[vankudothuadhinaik]

Fixes gh-160676.

Summary

When a sys.monitoring RAISE callback raises while reporting StopIteration from a for loop, the callback exception can be swallowed by the iterator-exhaustion path.

• Make _PyEval_MonitorRaise() return the monitoring callback result.
• Propagate callback errors through _PyForIter_VirtualIteratorNext() and the tier-2 _ITER_NEXT_INLINE path.
• Regenerate Python/executor_cases.c.h.
• Add a regression test covering a monitoring callback that raises RuntimeError for StopIteration.

Validation

• Focused regression test: 1 passed.
• Full test_monitoring suite: 101 passed.
• make -j2: passed.
• make regen-cases: generated Python/executor_cases.c.h matched the checked-in worktree version byte-for-byte.
• git diff --check: passed.

Limitations

The regression test demonstrated the tier-1 path. Tier-2 runtime coverage was not demonstrated because the available build had no experimental JIT support and active monitoring instrumentation avoided executor execution. Native macOS testing was not performed.

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[NekoAsakura]

_ITER_NEXT_INLINE needs to be covered in the test.

[NekoAsakura]

Escaping calls shouldn't be inside control flow statements. See #122693 (comment).

[vankudothuadhinaik]

Addressed in the current head: _PyEval_MonitorRaise() is called outside the control-flow branch and its result is assigned to err before branching, following the escaping-call convention. The generated executor file was regenerated and verified consistent. I also added tier-2 coverage that locates _ITER_NEXT_INLINE and checks callback-error propagation. The tier-2 interpreter CI job and its test_monitoring module passed; the job summary does not expose this individual method's pass/skip result, so I am not claiming more than the logs establish. Could you please re-review when convenient?

[vankudothuadhinaik]

Follow-up on the review feedback:

• The escaping call in Python/bytecodes.c is assigned to err before branching, so it is no longer inside control flow; the generated executor file is consistent with that pattern.
• The regression test warms up the loop, locates an executor containing _ITER_NEXT_INLINE, and asserts both that the monitoring callback offset matches the executor offset and that RuntimeError("monitor callback failed") propagates. Monitoring cleanup remains in finally.
• CI for head 4bc8ddfe23f430489e12e809efb30ccf261f6aed is green. The tier-2 interpreter build/test steps passed, and its full test_monitoring module is reported as passed. The job log does not report the individual method's pass-versus-skip status, so I am not claiming a method-level result from that log. Syntax compilation, git diff --check, and tier-2 regeneration checks also passed locally; a local runtime build was unavailable in the clean Windows environment.

Could you please re-review the updated implementation and test when convenient?

[NekoAsakura]

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[NekoAsakura]

Please explain in detail what this part of the test does.

[NekoAsakura]

This comment is very LLM-esque. Either simplify it to one line or remove it.