l_alloc_restricted.c

void* l_alloc_restricted (void *ud, void *ptr, size_t osize, size_t nsize) {
    _Executor* self = (_Executor*)ud;

    if(ptr == NULL) {
        /*
         * <http://www.lua.org/manual/5.2/manual.html#lua_Alloc>:
         * When ptr is NULL, osize encodes the kind of object that Lua is
         * allocating.
         *
         * Since we don't care about that, just mark it as 0
         */
        osize = 0;
    }

    if (nsize == 0) {
        free(ptr);
        self->memory_used -= osize; /* subtract old size from used memory */
        return NULL;
    }

    if (self->memory_used + (nsize - osize) > self->memory_limit) {
        /* too much memory in use */
        return NULL;
    }

    ptr = realloc(ptr, nsize);
    if (ptr) {
        /* reallocation successful */
        self->memory_used += (nsize - osize);
    }

    return ptr;
}