Function autovivify_ptr

library/LuaTypes.cpp:220–270

}

static void autovivify_ptr(lua_State *state, int fname_idx, void **pptr,
    const type_identity *target, int val_index)
{
    lua_getfield(state, val_index, "new");

    // false or nil => bail out
    if (!lua_toboolean(state, -1))
        field_error(state, fname_idx, "null and autovivify not requested", "write");

    // not 'true' => call df.new()
    if (!lua_isboolean(state, -1))
    {
        int top = lua_gettop(state);

        // Verify new points to a reasonable type of object
        const type_identity *suggested = get_object_identity(state, top, "autovivify", true, true);

        if (!is_type_compatible(state, target, 0, suggested, top+1, false))
            field_error(state, fname_idx, "incompatible suggested autovivify type", "write");

        lua_pop(state, 1);

        // Invoke df.new()
        lua_getfield(state, LUA_REGISTRYINDEX, DFHACK_NEW_NAME);
        lua_swap(state);
        lua_call(state, 1, 1);

        // Retrieve the pointer
        void *nval = get_object_internal(state, target, top, false);

        // shouldn't happen: this means suggested type is compatible,
        // but its new() result isn't for some reason.
        if (!nval)
            field_error(state, fname_idx, "inconsistent autovivify type", "write");

        *pptr = nval;
    }
    // otherwise use the target type
    else
    {
        if (!target)
            field_error(state, fname_idx, "trying to autovivify void*", "write");

        *pptr = target->allocate();

        if (!*pptr)
            field_error(state, fname_idx, "could not allocate in autovivify", "write");
    }

    lua_pop(state, 1);
}

static bool is_null(lua_State *state, int val_index)
{