Enable -Wconversion: ui.c.

Refactoring summary:
- ui_write(): len: int --> size_t
    * parse_abstract_ui_codes(): len: int --> size_t
    * string_convert(): lenp: int * --> size_t *
        - string_convert_ext(): lenp      : int * --> size_t *
                                unconvlenp: int * --> size_t *
            * utf8len_tab_zero: char[] --> uint8_t[]
            * iconv_string(): slen      : int --> size_t
                              unconvlenp: int * --> size_t *
                              resultlenp: int * --> size_t *
        - mch_print_text_out(): len: int --> size_t
    * out_pos: int --> size_t

8 files changed, 37 insertions, 39 deletions

diff --git a/src/nvim/CMakeLists.txt b/src/nvim/CMakeLists.txt
index 922b8b85a1..99e0b215de 100644
--- a/src/nvim/CMakeLists.txt
+++ b/src/nvim/CMakeLists.txt
@@ -84,7 +84,6 @@ set(CONV_SOURCES
   spell.c
   syntax.c
   tag.c
-  ui.c
   window.c)
 
 foreach(sfile ${CONV_SOURCES})
diff --git a/src/nvim/api/vim.c b/src/nvim/api/vim.c
index e3f426719e..33020c5b8c 100644
--- a/src/nvim/api/vim.c
+++ b/src/nvim/api/vim.c
@@ -578,7 +578,7 @@ Array vim_get_api_info(uint64_t channel_id)
 ///        `emsg` instead of `msg` to print each line)
 static void write_msg(String message, bool to_err)
 {
-  static int out_pos = 0, err_pos = 0;
+  static size_t out_pos = 0, err_pos = 0;
   static char out_line_buf[LINE_BUFFER_SIZE], err_line_buf[LINE_BUFFER_SIZE];
 
 #define PUSH_CHAR(i, pos, line_buf, msg)                                      \
diff --git a/src/nvim/digraph.c b/src/nvim/digraph.c
index 243468b680..cb6bfc9cc9 100644
--- a/src/nvim/digraph.c
+++ b/src/nvim/digraph.c
@@ -1532,7 +1532,9 @@ static int getexactdigraph(int char1, int char2, int meta_char)
 
     if (convert_setup(&vc, (char_u *)"utf-8", p_enc) == OK) {
       vc.vc_fail = true;
-      to = string_convert(&vc, buf, &i);
+      assert(i >= 0);
+      size_t len = (size_t)i;
+      to = string_convert(&vc, buf, &len);
 
       if (to != NULL) {
         retval = (*mb_ptr2char)(to);
diff --git a/src/nvim/ex_cmds.c b/src/nvim/ex_cmds.c
index 49f33c5017..ad49153a1e 100644
--- a/src/nvim/ex_cmds.c
+++ b/src/nvim/ex_cmds.c
@@ -5257,8 +5257,7 @@ void fix_help_buffer(void)
                 else {
                   /* Do the conversion.  If it fails
                    * use the unconverted text. */
-                  cp = string_convert(&vc, IObuff,
-                      NULL);
+                  cp = string_convert(&vc, IObuff, NULL);
                   if (cp == NULL)
                     cp = IObuff;
                 }
diff --git a/src/nvim/hardcopy.c b/src/nvim/hardcopy.c
index 2dbe33d6e2..cc6aa57419 100644
--- a/src/nvim/hardcopy.c
+++ b/src/nvim/hardcopy.c
@@ -96,7 +96,7 @@
  * Sets the current position at the start of line "page_line".
  * If margin is TRUE start in the left margin (for header and line number).
  *
- * int mch_print_text_out(char_u *p, int len);
+ * int mch_print_text_out(char_u *p, size_t len);
  * Output one character of text p[len] at the current position.
  * Return TRUE if there is no room for another character in the same line.
  *
@@ -495,7 +495,6 @@ static void prt_header(prt_settings_T *psettings, int pagenum, linenr_T lnum)
   int page_line;
   char_u      *tbuf;
   char_u      *p;
-  int l;
 
   /* Also use the space for the line number. */
   if (prt_use_number())
@@ -542,9 +541,9 @@ static void prt_header(prt_settings_T *psettings, int pagenum, linenr_T lnum)
   page_line = 0 - prt_header_height();
   mch_print_start_line(TRUE, page_line);
   for (p = tbuf; *p != NUL; ) {
-    if (mch_print_text_out(p,
-            (l = (*mb_ptr2len)(p))
-            )) {
+    int l = (*mb_ptr2len)(p);
+    assert(l >= 0);
+    if (mch_print_text_out(p, (size_t)l)) {
       ++page_line;
       if (page_line >= 0)       /* out of room in header */
         break;
@@ -884,7 +883,7 @@ static colnr_T hardcopy_line(prt_settings_T *psettings, int page_line, prt_pos_T
       ppos->ff = TRUE;
       need_break = 1;
     } else {
-      need_break = mch_print_text_out(line + col, outputlen);
+      need_break = mch_print_text_out(line + col, (size_t)outputlen);
       if (has_mbyte)
         print_pos += (*mb_ptr2cells)(line + col);
       else
@@ -2871,7 +2870,7 @@ void mch_print_start_line(int margin, int page_line)
   prt_half_width = FALSE;
 }
 
-int mch_print_text_out(char_u *p, int len)
+int mch_print_text_out(char_u *p, size_t len)
 {
   int need_break;
   char_u ch;
diff --git a/src/nvim/mbyte.c b/src/nvim/mbyte.c
index bc8f768724..660259498b 100644
--- a/src/nvim/mbyte.c
+++ b/src/nvim/mbyte.c
@@ -143,7 +143,7 @@ static char utf8len_tab[256] =
 /*
  * Like utf8len_tab above, but using a zero for illegal lead bytes.
  */
-static char utf8len_tab_zero[256] =
+static uint8_t utf8len_tab_zero[256] =
 {
   1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,
   1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,
@@ -1375,7 +1375,7 @@ static int dbcs_ptr2char(const char_u *p)
  */
 int utf_ptr2char(const char_u *p)
 {
-  int len;
+  uint8_t len;
 
   if (p[0] < 0x80)      /* be quick for ASCII */
     return p[0];
@@ -1427,12 +1427,12 @@ int utf_ptr2char(const char_u *p)
  */
 static int utf_safe_read_char_adv(char_u **s, size_t *n)
 {
-  int c, k;
+  int c;
 
   if (*n == 0)   /* end of buffer */
     return 0;
 
-  k = utf8len_tab_zero[**s];
+  uint8_t k = utf8len_tab_zero[**s];
 
   if (k == 1) {
     /* ASCII character or NUL */
@@ -1440,7 +1440,7 @@ static int utf_safe_read_char_adv(char_u **s, size_t *n)
     return *(*s)++;
   }
 
-  if ((size_t)k <= *n) {
+  if (k <= *n) {
     /* We have a multibyte sequence and it isn't truncated by buffer
      * limits so utf_ptr2char() is safe to use. Or the first byte is
      * illegal (k=0), and it's also safe to use utf_ptr2char(). */
@@ -3504,7 +3504,8 @@ void * my_iconv_open(char_u *to, char_u *from)
  * Returns the converted string in allocated memory.  NULL for an error.
  * If resultlenp is not NULL, sets it to the result length in bytes.
  */
-static char_u * iconv_string(vimconv_T *vcp, char_u *str, int slen, int *unconvlenp, int *resultlenp)
+static char_u * iconv_string(vimconv_T *vcp, char_u *str, size_t slen,
+                             size_t *unconvlenp, size_t *resultlenp)
 {
   const char  *from;
   size_t fromlen;
@@ -3534,8 +3535,7 @@ static char_u * iconv_string(vimconv_T *vcp, char_u *str, int slen, int *unconvl
     tolen = len - done - 2;
     /* Avoid a warning for systems with a wrong iconv() prototype by
      * casting the second argument to void *. */
-    if (iconv(vcp->vc_fd, (void *)&from, &fromlen, &to, &tolen)
-        != (size_t)-1) {
+    if (iconv(vcp->vc_fd, (void *)&from, &fromlen, &to, &tolen) != SIZE_MAX) {
       /* Finished, append a NUL. */
       *to = NUL;
       break;
@@ -3547,7 +3547,7 @@ static char_u * iconv_string(vimconv_T *vcp, char_u *str, int slen, int *unconvl
         && (ICONV_ERRNO == ICONV_EINVAL || ICONV_ERRNO == EINVAL)) {
       /* Handle an incomplete sequence at the end. */
       *to = NUL;
-      *unconvlenp = (int)fromlen;
+      *unconvlenp = fromlen;
       break;
     }
     /* Check both ICONV_EILSEQ and EILSEQ, because the dynamically loaded
@@ -3581,7 +3581,7 @@ static char_u * iconv_string(vimconv_T *vcp, char_u *str, int slen, int *unconvl
   }
 
   if (resultlenp != NULL && result != NULL)
-    *resultlenp = (int)(to - (char *)result);
+    *resultlenp = (size_t)(to - (char *)result);
   return result;
 }
 
@@ -3802,7 +3802,7 @@ int convert_setup_ext(vimconv_T *vcp, char_u *from, bool from_unicode_is_utf8,
  * Illegal chars are often changed to "?", unless vcp->vc_fail is set.
  * When something goes wrong, NULL is returned and "*lenp" is unchanged.
  */
-char_u * string_convert(vimconv_T *vcp, char_u *ptr, int *lenp)
+char_u * string_convert(vimconv_T *vcp, char_u *ptr, size_t *lenp)
 {
   return string_convert_ext(vcp, ptr, lenp, NULL);
 }
@@ -3812,18 +3812,17 @@ char_u * string_convert(vimconv_T *vcp, char_u *ptr, int *lenp)
  * an incomplete sequence at the end it is not converted and "*unconvlenp" is
  * set to the number of remaining bytes.
  */
-char_u * string_convert_ext(vimconv_T *vcp, char_u *ptr, int *lenp,
-                            int *unconvlenp)
+char_u * string_convert_ext(vimconv_T *vcp, char_u *ptr,
+                            size_t *lenp, size_t *unconvlenp)
 {
   char_u      *retval = NULL;
   char_u      *d;
-  int len;
-  int i;
   int l;
   int c;
 
+  size_t len;
   if (lenp == NULL)
-    len = (int)STRLEN(ptr);
+    len = STRLEN(ptr);
   else
     len = *lenp;
   if (len == 0)
@@ -3833,7 +3832,7 @@ char_u * string_convert_ext(vimconv_T *vcp, char_u *ptr, int *lenp,
     case CONV_TO_UTF8:            /* latin1 to utf-8 conversion */
       retval = xmalloc(len * 2 + 1);
       d = retval;
-      for (i = 0; i < len; ++i) {
+      for (size_t i = 0; i < len; ++i) {
         c = ptr[i];
         if (c < 0x80)
           *d++ = c;
@@ -3844,13 +3843,13 @@ char_u * string_convert_ext(vimconv_T *vcp, char_u *ptr, int *lenp,
       }
       *d = NUL;
       if (lenp != NULL)
-        *lenp = (int)(d - retval);
+        *lenp = (size_t)(d - retval);
       break;
 
     case CONV_9_TO_UTF8:          /* latin9 to utf-8 conversion */
       retval = xmalloc(len * 3 + 1);
       d = retval;
-      for (i = 0; i < len; ++i) {
+      for (size_t i = 0; i < len; ++i) {
         c = ptr[i];
         switch (c) {
           case 0xa4: c = 0x20ac; break;                 /* euro */
@@ -3866,19 +3865,19 @@ char_u * string_convert_ext(vimconv_T *vcp, char_u *ptr, int *lenp,
       }
       *d = NUL;
       if (lenp != NULL)
-        *lenp = (int)(d - retval);
+        *lenp = (size_t)(d - retval);
       break;
 
     case CONV_TO_LATIN1:          /* utf-8 to latin1 conversion */
     case CONV_TO_LATIN9:          /* utf-8 to latin9 conversion */
       retval = xmalloc(len + 1);
       d = retval;
-      for (i = 0; i < len; ++i) {
+      for (size_t i = 0; i < len; ++i) {
         l = utf_ptr2len_len(ptr + i, len - i);
         if (l == 0)
           *d++ = NUL;
         else if (l == 1) {
-          int l_w = utf8len_tab_zero[ptr[i]];
+          uint8_t l_w = utf8len_tab_zero[ptr[i]];
 
           if (l_w == 0) {
             /* Illegal utf-8 byte cannot be converted */
@@ -3929,7 +3928,7 @@ char_u * string_convert_ext(vimconv_T *vcp, char_u *ptr, int *lenp,
       }
       *d = NUL;
       if (lenp != NULL)
-        *lenp = (int)(d - retval);
+        *lenp = (size_t)(d - retval);
       break;
 
 # ifdef MACOS_CONVERT
diff --git a/src/nvim/term.c b/src/nvim/term.c
index fa85860cb0..bdeebc7f6e 100644
--- a/src/nvim/term.c
+++ b/src/nvim/term.c
@@ -545,7 +545,7 @@ void termcapinit(char_u *name)
 #  define OUT_SIZE      2047
 // Add one to allow term_write() in os_win32.c to append a NUL
 static char_u out_buf[OUT_SIZE + 1];
-static int out_pos = 0;                 /* number of chars in out_buf */
+static size_t out_pos = 0;                 /* number of chars in out_buf */
 
 // Clear the output buffer
 void out_buf_clear(void)
@@ -558,7 +558,7 @@ void out_buf_clear(void)
  */
 void out_flush(void)
 {
-  int len = out_pos;
+  size_t len = out_pos;
   out_pos = 0;
   ui_write(out_buf, len);
 }
diff --git a/src/nvim/ui.c b/src/nvim/ui.c
index af8989f397..c09cca1347 100644
--- a/src/nvim/ui.c
+++ b/src/nvim/ui.c
@@ -95,7 +95,7 @@ void ui_builtin_stop(void)
   UI_CALL(stop);
 }
 
-void ui_write(uint8_t *s, int len)
+void ui_write(uint8_t *s, size_t len)
 {
   if (silent_mode && !p_verbose) {
     // Don't output anything in silent mode ("ex -s") unless 'verbose' set
@@ -346,7 +346,7 @@ end:
   UI_CALL(highlight_set, (ui->rgb ? rgb_attrs : cterm_attrs));
 }
 
-static void parse_abstract_ui_codes(uint8_t *ptr, int len)
+static void parse_abstract_ui_codes(uint8_t *ptr, size_t len)
 {
   if (!ui_active()) {
     return;