ctime.cpp

#include <cstdlib>
#include <ctime>
#define DLLEXPORT extern "C" __declspec (dllexport)

DLLEXPORT double get_time()
{
    time_t currentTime, zeroTime = {0};
    time(&currentTime);
    return difftime(currentTime, zeroTime);
}

fpscompensation.gml

global._get_time = external_define("ctime.dll", "get_time", dll_cdecl, ty_real, 0);

globalvar get_time;
get_time = "return external_call(global._get_time);"

object_event_add(PlayerControl,ev_create,0,"
    lastTime = execute_string(get_time);
    time = lastTime;
");
object_event_add(PlayerControl,ev_step,ev_step_begin,"
    time = execute_string(get_time);
    time_delta = time - lastTime;
    lastTime = time;
    
    if (time_delta != 0)
    {
        global.target_fps = 1/time_delta;
    }
    else
    {
        global.target_fps = 1;
    }
    global.delta_factor = 30/global.target_fps;
    global.ticks_per_virtual = global.target_fps/30;
    global.skip_delta_factor = global.delta_factor/global.frameskip;
");

//the first thing I thought of that existed through the entire game
//in case the game closes during a menu or something
object_event_add(RateController,ev_other, ev_game_end,"
    external_free('ctime.dll');
");