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GH-139653: Only raise an exception (or fatal error) when the stack pointer is about to overflow the stack. #141711

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Merged
markshannon merged 5 commits into from
Nov 19, 2025
Merged

GH-139653: Only raise an exception (or fatal error) when the stack pointer is about to overflow the stack. #141711

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41e9404
Only raise an exception (or fatal error) when the stack pointer is ab…
markshannon Nov 17, 2025
1e7ae53
Fix typo and clarify
markshannon Nov 18, 2025
1de4a56
A couple more typos
markshannon Nov 19, 2025
7dcdf04
Update comment
markshannon Nov 20, 2025
b28b230
Fix typos
markshannon Nov 18, 2025
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Fix typos
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@markshannon
markshannon committed Nov 18, 2025
commit b28b230f9fd7811552a2806399e31df41833ad49
4 changes: 2 additions & 2 deletions Include/internal/pycore_ceval.h
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Expand Up @@ -221,9 +221,9 @@ static inline int _Py_MakeRecCheck(PyThreadState *tstate) {
// If it is below the hardware stack base, assume that we have the wrong stack limits, and do nothing.
// We could have the wrong stack limits becuase of limited platform support, or user-space threads.
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#if _Py_STACK_GROWS_DOWN
return here_addr < _tstate->c_stack_soft_limit && here_addr >= _tstate->c_stack_soft_limit - 2 * _PyOS_STACK_MARGIN_BYTES;;
return here_addr < _tstate->c_stack_soft_limit && here_addr >= _tstate->c_stack_soft_limit - 2 * _PyOS_STACK_MARGIN_BYTES;
#else
return here_addr > _tstate->c_stack_soft_limit && here_addr <= _tstate->c_stack_soft_limit + 2 * _PyOS_STACK_MARGIN_BYTES;;
return here_addr > _tstate->c_stack_soft_limit && here_addr <= _tstate->c_stack_soft_limit + 2 * _PyOS_STACK_MARGIN_BYTES;
#endif
}

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4 changes: 2 additions & 2 deletions InternalDocs/stack_protection.md
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Expand Up @@ -38,8 +38,8 @@ Recursion checks are performed by `_Py_EnterRecursiveCall()` or `_Py_EnterRecurs

```python
kb_used = (stack_top - stack_pointer)>>10
if stack_pointer < bottom_of_machine_stack
pass # Our stack limts could be wrong so it is safest to do nothing.
if stack_pointer < bottom_of_machine_stack:
pass # Our stack limits could be wrong so it is safest to do nothing.
elif stack_pointer < hard_limit:
FatalError(f"Unrecoverable stack overflow (used {kb_used} kB)")
elif stack_pointer < soft_limit:
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