gh-155109: Run tests exhausting the C stack with a limited C stack - #155120
Merged
serhiy-storchaka merged 4 commits intoAug 4, 2026
Conversation
Add the @support.run_with_limited_c_stack() decorator which runs the test in a thread with a small C stack, so that the outcome does not depend on RLIMIT_STACK. Use it in tests which recurse to a fixed depth -- @support.skip_if_huge_c_stack() failed to skip them with a 16 MiB stack. Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
serhiy-storchaka
requested review from
AlexWaygood,
Eclips4,
JelleZijlstra,
iritkatriel and
tomasr8
as code owners
August 3, 2026 13:44
On platforms where the interpreter cannot query the thread stack size it assumes Py_C_STACK_SIZE (4 MiB), so a smaller thread stack crashes instead of raising RecursionError. Verified on illumos and OpenBSD: a 2 MiB stack dumps core, 8 MiB raises RecursionError. Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Member
Author
|
@kulikjak, could you please test if this helps? |
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
AlexWaygood
removed their request for review
August 3, 2026 20:52
Member
Author
Contributor
|
Thanks! I tested your change and the test suite is green again. |
…h-155109-limited-c-stack
serhiy-storchaka
enabled auto-merge (squash)
August 4, 2026 09:15
serhiy-storchaka
added
needs backport to 3.14
|
Thanks @serhiy-storchaka for the PR 🌮🎉.. I'm working now to backport this PR to: 3.14, 3.15. |
|
Sorry, @serhiy-storchaka, I could not cleanly backport this to |
|
GH-155164 is a backport of this pull request to the 3.15 branch. |
bedevere-app
Bot
removed
the
needs backport to 3.15
|
GH-155165 is a backport of this pull request to the 3.14 branch. |
serhiy-storchaka
added a commit
that referenced
this pull request
Aug 4, 2026
…tack (GH-155120) (GH-155165) Add the @support.run_with_limited_c_stack() decorator which runs the test in a thread with a 8 MiB C stack, so that the outcome does not depend on RLIMIT_STACK. Use it in tests which recurse to a fixed depth -- @support.skip_if_huge_c_stack() failed to skip them with a 16 MiB stack. (cherry picked from commit ce5ae29) Co-authored-by: Claude Opus 5 (1M context) <noreply@anthropic.com>
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
2 participants
Add this suggestion to a batch that can be applied as a single commit.This suggestion is invalid because no changes were made to the code.Suggestions cannot be applied while the pull request is closed.Suggestions cannot be applied while viewing a subset of changes.Only one suggestion per line can be applied in a batch.Add this suggestion to a batch that can be applied as a single commit.Applying suggestions on deleted lines is not supported.You must change the existing code in this line in order to create a valid suggestion.Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be applied on multi-line comments.Suggestions cannot be applied while the pull request is queued to merge.Suggestion cannot be applied right now. Please check back later.
Add the
@support.run_with_limited_c_stack(depth)decorator: it runs the test in a thread with an 8 MiB C stack, so that the outcome does not depend onRLIMIT_STACK. If the thread stack size cannot be limited, it falls back to the old behavior — run in the current thread and skip if the C stack is too large.Use it in tests which recurse to a fixed depth.
@support.skip_if_huge_c_stack()estimates the remaining stack in interpreter loop frames (~328 bytes), so it fails to skip tests which recurse with much smaller C frames (~100 bytes) — they fail with a 16 MiB stack. It is kept for tests with unbounded recursion and fortest_call.test_super_deep(), which needs a deep stack.Tested on Linux with 1, 8, 16, 32 and 512 MiB and unlimited stack limits, and on illumos and OpenBSD.
skip_if_huge_c_stackunderestimates available C recursion depth #155109