cJSON_AddItemToObject does not have a way to detect OOM from add_item_to_object.cJSON_strdup

[mkmoisen]

cJSON_AddItemToObject is function returning void.

It calls add_item_to_object, which is a function returning cJSON_bool.

add_item_to_object calls cJSON_strdup here, which can fail if there is no memory left. Under this condition, add_item_to_object returns false, having never added the item to the object.

Finally, since cJSON_AddItemToObject returns NULL, the calling code cannot check for this condition.

I found this while trying to add test coverage in my code for out of memory errors, by manipulating the malloc_fn function via cJSON_InitHooks.

You can prove it like the following:

#include "cJSON.h"
#include <stdio.h>
#include <stdlib.h>

int times_without_failing = 0;
int times_before_failing = 0;

void *test_malloc_fail(size_t size)
{
    if (times_without_failing++ == times_before_failing) {
        printf("malloc reutrning none\n");
        return NULL;
    }
    printf("malloc returning real\n");
    return malloc(size);
}

void test_hooks(int i) {
    cJSON_Hooks hooks;

    hooks.malloc_fn = (void *) test_malloc_fail;
    hooks.free_fn = (void *) free;
    times_without_failing = 0;
    times_before_failing = i;
    cJSON_InitHooks(&hooks);

}

int main(void)
{
    test_hooks(2);
    cJSON *json = cJSON_CreateObject();
    cJSON *object = cJSON_CreateObject();
    cJSON_AddItemToObject(json, "foo", object);
    if (cJSON_HasObjectItem(json, "foo")) {
        printf("foo is in json\n");
    } else {
        printf("foo is not in json\n");
    }
    printf("done\n");
}

---

This prints out:

malloc returning real
malloc returning real
malloc reutrning none
foo is not in json
done

[Alanscut]

hi @mkmoisen , I totally agree with that. Many isssues are related with the memory allocation failure, but if all the function with memory allocation will return a flag or throws an exception when memory allocation failure, one could found the problem timely.
My suggestion is to change the return variable from void to boolean, true - adding successfully, false - adding failed. What do you think?

[Alanscut]

closed for #453