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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"`sysconfig --generate-posix-vars` can hang on cyclic variable definitions","articleBody":"# Bug report\n\n### Bug description:\n\nThis loop can run forever if there's a cycle in the Makefile variable definitions:\nhttps://github.com/python/cpython/blob/5334732f9c8a44722e4b339f4bb837b5b0226991/Lib/sysconfig/__main__.py#L79\n\nTo reproduce:\n```shell\nmake clean\necho 'foo=$(foo)' \u003e ./Modules/Setup.local\n./configure\nmake  # hangs forever\n```\nOr more minimally:\n```shell\nmake clean\necho 'foo=$(foo)' \u003e ./Modules/Setup.local\nmake Makefile\n./python -m sysconfig --generate-posix-vars  # hangs forever\n```\nLonger cycles are also possible, e.g. `v1=$(v2)`, `v2=$(v3)`, ...., `v999=$(v1)`.\n\n\nNote that this is less of an issue if the recursive variable definition gets expanded in the Makefile before `python -m sysconfig --generate-posix-vars` gets invoked. In that case, Make will detect the cycle and exit before the infinite loop occurs.\n\n@serhiy-storchaka you may be interested, this is very similar to #136073\n\n### CPython versions tested on:\n\nCPython main branch\n\n### Operating systems tested on:\n\nLinux\n\n\u003c!-- gh-linked-prs --\u003e\n### Linked PRs\n* gh-136166\n\u003c!-- /gh-linked-prs --\u003e\n","author":{"url":"https://github.com/brianschubert","@type":"Person","name":"brianschubert"},"datePublished":"2025-06-29T12:40:41.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":1},"url":"https://github.com/136097/cpython/issues/136097"}