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gh-137030: Fix YIELD_VALUE bytecode assertion#149184

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vstinner merged 2 commits intopython:mainfrom
vstinner:for_iter_gen
May 4, 2026
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gh-137030: Fix YIELD_VALUE bytecode assertion#149184
vstinner merged 2 commits intopython:mainfrom
vstinner:for_iter_gen

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@vstinner vstinner commented Apr 30, 2026 •
edited by bedevere-app Bot
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pythongh-137030: Fix YIELD_VALUE bytecode assertion
019d3ec 
Expect also INSTRUMENTED_FOR_ITER.
@vstinner vstinner requested a review from markshannon as a code owner April 30, 2026 11:29
@vstinner vstinner added skip news needs backport to 3.14 bugs and security fixes labels Apr 30, 2026
@bedevere-app bedevere-app Bot mentioned this pull request Apr 30, 2026
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vstinner commented Apr 30, 2026

@Fidget-Spinner @markshannon @emmatyping: Would you mind to review this fix?

See #137030 (comment) to reproduce the issue.

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read-the-docs-community Bot commented Apr 30, 2026 •
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Documentation build overview

📚 cpython-previews | 🛠️ Build #32485691 | 📁 Comparing a28cf41 against main (4599335)

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16 files changed · ± 16 modified

± Modified

markshannon
markshannon reviewed Apr 30, 2026
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Comment thread Python/bytecodes.c Outdated
@@ -1781,6 +1781,7 @@ dummy_func(
#if TIER_ONE
assert(frame->instr_ptr->op.code == INSTRUMENTED_LINE ||
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@markshannon markshannon Apr 30, 2026 •
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I'm not sure there's much value in this assert any more.
I'd be fine with removing the whole thing.

If you want to keep the check, this

Suggested change
assert(frame->instr_ptr->op.code == INSTRUMENTED_LINE ||
#if TIER_ONE && defined(Py_DEBUG)
if (!PyStackRef_IsNone(frame->f_executable)) {
int opcode = _Py_GetBaseCodeUnit(_PyFrame_GetCode(frame), frame->instr_ptr - _PyFrame_GetBytecode(frame)).op.code;
assert(opcode == SEND || opcode == FOR_ITER);
}
#endif

is probably a better formulation as it catches errors that would be hidden behind instrumentation.

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Ok, I updated my PR to use _Py_GetBaseCodeUnit().

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Use _Py_GetBaseCodeUnit()
a28cf41 
Co-Authored-by: Mark Shannon <mark@hotpy.org>
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markshannon commented Apr 30, 2026

@emmatyping can you confirm that this fixes the issue?

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emmatyping approved these changes May 1, 2026
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I can confirm this fixed the crash I found. Thanks for the fix!

@vstinner vstinner merged commit 952784a into python:main May 4, 2026
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miss-islington-app Bot commented May 4, 2026

Thanks @vstinner for the PR 🌮🎉.. I'm working now to backport this PR to: 3.14.
🐍🍒⛏🤖

@vstinner vstinner deleted the for_iter_gen branch May 4, 2026 16:10
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miss-islington-app Bot commented May 4, 2026

Sorry, @vstinner, I could not cleanly backport this to 3.14 due to a conflict.
Please backport using cherry_picker on command line.

cherry_picker 952784af4793e6f819bfecc6e0a50676c7256e3a 3.14

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bedevere-app Bot commented May 4, 2026

GH-149383 is a backport of this pull request to the 3.14 branch.

@bedevere-app bedevere-app Bot removed the needs backport to 3.14 bugs and security fixes label May 4, 2026
vstinner added a commit to vstinner/cpython that referenced this pull request May 4, 2026
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pythongh-137030: Fix YIELD_VALUE bytecode assertion (python#149184)
c7b3e65 
Co-authored-by: Mark Shannon <mark@hotpy.org>
(cherry picked from commit 952784a)
vstinner added a commit that referenced this pull request May 4, 2026
@vstinner @markshannon
[3.14] gh-137030: Fix YIELD_VALUE bytecode assertion (#149184) (#149383)
690b2bb 
gh-137030: Fix YIELD_VALUE bytecode assertion (#149184)


(cherry picked from commit 952784a)

Co-authored-by: Mark Shannon <mark@hotpy.org>
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