refactor: replace char_u with char or uint8_t (#22400)

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

17 files changed, 212 insertions, 206 deletions

diff --git a/src/nvim/digraph.c b/src/nvim/digraph.c
index a057978a5e..ae13164191 100644
--- a/src/nvim/digraph.c
+++ b/src/nvim/digraph.c
@@ -41,8 +41,8 @@
 typedef int result_T;
 
 typedef struct digraph {
-  char_u char1;
-  char_u char2;
+  uint8_t char1;
+  uint8_t char2;
   result_T result;
 } digr_T;
 
@@ -1493,7 +1493,7 @@ char *get_digraph_for_char(int val_arg)
 {
   const int val = val_arg;
   const digr_T *dp;
-  static char_u r[3];
+  static char r[3];
 
   for (int use_defaults = 0; use_defaults <= 1; use_defaults++) {
     if (use_defaults == 0) {
@@ -1503,10 +1503,10 @@ char *get_digraph_for_char(int val_arg)
     }
     for (int i = 0; use_defaults ? dp->char1 != NUL : i < user_digraphs.ga_len; i++) {
       if (dp->result == val) {
-        r[0] = dp->char1;
-        r[1] = dp->char2;
+        r[0] = (char)dp->char1;
+        r[1] = (char)dp->char2;
         r[2] = NUL;
-        return (char *)r;
+        return r;
       }
       dp++;
     }
@@ -1645,8 +1645,8 @@ static void registerdigraph(int char1, int char2, int n)
 
   // Add a new digraph to the table.
   dp = GA_APPEND_VIA_PTR(digr_T, &user_digraphs);
-  dp->char1 = (char_u)char1;
-  dp->char2 = (char_u)char2;
+  dp->char1 = (uint8_t)char1;
+  dp->char2 = (uint8_t)char2;
   dp->result = n;
 }
 
diff --git a/src/nvim/edit.c b/src/nvim/edit.c
index 2849268da2..9eb4802d97 100644
--- a/src/nvim/edit.c
+++ b/src/nvim/edit.c
@@ -2780,7 +2780,7 @@ static bool echeck_abbr(int c)
 // that the NL replaced.  The extra one stores the characters after the cursor
 // that were deleted (always white space).
 
-static char_u *replace_stack = NULL;
+static uint8_t *replace_stack = NULL;
 static ssize_t replace_stack_nr = 0;           // next entry in replace stack
 static ssize_t replace_stack_len = 0;          // max. number of entries
 
@@ -2801,11 +2801,11 @@ void replace_push(int c)
     replace_stack_len += 50;
     replace_stack = xrealloc(replace_stack, (size_t)replace_stack_len);
   }
-  char_u *p = replace_stack + replace_stack_nr - replace_offset;
+  uint8_t *p = replace_stack + replace_stack_nr - replace_offset;
   if (replace_offset) {
     memmove(p + 1, p, (size_t)replace_offset);
   }
-  *p = (char_u)c;
+  *p = (uint8_t)c;
   replace_stack_nr++;
 }
 
@@ -2868,13 +2868,13 @@ static void replace_pop_ins(void)
 static void mb_replace_pop_ins(int cc)
 {
   int n;
-  char_u buf[MB_MAXBYTES + 1];
+  uint8_t buf[MB_MAXBYTES + 1];
   int i;
 
   if ((n = MB_BYTE2LEN(cc)) > 1) {
-    buf[0] = (char_u)cc;
+    buf[0] = (uint8_t)cc;
     for (i = 1; i < n; i++) {
-      buf[i] = (char_u)replace_pop();
+      buf[i] = (uint8_t)replace_pop();
     }
     ins_bytes_len((char *)buf, (size_t)n);
   } else {
@@ -2893,10 +2893,10 @@ static void mb_replace_pop_ins(int cc)
       break;
     }
 
-    buf[0] = (char_u)c;
+    buf[0] = (uint8_t)c;
     assert(n > 1);
     for (i = 1; i < n; i++) {
-      buf[i] = (char_u)replace_pop();
+      buf[i] = (uint8_t)replace_pop();
     }
     if (utf_iscomposing(utf_ptr2char((char *)buf))) {
       ins_bytes_len((char *)buf, (size_t)n);
@@ -3113,7 +3113,7 @@ bool in_cinkeys(int keytyped, int when, bool line_is_empty)
           return true;
         }
 
-        if (keytyped == get_special_key_code((char_u *)look + 1)) {
+        if (keytyped == get_special_key_code(look + 1)) {
           return true;
         }
       }
diff --git a/src/nvim/eval.c b/src/nvim/eval.c
index da2a88346a..67fede1aea 100644
--- a/src/nvim/eval.c
+++ b/src/nvim/eval.c
@@ -1185,7 +1185,7 @@ int eval_foldexpr(char *arg, int *cp)
       // the number.
       char *s = tv.vval.v_string;
       if (!ascii_isdigit(*s) && *s != '-') {
-        *cp = (char_u)(*s++);
+        *cp = (uint8_t)(*s++);
       }
       retval = atol(s);
     }
@@ -1597,7 +1597,7 @@ void set_var_lval(lval_T *lp, char *endp, typval_T *rettv, int copy, const bool
   dictitem_T *di;
 
   if (lp->ll_tv == NULL) {
-    cc = (char_u)(*endp);
+    cc = (uint8_t)(*endp);
     *endp = NUL;
     if (lp->ll_blob != NULL) {
       if (op != NULL && *op != '=') {
@@ -1993,7 +1993,7 @@ void set_context_for_expression(expand_T *xp, char *arg, cmdidx_T cmdidx)
     }
     arg = xp->xp_pattern;
     if (*arg != NUL) {
-      while ((c = (char_u)(*++arg)) != NUL && (c == ' ' || c == '\t')) {}
+      while ((c = (uint8_t)(*++arg)) != NUL && (c == ' ' || c == '\t')) {}
     }
   }
 
@@ -2602,7 +2602,7 @@ static int eval5(char **arg, typval_T *rettv, int evaluate)
 
   // Repeat computing, until no '+', '-' or '.' is following.
   for (;;) {
-    int op = (char_u)(**arg);
+    int op = (uint8_t)(**arg);
     if (op != '+' && op != '-' && op != '.') {
       break;
     }
@@ -2747,7 +2747,7 @@ static int eval6(char **arg, typval_T *rettv, int evaluate, int want_string)
 
   // Repeat computing, until no '*', '/' or '%' is following.
   for (;;) {
-    op = (char_u)(**arg);
+    op = (uint8_t)(**arg);
     if (op != '*' && op != '/' && op != '%') {
       break;
     }
@@ -7441,9 +7441,9 @@ void ex_execute(exarg_T *eap)
       const size_t len = strlen(argstr);
       ga_grow(&ga, (int)len + 2);
       if (!GA_EMPTY(&ga)) {
-        ((char_u *)(ga.ga_data))[ga.ga_len++] = ' ';
+        ((char *)(ga.ga_data))[ga.ga_len++] = ' ';
       }
-      memcpy((char_u *)(ga.ga_data) + ga.ga_len, argstr, len + 1);
+      memcpy((char *)(ga.ga_data) + ga.ga_len, argstr, len + 1);
       if (eap->cmdidx != CMD_execute) {
         xfree((void *)argstr);
       }
@@ -7838,7 +7838,7 @@ repeat:
   // ":~" - path relative to the home directory
   // ":8" - shortname path - postponed till after
   while (src[*usedlen] == ':'
-         && ((c = (char_u)src[*usedlen + 1]) == '.' || c == '~' || c == '8')) {
+         && ((c = (uint8_t)src[*usedlen + 1]) == '.' || c == '~' || c == '8')) {
     *usedlen += 2;
     if (c == '8') {
       continue;
@@ -8084,7 +8084,7 @@ char *do_string_sub(char *str, char *pat, char *sub, typval_T *expr, const char
         if (zero_width == regmatch.startp[0]) {
           // avoid getting stuck on a match with an empty string
           int i = utfc_ptr2len(tail);
-          memmove((char_u *)ga.ga_data + ga.ga_len, tail, (size_t)i);
+          memmove((char *)ga.ga_data + ga.ga_len, tail, (size_t)i);
           ga.ga_len += i;
           tail += i;
           continue;
@@ -8103,7 +8103,7 @@ char *do_string_sub(char *str, char *pat, char *sub, typval_T *expr, const char
 
       // copy the text up to where the match is
       int i = (int)(regmatch.startp[0] - tail);
-      memmove((char_u *)ga.ga_data + ga.ga_len, tail, (size_t)i);
+      memmove((char *)ga.ga_data + ga.ga_len, tail, (size_t)i);
       // add the substituted text
       (void)vim_regsub(&regmatch, sub, expr,
                        (char *)ga.ga_data + ga.ga_len + i, sublen,
diff --git a/src/nvim/fileio.c b/src/nvim/fileio.c
index c93df43cff..6a13548027 100644
--- a/src/nvim/fileio.c
+++ b/src/nvim/fileio.c
@@ -107,19 +107,19 @@ enum {
 
 // Structure to pass arguments from buf_write() to buf_write_bytes().
 struct bw_info {
-  int bw_fd;                     // file descriptor
-  char *bw_buf;                  // buffer with data to be written
-  int bw_len;                    // length of data
-  int bw_flags;                  // FIO_ flags
-  char_u bw_rest[CONV_RESTLEN];  // not converted bytes
-  int bw_restlen;                // nr of bytes in bw_rest[]
-  int bw_first;                  // first write call
-  char *bw_conv_buf;             // buffer for writing converted chars
-  size_t bw_conv_buflen;         // size of bw_conv_buf
-  int bw_conv_error;             // set for conversion error
-  linenr_T bw_conv_error_lnum;   // first line with error or zero
-  linenr_T bw_start_lnum;        // line number at start of buffer
-  iconv_t bw_iconv_fd;           // descriptor for iconv() or -1
+  int bw_fd;                      // file descriptor
+  char *bw_buf;                   // buffer with data to be written
+  int bw_len;                     // length of data
+  int bw_flags;                   // FIO_ flags
+  uint8_t bw_rest[CONV_RESTLEN];  // not converted bytes
+  int bw_restlen;                 // nr of bytes in bw_rest[]
+  int bw_first;                   // first write call
+  char *bw_conv_buf;              // buffer for writing converted chars
+  size_t bw_conv_buflen;          // size of bw_conv_buf
+  int bw_conv_error;              // set for conversion error
+  linenr_T bw_conv_error_lnum;    // first line with error or zero
+  linenr_T bw_start_lnum;         // line number at start of buffer
+  iconv_t bw_iconv_fd;            // descriptor for iconv() or -1
 };
 
 typedef struct {
@@ -989,7 +989,7 @@ retry:
             int ni;
             long tlen = 0;
             for (;;) {
-              p = (char_u *)ml_get(read_buf_lnum) + read_buf_col;
+              p = (uint8_t *)ml_get(read_buf_lnum) + read_buf_col;
               int n = (int)strlen((char *)p);
               if ((int)tlen + n + 1 > size) {
                 // Filled up to "size", append partial line.
@@ -1798,7 +1798,7 @@ failed:
       msg_scrolled_ign = true;
 
       if (!read_stdin && !read_buffer) {
-        p = (char_u *)msg_trunc_attr(IObuff, false, 0);
+        p = (uint8_t *)msg_trunc_attr(IObuff, false, 0);
       }
 
       if (read_stdin || read_buffer || restart_edit != 0
@@ -1859,7 +1859,7 @@ failed:
 
   // When opening a new file locate undo info and read it.
   if (read_undo_file) {
-    char_u hash[UNDO_HASH_SIZE];
+    uint8_t hash[UNDO_HASH_SIZE];
 
     sha256_finish(&sha_ctx, hash);
     u_read_undo(NULL, hash, fname);
@@ -3208,7 +3208,7 @@ restore_backup:
     // Skip the BOM when appending and the file already existed, the BOM
     // only makes sense at the start of the file.
     if (buf->b_p_bomb && !write_bin && (!append || perm < 0)) {
-      write_info.bw_len = make_bom((char_u *)buffer, fenc);
+      write_info.bw_len = make_bom(buffer, fenc);
       if (write_info.bw_len > 0) {
         // don't convert
         write_info.bw_flags = FIO_NOCONVERT | wb_flags;
@@ -3991,9 +3991,10 @@ static int buf_write_bytes(struct bw_info *ip)
 /// @param flags FIO_ flags that specify which encoding to use
 ///
 /// @return true for an error, false when it's OK.
-static bool ucs2bytes(unsigned c, char **pp, int flags) FUNC_ATTR_NONNULL_ALL
+static bool ucs2bytes(unsigned c, char **pp, int flags)
+  FUNC_ATTR_NONNULL_ALL
 {
-  char_u *p = (char_u *)(*pp);
+  uint8_t *p = (uint8_t *)(*pp);
   bool error = false;
 
   if (flags & FIO_UCS4) {
@@ -4170,8 +4171,9 @@ static char *check_for_bom(const char *p_in, int size, int *lenp, int flags)
 /// Generate a BOM in "buf[4]" for encoding "name".
 ///
 /// @return  the length of the BOM (zero when no BOM).
-static int make_bom(char_u *buf, char *name)
+static int make_bom(char *buf_in, char *name)
 {
+  uint8_t *buf = (uint8_t *)buf_in;
   int flags = get_fio_flags(name);
 
   // Can't put a BOM in a non-Unicode file.
@@ -4187,7 +4189,7 @@ static int make_bom(char_u *buf, char *name)
   }
   char *p = (char *)buf;
   (void)ucs2bytes(0xfeff, &p, flags);
-  return (int)((char_u *)p - buf);
+  return (int)((uint8_t *)p - buf);
 }
 
 /// Shorten filename of a buffer.
@@ -4953,7 +4955,7 @@ int buf_check_timestamp(buf_T *buf)
     // Reload the buffer.
     buf_reload(buf, orig_mode, reload == RELOAD_DETECT);
     if (buf->b_p_udf && buf->b_ffname != NULL) {
-      char_u hash[UNDO_HASH_SIZE];
+      uint8_t hash[UNDO_HASH_SIZE];
 
       // Any existing undo file is unusable, write it now.
       u_compute_hash(buf, hash);
diff --git a/src/nvim/grid_defs.h b/src/nvim/grid_defs.h
index db31f7b984..830c74e86d 100644
--- a/src/nvim/grid_defs.h
+++ b/src/nvim/grid_defs.h
@@ -50,7 +50,7 @@ struct ScreenGrid {
   schar_T *chars;
   sattr_T *attrs;
   size_t *line_offset;
-  char_u *line_wraps;
+  char *line_wraps;
 
   // last column that was drawn (not cleared with the default background).
   // only used when "throttled" is set. Not allocated by grid_alloc!
diff --git a/src/nvim/help.c b/src/nvim/help.c
index 5fa48e0cee..968f0bc2f4 100644
--- a/src/nvim/help.c
+++ b/src/nvim/help.c
@@ -1022,7 +1022,7 @@ static void helptags_one(char *dir, const char *ext, const char *tagfname, bool
           *p2 = NUL;
           vim_snprintf(NameBuff, MAXPATHL,
                        _("E154: Duplicate tag \"%s\" in file %s/%s"),
-                       ((char_u **)ga.ga_data)[i], dir, p2 + 1);
+                       ((char **)ga.ga_data)[i], dir, p2 + 1);
           emsg(NameBuff);
           *p2 = '\t';
           break;
diff --git a/src/nvim/keycodes.c b/src/nvim/keycodes.c
index 8114efc10c..404087fec3 100644
--- a/src/nvim/keycodes.c
+++ b/src/nvim/keycodes.c
@@ -723,7 +723,7 @@ int find_special_key(const char **const srcp, const size_t src_len, int *const m
         if (modifiers != 0 && last_dash[l + 1] == '>') {
           key = utf_ptr2char(last_dash + off);
         } else {
-          key = get_special_key_code((char_u *)last_dash + off);
+          key = get_special_key_code(last_dash + off);
           if (!(flags & FSK_KEEP_X_KEY)) {
             key = handle_x_keys(key);
           }
@@ -822,18 +822,18 @@ int find_special_key_in_table(int c)
 ///                   a termcap name.
 ///
 /// @return Key code or 0 if not found.
-int get_special_key_code(const char_u *name)
+int get_special_key_code(const char *name)
   FUNC_ATTR_NONNULL_ALL FUNC_ATTR_PURE FUNC_ATTR_WARN_UNUSED_RESULT
 {
   for (int i = 0; key_names_table[i].name != NULL; i++) {
     const char *const table_name = key_names_table[i].name;
     int j;
-    for (j = 0; ascii_isident(name[j]) && table_name[j] != NUL; j++) {
-      if (TOLOWER_ASC(table_name[j]) != TOLOWER_ASC(name[j])) {
+    for (j = 0; ascii_isident((uint8_t)name[j]) && table_name[j] != NUL; j++) {
+      if (TOLOWER_ASC(table_name[j]) != TOLOWER_ASC((uint8_t)name[j])) {
         break;
       }
     }
-    if (!ascii_isident(name[j]) && table_name[j] == NUL) {
+    if (!ascii_isident((uint8_t)name[j]) && table_name[j] == NUL) {
       return key_names_table[i].key;
     }
   }
diff --git a/src/nvim/mapping.c b/src/nvim/mapping.c
index 60524b9fb7..3c4ce0ee2b 100644
--- a/src/nvim/mapping.c
+++ b/src/nvim/mapping.c
@@ -1162,8 +1162,9 @@ static bool expand_buffer = false;
 /// @param cpo_flags  Value of various flags present in &cpo
 ///
 /// @return  NULL when there is a problem.
-static char *translate_mapping(char_u *str, int cpo_flags)
+static char *translate_mapping(char *str_in, int cpo_flags)
 {
+  uint8_t *str = (uint8_t *)str_in;
   garray_T ga;
   ga_init(&ga, 1, 40);
 
@@ -1346,7 +1347,7 @@ int ExpandMappings(char *pat, regmatch_T *regmatch, int *numMatches, char ***mat
         continue;
       }
 
-      char *p = translate_mapping((char_u *)mp->m_keys, CPO_TO_CPO_FLAGS);
+      char *p = translate_mapping(mp->m_keys, CPO_TO_CPO_FLAGS);
       if (p == NULL) {
         continue;
       }
diff --git a/src/nvim/mbyte.c b/src/nvim/mbyte.c
index d8be4f4997..35af7479b0 100644
--- a/src/nvim/mbyte.c
+++ b/src/nvim/mbyte.c
@@ -1930,16 +1930,16 @@ theend:
 
 /// @return  true if string "s" is a valid utf-8 string.
 /// When "end" is NULL stop at the first NUL.  Otherwise stop at "end".
-bool utf_valid_string(const char_u *s, const char_u *end)
+bool utf_valid_string(const char *s, const char *end)
 {
-  const char_u *p = s;
+  const uint8_t *p = (uint8_t *)s;
 
-  while (end == NULL ? *p != NUL : p < end) {
+  while (end == NULL ? *p != NUL : p < (uint8_t *)end) {
     int l = utf8len_tab_zero[*p];
     if (l == 0) {
       return false;  // invalid lead byte
     }
-    if (end != NULL && p + l > end) {
+    if (end != NULL && p + l > (uint8_t *)end) {
       return false;  // incomplete byte sequence
     }
     p++;
@@ -2454,8 +2454,8 @@ char *string_convert(const vimconv_T *const vcp, char *ptr, size_t *lenp)
 // set to the number of remaining bytes.
 char *string_convert_ext(const vimconv_T *const vcp, char *ptr, size_t *lenp, size_t *unconvlenp)
 {
-  char_u *retval = NULL;
-  char_u *d;
+  uint8_t *retval = NULL;
+  uint8_t *d;
   int c;
 
   size_t len;
@@ -2475,10 +2475,10 @@ char *string_convert_ext(const vimconv_T *const vcp, char *ptr, size_t *lenp, si
     for (size_t i = 0; i < len; i++) {
       c = (uint8_t)ptr[i];
       if (c < 0x80) {
-        *d++ = (char_u)c;
+        *d++ = (uint8_t)c;
       } else {
-        *d++ = (char_u)(0xc0 + (char_u)((unsigned)c >> 6));
-        *d++ = (char_u)(0x80 + (c & 0x3f));
+        *d++ = (uint8_t)(0xc0 + (uint8_t)((unsigned)c >> 6));
+        *d++ = (uint8_t)(0x80 + (c & 0x3f));
       }
     }
     *d = NUL;
@@ -2573,7 +2573,7 @@ char *string_convert_ext(const vimconv_T *const vcp, char *ptr, size_t *lenp, si
         }
         if (!utf_iscomposing(c)) {              // skip composing chars
           if (c < 0x100) {
-            *d++ = (char_u)c;
+            *d++ = (uint8_t)c;
           } else if (vcp->vc_fail) {
             xfree(retval);
             return NULL;
@@ -2594,7 +2594,7 @@ char *string_convert_ext(const vimconv_T *const vcp, char *ptr, size_t *lenp, si
     break;
 
   case CONV_ICONV:  // conversion with vcp->vc_fd
-    retval = (char_u *)iconv_string(vcp, ptr, len, unconvlenp, lenp);
+    retval = (uint8_t *)iconv_string(vcp, ptr, len, unconvlenp, lenp);
     break;
   }
 
diff --git a/src/nvim/memline.c b/src/nvim/memline.c
index e9988eb844..0d8da68a02 100644
--- a/src/nvim/memline.c
+++ b/src/nvim/memline.c
@@ -179,19 +179,19 @@ enum {
 // different machines. b0_magic_* is used to check the byte order and size of
 // variables, because the rest of the swap file is not portable.
 struct block0 {
-  char_u b0_id[2];                   ///< ID for block 0: BLOCK0_ID0 and BLOCK0_ID1.
+  char b0_id[2];                     ///< ID for block 0: BLOCK0_ID0 and BLOCK0_ID1.
   char b0_version[10];               // Vim version string
-  char_u b0_page_size[4];            // number of bytes per page
-  char_u b0_mtime[4];                // last modification time of file
-  char_u b0_ino[4];                  // inode of b0_fname
-  char_u b0_pid[4];                  // process id of creator (or 0)
+  char b0_page_size[4];              // number of bytes per page
+  char b0_mtime[4];                  // last modification time of file
+  char b0_ino[4];                    // inode of b0_fname
+  char b0_pid[4];                    // process id of creator (or 0)
   char b0_uname[B0_UNAME_SIZE];      // name of user (uid if no name)
   char b0_hname[B0_HNAME_SIZE];      // host name (if it has a name)
   char b0_fname[B0_FNAME_SIZE_ORG];  // name of file being edited
   long b0_magic_long;                // check for byte order of long
   int b0_magic_int;                  // check for byte order of int
   int16_t b0_magic_short;            // check for byte order of short
-  char_u b0_magic_char;              // check for last char
+  char b0_magic_char;                // check for last char
 };
 
 // Note: b0_dirty and b0_flags are put at the end of the file name.  For very
@@ -3556,19 +3556,21 @@ static bool fnamecmp_ino(char *fname_c, char *fname_s, long ino_block0)
 
 /// Move a long integer into a four byte character array.
 /// Used for machine independency in block zero.
-static void long_to_char(long n, char_u *s)
+static void long_to_char(long n, char *s_in)
 {
-  s[0] = (char_u)(n & 0xff);
+  uint8_t *s= (uint8_t *)s_in;
+  s[0] = (uint8_t)(n & 0xff);
   n = (unsigned)n >> 8;
-  s[1] = (char_u)(n & 0xff);
+  s[1] = (uint8_t)(n & 0xff);
   n = (unsigned)n >> 8;
-  s[2] = (char_u)(n & 0xff);
+  s[2] = (uint8_t)(n & 0xff);
   n = (unsigned)n >> 8;
-  s[3] = (char_u)(n & 0xff);
+  s[3] = (uint8_t)(n & 0xff);
 }
 
-static long char_to_long(const char_u *s)
+static long char_to_long(const char *s_in)
 {
+  const uint8_t *s = (uint8_t *)s_in;
   long retval;
 
   retval = s[3];
diff --git a/src/nvim/ops.c b/src/nvim/ops.c
index d2a96be5ad..884eeef433 100644
--- a/src/nvim/ops.c
+++ b/src/nvim/ops.c
@@ -1186,7 +1186,7 @@ int do_execreg(int regname, int colon, int addcr, int silent)
 /// used only after other typeahead has been processed.
 static void put_reedit_in_typebuf(int silent)
 {
-  char_u buf[3];
+  uint8_t buf[3];
 
   if (restart_edit == NUL) {
     return;
@@ -1197,7 +1197,7 @@ static void put_reedit_in_typebuf(int silent)
     buf[1] = 'R';
     buf[2] = NUL;
   } else {
-    buf[0] = (char_u)(restart_edit == 'I' ? 'i' : restart_edit);
+    buf[0] = (uint8_t)(restart_edit == 'I' ? 'i' : restart_edit);
     buf[1] = NUL;
   }
   if (ins_typebuf((char *)buf, REMAP_NONE, 0, true, silent) == OK) {
diff --git a/src/nvim/option.c b/src/nvim/option.c
index 6ddc3b5cfb..04cf7eede4 100644
--- a/src/nvim/option.c
+++ b/src/nvim/option.c
@@ -839,9 +839,8 @@ static void do_set_num(int opt_idx, int opt_flags, char **argp, int nextchar, co
 
 // Handle some special cases with string option values
 static void munge_string_opt_val(char **varp, char **oldval, char **const origval,
-                                 char_u **const origval_l, char_u **const origval_g,
-                                 char **const argp, char *const whichwrap, size_t whichwraplen,
-                                 char **const save_argp)
+                                 char **const origval_l, char **const origval_g, char **const argp,
+                                 char *const whichwrap, size_t whichwraplen, char **const save_argp)
 {
   // Set 'keywordprg' to ":help" if an empty
   // value was passed to :set by the user.
@@ -870,11 +869,11 @@ static void munge_string_opt_val(char **varp, char **oldval, char **const origva
     if (*origval == *oldval) {
       *origval = *varp;
     }
-    if (*origval_l == (char_u *)(*oldval)) {
-      *origval_l = *(char_u **)varp;
+    if (*origval_l == *oldval) {
+      *origval_l = *varp;
     }
-    if (*origval_g == (char_u *)(*oldval)) {
-      *origval_g = *(char_u **)varp;
+    if (*origval_g == *oldval) {
+      *origval_g = *varp;
     }
     *oldval = *varp;
   } else if (varp == &p_ww && ascii_isdigit(**argp)) {
@@ -919,8 +918,8 @@ static void do_set_string(int opt_idx, int opt_flags, char **argp, int nextchar,
   char *varp = varp_arg;
   char *save_arg = NULL;
   char *s = NULL;
-  char_u *origval_l = NULL;
-  char_u *origval_g = NULL;
+  char *origval_l = NULL;
+  char *origval_g = NULL;
   char whichwrap[80];
 
   // When using ":set opt=val" for a global option
@@ -935,12 +934,12 @@ static void do_set_string(int opt_idx, int opt_flags, char **argp, int nextchar,
   char *oldval = *(char **)varp;
 
   if ((opt_flags & (OPT_LOCAL | OPT_GLOBAL)) == 0) {
-    origval_l = *(char_u **)get_varp_scope(&(options[opt_idx]), OPT_LOCAL);
-    origval_g = *(char_u **)get_varp_scope(&(options[opt_idx]), OPT_GLOBAL);
+    origval_l = *(char **)get_varp_scope(&(options[opt_idx]), OPT_LOCAL);
+    origval_g = *(char **)get_varp_scope(&(options[opt_idx]), OPT_GLOBAL);
 
     // A global-local string option might have an empty option as value to
     // indicate that the global value should be used.
-    if (((int)options[opt_idx].indir & PV_BOTH) && origval_l == (char_u *)empty_option) {
+    if (((int)options[opt_idx].indir & PV_BOTH) && origval_l == empty_option) {
       origval_l = origval_g;
     }
   }
@@ -1132,8 +1131,8 @@ static void do_set_string(int opt_idx, int opt_flags, char **argp, int nextchar,
 
   // origval may be freed by did_set_string_option(), make a copy.
   char *saved_origval = (origval != NULL) ? xstrdup(origval) : NULL;
-  char *saved_origval_l = (origval_l != NULL) ? xstrdup((char *)origval_l) : NULL;
-  char *saved_origval_g = (origval_g != NULL) ? xstrdup((char *)origval_g) : NULL;
+  char *saved_origval_l = (origval_l != NULL) ? xstrdup(origval_l) : NULL;
+  char *saved_origval_g = (origval_g != NULL) ? xstrdup(origval_g) : NULL;
 
   // newval (and varp) may become invalid if the buffer is closed by
   // autocommands.
@@ -4672,7 +4671,7 @@ void set_context_in_set_cmd(expand_T *xp, char *arg, int opt_flags)
         return;
       }
     }
-    int key = get_special_key_code((char_u *)arg + 1);
+    int key = get_special_key_code(arg + 1);
     if (key == 0) {                 // unknown name
       xp->xp_context = EXPAND_NOTHING;
       return;
diff --git a/src/nvim/regexp_defs.h b/src/nvim/regexp_defs.h
index b27a5b5942..ef155e8d46 100644
--- a/src/nvim/regexp_defs.h
+++ b/src/nvim/regexp_defs.h
@@ -98,11 +98,11 @@ typedef struct {
   bool re_in_use;
 
   int regstart;
-  char_u reganch;
-  char_u *regmust;
+  uint8_t reganch;
+  uint8_t *regmust;
   int regmlen;
-  char_u reghasz;
-  char_u program[];
+  uint8_t reghasz;
+  uint8_t program[];
 } bt_regprog_T;
 
 // Structure representing a NFA state.
@@ -130,7 +130,7 @@ typedef struct {
 
   int reganch;                          // pattern starts with ^
   int regstart;                         // char at start of pattern
-  char_u *match_text;      // plain text to match with
+  uint8_t *match_text;      // plain text to match with
 
   int has_zend;                         // pattern contains \ze
   int has_backref;                      // pattern contains \1 .. \9
@@ -158,19 +158,19 @@ typedef struct {
 // from 1 to zero the matches need to be freed.
 struct reg_extmatch {
   int16_t refcnt;
-  char_u *matches[NSUBEXP];
+  uint8_t *matches[NSUBEXP];
 };
 
 struct regengine {
   /// bt_regcomp or nfa_regcomp
-  regprog_T *(*regcomp)(char_u *, int);
+  regprog_T *(*regcomp)(uint8_t *, int);
   /// bt_regfree or nfa_regfree
   void (*regfree)(regprog_T *);
   /// bt_regexec_nl or nfa_regexec_nl
-  int (*regexec_nl)(regmatch_T *, char_u *, colnr_T, bool);
+  int (*regexec_nl)(regmatch_T *, uint8_t *, colnr_T, bool);
   /// bt_regexec_mult or nfa_regexec_mult
   long (*regexec_multi)(regmmatch_T *, win_T *, buf_T *, linenr_T, colnr_T, proftime_T *, int *);
-  // char_u *expr;
+  // uint8_t *expr;
 };
 
 // Flags used by vim_regsub() and vim_regsub_both()
diff --git a/src/nvim/spell.c b/src/nvim/spell.c
index 117a770e50..dbe8ad5763 100644
--- a/src/nvim/spell.c
+++ b/src/nvim/spell.c
@@ -737,7 +737,7 @@ static void find_word(matchinf_T *mip, int mode)
         // If the word ends the sequence of compound flags of the
         // words must match with one of the COMPOUNDRULE items and
         // the number of syllables must not be too large.
-        mip->mi_compflags[mip->mi_complen] = (char_u)((unsigned)flags >> 24);
+        mip->mi_compflags[mip->mi_complen] = (uint8_t)((unsigned)flags >> 24);
         mip->mi_compflags[mip->mi_complen + 1] = NUL;
         if (word_ends) {
           char fword[MAXWLEN] = { 0 };
@@ -2354,8 +2354,8 @@ void clear_spell_chartab(spelltab_T *sp)
   CLEAR_FIELD(sp->st_isu);
 
   for (int i = 0; i < 256; i++) {
-    sp->st_fold[i] = (char_u)i;
-    sp->st_upper[i] = (char_u)i;
+    sp->st_fold[i] = (uint8_t)i;
+    sp->st_upper[i] = (uint8_t)i;
   }
 
   // We include digits. A word shouldn't start with a digit, but handling
@@ -2366,11 +2366,11 @@ void clear_spell_chartab(spelltab_T *sp)
   for (int i = 'A'; i <= 'Z'; i++) {
     sp->st_isw[i] = true;
     sp->st_isu[i] = true;
-    sp->st_fold[i] = (char_u)(i + 0x20);
+    sp->st_fold[i] = (uint8_t)(i + 0x20);
   }
   for (int i = 'a'; i <= 'z'; i++) {
     sp->st_isw[i] = true;
-    sp->st_upper[i] = (char_u)(i - 0x20);
+    sp->st_upper[i] = (uint8_t)(i - 0x20);
   }
 }
 
@@ -2391,8 +2391,8 @@ void init_spell_chartab(void)
     // The folded/upper-cased value is different between latin1 and
     // utf8 for 0xb5, causing E763 for no good reason.  Use the latin1
     // value for utf-8 to avoid this.
-    spelltab.st_fold[i] = (f < 256) ? (char_u)f : (char_u)i;
-    spelltab.st_upper[i] = (u < 256) ? (char_u)u : (char_u)i;
+    spelltab.st_fold[i] = (f < 256) ? (uint8_t)f : (uint8_t)i;
+    spelltab.st_upper[i] = (u < 256) ? (uint8_t)u : (uint8_t)i;
   }
 }
 
diff --git a/src/nvim/spell_defs.h b/src/nvim/spell_defs.h
index 93cf335c3a..bda43a94d1 100644
--- a/src/nvim/spell_defs.h
+++ b/src/nvim/spell_defs.h
@@ -206,8 +206,8 @@ typedef struct langp_S {
 typedef struct {
   bool st_isw[256];           // flags: is word char
   bool st_isu[256];           // flags: is uppercase char
-  char_u st_fold[256];        // chars: folded case
-  char_u st_upper[256];       // chars: upper case
+  uint8_t st_fold[256];        // chars: folded case
+  uint8_t st_upper[256];       // chars: upper case
 } spelltab_T;
 
 // Use our own character-case definitions, because the current locale may
diff --git a/src/nvim/spellfile.c b/src/nvim/spellfile.c
index e9dd0a4d5e..bb2ef1a458 100644
--- a/src/nvim/spellfile.c
+++ b/src/nvim/spellfile.c
@@ -1079,7 +1079,7 @@ 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((char_u *)flags, flagslen, (char *)fol);
+    set_spell_charflags(flags, flagslen, (char *)fol);
   }
 
   xfree(flags);
@@ -1314,7 +1314,7 @@ static int read_words_section(FILE *fd, slang_T *lp, int len)
   int done = 0;
   int i;
   int c;
-  char_u word[MAXWLEN];
+  uint8_t word[MAXWLEN];
 
   while (done < len) {
     // Read one word at a time.
@@ -1323,7 +1323,7 @@ static int read_words_section(FILE *fd, slang_T *lp, int len)
       if (c == EOF) {
         return SP_TRUNCERROR;
       }
-      word[i] = (char_u)c;
+      word[i] = (uint8_t)c;
       if (word[i] == NUL) {
         break;
       }
@@ -1480,7 +1480,7 @@ static int read_compound(FILE *fd, slang_T *slang, int len)
     // Add all flags to "sl_compallflags".
     if (vim_strchr("?*+[]/", c) == NULL
         && !byte_in_str(slang->sl_compallflags, c)) {
-      *ap++ = (char_u)c;
+      *ap++ = (uint8_t)c;
       *ap = NUL;
     }
 
@@ -1493,7 +1493,7 @@ static int read_compound(FILE *fd, slang_T *slang, int len)
         atstart = 0;
       } else {
         if (!byte_in_str(slang->sl_compstartflags, c)) {
-          *cp++ = (char_u)c;
+          *cp++ = (uint8_t)c;
           *cp = NUL;
         }
         if (atstart == 1) {
@@ -1508,7 +1508,7 @@ static int read_compound(FILE *fd, slang_T *slang, int len)
         XFREE_CLEAR(slang->sl_comprules);
         crp = NULL;
       } else {
-        *crp++ = (char_u)c;
+        *crp++ = (uint8_t)c;
       }
     }
 
@@ -1709,7 +1709,7 @@ static int spell_read_tree(FILE *fd, char **bytsp, long *bytsp_len, idx_T **idxs
   *idxsp = ip;
 
   // Recursively read the tree and store it in the array.
-  idx = read_tree_node(fd, (char_u *)bp, ip, (int)len, 0, prefixtree, prefixcnt);
+  idx = read_tree_node(fd, bp, ip, (int)len, 0, prefixtree, prefixcnt);
   if (idx < 0) {
     return idx;
   }
@@ -1729,9 +1729,10 @@ static int spell_read_tree(FILE *fd, char **bytsp, long *bytsp_len, idx_T **idxs
 /// @param startidx  current index in "byts" and "idxs"
 /// @param prefixtree  true for reading PREFIXTREE
 /// @param maxprefcondnr  maximum for <prefcondnr>
-static idx_T read_tree_node(FILE *fd, char_u *byts, idx_T *idxs, int maxidx, idx_T startidx,
+static idx_T read_tree_node(FILE *fd, char *byts_in, idx_T *idxs, int maxidx, idx_T startidx,
                             bool prefixtree, int maxprefcondnr)
 {
+  uint8_t *byts = (uint8_t *)byts_in;
   int len;
   int n;
   idx_T idx = startidx;
@@ -1746,7 +1747,7 @@ static idx_T read_tree_node(FILE *fd, char_u *byts, idx_T *idxs, int maxidx, idx
   if (startidx + len >= maxidx) {
     return SP_FORMERROR;
   }
-  byts[idx++] = (char_u)len;
+  byts[idx++] = (uint8_t)len;
 
   // Read the byte values, flag/region bytes and shared indexes.
   for (int i = 1; i <= len; i++) {
@@ -1806,7 +1807,7 @@ static idx_T read_tree_node(FILE *fd, char_u *byts, idx_T *idxs, int maxidx, idx
         c = getc(fd);                                   // <xbyte>
       }
     }
-    byts[idx++] = (char_u)c;
+    byts[idx++] = (uint8_t)c;
   }
 
   // Recursively read the children for non-shared siblings.
@@ -1818,7 +1819,7 @@ static idx_T read_tree_node(FILE *fd, char_u *byts, idx_T *idxs, int maxidx, idx
         idxs[startidx + i] &= ~SHARED_MASK;
       } else {
         idxs[startidx + i] = idx;
-        idx = read_tree_node(fd, byts, idxs, maxidx, idx,
+        idx = read_tree_node(fd, (char *)byts, idxs, maxidx, idx,
                              prefixtree, maxprefcondnr);
         if (idx < 0) {
           break;
@@ -2783,11 +2784,11 @@ static void aff_process_flags(afffile_T *affile, affentry_T *entry)
   if (entry->ae_flags != NULL
       && (affile->af_compforbid != 0 || affile->af_comppermit != 0)) {
     for (p = entry->ae_flags; *p != NUL;) {
-      char_u *prevp = (char_u *)p;
+      char *prevp = p;
       unsigned flag = get_affitem(affile->af_flagtype, &p);
       if (flag == affile->af_comppermit || flag == affile->af_compforbid) {
         STRMOVE(prevp, p);
-        p = (char *)prevp;
+        p = prevp;
         if (flag == affile->af_comppermit) {
           entry->ae_comppermit = true;
         } else {
@@ -2894,12 +2895,12 @@ static void process_compflags(spellinfo_T *spin, afffile_T *aff, char *compflags
     STRCAT(p, "/");
   }
   spin->si_compflags = p;
-  char_u *tp = (char_u *)p + strlen(p);
+  uint8_t *tp = (uint8_t *)p + strlen(p);
 
   for (p = compflags; *p != NUL;) {
     if (vim_strchr("/?*+[]", (uint8_t)(*p)) != NULL) {
       // Copy non-flag characters directly.
-      *tp++ = (char_u)(*p++);
+      *tp++ = (uint8_t)(*p++);
     } else {
       // First get the flag number, also checks validity.
       prevp = p;
@@ -3640,7 +3641,7 @@ static int spell_read_wordfile(spellinfo_T *spin, char *fname)
   char rline[MAXLINELEN];
   char *line;
   char *pc = NULL;
-  char_u *p;
+  char *p;
   int l;
   int retval = OK;
   bool did_word = false;
@@ -3748,7 +3749,7 @@ static int spell_read_wordfile(spellinfo_T *spin, char *fname)
     regionmask = spin->si_region;
 
     // Check for flags and region after a slash.
-    p = (char_u *)vim_strchr(line, '/');
+    p = vim_strchr(line, '/');
     if (p != NULL) {
       *p++ = NUL;
       while (*p != NUL) {
@@ -3758,13 +3759,13 @@ static int spell_read_wordfile(spellinfo_T *spin, char *fname)
           flags |= WF_BANNED;
         } else if (*p == '?') {                  // Rare word.
           flags |= WF_RARE;
-        } else if (ascii_isdigit(*p)) {              // region number(s)
+        } else if (ascii_isdigit((uint8_t)(*p))) {              // region number(s)
           if ((flags & WF_REGION) == 0) {           // first one
             regionmask = 0;
           }
           flags |= WF_REGION;
 
-          l = *p - '0';
+          l = (uint8_t)(*p) - '0';
           if (l == 0 || l > spin->si_region_count) {
             smsg(_("Invalid region nr in %s line %ld: %s"),
                  fname, lnum, p);
@@ -3817,7 +3818,7 @@ static int spell_read_wordfile(spellinfo_T *spin, char *fname)
 static void *getroom(spellinfo_T *spin, size_t len, bool align)
   FUNC_ATTR_NONNULL_RET
 {
-  char_u *p;
+  char *p;
   sblock_T *bl = spin->si_blocks;
 
   assert(len <= SBLOCKSIZE);
@@ -3837,7 +3838,7 @@ static void *getroom(spellinfo_T *spin, size_t len, bool align)
     spin->si_blocks_cnt++;
   }
 
-  p = bl->sb_data + bl->sb_used;
+  p = (char *)bl->sb_data + bl->sb_used;
   bl->sb_used += (int)len;
 
   return p;
@@ -3876,7 +3877,7 @@ static wordnode_T *wordtree_alloc(spellinfo_T *spin)
 /// Control characters and trailing '/' are invalid.  Space is OK.
 static bool valid_spell_word(const char *word, const char *end)
 {
-  if (!utf_valid_string((char_u *)word, (char_u *)end)) {
+  if (!utf_valid_string(word, end)) {
     return false;
   }
   for (const char *p = word; *p != NUL && p < end; p += utfc_ptr2len(p)) {
@@ -3913,7 +3914,7 @@ static int store_word(spellinfo_T *spin, char *word, int flags, int region, cons
   }
 
   (void)spell_casefold(curwin, word, len, foldword, MAXWLEN);
-  for (const char_u *p = (char_u *)pfxlist; res == OK; p++) {
+  for (const char *p = pfxlist; res == OK; p++) {
     if (!need_affix || (p != NULL && *p != NUL)) {
       res = tree_add_word(spin, (char_u *)foldword, spin->si_foldroot, ct | flags,
                           region, p == NULL ? 0 : *p);
@@ -3925,7 +3926,7 @@ static int store_word(spellinfo_T *spin, char *word, int flags, int region, cons
   spin->si_foldwcount++;
 
   if (res == OK && (ct == WF_KEEPCAP || (flags & WF_KEEPCAP))) {
-    for (const char_u *p = (char_u *)pfxlist; res == OK; p++) {
+    for (const char *p = pfxlist; res == OK; p++) {
       if (!need_affix || (p != NULL && *p != NUL)) {
         res = tree_add_word(spin, (char_u *)word, spin->si_keeproot, flags,
                             region, p == NULL ? 0 : *p);
@@ -5727,8 +5728,9 @@ static void init_spellfile(void)
 /// Set the spell character tables from strings in the .spl file.
 ///
 /// @param cnt  length of "flags"
-static void set_spell_charflags(const char_u *flags, int cnt, char *fol)
+static void set_spell_charflags(const char *flags_in, int cnt, char *fol)
 {
+  const uint8_t *flags = (uint8_t *)flags_in;
   // We build the new tables here first, so that we can compare with the
   // previous one.
   spelltab_T new_st;
@@ -5745,9 +5747,9 @@ static void set_spell_charflags(const char_u *flags, int cnt, char *fol)
 
     if (*p != NUL) {
       c = mb_ptr2char_adv((const char **)&p);
-      new_st.st_fold[i + 128] = (char_u)c;
+      new_st.st_fold[i + 128] = (uint8_t)c;
       if (i + 128 != c && new_st.st_isu[i + 128] && c < 256) {
-        new_st.st_upper[c] = (char_u)(i + 128);
+        new_st.st_upper[c] = (uint8_t)(i + 128);
       }
     }
   }
diff --git a/src/nvim/spellsuggest.c b/src/nvim/spellsuggest.c
index ea2d5e6ff7..2823e74c2f 100644
--- a/src/nvim/spellsuggest.c
+++ b/src/nvim/spellsuggest.c
@@ -189,28 +189,28 @@ typedef enum {
 
 /// Struct to keep the state at each level in suggest_try_change().
 typedef struct trystate_S {
-  state_T ts_state;         ///< state at this level, STATE_
-  int ts_score;             ///< score
-  idx_T ts_arridx;          ///< index in tree array, start of node
-  int16_t ts_curi;          ///< index in list of child nodes
-  char_u ts_fidx;           ///< index in fword[], case-folded bad word
-  char_u ts_fidxtry;        ///< ts_fidx at which bytes may be changed
-  char_u ts_twordlen;       ///< valid length of tword[]
-  char_u ts_prefixdepth;    ///< stack depth for end of prefix or
-                            ///< PFD_PREFIXTREE or PFD_NOPREFIX
-  char_u ts_flags;          ///< TSF_ flags
-  char_u ts_tcharlen;       ///< number of bytes in tword character
-  char_u ts_tcharidx;       ///< current byte index in tword character
-  char_u ts_isdiff;         ///< DIFF_ values
-  char_u ts_fcharstart;     ///< index in fword where badword char started
-  char_u ts_prewordlen;     ///< length of word in "preword[]"
-  char_u ts_splitoff;       ///< index in "tword" after last split
-  char_u ts_splitfidx;      ///< "ts_fidx" at word split
-  char_u ts_complen;        ///< nr of compound words used
-  char_u ts_compsplit;      ///< index for "compflags" where word was spit
-  char_u ts_save_badflags;  ///< su_badflags saved here
-  char_u ts_delidx;         ///< index in fword for char that was deleted,
-                            ///< valid when "ts_flags" has TSF_DIDDEL
+  state_T ts_state;          ///< state at this level, STATE_
+  int ts_score;              ///< score
+  idx_T ts_arridx;           ///< index in tree array, start of node
+  int16_t ts_curi;           ///< index in list of child nodes
+  uint8_t ts_fidx;           ///< index in fword[], case-folded bad word
+  uint8_t ts_fidxtry;        ///< ts_fidx at which bytes may be changed
+  uint8_t ts_twordlen;       ///< valid length of tword[]
+  uint8_t ts_prefixdepth;    ///< stack depth for end of prefix or
+                             ///< PFD_PREFIXTREE or PFD_NOPREFIX
+  uint8_t ts_flags;          ///< TSF_ flags
+  uint8_t ts_tcharlen;       ///< number of bytes in tword character
+  uint8_t ts_tcharidx;       ///< current byte index in tword character
+  uint8_t ts_isdiff;         ///< DIFF_ values
+  uint8_t ts_fcharstart;     ///< index in fword where badword char started
+  uint8_t ts_prewordlen;     ///< length of word in "preword[]"
+  uint8_t ts_splitoff;       ///< index in "tword" after last split
+  uint8_t ts_splitfidx;      ///< "ts_fidx" at word split
+  uint8_t ts_complen;        ///< nr of compound words used
+  uint8_t ts_compsplit;      ///< index for "compflags" where word was spit
+  uint8_t ts_save_badflags;  ///< su_badflags saved here
+  uint8_t ts_delidx;         ///< index in fword for char that was deleted,
+                             ///< valid when "ts_flags" has TSF_DIDDEL
 } trystate_T;
 
 // values for ts_isdiff
@@ -243,7 +243,7 @@ static long spell_suggest_timeout = 5000;
 /// Returns true when the sequence of flags in "compflags" plus "flag" can
 /// possibly form a valid compounded word.  This also checks the COMPOUNDRULE
 /// lines if they don't contain wildcards.
-static bool can_be_compound(trystate_T *sp, slang_T *slang, char_u *compflags, int flag)
+static bool can_be_compound(trystate_T *sp, slang_T *slang, uint8_t *compflags, int flag)
 {
   // If the flag doesn't appear in sl_compstartflags or sl_compallflags
   // then it can't possibly compound.
@@ -256,7 +256,7 @@ static bool can_be_compound(trystate_T *sp, slang_T *slang, char_u *compflags, i
   // possibly can form a match with COMPOUNDRULE patterns.  This only
   // makes sense when we have two or more words.
   if (slang->sl_comprules != NULL && sp->ts_complen > sp->ts_compsplit) {
-    compflags[sp->ts_complen] = (char_u)flag;
+    compflags[sp->ts_complen] = (uint8_t)flag;
     compflags[sp->ts_complen + 1] = NUL;
     bool v = match_compoundrule(slang, compflags + sp->ts_compsplit);
     compflags[sp->ts_complen] = NUL;
@@ -349,7 +349,7 @@ static int badword_captype(char *word, char *end)
 /// @return  the offset.
 static int bytes2offset(char **pp)
 {
-  char_u *p = (char_u *)(*pp);
+  uint8_t *p = (uint8_t *)(*pp);
   int nr;
 
   int c = *p++;
@@ -1145,10 +1145,10 @@ static void suggest_trie_walk(suginfo_T *su, langp_T *lp, char *fword, bool soun
   // words and split word.  NUL terminated
   // when going deeper but not when coming
   // back.
-  char_u compflags[MAXWLEN];        // compound flags, one for each word
+  uint8_t compflags[MAXWLEN];        // compound flags, one for each word
   int newscore;
   int score;
-  char_u *byts, *fbyts, *pbyts;
+  uint8_t *byts, *fbyts, *pbyts;
   idx_T *idxs, *fidxs, *pidxs;
   int c, c2, c3;
   int n = 0;
@@ -1165,7 +1165,7 @@ static void suggest_trie_walk(suginfo_T *su, langp_T *lp, char *fword, bool soun
   bool goodword_ends;
 #ifdef DEBUG_TRIEWALK
   // Stores the name of the change made at each level.
-  char_u changename[MAXWLEN][80];
+  uint8_t changename[MAXWLEN][80];
 #endif
   int breakcheckcount = 1000;
   bool compound_ok;
@@ -1181,7 +1181,7 @@ static void suggest_trie_walk(suginfo_T *su, langp_T *lp, char *fword, bool soun
 
   if (soundfold) {
     // Going through the soundfold tree.
-    byts = fbyts = (char_u *)slang->sl_sbyts;
+    byts = fbyts = (uint8_t *)slang->sl_sbyts;
     idxs = fidxs = slang->sl_sidxs;
     pbyts = NULL;
     pidxs = NULL;
@@ -1190,9 +1190,9 @@ static void suggest_trie_walk(suginfo_T *su, langp_T *lp, char *fword, bool soun
   } else {
     // When there are postponed prefixes we need to use these first.  At
     // the end of the prefix we continue in the case-fold tree.
-    fbyts = (char_u *)slang->sl_fbyts;
+    fbyts = (uint8_t *)slang->sl_fbyts;
     fidxs = slang->sl_fidxs;
-    pbyts = (char_u *)slang->sl_pbyts;
+    pbyts = (uint8_t *)slang->sl_pbyts;
     pidxs = slang->sl_pidxs;
     if (pbyts != NULL) {
       byts = pbyts;
@@ -1239,7 +1239,7 @@ static void suggest_trie_walk(suginfo_T *su, langp_T *lp, char *fword, bool soun
         n = (int)sp->ts_state;
         PROF_STORE(sp->ts_state)
         sp->ts_state = STATE_ENDNUL;
-        sp->ts_save_badflags = (char_u)su->su_badflags;
+        sp->ts_save_badflags = (uint8_t)su->su_badflags;
 
         // At end of a prefix or at start of prefixtree: check for
         // following word.
@@ -1256,7 +1256,7 @@ static void suggest_trie_walk(suginfo_T *su, langp_T *lp, char *fword, bool soun
           go_deeper(stack, depth, 0);
           depth++;
           sp = &stack[depth];
-          sp->ts_prefixdepth = (char_u)(depth - 1);
+          sp->ts_prefixdepth = (uint8_t)(depth - 1);
           byts = fbyts;
           idxs = fidxs;
           sp->ts_arridx = 0;
@@ -1266,7 +1266,7 @@ static void suggest_trie_walk(suginfo_T *su, langp_T *lp, char *fword, bool soun
           tword[sp->ts_twordlen] = NUL;
           make_case_word(tword + sp->ts_splitoff,
                          preword + sp->ts_prewordlen, flags);
-          sp->ts_prewordlen = (char_u)strlen(preword);
+          sp->ts_prewordlen = (uint8_t)strlen(preword);
           sp->ts_splitoff = sp->ts_twordlen;
         }
         break;
@@ -1276,7 +1276,7 @@ static void suggest_trie_walk(suginfo_T *su, langp_T *lp, char *fword, bool soun
         // Past bytes in node and/or past NUL bytes.
         PROF_STORE(sp->ts_state)
         sp->ts_state = STATE_ENDNUL;
-        sp->ts_save_badflags = (char_u)su->su_badflags;
+        sp->ts_save_badflags = (uint8_t)su->su_badflags;
         break;
       }
 
@@ -1379,7 +1379,7 @@ static void suggest_trie_walk(suginfo_T *su, langp_T *lp, char *fword, bool soun
             break;
           }
 
-          compflags[sp->ts_complen] = (char_u)((unsigned)flags >> 24);
+          compflags[sp->ts_complen] = (uint8_t)((unsigned)flags >> 24);
           compflags[sp->ts_complen + 1] = NUL;
           xstrlcpy(preword + sp->ts_prewordlen,
                    tword + sp->ts_splitoff,
@@ -1577,7 +1577,7 @@ static void suggest_trie_walk(suginfo_T *su, langp_T *lp, char *fword, bool soun
                 < slang->sl_compmax)
             && (can_be_compound(sp, slang, compflags, (int)((unsigned)flags >> 24)))) {
           try_compound = true;
-          compflags[sp->ts_complen] = (char_u)((unsigned)flags >> 24);
+          compflags[sp->ts_complen] = (uint8_t)((unsigned)flags >> 24);
           compflags[sp->ts_complen + 1] = NUL;
         }
 
@@ -1596,7 +1596,7 @@ static void suggest_trie_walk(suginfo_T *su, langp_T *lp, char *fword, bool soun
           sp->ts_curi--;                    // do the same NUL again
           compflags[sp->ts_complen] = NUL;
         } else {
-          sp->ts_flags &= (char_u) ~TSF_DIDSPLIT;
+          sp->ts_flags &= (uint8_t) ~TSF_DIDSPLIT;
         }
 
         if (try_split || try_compound) {
@@ -1641,7 +1641,7 @@ static void suggest_trie_walk(suginfo_T *su, langp_T *lp, char *fword, bool soun
             }
 #endif
             // Save things to be restored at STATE_SPLITUNDO.
-            sp->ts_save_badflags = (char_u)su->su_badflags;
+            sp->ts_save_badflags = (uint8_t)su->su_badflags;
             PROF_STORE(sp->ts_state)
             sp->ts_state = STATE_SPLITUNDO;
 
@@ -1652,7 +1652,7 @@ static void suggest_trie_walk(suginfo_T *su, langp_T *lp, char *fword, bool soun
             if (!try_compound && !fword_ends) {
               STRCAT(preword, " ");
             }
-            sp->ts_prewordlen = (char_u)strlen(preword);
+            sp->ts_prewordlen = (uint8_t)strlen(preword);
             sp->ts_splitoff = sp->ts_twordlen;
             sp->ts_splitfidx = sp->ts_fidx;
 
@@ -1673,12 +1673,12 @@ static void suggest_trie_walk(suginfo_T *su, langp_T *lp, char *fword, bool soun
               if (fword_ends) {
                 // Copy the skipped character to preword.
                 memmove(preword + sp->ts_prewordlen, fword + sp->ts_fidx, (size_t)l);
-                sp->ts_prewordlen = (char_u)(sp->ts_prewordlen + l);
+                sp->ts_prewordlen = (uint8_t)(sp->ts_prewordlen + l);
                 preword[sp->ts_prewordlen] = NUL;
               } else {
                 sp->ts_score -= SCORE_SPLIT - SCORE_SUBST;
               }
-              sp->ts_fidx = (char_u)(sp->ts_fidx + l);
+              sp->ts_fidx = (uint8_t)(sp->ts_fidx + l);
             }
 
             // When compounding include compound flag in
@@ -1803,7 +1803,7 @@ static void suggest_trie_walk(suginfo_T *su, langp_T *lp, char *fword, bool soun
             // First byte.
             sp->ts_tcharidx = 0;
             sp->ts_tcharlen = MB_BYTE2LEN(c);
-            sp->ts_fcharstart = (char_u)(sp->ts_fidx - 1);
+            sp->ts_fcharstart = (uint8_t)(sp->ts_fidx - 1);
             sp->ts_isdiff = (newscore != 0)
                             ? DIFF_YES : DIFF_NONE;
           } else if (sp->ts_isdiff == DIFF_INSERT && sp->ts_fidx > 0) {
@@ -1816,8 +1816,8 @@ static void suggest_trie_walk(suginfo_T *su, langp_T *lp, char *fword, bool soun
             if (sp->ts_isdiff == DIFF_YES) {
               // Correct ts_fidx for the byte length of the
               // character (we didn't check that before).
-              sp->ts_fidx = (char_u)(sp->ts_fcharstart
-                                     + utfc_ptr2len(fword + sp->ts_fcharstart));
+              sp->ts_fidx = (uint8_t)(sp->ts_fcharstart
+                                      + utfc_ptr2len(fword + sp->ts_fcharstart));
 
               // For changing a composing character adjust
               // the score from SCORE_SUBST to
@@ -1905,7 +1905,7 @@ static void suggest_trie_walk(suginfo_T *su, langp_T *lp, char *fword, bool soun
         // results.
         c = utf_ptr2char(fword + sp->ts_fidx);
         stack[depth].ts_fidx =
-          (char_u)(stack[depth].ts_fidx + utfc_ptr2len(fword + sp->ts_fidx));
+          (uint8_t)(stack[depth].ts_fidx + utfc_ptr2len(fword + sp->ts_fidx));
         if (utf_iscomposing(c)) {
           stack[depth].ts_score -= SCORE_DEL - SCORE_DELCOMP;
         } else if (c == utf_ptr2char(fword + stack[depth].ts_fidx)) {
@@ -1985,7 +1985,7 @@ static void suggest_trie_walk(suginfo_T *su, langp_T *lp, char *fword, bool soun
           // There are following bytes for the same character.
           // We must find all bytes before trying
           // delete/insert/swap/etc.
-          sp->ts_tcharlen = (char_u)fl;
+          sp->ts_tcharlen = (uint8_t)fl;
           sp->ts_tcharidx = 1;
           sp->ts_isdiff = DIFF_INSERT;
         }
@@ -2061,7 +2061,7 @@ static void suggest_trie_walk(suginfo_T *su, langp_T *lp, char *fword, bool soun
         fl = utf_char2len(c2);
         memmove(p, p + n, (size_t)fl);
         utf_char2bytes(c, p + fl);
-        stack[depth].ts_fidxtry = (char_u)(sp->ts_fidx + n + fl);
+        stack[depth].ts_fidxtry = (uint8_t)(sp->ts_fidx + n + fl);
       } else {
         // If this swap doesn't work then SWAP3 won't either.
         PROF_STORE(sp->ts_state)
@@ -2118,7 +2118,7 @@ static void suggest_trie_walk(suginfo_T *su, langp_T *lp, char *fword, bool soun
         memmove(p, p + n + fl, (size_t)tl);
         utf_char2bytes(c2, p + tl);
         utf_char2bytes(c, p + fl + tl);
-        stack[depth].ts_fidxtry = (char_u)(sp->ts_fidx + n + fl + tl);
+        stack[depth].ts_fidxtry = (uint8_t)(sp->ts_fidx + n + fl + tl);
       } else {
         PROF_STORE(sp->ts_state)
         sp->ts_state = STATE_REP_INI;
@@ -2166,7 +2166,7 @@ static void suggest_trie_walk(suginfo_T *su, langp_T *lp, char *fword, bool soun
         fl += utf_ptr2len(p + n + fl);
         memmove(p, p + n, (size_t)fl);
         utf_char2bytes(c, p + fl);
-        stack[depth].ts_fidxtry = (char_u)(sp->ts_fidx + n + fl);
+        stack[depth].ts_fidxtry = (uint8_t)(sp->ts_fidx + n + fl);
       } else {
         PROF_STORE(sp->ts_state)
         sp->ts_state = STATE_REP_INI;
@@ -2203,7 +2203,7 @@ static void suggest_trie_walk(suginfo_T *su, langp_T *lp, char *fword, bool soun
         tl = utf_ptr2len(p + n);
         memmove(p + tl, p, (size_t)n);
         utf_char2bytes(c, p);
-        stack[depth].ts_fidxtry = (char_u)(sp->ts_fidx + n + tl);
+        stack[depth].ts_fidxtry = (uint8_t)(sp->ts_fidx + n + tl);
       } else {
         PROF_STORE(sp->ts_state)
         sp->ts_state = STATE_REP_INI;
@@ -2293,7 +2293,7 @@ static void suggest_trie_walk(suginfo_T *su, langp_T *lp, char *fword, bool soun
             repextra += tl - fl;
           }
           memmove(p, ftp->ft_to, (size_t)tl);
-          stack[depth].ts_fidxtry = (char_u)(sp->ts_fidx + tl);
+          stack[depth].ts_fidxtry = (uint8_t)(sp->ts_fidx + tl);
           stack[depth].ts_tcharlen = 0;
           break;
         }
@@ -2381,7 +2381,7 @@ static void find_keepcap_word(slang_T *slang, char *fword, char *kword)
   int c;
   idx_T lo, hi, m;
   char *p;
-  char_u *byts = (char_u *)slang->sl_kbyts;      // array with bytes of the words
+  uint8_t *byts = (uint8_t *)slang->sl_kbyts;      // array with bytes of the words
   idx_T *idxs = slang->sl_kidxs;      // array with indexes
 
   if (byts == NULL) {
@@ -2683,11 +2683,11 @@ static int stp_sal_score(suggest_T *stp, suginfo_T *su, slang_T *slang, char *ba
 /// handled already.
 typedef struct {
   int16_t sft_score;   ///< lowest score used
-  char_u sft_word[];   ///< soundfolded word
+  uint8_t sft_word[];   ///< soundfolded word
 } sftword_T;
 
 static sftword_T dumsft;
-#define HIKEY2SFT(p)  ((sftword_T *)((p) - (dumsft.sft_word - (char_u *)&dumsft)))
+#define HIKEY2SFT(p)  ((sftword_T *)((p) - (dumsft.sft_word - (uint8_t *)&dumsft)))
 #define HI2SFT(hi)     HIKEY2SFT((hi)->hi_key)
 
 /// Prepare for calling suggest_try_soundalike().
@@ -2779,7 +2779,7 @@ static void add_sound_suggest(suginfo_T *su, char *goodword, int score, langp_T
   char theword[MAXWLEN];
   int i;
   int wlen;
-  char_u *byts;
+  uint8_t *byts;
   idx_T *idxs;
   int n;
   int wordcount;
@@ -2824,7 +2824,7 @@ static void add_sound_suggest(suginfo_T *su, char *goodword, int score, langp_T
     // previous wordnr.
     orgnr += bytes2offset(&nrline);
 
-    byts = (char_u *)slang->sl_fbyts;
+    byts = (uint8_t *)slang->sl_fbyts;
     idxs = slang->sl_fidxs;
 
     // Lookup the word "orgnr" one of the two tries.
@@ -2954,10 +2954,10 @@ static int soundfold_find(slang_T *slang, char *word)
 {
   idx_T arridx = 0;
   int wlen = 0;
-  char_u *ptr = (char_u *)word;
+  uint8_t *ptr = (uint8_t *)word;
   int wordnr = 0;
 
-  char_u *byts = (char_u *)slang->sl_sbyts;
+  uint8_t *byts = (uint8_t *)slang->sl_sbyts;
   idx_T *idxs = slang->sl_sidxs;
 
   for (;;) {
@@ -3236,15 +3236,15 @@ static void rescore_one(suginfo_T *su, suggest_T *stp)
   // Only rescore suggestions that have no sal score yet and do have a
   // language.
   if (slang != NULL && !GA_EMPTY(&slang->sl_sal) && !stp->st_had_bonus) {
-    char_u *p;
+    char *p;
     if (slang == su->su_sallang) {
-      p = (char_u *)su->su_sal_badword;
+      p = su->su_sal_badword;
     } else {
       spell_soundfold(slang, su->su_fbadword, true, sal_badword);
-      p = (char_u *)sal_badword;
+      p = sal_badword;
     }
 
-    stp->st_altscore = stp_sal_score(stp, su, slang, (char *)p);
+    stp->st_altscore = stp_sal_score(stp, su, slang, p);
     if (stp->st_altscore == SCORE_MAXMAX) {
       stp->st_altscore = SCORE_BIG;
     }