GetLastError() not preserved across GIL operations on Windows

[zooba]

Bug report

Changes to TLS usage in 3.13 may cause the last error code to be reset when ensuring, checking or releasing the GIL. We need to preserve the value.

PyGILState_Check was already updated, but the other public APIs need the same update. Potentially some of our internal/public ones too. It might just be best to add it to the PyThread_tss_* functions.

Linked PRs

• gh-116012: Preserve GetLastError() across calls to TlsGetValue on Windows #116014

[zooba]

Okay, I can confirm that TlsGetValue breaks convention by clearing the last error code on success, as it has no return value that uniquely indicates failure. So we just need to wrap its calls up.