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Segfault when comparing infinite data structures #330

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opened 2024-05-19 01:07:05 +00:00 by gaelan · 1 comment

gaelan commented

2024-05-19 01:07:05 +00:00

Describe the bug

When comparing two infinitely nested data structures (and pointer equality doesn't suffice), Lix segfaults.

Steps To Reproduce

let a = rec { foo = [foo]; }; b = rec { foo = [foo]; }; in a == b

Causes Lix to segfault.

Expected behavior

If possible, define a result (I have no idea if there's a sensible argument to be made for either true or false, nor whether there's any way to efficiently determine this result). Otherwise, fail with a nice error instead of segfaulting.

`nix --version` output

nix (Lix, like Nix) 2.90.0-beta.1-lixpre20240506-b6799ab

Additional context

Inherited from Nix, present since at least 2022.

## Describe the bug When comparing two infinitely nested data structures (and pointer equality doesn't suffice), Lix segfaults. ## Steps To Reproduce ``` let a = rec { foo = [foo]; }; b = rec { foo = [foo]; }; in a == b ``` Causes Lix to segfault. ## Expected behavior If possible, define a result (I have no idea if there's a sensible argument to be made for either true or false, nor whether there's any way to efficiently determine this result). Otherwise, fail with a nice error instead of segfaulting. ## `nix --version` output nix (Lix, like Nix) 2.90.0-beta.1-lixpre20240506-b6799ab ## Additional context Inherited from Nix, present since at least 2022.

gaelan added the

bug

label 2024-05-19 01:07:05 +00:00

pennae commented

2024-05-23 19:25:33 +00:00

Owner

defining a result won't really be possible, but we should definitely limit recursion depth on comparisons (lix already does this for the evaluator itself, but comparisons themselves aren't subject to this yet). reusing the same stack depth limit we already have for eval should be fine, and give an obvious place to tune if anyfew run into this trapping.

qyriad added the

Area/evaluator

E/help wanted

labels 2024-05-24 21:24:19 +00:00

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Reference: lix-project/lix#330

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