Additional cleanup for SDL_RWprintf() (thanks @sezero!)

include/SDL3/SDL_rwops.h

@@ -518,7 +518,7 @@ extern DECLSPEC size_t SDLCALL SDL_RWwrite(SDL_RWops *context, const void *ptr,
  * \sa SDL_RWseek
  * \sa SDL_RWwrite
  */
-extern DECLSPEC size_t SDLCALL SDL_RWprintf(SDL_RWops *context, SDL_PRINTF_FORMAT_STRING const char *fmt, ...);
+extern DECLSPEC size_t SDLCALL SDL_RWprintf(SDL_RWops *context, SDL_PRINTF_FORMAT_STRING const char *fmt, ...)  SDL_PRINTF_VARARG_FUNC(2);
 
 /**
  * Print to an SDL_RWops data stream.

src/file/SDL_rwops.c

@@ -812,14 +812,17 @@ size_t SDL_RWprintf(SDL_RWops *context, SDL_PRINTF_FORMAT_STRING const char *fmt
 {
     va_list ap;
     int size;
-    char *string = NULL;
+    char *string;
     size_t bytes;
 
     va_start(ap, fmt);
     size = SDL_vasprintf(&string, fmt, ap);
     va_end(ap);
+    if (size < 0) {
+        return 0;
+    }
 
-    bytes = SDL_RWwrite(context, string, size);
+    bytes = SDL_RWwrite(context, string, (size_t)size);
     SDL_free(string);
     return bytes;
 }
@@ -827,12 +830,15 @@ size_t SDL_RWprintf(SDL_RWops *context, SDL_PRINTF_FORMAT_STRING const char *fmt
 size_t SDL_RWvprintf(SDL_RWops *context, const char *fmt, va_list ap)
 {
     int size;
-    char *string = NULL;
+    char *string;
     size_t bytes;
 
     size = SDL_vasprintf(&string, fmt, ap);
+    if (size < 0) {
+        return 0;
+    }
 
-    bytes = SDL_RWwrite(context, string, size);
+    bytes = SDL_RWwrite(context, string, (size_t)size);
     SDL_free(string);
     return bytes;
 }