wip ~ increase warning level for cl compiles (and fix warnings)

Author: rivy

Makefile.win

@@ -604,7 +604,7 @@ STRIP := $()
 ## /subsystem:console,4.00 :: generate "Win32 character-mode" console application; 4.00 => minimum supported system is Win9x/NT; supported only by MSVC 9 (`cl` version "15xx" from 2008) or less
 ## /subsystem:console,5.01 :: generate "Win32 character-mode" console application; 5.01 => minimum supported system is XP; supported by MSVC 10 (`cl` version "16xx") or later when compiling for 32-bit
 ## /subsystem:console,5.02 :: generate "Win32 character-mode" console application; 5.02 => minimum supported system is XP; supported by MSVC 10 (`cl` version "16xx") or later when compiling for 64-bit
-CFLAGS = /nologo /W3 /WX /EHs $(call %cflags_incs,${INCLUDE_DIRS})## requires delayed expansion (b/c uses `%shell_quote` which is defined later)
+CFLAGS = /nologo /W4 /WX /EHs $(call %cflags_incs,${INCLUDE_DIRS})## requires delayed expansion (b/c uses `%shell_quote` which is defined later)
 %cflags_incs = $(call %map,$(eval %f=/I $(call %shell_quote,$${1}))%f,$(strip ${1}))
 CFLAGS_COMPILE_ONLY := -c
 CFLAGS_ARCH_32 := $(if $(filter clang-cl,${CC}),-m32,)

ch.c

@@ -147,7 +147,7 @@ static int ch_addbuf();
  */
 static int ch_get(void)
 {
-    struct buf *bp;
+    struct buf *bp = NULL;
     struct bufnode *bn;
     int n;
     int read_again;
@@ -253,9 +253,9 @@ static int ch_get(void)
          * If we read less than a full block, that's ok.
          * We use partial block and pick up the rest next time.
          */
-        if (ch_ungotchar != -1)
+        if (ch_ungotchar > -1)
         {
-            bp->data[bp->datasize] = ch_ungotchar;
+            bp->data[bp->datasize] = (char)ch_ungotchar;
             n = 1;
             ch_ungotchar = -1;
         } else if (ch_flags & CH_HELPFILE)

charset.c

@@ -616,10 +616,7 @@ public int utf_len(int ch)
 /*
  * Does the parameter point to the lead byte of a well-formed UTF-8 character?
  */
-    public int
-is_utf8_well_formed(ss, slen)
-    char *ss;
-    size_t slen;
+public int is_utf8_well_formed(char *ss, size_t slen)
 {
     size_t i;
     size_t len;

cmdbuf.c

@@ -1195,7 +1195,7 @@ public int cmd_char(int c)
 
     if (!utf_mode)
     {
-        cmd_mbc_buf[0] = c;
+        cmd_mbc_buf[0] = (char)c;
         len = 1;
     } else
     {
@@ -1204,7 +1204,7 @@ public int cmd_char(int c)
         {
          retry:
             cmd_mbc_buf_index = 1;
-            *cmd_mbc_buf = c;
+            *cmd_mbc_buf = (char)c;
             if (IS_ASCII_OCTET(c))
                 cmd_mbc_buf_len = 1;
 #if MSDOS_COMPILER || OS2
@@ -1226,7 +1226,7 @@ public int cmd_char(int c)
             }
         } else if (IS_UTF8_TRAIL(c))
         {
-            cmd_mbc_buf[cmd_mbc_buf_index++] = c;
+            cmd_mbc_buf[cmd_mbc_buf_index++] = (char)c;
             if (cmd_mbc_buf_index < cmd_mbc_buf_len)
                 return (CC_OK);
             if (!is_utf8_well_formed(cmd_mbc_buf, cmd_mbc_buf_index))
@@ -1477,6 +1477,7 @@ static void read_cmdhist(void (*action)(void*,struct mlist*,char*), void *uparam
 
 static void addhist_init(void *uparam, struct mlist *ml, char *string)
 {
+    (void)uparam; // avoid unreferenced parameter warning
     if (ml != NULL)
         cmd_addhist(ml, string, 0);
     else if (string != NULL)
@@ -1590,6 +1591,7 @@ static void copy_hist(void *uparam, struct mlist *ml, char *string)
  */
 static void make_file_private(FILE *f)
 {
+   (void)f; // avoid unreferenced parameter warning
 #if HAVE_FCHMOD
     int do_chmod = 1;
 #if HAVE_STAT