
 static unsigned affitem2flag(int flagtype, char_u *item, char_u *fname, int lnum)
 {
   unsigned res;
-  char_u *p = item;
+  char *p = (char *)item;
 
   res = get_affitem(flagtype, &p);
   if (res == 0) {
@@ -2869,7 +2869,7 @@ static unsigned affitem2flag(int flagtype, char_u *item, char_u *fname, int lnum
 // Get one affix name from "*pp" and advance the pointer.
 // Returns ZERO_FLAG for "0".
 // Returns zero for an error, still advances the pointer then.
-static unsigned get_affitem(int flagtype, char_u **pp)
+static unsigned get_affitem(int flagtype, char **pp)
 {
   int res;
 
@@ -2878,18 +2878,18 @@ static unsigned get_affitem(int flagtype, char_u **pp)
       (*pp)++;            // always advance, avoid getting stuck
       return 0;
     }
-    res = getdigits_int((char **)pp, true, 0);
+    res = getdigits_int(pp, true, 0);
     if (res == 0) {
       res = ZERO_FLAG;
     }
   } else {
-    res = mb_ptr2char_adv((const char_u **)pp);
+    res = mb_ptr2char_adv((const char **)pp);
     if (flagtype == AFT_LONG || (flagtype == AFT_CAPLONG
                                  && res >= 'A' && res <= 'Z')) {
       if (**pp == NUL) {
         return 0;
       }
-      res = mb_ptr2char_adv((const char_u **)pp) + (res << 16);
+      res = mb_ptr2char_adv((const char **)pp) + (res << 16);
     }
   }
   return (unsigned)res;
@@ -2927,13 +2927,13 @@ static void process_compflags(spellinfo_T *spin, afffile_T *aff, char *compflags
   tp = (char_u *)p + strlen(p);
 
   for (p = compflags; *p != NUL;) {
-    if (vim_strchr("/?*+[]", *p) != NULL) {
+    if (vim_strchr("/?*+[]", (uint8_t)(*p)) != NULL) {
       // Copy non-flag characters directly.
       *tp++ = (char_u)(*p++);
     } else {
       // First get the flag number, also checks validity.
       prevp = p;
-      flag = get_affitem(aff->af_flagtype, (char_u **)&p);
+      flag = get_affitem(aff->af_flagtype, &p);
       if (flag != 0) {
         // Find the flag in the hashtable.  If it was used before, use
         // the existing ID.  Otherwise add a new entry.
@@ -2990,10 +2990,10 @@ static bool flag_in_afflist(int flagtype, char_u *afflist, unsigned flag)
   case AFT_CAPLONG:
   case AFT_LONG:
     for (p = (char *)afflist; *p != NUL;) {
-      n = (unsigned)mb_ptr2char_adv((const char_u **)&p);
+      n = (unsigned)mb_ptr2char_adv((const char **)&p);
       if ((flagtype == AFT_LONG || (n >= 'A' && n <= 'Z'))
           && *p != NUL) {
-        n = (unsigned)mb_ptr2char_adv((const char_u **)&p) + (n << 16);
+        n = (unsigned)mb_ptr2char_adv((const char **)&p) + (n << 16);
       }
       if (n == flag) {
         return true;
@@ -3266,7 +3266,7 @@ static int spell_read_dic(spellinfo_T *spin, char_u *fname, afffile_T *affile)
       if (spin->si_compflags != NULL) {
         // Need to store the list of compound flags with the word.
         // Concatenate them to the list of prefix IDs.
-        get_compflags(affile, afflist, store_afflist + pfxlen);
+        get_compflags(affile, (char *)afflist, store_afflist + pfxlen);
       }
     }
 
@@ -3352,19 +3352,19 @@ static int get_affix_flags(afffile_T *affile, char_u *afflist)
 // and return the number of affixes.
 static int get_pfxlist(afffile_T *affile, char_u *afflist, char_u *store_afflist)
 {
-  char_u *p;
+  char *p;
   char *prevp;
   int cnt = 0;
   int id;
   char key[AH_KEY_LEN];
   hashitem_T *hi;
 
-  for (p = afflist; *p != NUL;) {
-    prevp = (char *)p;
+  for (p = (char *)afflist; *p != NUL;) {
+    prevp = p;
     if (get_affitem(affile->af_flagtype, &p) != 0) {
       // A flag is a postponed prefix flag if it appears in "af_pref"
       // and its ID is not zero.
-      xstrlcpy(key, prevp, (size_t)(p - (char_u *)prevp) + 1);
+      xstrlcpy(key, prevp, (size_t)(p - prevp) + 1);
       hi = hash_find(&affile->af_pref, (char *)key);
       if (!HASHITEM_EMPTY(hi)) {
         id = HI2AH(hi)->ah_newID;
@@ -3385,19 +3385,19 @@ static int get_pfxlist(afffile_T *affile, char_u *afflist, char_u *store_afflist
 // Get the list of compound IDs from the affix list "afflist" that are used
 // for compound words.
 // Puts the flags in "store_afflist[]".
-static void get_compflags(afffile_T *affile, char_u *afflist, char_u *store_afflist)
+static void get_compflags(afffile_T *affile, char *afflist, char_u *store_afflist)
 {
-  char_u *p;
+  char *p;
   char *prevp;
   int cnt = 0;
   char key[AH_KEY_LEN];
   hashitem_T *hi;
 
   for (p = afflist; *p != NUL;) {
-    prevp = (char *)p;
+    prevp = p;
     if (get_affitem(affile->af_flagtype, &p) != 0) {
       // A flag is a compound flag if it appears in "af_comp".
-      xstrlcpy(key, prevp, (size_t)(p - (char_u *)prevp) + 1);
+      xstrlcpy(key, prevp, (size_t)(p - prevp) + 1);
       hi = hash_find(&affile->af_comp, (char *)key);
       if (!HASHITEM_EMPTY(hi)) {
         store_afflist[cnt++] = (char_u)HI2CI(hi)->ci_newID;
@@ -3437,7 +3437,7 @@ static int store_aff_word(spellinfo_T *spin, char *word, char_u *afflist, afffil
   char newword[MAXWLEN];
   int retval = OK;
   int i, j;
-  char_u *p;
+  char *p;
   int use_flags;
   char *use_pfxlist;
   int use_pfxlen;
@@ -3490,7 +3490,7 @@ static int store_aff_word(spellinfo_T *spin, char *word, char_u *afflist, afffil
               } else {
                 xstrlcpy(newword, ae->ae_add, MAXWLEN);
               }
-              p = (char_u *)word;
+              p = word;
               if (ae->ae_chop != NULL) {
                 // Skip chop string.
                 i = mb_charlen(ae->ae_chop);
@@ -3504,7 +3504,7 @@ static int store_aff_word(spellinfo_T *spin, char *word, char_u *afflist, afffil
               xstrlcpy(newword, word, MAXWLEN);
               if (ae->ae_chop != NULL) {
                 // Remove chop string.
-                p = (char_u *)newword + strlen(newword);
+                p = newword + strlen(newword);
                 i = mb_charlen(ae->ae_chop);
                 for (; i > 0; i--) {
                   MB_PTR_BACK(newword, p);
@@ -3567,7 +3567,7 @@ static int store_aff_word(spellinfo_T *spin, char *word, char_u *afflist, afffil
 
                 if (spin->si_compflags != NULL) {
                   // Get compound IDS from the affix list.
-                  get_compflags(affile, ae->ae_flags,
+                  get_compflags(affile, (char *)ae->ae_flags,
                                 (char_u *)use_pfxlist + use_pfxlen);
                 } else {
                   use_pfxlist[use_pfxlen] = NUL;
@@ -5702,7 +5702,7 @@ static void init_spellfile(void)
     // Find the end of the language name.  Exclude the region.  If there
     // is a path separator remember the start of the tail.
     for (lend = (char_u *)curwin->w_s->b_p_spl; *lend != NUL
-         && vim_strchr(",._", *lend) == NULL; lend++) {
+         && vim_strchr(",._", (uint8_t)(*lend)) == NULL; lend++) {
       if (vim_ispathsep(*lend)) {
         aspath = true;
         lstart = lend + 1;
@@ -5765,7 +5765,7 @@ static void set_spell_charflags(const char_u *flags, int cnt, char_u *fol)
   // previous one.
   spelltab_T new_st;
   int i;
-  char_u *p = fol;
+  char *p = (char *)fol;
   int c;
 
   clear_spell_chartab(&new_st);
@@ -5777,7 +5777,7 @@ static void set_spell_charflags(const char_u *flags, int cnt, char_u *fol)
     }
 
     if (*p != NUL) {
-      c = mb_ptr2char_adv((const char_u **)&p);
+      c = mb_ptr2char_adv((const char **)&p);
       new_st.st_fold[i + 128] = (char_u)c;
       if (i + 128 != c && new_st.st_isu[i + 128] && c < 256) {
         new_st.st_upper[c] = (char_u)(i + 128);
@@ -5845,7 +5845,7 @@ static int write_spell_prefcond(FILE *fd, garray_T *gap, size_t *fwv)
 // Use map string "map" for languages "lp".
 static void set_map_str(slang_T *lp, char_u *map)
 {
-  char_u *p;
+  char *p;
   int headc = 0;
   int c;
   int i;
@@ -5865,8 +5865,8 @@ static void set_map_str(slang_T *lp, char_u *map)
   // The similar characters are stored separated with slashes:
   // "aaa/bbb/ccc/".  Fill sl_map_array[c] with the character before c and
   // before the same slash.  For characters above 255 sl_map_hash is used.
-  for (p = map; *p != NUL;) {
-    c = mb_cptr2char_adv((const char_u **)&p);
+  for (p = (char *)map; *p != NUL;) {
+    c = mb_cptr2char_adv((const char **)&p);
     if (c == '/') {
       headc = 0;
     } else {
diff --git a/src/nvim/spellsuggest.c b/src/nvim/spellsuggest.c
index 0b18958af3..c2888b3945 100644
--- a/src/nvim/spellsuggest.c
+++ b/src/nvim/spellsuggest.c
@@ -738,7 +738,7 @@ static void spell_find_suggest(char_u *badptr, int badlen, suginfo_T *su, int ma
   if (badlen != 0) {
     su->su_badlen = badlen;
   } else {
-    size_t tmplen = spell_check(curwin, (char_u *)su->su_badptr, &attr, NULL, false);
+    size_t tmplen = spell_check(curwin, su->su_badptr, &attr, NULL, false);
     assert(tmplen <= INT_MAX);
     su->su_badlen = (int)tmplen;
   }
@@ -3225,7 +3225,7 @@ static void check_suggestions(suginfo_T *su, garray_T *gap)
     xstrlcpy(longword + len, su->su_badptr + stp[i].st_orglen,
              (size_t)(MAXWLEN - len + 1));
     attr = HLF_COUNT;
-    (void)spell_check(curwin, (char_u *)longword, &attr, NULL, false);
+    (void)spell_check(curwin, longword, &attr, NULL, false);
     if (attr != HLF_COUNT) {
       // Remove this entry.
       xfree(stp[i].st_word);
@@ -3585,12 +3585,12 @@ static int spell_edit_score(slang_T *slang, const char_u *badword, const char_u
     // Get the characters from the multi-byte strings and put them in an
     // int array for easy access.
     badlen = 0;
-    for (const char_u *p = badword; *p != NUL;) {
+    for (const char *p = (char *)badword; *p != NUL;) {
       wbadword[badlen++] = mb_cptr2char_adv(&p);
     }
     wbadword[badlen++] = 0;
     goodlen = 0;
-    for (const char_u *p = goodword; *p != NUL;) {
+    for (const char *p = (char *)goodword; *p != NUL;) {
       wgoodword[goodlen++] = mb_cptr2char_adv(&p);
     }
     wgoodword[goodlen++] = 0;
@@ -3691,12 +3691,12 @@ static int spell_edit_score_limit_w(slang_T *slang, const char_u *badword, const
   // Get the characters from the multi-byte strings and put them in an
   // int array for easy access.
   bi = 0;
-  for (const char_u *p = badword; *p != NUL;) {
+  for (const char *p = (char *)badword; *p != NUL;) {
     wbadword[bi++] = mb_cptr2char_adv(&p);
   }
   wbadword[bi++] = 0;
   gi = 0;
-  for (const char_u *p = goodword; *p != NUL;) {
+  for (const char *p = (char *)goodword; *p != NUL;) {
     wgoodword[gi++] = mb_cptr2char_adv(&p);
   }
   wgoodword[gi++] = 0;
diff --git a/src/nvim/statusline.c b/src/nvim/statusline.c
index e0c531859c..46cd600d81 100644
--- a/src/nvim/statusline.c
+++ b/src/nvim/statusline.c
@@ -1368,7 +1368,7 @@ int build_stl_str_hl(win_T *wp, char *out, size_t outlen, char *fmt, char *opt_n
 
     // An invalid item was specified.
     // Continue processing on the next character of the format string.
-    if (vim_strchr(STL_ALL, *fmt_p) == NULL) {
+    if (vim_strchr(STL_ALL, (uint8_t)(*fmt_p)) == NULL) {
       fmt_p++;
       continue;
     }
@@ -1682,7 +1682,7 @@ int build_stl_str_hl(win_T *wp, char *out, size_t outlen, char *fmt, char *opt_n
         vim_snprintf(buf_tmp, sizeof(buf_tmp), ",%s", wp->w_buffer->b_p_ft);
         // Uppercase the file extension
         for (char *t = buf_tmp; *t != 0; t++) {
-          *t = (char)TOUPPER_LOC(*t);
+          *t = (char)TOUPPER_LOC((uint8_t)(*t));
         }
         str = buf_tmp;
       }
diff --git a/src/nvim/strings.c b/src/nvim/strings.c
index f0f9fbf51b..53b4d7082b 100644
--- a/src/nvim/strings.c
+++ b/src/nvim/strings.c
@@ -372,7 +372,7 @@ int vim_stricmp(const char *s1, const char *s2)
   int i;
 
   for (;;) {
-    i = (int)TOLOWER_LOC(*s1) - (int)TOLOWER_LOC(*s2);
+    i = (int)TOLOWER_LOC((uint8_t)(*s1)) - (int)TOLOWER_LOC((uint8_t)(*s2));
     if (i != 0) {
       return i;                             // this character different
     }
@@ -396,7 +396,7 @@ int vim_strnicmp(const char *s1, const char *s2, size_t len)
   int i;
 
   while (len > 0) {
-    i = (int)TOLOWER_LOC(*s1) - (int)TOLOWER_LOC(*s2);
+    i = (int)TOLOWER_LOC((uint8_t)(*s1)) - (int)TOLOWER_LOC((uint8_t)(*s2));
     if (i != 0) {
       return i;                             // this character different
     }
diff --git a/src/nvim/syntax.c b/src/nvim/syntax.c
index 721cc7707a..f18f445867 100644
--- a/src/nvim/syntax.c
+++ b/src/nvim/syntax.c
@@ -3524,7 +3524,7 @@ static void put_pattern(const char *const s, const int c, const synpat_T *const
   msg_putchar(c);
 
   // output the pattern, in between a char that is not in the pattern
-  for (i = 0; vim_strchr(spp->sp_pattern, sepchars[i]) != NULL;) {
+  for (i = 0; vim_strchr(spp->sp_pattern, (uint8_t)sepchars[i]) != NULL;) {
     if (sepchars[++i] == NUL) {
       i = 0;            // no good char found, just use the first one
       break;
@@ -4000,7 +4000,7 @@ static void syn_cmd_include(exarg_T *eap, int syncing)
   // filename to include.
   eap->argt |= (EX_XFILE | EX_NOSPC);
   separate_nextcmd(eap);
-  if (*eap->arg == '<' || *eap->arg == '$' || path_is_absolute((char_u *)eap->arg)) {
+  if (*eap->arg == '<' || *eap->arg == '$' || path_is_absolute(eap->arg)) {
     // For an absolute path, "$VIM/..." or "<sfile>.." we ":source" the
     // file.  Need to expand the file name first.  In other cases
     // ":runtime!" is used.
diff --git a/src/nvim/tag.c b/src/nvim/tag.c
index 73aa6eb9ca..75a2849fbd 100644
--- a/src/nvim/tag.c
+++ b/src/nvim/tag.c
@@ -1019,7 +1019,7 @@ static int add_llist_tags(char *tag, int num_matches, char **matches)
     // Get the line number or the search pattern used to locate
     // the tag.
     lnum = 0;
-    if (isdigit(*tagp.command)) {
+    if (isdigit((uint8_t)(*tagp.command))) {
       // Line number is used to locate the tag
       lnum = atol(tagp.command);
     } else {
@@ -1199,7 +1199,7 @@ static void prepare_pats(pat_T *pats, int has_re)
     } else {
       for (pats->headlen = 0; pats->head[pats->headlen] != NUL; pats->headlen++) {
         if (vim_strchr(magic_isset() ? ".[~*\\$" : "\\$",
-                       pats->head[pats->headlen]) != NULL) {
+                       (uint8_t)pats->head[pats->headlen]) != NULL) {
           break;
         }
       }
diff --git a/src/nvim/testing.c b/src/nvim/testing.c
index edb24c6dc5..e9bad2a0b3 100644
--- a/src/nvim/testing.c
+++ b/src/nvim/testing.c
@@ -119,10 +119,10 @@ static void ga_concat_shorten_esc(garray_T *gap, const char_u *str)
 
   for (const char_u *p = str; *p != NUL; p++) {
     int same_len = 1;
-    const char_u *s = p;
+    const char *s = (char *)p;
     const int c = mb_ptr2char_adv(&s);
-    const int clen = (int)(s - p);
-    while (*s != NUL && c == utf_ptr2char((char *)s)) {
+    const int clen = (int)((char_u *)s - p);
+    while (*s != NUL && c == utf_ptr2char(s)) {
       same_len++;
       s += clen;
     }
@@ -133,7 +133,7 @@ static void ga_concat_shorten_esc(garray_T *gap, const char_u *str)
       vim_snprintf((char *)buf, NUMBUFLEN, "%d", same_len);
       ga_concat(gap, (char *)buf);
       ga_concat(gap, " times]");
-      p = s - 1;
+      p = (char_u *)s - 1;
     } else {
       ga_concat_esc(gap, p, clen);
     }
diff --git a/src/nvim/undo.c b/src/nvim/undo.c
index 85e261fc39..3e4aae62c9 100644
--- a/src/nvim/undo.c
+++ b/src/nvim/undo.c
@@ -1359,7 +1359,7 @@ theend:
 /// a bit more verbose.
 /// Otherwise use curbuf->b_ffname to generate the undo file name.
 /// "hash[UNDO_HASH_SIZE]" must be the hash value of the buffer text.
-void u_read_undo(char *name, const char_u *hash, const char_u *orig_name FUNC_ATTR_UNUSED)
+void u_read_undo(char *name, const char_u *hash, const char *orig_name FUNC_ATTR_UNUSED)
   FUNC_ATTR_NONNULL_ARG(2)
 {
   u_header_T **uhp_table = NULL;
@@ -1377,7 +1377,7 @@ void u_read_undo(char *name, const char_u *hash, const char_u *orig_name FUNC_AT
     // owner of the text file or equal to the current user.
     FileInfo file_info_orig;
     FileInfo file_info_undo;
-    if (os_fileinfo((const char *)orig_name, &file_info_orig)
+    if (os_fileinfo(orig_name, &file_info_orig)
         && os_fileinfo(file_name, &file_info_undo)
         && file_info_orig.stat.st_uid != file_info_undo.stat.st_uid
         && file_info_undo.stat.st_uid != getuid()) {
diff --git a/src/nvim/usercmd.c b/src/nvim/usercmd.c
index 9c4fdd4ead..a8e4603aa2 100644
--- a/src/nvim/usercmd.c
+++ b/src/nvim/usercmd.c
@@ -1424,7 +1424,7 @@ static size_t uc_check_code(char *code, size_t len, char *buf, ucmd_T *cmd, exar
     ct_NONE,
   } type = ct_NONE;
 
-  if ((vim_strchr("qQfF", *p) != NULL) && p[1] == '-') {
+  if ((vim_strchr("qQfF", (uint8_t)(*p)) != NULL) && p[1] == '-') {
     quote = (*p == 'q' || *p == 'Q') ? 1 : 2;
     p += 2;
     l -= 2;
diff --git a/src/nvim/window.c b/src/nvim/window.c
index 627d418a55..f16e9b8436 100644
--- a/src/nvim/window.c
+++ b/src/nvim/window.c
@@ -6767,7 +6767,7 @@ char_u *grab_file_name(long count, linenr_T *file_lnum)
       return NULL;
     }
     // Only recognize ":123" here
-    if (file_lnum != NULL && ptr[len] == ':' && isdigit(ptr[len + 1])) {
+    if (file_lnum != NULL && ptr[len] == ':' && isdigit((uint8_t)ptr[len + 1])) {
       char *p = ptr + len + 1;
 
       *file_lnum = (linenr_T)getdigits_long(&p, false, 0);
@@ -6790,8 +6790,8 @@ char_u *grab_file_name(long count, linenr_T *file_lnum)
 // FNAME_INCL       apply "includeexpr"
 char_u *file_name_at_cursor(int options, long count, linenr_T *file_lnum)
 {
-  return file_name_in_line((char_u *)get_cursor_line_ptr(),
-                           curwin->w_cursor.col, options, count, (char_u *)curbuf->b_ffname,
+  return file_name_in_line(get_cursor_line_ptr(),
+                           curwin->w_cursor.col, options, count, curbuf->b_ffname,
                            file_lnum);
 }
 
@@ -6799,11 +6799,11 @@ char_u *file_name_at_cursor(int options, long count, linenr_T *file_lnum)
 /// @param file_lnum  line number after the file name
 ///
 /// @return  the name of the file under or after ptr[col]. Otherwise like file_name_at_cursor().
-char_u *file_name_in_line(char_u *line, int col, int options, long count, char_u *rel_fname,
+char_u *file_name_in_line(char *line, int col, int options, long count, char *rel_fname,
                           linenr_T *file_lnum)
 {
   // search forward for what could be the start of a file name
-  char *ptr = (char *)line + col;
+  char *ptr = line + col;
   while (*ptr != NUL && !vim_isfilec((uint8_t)(*ptr))) {
     MB_PTR_ADV(ptr);
   }
@@ -6820,8 +6820,8 @@ char_u *file_name_in_line(char_u *line, int col, int options, long count, char_u
 
   // Search backward for first char of the file name.
   // Go one char back to ":" before "//" even when ':' is not in 'isfname'.
-  while ((char_u *)ptr > line) {
-    if ((len = (size_t)(utf_head_off((char *)line, ptr - 1))) > 0) {
+  while (ptr > line) {
+    if ((len = (size_t)(utf_head_off(line, ptr - 1))) > 0) {
       ptr -= len + 1;
     } else if (vim_isfilec((uint8_t)ptr[-1])
                || ((options & FNAME_HYP) && path_is_url(ptr - 1))) {
@@ -6836,7 +6836,7 @@ char_u *file_name_in_line(char_u *line, int col, int options, long count, char_u
   len = 0;
   while (vim_isfilec((uint8_t)ptr[len]) || (ptr[len] == '\\' && ptr[len + 1] == ' ')
          || ((options & FNAME_HYP) && path_is_url(ptr + len))
-         || (is_url && vim_strchr(":?&=", ptr[len]) != NULL)) {
+         || (is_url && vim_strchr(":?&=", (uint8_t)ptr[len]) != NULL)) {
     // After type:// we also include :, ?, & and = as valid characters, so that
     // http://google.com:8080?q=this&that=ok works.
     if ((ptr[len] >= 'A' && ptr[len] <= 'Z')
@@ -6857,7 +6857,7 @@ char_u *file_name_in_line(char_u *line, int col, int options, long count, char_u
 
   // If there is trailing punctuation, remove it.
   // But don't remove "..", could be a directory name.
-  if (len > 2 && vim_strchr(".,:;!", ptr[len - 1]) != NULL
+  if (len > 2 && vim_strchr(".,:;!", (uint8_t)ptr[len - 1]) != NULL
       && ptr[len - 2] != '.') {
     len--;
   }
@@ -6878,17 +6878,17 @@ char_u *file_name_in_line(char_u *line, int col, int options, long count, char_u
       p = skipwhite(p);
     }
     if (*p != NUL) {
-      if (!isdigit(*p)) {
+      if (!isdigit((uint8_t)(*p))) {
         p++;                        // skip the separator
       }
       p = skipwhite(p);
-      if (isdigit(*p)) {
+      if (isdigit((uint8_t)(*p))) {
         *file_lnum = (linenr_T)getdigits_long(&p, false, 0);
       }
     }
   }
 
-  return (char_u *)find_file_name_in_path(ptr, len, options, count, (char *)rel_fname);
+  return (char_u *)find_file_name_in_path(ptr, len, options, count, rel_fname);
 }
 
 /// Add or remove a status line from window(s), according to the