How to Fix “ds_list index out of range” in GameMaker

The ds_list out-of-range error is an off-by-one or empty-list access. Bounds-checking before you read fixes it. Here is how.

How to fix it

1. Bounds-check before access

Confirm the index is at least zero and less than ds_list_size before reading. Accessing position ds_list_size is always one past the end.

2. Fix loop bounds

A loop over a list should run while the index is less than the size, not less than or equal. The off-by-one at the top of the loop is the usual culprit.

3. Handle empty lists

Code that reads the first or last element crashes on an empty list. Check the size is greater than zero before indexing, especially for lists filled at runtime.

Catching the ones you can't reproduce

The hardest version of this to fix is the one you can't reproduce — it only happens on a player's hardware, OS, driver, or save state, under conditions that simply aren't present on your machine. A report that says “it crashed” or “it froze” gives you nothing to act on, so the bug survives release after release while quietly costing you players.

Automatic error capture closes that gap. Each failure arrives with its full stack trace, the device and OS, the build number, and a breadcrumb trail of what the player did right before it broke, so even a failure you have never seen becomes a specific, reproducible issue. Fold identical failures into one signature ranked by how many players each hits, and your worklist sorts itself worst-first instead of arriving as a stream of vague complaints.

This is where a tool like Bugnet earns its place. Its SDK captures every GameMaker error automatically with the full stack trace plus device, OS, memory, build, and game-state context, folds duplicates into one grouped issue with an occurrence count, and ties each to the build it first appeared on — so you fix the problem that hurts the most players first and confirm it is gone when its signature disappears from the next release.