[3.12] Lambda generators cause assertion failure: python: Objects/genobject.c:400: gen_close: Assertion exception_handler_depth > 0' failed.`

@iritkatriel

Crash report

What happened?

When CPython 3.12 is built with assertions enabled, the following snippet causes the interpreter to crash:

x = lambda: (yield 3)
next(x())

$ ./python /tmp/LambdasTest.py 
python: Objects/genobject.c:400: gen_close: Assertion `exception_handler_depth > 0' failed.
Aborted (core dumped)

This doesn't happen with 3.11 or with main. From a quick bisect:

[3.12] gh-100762: Fix optimization in gen_close (GH-111069) #115818 (eb4774d) broke it on 3.12
gh-111354: simplify detection of RESUME after YIELD_VALUE at except-depth 1 #111459 (52cc4af) fixed it on main

This was triggered in the wild by Nuitka's test suite: Nuitka/Nuitka#2893.

CC @iritkatriel

CPython versions tested on:

3.12

Operating systems tested on:

Linux

Output from running 'python -VV' on the command line:

Python 3.12.3+ (heads/3.12:6d9677d78e, Jun 1 2024, 11:06:51) [GCC 14.1.1 20240516]

Linked PRs

Gentle ping.

Given no reply, I'm going to revert this change in Gentoo. Hope that doesn't cause more issues.

dev-lang/python: Bump to 3.12.4_p1

Thanks. I agree, let's revert the bad commit in 3.12.

gh-119897: Add test for lambda generator invocation (#120658)

pythongh-119897: Add test for lambda generator invocation (pythonGH-1…

[3.12] gh-119897: Revert buggy optimization which was removed in 3.13 (…

Thanks.

Thank you!

[3.13] gh-119897: Add test for lambda generator invocation (GH-120658) (

pythongh-119897: Add test for lambda generator invocation (python#120658

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[3.12] Lambda generators cause assertion failure: `python: Objects/genobject.c:400: gen_close: Assertion` exception_handler_depth > 0' failed.` #119897

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What happened?

CPython versions tested on:

Operating systems tested on:

Output from running 'python -VV' on the command line:

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[3.12] Lambda generators cause assertion failure: python: Objects/genobject.c:400: gen_close: Assertion exception_handler_depth > 0' failed.` #119897

Description

Crash report

What happened?

CPython versions tested on:

Operating systems tested on:

Output from running 'python -VV' on the command line:

Linked PRs

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mgorny commented on Jun 10, 2024

mgorny commented on Jun 12, 2024

iritkatriel commented on Jun 13, 2024

iritkatriel commented on Jun 18, 2024

mgorny commented on Jun 18, 2024

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[3.12] Lambda generators cause assertion failure: `python: Objects/genobject.c:400: gen_close: Assertion` exception_handler_depth > 0' failed.` #119897