Question: Does GameMaker have garbage collection?

Answer

GameMaker Language (GML), which is used for scripting in GameMaker Studio, takes care of memory management automatically. It uses a form of garbage collection to free up memory that is no longer needed. Here's how it works:

Automatic Memory Management

In GameMaker, you don't usually need to manually allocate or free memory as you would in languages like C or C++. Instead, when you create instances of objects or data structures, GameMaker manages the memory for you.

Instances and Objects

When an instance of an object is destroyed, either through code using instance_destroy() or because it goes out of scope at the end of an event or script, GameMaker will automatically free up the memory associated with that instance.

// Example of destroying an instance
if (instance_exists(enemy))
{
    instance_destroy(enemy);
}

Data Structures

For data structures such as arrays, lists, grids, maps, etc., GameMaker provides functions to explicitly destroy them when they are no longer needed.

// Create a ds_list
var my_list = ds_list_create();

// Add some items to the list
ds_list_add(my_list, "item1");
ds_list_add(my_list, "item2");

// When done with the list, you must manually destroy it
ds_list_destroy(my_list);

If you forget to destroy data structures, they will remain in memory, potentially causing memory leaks. However, if a room ends and there are still data structures that haven't been destroyed, GameMaker will clean them up as part of the room end process, but relying on this is not good practice.

Surfaces and Textures

Surfaces and textures also need to be managed. If you create a surface, you should free it when it's no longer needed by using surface_free(). Similarly, texture assets created dynamically via code should be removed with texture_delete().

// Example of creating and freeing a surface
var my_surface = surface_create(256, 256);

// ... drawing actions ...

// Free the surface once it is no longer needed
if (surface_exists(my_surface))
{
    surface_free(my_surface);
}

Conclusion

GameMaker helps manage memory for you through its garbage collection mechanisms, but there are certain resources that require manual intervention to avoid memory leaks. Properly managing memory by destroying instances and cleaning up data structures, surfaces, and other dynamically allocated resources as soon as they're no longer needed is essential for the performance and stability of your games.