rework malloc mock function

test/cmp_max_used_bits/test_cmp_max_used_bits_list.c

@@ -35,13 +35,16 @@ static int malloc_fail;
 
 void* malloc(size_t size)
 {
-    static void* (*real_malloc)(size_t) = NULL;
+	static void* (*real_malloc)(size_t size) = NULL;
 
 	if(malloc_fail)
 		return NULL;
 
-    if (!real_malloc)
-        real_malloc = (void *(*)(size_t))dlsym(RTLD_NEXT, "malloc");
+	if (!real_malloc) {
+		*(void **)(&real_malloc) = dlsym(RTLD_NEXT, "malloc");
+		/* The cast removes a gcc warning https://stackoverflow.com/a/31528674 */
+		TEST_ASSERT_NOT_NULL(real_malloc);
+	}
 
 	fprintf(stderr, "malloc(%zu)\n", size);
 	return real_malloc(size);