Merge #2470: Remove char_u (5)

Reviewed-by: Scott Prager <splinterofchaos@gmail.com>
Reviewed-by: Michael Reed <m.reed@mykolab.com>
Reviewed-by: Eliseo Martínez <eliseomarmol@gmail.com>

24 files changed, 263 insertions, 266 deletions

diff --git a/src/nvim/buffer.c b/src/nvim/buffer.c
index 395b20b219..094e80086c 100644
--- a/src/nvim/buffer.c
+++ b/src/nvim/buffer.c
@@ -1661,7 +1661,7 @@ buf_T *buflist_findname_exp(char_u *fname)
   buf_T       *buf = NULL;
 
   /* First make the name into a full path name */
-  ffname = FullName_save(fname,
+  ffname = (char_u *)FullName_save((char *)fname,
 #ifdef UNIX
       TRUE                  /* force expansion, get rid of symbolic links */
 #else
@@ -3569,7 +3569,7 @@ void fname_expand(buf_T *buf, char_u **ffname, char_u **sfname)
     return;
   if (*sfname == NULL)          /* if no short file name given, use ffname */
     *sfname = *ffname;
-  *ffname = fix_fname(*ffname);     /* expand to full path */
+  *ffname = (char_u *)fix_fname((char *)*ffname);     /* expand to full path */
 
 #ifdef FEAT_SHORTCUT
   if (!buf->b_p_bin) {
diff --git a/src/nvim/diff.c b/src/nvim/diff.c
index d4fbb290c1..b21bc1f2f4 100644
--- a/src/nvim/diff.c
+++ b/src/nvim/diff.c
@@ -867,7 +867,7 @@ void ex_diffpatch(exarg_T *eap)
 
 #ifdef UNIX
   // Get the absolute path of the patchfile, changing directory below.
-  fullname = FullName_save(eap->arg, FALSE);
+  fullname = (char_u *)FullName_save((char *)eap->arg, FALSE);
 #endif  // ifdef UNIX
 
 #ifdef UNIX
diff --git a/src/nvim/eval.c b/src/nvim/eval.c
index c4c2821b80..8a98eae21f 100644
--- a/src/nvim/eval.c
+++ b/src/nvim/eval.c
@@ -7347,7 +7347,7 @@ static buf_T *find_buffer(typval_T *avar)
        * buffer, these don't use the full path. */
       FOR_ALL_BUFFERS(bp) {
         if (bp->b_fname != NULL
-            && (path_with_url(bp->b_fname)
+            && (path_with_url((char *)bp->b_fname)
                 || bt_nofile(bp)
                 )
             && STRCMP(bp->b_fname, avar->vval.v_string) == 0) {
@@ -12484,7 +12484,7 @@ static void f_resolve(typval_T *argvars, typval_T *rettv)
         /* Ensure that the result will have a trailing path separator
          * if the argument has one. */
         if (remain == NULL && has_trailing_pathsep)
-          add_pathsep(buf);
+          add_pathsep((char *)buf);
 
         /* Separate the first path component in the link value and
          * concatenate the remainders. */
@@ -15490,7 +15490,7 @@ static void f_undofile(typval_T *argvars, typval_T *rettv)
       /* If there is no file name there will be no undo file. */
       rettv->vval.v_string = NULL;
     } else {
-      char_u *ffname = FullName_save(fname, FALSE);
+      char_u *ffname = (char_u *)FullName_save((char *)fname, FALSE);
 
       if (ffname != NULL)
         rettv->vval.v_string = u_get_undo_file_name(ffname, FALSE);
@@ -19912,7 +19912,7 @@ repeat:
 
     /* FullName_save() is slow, don't use it when not needed. */
     if (*p != NUL || !vim_isAbsName(*fnamep)) {
-      *fnamep = FullName_save(*fnamep, *p != NUL);
+      *fnamep = (char_u *)FullName_save((char *)*fnamep, *p != NUL);
       xfree(*bufp);          /* free any allocated file name */
       *bufp = *fnamep;
       if (*fnamep == NULL)
@@ -19927,7 +19927,7 @@ repeat:
       *bufp = *fnamep;
       if (*fnamep == NULL)
         return -1;
-      add_pathsep(*fnamep);
+      add_pathsep((char *)*fnamep);
     }
   }
 
@@ -19946,7 +19946,7 @@ repeat:
       if (c == '.' && **fnamep == '~')
         p = pbuf = expand_env_save(*fnamep);
       else
-        p = pbuf = FullName_save(*fnamep, FALSE);
+        p = pbuf = (char_u *)FullName_save((char *)*fnamep, FALSE);
     } else
       p = *fnamep;
 
diff --git a/src/nvim/ex_cmds.c b/src/nvim/ex_cmds.c
index 78200e4689..62c2d4ac98 100644
--- a/src/nvim/ex_cmds.c
+++ b/src/nvim/ex_cmds.c
@@ -1530,7 +1530,7 @@ void write_viminfo(char_u *file, int forceit)
 #endif
 
     // Make tempname
-    tempname = modname(fname, (char_u *)".tmp", FALSE);
+    tempname = (char_u *)modname((char *)fname, ".tmp", FALSE);
     if (tempname != NULL) {
       /*
        * Check if tempfile already exists.  Never overwrite an
@@ -2080,7 +2080,7 @@ int do_write(exarg_T *eap)
     other = FALSE;
   } else {
     fname = ffname;
-    free_fname = fix_fname(ffname);
+    free_fname = (char_u *)fix_fname((char *)ffname);
     /*
      * When out-of-memory, keep unexpanded file name, because we MUST be
      * able to write the file in this situation.
@@ -2579,7 +2579,7 @@ do_ecmd (
         ffname = curbuf->b_ffname;
         sfname = curbuf->b_fname;
       }
-      free_fname = fix_fname(ffname);       /* may expand to full path name */
+      free_fname = (char_u *)fix_fname((char *)ffname);       /* may expand to full path name */
       if (free_fname != NULL)
         ffname = free_fname;
       other_file = otherfile(ffname);
@@ -5126,7 +5126,7 @@ void fix_help_buffer(void)
           char_u      *cp;
 
           /* Find all "doc/ *.txt" files in this directory. */
-          add_pathsep(NameBuff);
+          add_pathsep((char *)NameBuff);
           STRCAT(NameBuff, "doc/*.??[tx]");
 
           // Note: We cannot just do `&NameBuff` because it is a statically sized array
@@ -5297,7 +5297,7 @@ void ex_helptags(exarg_T *eap)
 
   /* Get a list of all files in the help directory and in subdirectories. */
   STRCPY(NameBuff, dirname);
-  add_pathsep(NameBuff);
+  add_pathsep((char *)NameBuff);
   STRCAT(NameBuff, "**");
 
   // Note: We cannot just do `&NameBuff` because it is a statically sized array
@@ -5419,7 +5419,7 @@ helptags_one (
    * Do this before scanning through all the files.
    */
   STRCPY(NameBuff, dir);
-  add_pathsep(NameBuff);
+  add_pathsep((char *)NameBuff);
   STRCAT(NameBuff, tagfname);
   fd_tags = mch_fopen((char *)NameBuff, "w");
   if (fd_tags == NULL) {
diff --git a/src/nvim/ex_cmds2.c b/src/nvim/ex_cmds2.c
index b79d09885c..08d84c2440 100644
--- a/src/nvim/ex_cmds2.c
+++ b/src/nvim/ex_cmds2.c
@@ -495,7 +495,7 @@ dbg_parsearg (
     if (p == NULL)
       return FAIL;
     if (*p != '*') {
-      bp->dbg_name = fix_fname(p);
+      bp->dbg_name = (char_u *)fix_fname((char *)p);
       xfree(p);
     } else
       bp->dbg_name = p;
@@ -1692,7 +1692,7 @@ void do_argfile(exarg_T *eap, int argn)
        */
       other = TRUE;
       if (P_HID(curbuf)) {
-        p = fix_fname(alist_name(&ARGLIST[argn]));
+        p = (char_u *)fix_fname((char *)alist_name(&ARGLIST[argn]));
         other = otherfile(p);
         xfree(p);
       }
@@ -2144,7 +2144,7 @@ int do_in_runtimepath(char_u *name, int all, DoInRuntimepathCB callback,
         if (!did_one)
           did_one = (cookie == NULL);
       } else if (STRLEN(buf) + STRLEN(name) + 2 < MAXPATHL) {
-        add_pathsep(buf);
+        add_pathsep((char *)buf);
         tail = buf + STRLEN(buf);
 
         /* Loop over all patterns in "name" */
@@ -2313,7 +2313,7 @@ do_source (
   p = expand_env_save(fname);
   if (p == NULL)
     return retval;
-  fname_exp = fix_fname(p);
+  fname_exp = (char_u *)fix_fname((char *)p);
   xfree(p);
   if (fname_exp == NULL)
     return retval;
@@ -3305,7 +3305,7 @@ static void script_host_execute(char *name, exarg_T *eap)
 static void script_host_execute_file(char *name, exarg_T *eap)
 {
   uint8_t buffer[MAXPATHL];
-  vim_FullName(eap->arg, buffer, sizeof(buffer), false);
+  vim_FullName((char *)eap->arg, (char *)buffer, sizeof(buffer), false);
 
   list_T *args = list_alloc();
   // filename
diff --git a/src/nvim/ex_docmd.c b/src/nvim/ex_docmd.c
index 9ff19521b6..289bb85f4d 100644
--- a/src/nvim/ex_docmd.c
+++ b/src/nvim/ex_docmd.c
@@ -7544,7 +7544,7 @@ static void ex_mkrc(exarg_T *eap)
       char_u      *tbuf;
 
       tbuf = xmalloc(MAXPATHL);
-      if (vim_FullName(fname, tbuf, MAXPATHL, FALSE) == OK)
+      if (vim_FullName((char *)fname, (char *)tbuf, MAXPATHL, FALSE) == OK)
         set_vim_var_string(VV_THIS_SESSION, tbuf, -1);
       xfree(tbuf);
     }
@@ -8155,7 +8155,7 @@ eval_vars (
         /* Still need to turn the fname into a full path.  It is
          * postponed to avoid a delay when <afile> is not used. */
         autocmd_fname_full = TRUE;
-        result = FullName_save(autocmd_fname, FALSE);
+        result = (char_u *)FullName_save((char *)autocmd_fname, FALSE);
         xfree(autocmd_fname);
         autocmd_fname = result;
       }
@@ -8975,7 +8975,7 @@ ses_arglist (
     if (s != NULL) {
       if (fullname) {
         buf = xmalloc(MAXPATHL);
-        (void)vim_FullName(s, buf, MAXPATHL, FALSE);
+        (void)vim_FullName((char *)s, (char *)buf, MAXPATHL, FALSE);
         s = buf;
       }
       if (fputs("argadd ", fd) < 0 || ses_put_fname(fd, s, flagp) == FAIL
@@ -9089,7 +9089,7 @@ static char_u *get_view_file(int c)
       ++len;
   retval = xmalloc(STRLEN(sname) + len + STRLEN(p_vdir) + 9);
   STRCPY(retval, p_vdir);
-  add_pathsep(retval);
+  add_pathsep((char *)retval);
   s = retval + STRLEN(retval);
   for (p = sname; *p; ++p) {
     if (*p == '=') {
diff --git a/src/nvim/ex_getln.c b/src/nvim/ex_getln.c
index 1a04f1bd91..3af035a6e3 100644
--- a/src/nvim/ex_getln.c
+++ b/src/nvim/ex_getln.c
@@ -3890,7 +3890,7 @@ static void expand_shellcmd(char_u *filepat, int *num_file, char_u ***file,
     if (l > MAXPATHL - 5)
       break;
     STRLCPY(buf, s, l + 1);
-    add_pathsep(buf);
+    add_pathsep((char *)buf);
     l = STRLEN(buf);
     STRLCPY(buf + l, pat, MAXPATHL - l);
 
@@ -4107,7 +4107,7 @@ void globpath(char_u *path, char_u *file, garray_T *ga, int expand_options)
     // Copy one item of the path to buf[] and concatenate the file name.
     copy_option_part(&path, buf, MAXPATHL, ",");
     if (STRLEN(buf) + STRLEN(file) + 2 < MAXPATHL) {
-      add_pathsep(buf);
+      add_pathsep((char *)buf);
       STRCAT(buf, file);  // NOLINT
 
       char_u **p;
diff --git a/src/nvim/file_search.c b/src/nvim/file_search.c
index 2777271377..855de6595f 100644
--- a/src/nvim/file_search.c
+++ b/src/nvim/file_search.c
@@ -313,7 +313,7 @@ vim_findfile_init (
     if (!vim_isAbsName(rel_fname) && len + 1 < MAXPATHL) {
       /* Make the start dir an absolute path name. */
       STRLCPY(ff_expand_buffer, rel_fname, len + 1);
-      search_ctx->ffsc_start_dir = FullName_save(ff_expand_buffer, FALSE);
+      search_ctx->ffsc_start_dir = (char_u *)FullName_save((char *)ff_expand_buffer, FALSE);
     } else
       search_ctx->ffsc_start_dir = vim_strnsave(rel_fname, len);
     if (*++path != NUL)
@@ -465,7 +465,7 @@ vim_findfile_init (
     goto error_return;
   }
   STRCPY(ff_expand_buffer, search_ctx->ffsc_start_dir);
-  add_pathsep(ff_expand_buffer);
+  add_pathsep((char *)ff_expand_buffer);
   {
     size_t eb_len = STRLEN(ff_expand_buffer);
     char_u *buf = xmalloc(eb_len + STRLEN(search_ctx->ffsc_fix_path) + 1);
@@ -474,7 +474,7 @@ vim_findfile_init (
     STRCPY(buf + eb_len, search_ctx->ffsc_fix_path);
     if (os_isdir(buf)) {
       STRCAT(ff_expand_buffer, search_ctx->ffsc_fix_path);
-      add_pathsep(ff_expand_buffer);
+      add_pathsep((char *)ff_expand_buffer);
     } else {
       char_u *p =  path_tail(search_ctx->ffsc_fix_path);
       char_u *wc_path = NULL;
@@ -484,7 +484,7 @@ vim_findfile_init (
       if (p > search_ctx->ffsc_fix_path) {
         len = (int)(p - search_ctx->ffsc_fix_path) - 1;
         STRNCAT(ff_expand_buffer, search_ctx->ffsc_fix_path, len);
-        add_pathsep(ff_expand_buffer);
+        add_pathsep((char *)ff_expand_buffer);
       } else
         len = (int)STRLEN(search_ctx->ffsc_fix_path);
 
@@ -695,12 +695,12 @@ char_u *vim_findfile(void *search_ctx_arg)
         if (!vim_isAbsName(stackp->ffs_fix_path)
             && search_ctx->ffsc_start_dir) {
           STRCPY(file_path, search_ctx->ffsc_start_dir);
-          add_pathsep(file_path);
+          add_pathsep((char *)file_path);
         }
 
         /* append the fix part of the search path */
         STRCAT(file_path, stackp->ffs_fix_path);
-        add_pathsep(file_path);
+        add_pathsep((char *)file_path);
 
         rest_of_wildcards = stackp->ffs_wc_path;
         if (*rest_of_wildcards != NUL) {
@@ -749,7 +749,7 @@ char_u *vim_findfile(void *search_ctx_arg)
          * Expand wildcards like "*" and "$VAR".
          * If the path is a URL don't try this.
          */
-        if (path_with_url(dirptrs[0])) {
+        if (path_with_url((char *)dirptrs[0])) {
           stackp->ffs_filearray = (char_u **)xmalloc(sizeof(char *));
           stackp->ffs_filearray[0] = vim_strsave(dirptrs[0]);
           stackp->ffs_filearray_size = 1;
@@ -777,14 +777,14 @@ char_u *vim_findfile(void *search_ctx_arg)
            */
           for (int i = stackp->ffs_filearray_cur;
                i < stackp->ffs_filearray_size; ++i) {
-            if (!path_with_url(stackp->ffs_filearray[i])
+            if (!path_with_url((char *)stackp->ffs_filearray[i])
                 && !os_isdir(stackp->ffs_filearray[i]))
               continue;                 /* not a directory */
 
             /* prepare the filename to be checked for existence
              * below */
             STRCPY(file_path, stackp->ffs_filearray[i]);
-            add_pathsep(file_path);
+            add_pathsep((char *)file_path);
             STRCAT(file_path, search_ctx->ffsc_file_to_search);
 
             /*
@@ -798,7 +798,7 @@ char_u *vim_findfile(void *search_ctx_arg)
               suf = curbuf->b_p_sua;
             for (;; ) {
               /* if file exists and we didn't already find it */
-              if ((path_with_url(file_path)
+              if ((path_with_url((char *)file_path)
                    || (os_file_exists(file_path)
                        && (search_ctx->ffsc_find_what
                            == FINDFILE_BOTH
@@ -836,7 +836,7 @@ char_u *vim_findfile(void *search_ctx_arg)
                 stackp->ffs_filearray_cur = (char_u)(i + 1);
                 ff_push(search_ctx, stackp);
 
-                if (!path_with_url(file_path))
+                if (!path_with_url((char *)file_path))
                   simplify_filename(file_path);
                 if (os_dirname(ff_expand_buffer, MAXPATHL)
                     == OK) {
@@ -936,7 +936,7 @@ char_u *vim_findfile(void *search_ctx_arg)
         break;
 
       STRCPY(file_path, search_ctx->ffsc_start_dir);
-      add_pathsep(file_path);
+      add_pathsep((char *)file_path);
       STRCAT(file_path, search_ctx->ffsc_fix_path);
 
       /* create a new stack entry */
@@ -1097,7 +1097,7 @@ static int ff_check_visited(ff_visited_T **visited_list, char_u *fname, char_u *
   FileID file_id;
   // For an URL we only compare the name, otherwise we compare the
   // device/inode.
-  if (path_with_url(fname)) {
+  if (path_with_url((char *)fname)) {
     STRLCPY(ff_expand_buffer, fname, MAXPATHL);
     url = true;
   } else {
@@ -1404,7 +1404,7 @@ find_file_in_path_option (
      * filename on the first call.
      */
     if (first == TRUE) {
-      if (path_with_url(ff_file_to_find)) {
+      if (path_with_url((char *)ff_file_to_find)) {
         file_name = vim_strsave(ff_file_to_find);
         goto theend;
       }
diff --git a/src/nvim/fileio.c b/src/nvim/fileio.c
index 98a2cb4076..f5cf226da4 100644
--- a/src/nvim/fileio.c
+++ b/src/nvim/fileio.c
@@ -2814,7 +2814,7 @@ buf_write (
           /*
            * Make backup file name.
            */
-          backup = modname(rootname, backup_ext, FALSE);
+          backup = (char_u *)modname((char *)rootname, (char *)backup_ext, FALSE);
           if (backup == NULL) {
             xfree(rootname);
             some_error = TRUE;                          /* out of memory */
@@ -2985,7 +2985,7 @@ nobackup:
         if (rootname == NULL)
           backup = NULL;
         else {
-          backup = modname(rootname, backup_ext, FALSE);
+          backup = (char_u *)modname((char *)rootname, (char *)backup_ext, FALSE);
           xfree(rootname);
         }
 
@@ -3595,7 +3595,7 @@ restore_backup:
    * the backup file our 'original' file.
    */
   if (*p_pm && dobackup) {
-    char *org = (char *)modname(fname, p_pm, FALSE);
+    char *org = modname((char *)fname, (char *)p_pm, FALSE);
 
     if (backup != NULL) {
       /*
@@ -4310,7 +4310,7 @@ void shorten_fnames(int force)
   FOR_ALL_BUFFERS(buf) {
     if (buf->b_fname != NULL
         && !bt_nofile(buf)
-        && !path_with_url(buf->b_fname)
+        && !path_with_url((char *)buf->b_fname)
         && (force
             || buf->b_sfname == NULL
             || path_is_absolute_path(buf->b_sfname))) {
@@ -4333,108 +4333,108 @@ void shorten_fnames(int force)
   redraw_tabline = TRUE;
 }
 
-/*
- * add extension to file name - change path/fo.o.h to path/fo.o.h.ext
- *
- * Assumed that fname is a valid name found in the filesystem we assure that
- * the return value is a different name and ends in 'ext'.
- * "ext" MUST be at most 4 characters long if it starts with a dot, 3
- * characters otherwise.
- * Space for the returned name is allocated, must be freed later.
- * Returns NULL when out of memory.
- */
-char_u *
-modname (
-    char_u *fname,
-    char_u *ext,
-    int prepend_dot                /* may prepend a '.' to file name */
-)
+/// Get new filename ended by given extension.
+///
+/// @param fname        The original filename.
+///                     If NULL, use current directory name and ext to
+///                     compute new filename.
+/// @param ext          The extension to add to the filename.
+///                     4 chars max if prefixed with a dot, 3 otherwise.
+/// @param prepend_dot  If true, prefix ext with a dot.
+///                     Does nothing if ext already starts with a dot, or
+///                     if fname is NULL.
+///
+/// @return [allocated] - A new filename, made up from:
+///                       * fname + ext, if fname not NULL.
+///                       * current dir + ext, if fname is NULL.
+///                         On Windows, and if ext starts with ".", a "_" is
+///                         preprended to ext (for filename to be valid).
+///                       Result is guaranteed to:
+///                       * be ended by <ext>.
+///                       * have a basename with at most BASENAMELEN chars:
+///                         original basename is truncated if necessary.
+///                       * be different than original: basename chars are
+///                         replaced by "_" if necessary. If that can't be done
+///                         because truncated value of original filename was
+///                         made of all underscores, replace first "_" by "v".
+///                     - NULL, if fname is NULL and there was a problem trying
+///                       to get current directory.
+char *modname(const char *fname, const char *ext, bool prepend_dot)
+  FUNC_ATTR_NONNULL_ARG(2)
 {
-  char_u      *retval;
-  char_u      *s;
-  char_u      *e;
-  char_u      *ptr;
-  int fnamelen, extlen;
-
-  extlen = (int)STRLEN(ext);
+  char *retval;
+  size_t fnamelen;
+  size_t extlen = strlen(ext);
 
-  /*
-   * If there is no file name we must get the name of the current directory
-   * (we need the full path in case :cd is used).
-   */
+  // If there is no file name we must get the name of the current directory
+  // (we need the full path in case :cd is used).
   if (fname == NULL || *fname == NUL) {
-    retval = xmalloc(MAXPATHL + extlen + 3);
-    if (os_dirname(retval, MAXPATHL) == FAIL ||
-        (fnamelen = (int)STRLEN(retval)) == 0) {
+    retval = xmalloc(MAXPATHL + extlen + 3);  // +3 for PATHSEP, "_" (Win), NUL
+    if (os_dirname((char_u *)retval, MAXPATHL) == FAIL ||
+        (fnamelen = strlen(retval)) == 0) {
       xfree(retval);
       return NULL;
     }
-    if (!after_pathsep((char *)retval, (char *)retval + fnamelen)) {
-      retval[fnamelen++] = PATHSEP;
-      retval[fnamelen] = NUL;
-    }
-    prepend_dot = FALSE;            /* nothing to prepend a dot to */
+    add_pathsep(retval);
+    fnamelen = strlen(retval);
+    prepend_dot = FALSE;  // nothing to prepend a dot to
   } else {
-    fnamelen = (int)STRLEN(fname);
+    fnamelen = strlen(fname);
     retval = xmalloc(fnamelen + extlen + 3);
-    STRCPY(retval, fname);
+    strcpy(retval, fname);
   }
 
-  /*
-   * search backwards until we hit a '/', '\' or ':'.
-   * Then truncate what is after the '/', '\' or ':' to BASENAMELEN characters.
-   */
+  // Search backwards until we hit a '/', '\' or ':'.
+  // Then truncate what is after the '/', '\' or ':' to BASENAMELEN characters.
+  char *ptr = NULL;
   for (ptr = retval + fnamelen; ptr > retval; mb_ptr_back(retval, ptr)) {
     if (vim_ispathsep(*ptr)) {
-      ++ptr;
+      ptr++;
       break;
     }
   }
 
-  /* the file name has at most BASENAMELEN characters. */
-  if (STRLEN(ptr) > BASENAMELEN)
+  // the file name has at most BASENAMELEN characters.
+  if (strlen(ptr) > BASENAMELEN) {
     ptr[BASENAMELEN] = '\0';
+  }
 
-  s = ptr + STRLEN(ptr);
+  char *s;
+  s = ptr + strlen(ptr);
 
 #if defined(WIN3264)
-  /*
-   * If there is no file name, and the extension starts with '.', put a
-   * '_' before the dot, because just ".ext" may be invalid if it's on a
-   * FAT partition, and on HPFS it doesn't matter.
-   */
-  else if ((fname == NULL || *fname == NUL) && *ext == '.')
+  // If there is no file name, and the extension starts with '.', put a
+  // '_' before the dot, because just ".ext" may be invalid if it's on a
+  // FAT partition, and on HPFS it doesn't matter.
+  else if ((fname == NULL || *fname == NUL) && *ext == '.') {
     *s++ = '_';
+  }
 #endif
 
-  /*
-   * Append the extension.
-   * ext can start with '.' and cannot exceed 3 more characters.
-   */
-  STRCPY(s, ext);
+  // Append the extension.
+  // ext can start with '.' and cannot exceed 3 more characters.
+  strcpy(s, ext);
 
-  /*
-   * Prepend the dot.
-   */
-  if (prepend_dot && *(e = path_tail(retval)) != '.') {
+  char *e;
+  // Prepend the dot if needed.
+  if (prepend_dot && *(e = (char *)path_tail((char_u *)retval)) != '.') {
     STRMOVE(e + 1, e);
     *e = '.';
   }
 
-  /*
-   * Check that, after appending the extension, the file name is really
-   * different.
-   */
-  if (fname != NULL && STRCMP(fname, retval) == 0) {
-    /* we search for a character that can be replaced by '_' */
+  // Check that, after appending the extension, the file name is really
+  // different.
+  if (fname != NULL && strcmp(fname, retval) == 0) {
+    // we search for a character that can be replaced by '_'
     while (--s >= ptr) {
       if (*s != '_') {
         *s = '_';
         break;
       }
     }
-    if (s < ptr)        /* fname was "________.<ext>", how tricky! */
+    if (s < ptr) {  // fname was "________.<ext>", how tricky!
       *ptr = 'v';
+    }
   }
   return retval;
 }
@@ -6597,7 +6597,7 @@ apply_autocmds_group (
         || event == EVENT_TABCLOSED)
       fname = vim_strsave(fname);
     else
-      fname = FullName_save(fname, FALSE);
+      fname = (char_u *)FullName_save((char *)fname, FALSE);
   }
   if (fname == NULL) {      /* out of memory */
     xfree(sfname);
@@ -6923,7 +6923,7 @@ int has_autocmd(event_T event, char_u *sfname, buf_T *buf)
   char_u      *tail = path_tail(sfname);
   int retval = FALSE;
 
-  fname = FullName_save(sfname, FALSE);
+  fname = (char_u *)FullName_save((char *)sfname, FALSE);
   if (fname == NULL)
     return FALSE;
 
diff --git a/src/nvim/hardcopy.c b/src/nvim/hardcopy.c
index cf33703fdb..819015a85d 100644
--- a/src/nvim/hardcopy.c
+++ b/src/nvim/hardcopy.c
@@ -1532,7 +1532,7 @@ static int prt_find_resource(char *name, struct prt_ps_resource_S *resource)
   STRLCPY(resource->name, name, 64);
   /* Look for named resource file in runtimepath */
   STRCPY(buffer, "print");
-  add_pathsep(buffer);
+  add_pathsep((char *)buffer);
   vim_strcat(buffer, (char_u *)name, MAXPATHL);
   vim_strcat(buffer, (char_u *)".ps", MAXPATHL);
   resource->filename[0] = NUL;
diff --git a/src/nvim/if_cscope.c b/src/nvim/if_cscope.c
index a7052149e0..b5751f0a6e 100644
--- a/src/nvim/if_cscope.c
+++ b/src/nvim/if_cscope.c
@@ -2054,7 +2054,7 @@ static char *cs_resolve_file(int i, char *name)
   } else if (csdir != NULL && csinfo[i].fname != NULL && *csdir != NUL) {
     /* Check for csdir to be non empty to avoid empty path concatenated to
      * cscope output. */
-    fullname = (char *)concat_fnames(csdir, (char_u *)name, TRUE);
+    fullname = concat_fnames((char *)csdir, name, TRUE);
   } else {
     fullname = xstrdup(name);
   }
diff --git a/src/nvim/macros.h b/src/nvim/macros.h
index 46f591eb33..51542bd3a7 100644
--- a/src/nvim/macros.h
+++ b/src/nvim/macros.h
@@ -128,12 +128,12 @@
 /* Get the length of the character p points to */
 # define MB_PTR2LEN(p)          (has_mbyte ? (*mb_ptr2len)(p) : 1)
 /* Advance multi-byte pointer, skip over composing chars. */
-# define mb_ptr_adv(p)      p += has_mbyte ? (*mb_ptr2len)(p) : 1
+# define mb_ptr_adv(p)      (p += has_mbyte ? (*mb_ptr2len)((char_u *)p) : 1)
 /* Advance multi-byte pointer, do not skip over composing chars. */
-# define mb_cptr_adv(p)     p += \
-  enc_utf8 ? utf_ptr2len(p) : has_mbyte ? (*mb_ptr2len)(p) : 1
+# define mb_cptr_adv(p)     (p += \
+  enc_utf8 ? utf_ptr2len(p) : has_mbyte ? (*mb_ptr2len)(p) : 1)
 /* Backup multi-byte pointer. Only use with "p" > "s" ! */
-# define mb_ptr_back(s, p)  p -= has_mbyte ? ((*mb_head_off)(s, p - 1) + 1) : 1
+# define mb_ptr_back(s, p)  (p -= has_mbyte ? ((*mb_head_off)((char_u *)s, (char_u *)p - 1) + 1) : 1)
 /* get length of multi-byte char, not including composing chars */
 # define mb_cptr2len(p)     (enc_utf8 ? utf_ptr2len(p) : (*mb_ptr2len)(p))
 
diff --git a/src/nvim/main.c b/src/nvim/main.c
index e1d53183aa..c1270c6181 100644
--- a/src/nvim/main.c
+++ b/src/nvim/main.c
@@ -1282,7 +1282,7 @@ scripterror:
           && !os_isdir(alist_name(&GARGLIST[0]))) {
         char_u      *r;
 
-        r = concat_fnames(p, path_tail(alist_name(&GARGLIST[0])), TRUE);
+        r = (char_u *)concat_fnames((char *)p, (char *)path_tail(alist_name(&GARGLIST[0])), TRUE);
         xfree(p);
         p = r;
       }
diff --git a/src/nvim/memfile.c b/src/nvim/memfile.c
index bbe2e62021..b6a341d5e8 100644
--- a/src/nvim/memfile.c
+++ b/src/nvim/memfile.c
@@ -893,7 +893,7 @@ blocknr_T mf_trans_del(memfile_T *mfp, blocknr_T old_nr)
 /// name so we must work out the full path name.
 void mf_set_ffname(memfile_T *mfp)
 {
-  mfp->mf_ffname = FullName_save(mfp->mf_fname, false);
+  mfp->mf_ffname = (char_u *)FullName_save((char *)mfp->mf_fname, false);
 }
 
 /// Make name of memfile's swapfile a full path.
diff --git a/src/nvim/memline.c b/src/nvim/memline.c
index 8e87bef244..29263144a4 100644
--- a/src/nvim/memline.c
+++ b/src/nvim/memline.c
@@ -1332,20 +1332,20 @@ recover_names (
         num_names = recov_file_names(names, fname_res, TRUE);
     } else {                      /* check directory dir_name */
       if (fname == NULL) {
-        names[0] = concat_fnames(dir_name, (char_u *)"*.sw?", TRUE);
+        names[0] = (char_u *)concat_fnames((char *)dir_name, "*.sw?", TRUE);
         /* For Unix names starting with a dot are special.  MS-Windows
          * supports this too, on some file systems. */
-        names[1] = concat_fnames(dir_name, (char_u *)".*.sw?", TRUE);
-        names[2] = concat_fnames(dir_name, (char_u *)".sw?", TRUE);
+        names[1] = (char_u *)concat_fnames((char *)dir_name, ".*.sw?", TRUE);
+        names[2] = (char_u *)concat_fnames((char *)dir_name, ".sw?", TRUE);
         num_names = 3;
       } else {
         p = dir_name + STRLEN(dir_name);
         if (after_pathsep((char *)dir_name, (char *)p) && p[-1] == p[-2]) {
           /* Ends with '//', Use Full path for swap name */
-          tail = make_percent_swname(dir_name, fname_res);
+          tail = (char_u *)make_percent_swname((char *)dir_name, (char *)fname_res);
         } else {
           tail = path_tail(fname_res);
-          tail = concat_fnames(dir_name, tail, TRUE);
+          tail = (char_u *)concat_fnames((char *)dir_name, (char *)tail, TRUE);
         }
         num_names = recov_file_names(names, tail, FALSE);
         xfree(tail);
@@ -1364,7 +1364,7 @@ recover_names (
      * Try finding a swap file by simply adding ".swp" to the file name.
      */
     if (*dirp == NUL && file_count + num_files == 0 && fname != NULL) {
-      char_u *swapname = modname(fname_res, (char_u *)".swp", TRUE);
+      char_u *swapname = (char_u *)modname((char *)fname_res, ".swp", TRUE);
       if (swapname != NULL) {
         if (os_file_exists(swapname)) {
           files = (char_u **)xmalloc(sizeof(char_u *));
@@ -1441,17 +1441,18 @@ recover_names (
  * Append the full path to name with path separators made into percent
  * signs, to dir. An unnamed buffer is handled as "" (<currentdir>/"")
  */
-static char_u *make_percent_swname(char_u *dir, char_u *name)
+static char *make_percent_swname(const char *dir, char *name)
+  FUNC_ATTR_NONNULL_ARG(1)
 {
-  char_u *d, *s, *f;
-
-  f = fix_fname(name != NULL ? name : (char_u *) "");
-  d = NULL;
+  char *d = NULL;
+  char *f = fix_fname(name != NULL ? name : "");
   if (f != NULL) {
-    s = (char_u *)xstrdup((char *)f);
-    for (d = s; *d != NUL; mb_ptr_adv(d))