luaL_tolstring

luaL_tolstring[-0, +1, e]

const char *luaL_tolstring (lua_State *L, int idx, size_t *len);

Converts any Lua value at the given index to a C string in a reasonable format. The resulting string is pushed onto the stack and also returned by the function. If len is not NULL, the function also sets *len with the string length.

If the value has a metatable with a __tostring field, then luaL_tolstring calls the corresponding metamethod with the value as argument, and uses the result of the call as its result.