gh-150587: Guard specialized list-int subscript indices#153004
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KRRT7 wants to merge 3 commits into
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gh-150587: Guard specialized list-int subscript indices#153004KRRT7 wants to merge 3 commits into
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Fidget-Spinner
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Jul 4, 2026
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LGTM, thanks for catching this bug, just one request.
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This PR is marked as fixing #150587, but that issue is closed as not planned. What is this fixing? |
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@markshannon that is my own issue, the original issue was for a much bigger PR and I've since then, scoped it down, will update the body / title. |
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Wait upon closer inspection, the current code already deopts in the subscript op if it sees a negative index. I think there's no bug here? Correct me if I'm wrong. Also GUARD_TOS_INT checks for a compact long already, then the subscript op itself checks for the range . |
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Fixes gh-150587.
This supersedes the earlier closed PR gh-150588. That patch was moved into gh-150425 at the time, but the broad performance PR has not landed, so this keeps the correctness fix as a focused standalone change.
This makes the runtime invariant explicit for the specialized list/int subscript and store-subscript paths. Both opcodes are selected only after seeing a compact non-negative int index, but their runtime guard only ensures an exact int. If the same specialized code later sees a non-compact exact int, it must fall back before calling
_PyLong_CompactValue().Changes:
_PyLong_CompactValue()inBINARY_OP_SUBSCR_LIST_INTandSTORE_SUBSCR_LIST_INT._testinternalcapigenerated case headers.0, then calls it with2**30 + 2and verifies genericIndexErrorbehavior instead of using the low digit as the list index.Tests:
./python.exe -m test test_opcache -v./python.exe -m test test_opcache -m test_binary_subscr -m test_store_subscr -venv PYTHON_JIT=1 ./python.exe -m test test_opcache -m test_binary_subscr -m test_store_subscr -v