Bug report

Bug description:

Repro: Check outthis commit, build, and runpython -mtest test_monitoring -mtest_implicit_stop_iteration.

Context: The unspecialized implementation ofFOR_ITER has some built-in opcode fusion, in thatit skips the followingEND_FOR andPOP_TOP whentp_iternext returnsNULL. When the iterator is a generator, as it is inExceptionMonitoringTest.test_implicit_stop_iteration(), that means we skip themonitor_stop_iteration() call inINSTRUMENTED_END_FOR.

test_implicit_stop_iteration() passes as written, though, because theFOR_ITER in the helper function has been specialized toFOR_ITER_GEN by the time the generator finishes, andFOR_ITER_GEN's implementation doesn't perform the same fusion asFOR_ITER.

This bug can be exposed by makingthis change totest_implicit_stop_iteration(), so theFOR_ITER stays unspecialized while iterating over the generator in question.

CPython versions tested on:

CPython main branch

Operating systems tested on:

Linux

Linked PRs

• GH-116090: Fix test and clarify behavior for exception events when exhausting a generator. #120697
• GH-116090: FireRAISE events from_FOR_ITER_TIER_TWO #122413
• [3.13] GH-116090: FireRAISE events from_FOR_ITER_TIER_TWO (GH-122413) #122419