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GH-104584: Restore frame->stacktop on optimizer error #108953

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Merged
brandtbucher merged 2 commits into from
Sep 6, 2023
Merged

GH-104584: Restore frame->stacktop on optimizer error #108953

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42190b6
Restore stack_pointer on optimizer error
brandtbucher Sep 5, 2023
453da35
blurb add
brandtbucher Sep 5, 2023
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2 changes: 2 additions & 0 deletions Misc/NEWS.d/next/Core and Builtins/2023-09-05-11-31-27.gh-issue-104584.IRSXA2.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1,2 @@
Fix a crash when running with :envvar:`PYTHONUOPS` or :option:`-X uops <-X>`
enabled and an error occurs during optimization.
1 change: 1 addition & 0 deletions Python/optimizer.c
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Expand Up @@ -169,6 +169,7 @@ _PyOptimizer_BackEdge(_PyInterpreterFrame *frame, _Py_CODEUNIT *src, _Py_CODEUNI
if (err <= 0) {
assert(executor == NULL);
if (err < 0) {
_PyFrame_SetStackPointer(frame, stack_pointer);
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@gvanrossum gvanrossum Sep 5, 2023

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Oh, interesting. It seems this is needed because when JUMP_BACKWARD calls _PyOptimizer_BackEdge it doesn't update the stack pointer in the frame, it just passes the stack pointer to the optimizer, which upon success passes it to the executor, which will eventually call STORE_SP() to update the stack pointer in the frame. And sure, this PR seems to fix the hole, but I wonder if it wouldn't be more robust to just save it before even calling _PyOptimizer_BackEdge.

return NULL;
}
goto jump_to_destination;
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