vim-patch:9.1.2147: Compile warning in strings.c (#37842)

Problem:  Compile warning in strings.c
Solution: Use const qualifier (John Marriott).

closes: vim/vim#19387

388654af27

Co-authored-by: John Marriott <basilisk@internode.on.net>

src/nvim/memory.c

@@ -273,8 +273,8 @@ size_t xstrnlen(const char *s, size_t n)
 char *xstrchrnul(const char *str, char c)
   FUNC_ATTR_NONNULL_RET FUNC_ATTR_NONNULL_ALL FUNC_ATTR_PURE
 {
-  char *p = strchr(str, c);
+  const char *p = strchr(str, c);
-  return p ? p : (char *)(str + strlen(str));
+  return p ? (char *)p : (char *)(str + strlen(str));
 }
 
 /// A version of memchr() that returns a pointer one past the end
@@ -288,8 +288,8 @@ char *xstrchrnul(const char *str, char c)
 void *xmemscan(const void *addr, char c, size_t size)
   FUNC_ATTR_NONNULL_RET FUNC_ATTR_NONNULL_ALL FUNC_ATTR_PURE
 {
-  char *p = memchr(addr, c, size);
+  const char *p = memchr(addr, c, size);
-  return p ? p : (char *)addr + size;
+  return p ? (char *)p : (char *)addr + size;
 }
 
 /// Replaces every instance of `c` with `x`.
@@ -524,7 +524,7 @@ char *xstrndup(const char *str, size_t len)
   FUNC_ATTR_MALLOC FUNC_ATTR_WARN_UNUSED_RESULT FUNC_ATTR_NONNULL_RET
   FUNC_ATTR_NONNULL_ALL
 {
-  char *p = memchr(str, NUL, len);
+  const char *p = memchr(str, NUL, len);
   return xmemdupz(str, p ? (size_t)(p - str) : len);
 }
 

src/nvim/strings.c

@@ -1100,9 +1100,7 @@ static int parse_fmt_types(const char ***ap_types, int *num_posarg, const char *
 
   while (*p != NUL) {
     if (*p != '%') {
-      char *q = strchr(p + 1, '%');
+      size_t n = (size_t)(xstrchrnul(p + 1, '%') - p);
-      size_t n = (q == NULL) ? strlen(p) : (size_t)(q - p);
-
       p += n;
     } else {
       // allowed values: \0, h, l, L