Impossible to trace error: stack overflow (possible infinite recursion)

[yajo]

Describe the bug

Something I've done started producing an infinite recursion. Nix just fails, but there's no stack trace, so AFAIK there's no possible way to know what triggers the problem.

Steps To Reproduce

nix flake check --show-trace 'gitlab:moduon/mrchef?rev=7f6177504daaa74d1b8dc64b256fbf15866efb3a'

Expected behavior

I'm passing --show-trace, so there should be a trace.

nix-env --version output
nix-env (Nix) 2.7.0

Additional context

I'm building a python app to manage git meta-repositories. Sort of a better replacement for git-submodules.

I asked in https://discourse.nixos.org/t/how-to-debug-infinite-recursion/18470?u=yajo but so far I've started to believe this is a bug in nix.

The ref above points to https://gitlab.com/moduon/mrchef/-/merge_requests/1 where I isolated the test case that reproduces this problem.

Edit: the final fix was nix-community/poetry2nix#585. I could have found that in minutes, not days, if I had a proper stack trace.

@moduon MT-83

[Artturin]

Try show-trace with #6204

[yajo]

Still unhelpful 😕

> nix run 'github:NixOs/nix/refs/pull/6204/head' -- flake check --show-trace 'gitlab:moduon/mrchef?rev=7f6177504daaa74d1b8dc64b256fbf15866efb3a'
warning: unknown flake output 'lib'
[0/1 built] checking flake output 'checks'error: stack overflow (possible infinite recursion)

Not a clue on where the infinite recursion happened.

[roberth]

These are detected overflows of the C++ stack.
We could potentially use the heap to store more of the Nix evaluation stack, turning some of these errors into successful evaluations, and others into diverging programs that either run out of heap space, or, if we decide to, error out because of a more artificial limit that isn't as low as the C++ stack's limit.

[roberth]

If we decide to implement our own limit on the stack size, we can throw a proper exception that can return a proper stack trace or start the debugger.

[nixos-discourse]

This issue has been mentioned on NixOS Discourse. There might be relevant details there:

https://discourse.nixos.org/t/2023-06-22-nix-team-meeting-minutes-65/29643/1

[yajo]

Is there any progress on this issue? Diagnosing the source of these kind of errors is extremely frustrating. I'm having another one and I don't know even where to start.

[roberth]

@yajo There actually is! You could try #8879