[Nix#8530] throwing/asserting in tryEval has exponential complexity after evaluating certain values #137

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opened 2024-03-16 06:45:07 +00:00 by lix-bot · 0 comments

lix-bot commented

2024-03-16 06:45:07 +00:00

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Upstream-Issue: NixOS/nix#8530

Describe the bug

Under the same conditions:

builtins.throw "" works
builtins.throw x hangs
builtins.trace x (builtins.throw "") works
builtins.seq x (builtins.throw "") hangs
builtins.seq x (builtins.trace "a" builtins.throw "") prints "a" and hangs
assert false; x works
builtins.seq x (assert false; x) hangs

I tried on Nix 2.10, 2.11, 2.12, 2.14, 2.15 and could reproduce on all of them

Steps To Reproduce

Clone this repo
Run nix flake check
Adjust debugThrow function in default.nix as needed
See as it hangs or doesn't hang depending on the conditions

Expected behavior

It never hangs.

nix-env --version output

nix-env (Nix) 2.15.1

Additional context

I encountered this in the wild while working with Nix, I'll try to make a smaller example and will update this issue.

edit: I tried stripping some things down, and now it simply takes a long time to execute... perhaps this is a case of exponential complexity

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Upstream-Issue: https://git.lix.systems/NixOS/nix/issues/8530 **Describe the bug** Under the same conditions: - `builtins.throw ""` works - `builtins.throw x` hangs - `builtins.trace x (builtins.throw "")` works - `builtins.seq x (builtins.throw "")` hangs - `builtins.seq x (builtins.trace "a" builtins.throw "")` prints "a" and hangs - `assert false; x` works - `builtins.seq x (assert false; x)` hangs I tried on Nix 2.10, 2.11, 2.12, 2.14, 2.15 and could reproduce on all of them **Steps To Reproduce** 1. Clone [this repo](https://github.com/chayleaf/notnft/tree/97a88a3fa864a842427617b1f1926281d511ddaa) 2. Run `nix flake check` 3. Adjust `debugThrow` function in `default.nix` as needed 4. See as it hangs or doesn't hang depending on the conditions **Expected behavior** It never hangs. **`nix-env --version` output** `nix-env (Nix) 2.15.1` **Additional context** I encountered this in the wild while working with Nix, I'll try to make a smaller example and will update this issue. edit: I tried stripping some things down, and now it simply takes a long time to execute... perhaps this is a case of exponential complexity **Priorities** Add :+1: to [issues you find important](https://github.com/NixOS/nix/issues?q=is%3Aissue+is%3Aopen+sort%3Areactions-%2B1-desc).