Function call_lua

example/lua_callback_result.cpp:94–119

If do_work succeeds, we return the resulting int answer. If it fails, we'll communicate that failure to our caller.

// If do_work succeeds, we return the resulting int answer. If it fails, we'll
// communicate that failure to our caller.
leaf::result<int> call_lua( lua_State * L )
{
    leaf::error_monitor cur_err;

    // Ask the Lua interpreter to call the global Lua function call_do_work.
    lua_getfield( L, LUA_GLOBALSINDEX, "call_do_work" );
    if( int err = lua_pcall(L, 0, 1, 0) ) // Ask Lua to call the global function call_do_work.
    {
        std::string msg = lua_tostring(L, 1);
        lua_pop(L, 1);

        // We got a Lua error which may be the error we're reporting from
        // do_work, or some other error. If it is another error,
        // cur_err.assigned_error_id() will return a new leaf::error_id,
        // otherwise we'll be working with the original value returned by
        // leaf::new_error in do_work.
        return cur_err.assigned_error_id().load( e_lua_pcall_error{err}, e_lua_error_message{std::move(msg)} );
    }
    else
    {
        // Success! Just return the int answer.
        int answer = lua_tonumber(L, -1);
        lua_pop(L, 1);
        return answer;
    }
}

int main()
{