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GH-137573: Check C stack depth before stack allocating JIT optimizer struct #137676

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GH-137573: Check C stack depth before stack allocating JIT optimizer struct #137676

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@markshannon markshannon commented Aug 12, 2025 •
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AA-Turner
AA-Turner reviewed Aug 12, 2025
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Just so I'm clear: you plan to move this to the thread state later but only on main right? So that we don't change the struct layout in an rc for 3.14?

markshannon and others added 2 commits August 13, 2025 11:44
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Update Lib/test/test_call.py
0a889df 
Co-authored-by: Adam Turner <9087854+AA-Turner@users.noreply.github.com>
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Account for trace buffer as well
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Can you please add a Py_NO_INLINE to the _PyOptimizer_Optimize function too? I don't think this will fix it as if it's inlined, the alloca might be hoisted out to the main interpreter loop by the compiler.

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Can you please add a Py_NO_INLINE to the _PyOptimizer_Optimize function too? I don't think this will fix it as if it's inlined, the alloca might be hoisted out to the main interpreter loop by the compiler.

Yes, but not in this PR as it seems unrelated

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Just so I'm clear: you plan to move this to the thread state later but only on main right? So that we don't change the struct layout in an rc for 3.14?

Yes, that's the plan.

@markshannon markshannon added the needs backport to 3.14 bugs and security fixes label Aug 13, 2025
Fidget-Spinner
Fidget-Spinner reviewed Aug 14, 2025
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Python/optimizer_analysis.c
@@ -695,6 +695,11 @@ _Py_uop_analyze_and_optimize(
)
{
OPT_STAT_INC(optimizer_attempts);
/* Make sure we have enough C stack space for the optimizer */
int margin = 1 + sizeof(JitOptContext)/_PyOS_STACK_MARGIN_BYTES;
if (_Py_ReachedRecursionLimitWithMargin(_PyThreadState_GET(), margin)) {
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To work properly, the optimize_uops function or this function must be marked Py_NO_INLINE as well.

Otherwise, the compiler can just inline the functions and hoist the alloca above the check, making the check useless.

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