[shalseth]

Teach the manual frame pointer unwinder in _testinternalcapi the SPARC V9 frame layout. There's no frame record on SPARC: the caller's %fp (biased by 2047) and its return address are in slots 14 and 15 of the register window save area at fp, and they're only in memory after a flushw.

Tested on a SPARC T7-1 and a T4-1 (Linux, GCC 16): ManualStackUnwindTests fails without the change and passes with it, and the unwinder walks all the way down to _start. No change on x86_64.

The GNU backtrace test still fails on sparc64, that's the missing unwind tables from the issue (GCC PR 128091), not this code.

• Issue: test_c_stack_unwind fails on Linux sparc64 #160253

[python-cla-bot]

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[shalseth]

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[shalseth]

A patch for the related GCC bug in #160626 is now merged: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=128091

If this PR is merged, SPARC will have a fully clean test suite on 3.15.

[encukou]

Thank you. I have no way to test this, but for #ifdef blocks in test-only code, I'n inclined to just trust you.
Note that per PEP 11, we don't do backports for unsupported platforms: I can merge for 3.16 but ask you to keep a 3.15 patch.

If you'd like to provide/coordinate support for CPython on SPARC, you might want to add yourself here: https://devguide.python.org/developer-workflow/porting/#ports

@kulikjak, do you want to test this? (Assuming you have access to a SPARC box, from #78952 (comment))

[shalseth]

Thank you. I have no way to test this, but for #ifdef blocks in test-only code, I'n inclined to just trust you. Note that per PEP 11, we don't do backports for unsupported platforms: I can merge for 3.16 but ask you to keep a 3.15 patch.

Thanks! 3.16 is fine. It's tested on Linux, haven't touched Solaris.

If you'd like to provide/coordinate support for CPython on SPARC, you might want to add yourself here: https://devguide.python.org/developer-workflow/porting/#ports

Yes, sent PR: python/devguide#1955