Use posix_spawn_file_actions_adddup2() to clear FD_CLOEXEC.
#1147
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On FreeBSD, OpenBSD, Android, and Glibc ≥ 2.29, `posix_spawn_file_actions_adddup2()` automatically clears `FD_CLOEXEC` if the file descriptors passed to it are equal. Relying on this behaviour eliminates a race condition when spawning child processes. Some older Linuxes (Amazon Linux 2 in particular) don't have this functionality, so we do a runtime check of the Glibc version.
grynspan
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enhancement
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grynspan
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suzannaratcliff
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Confirmed that swift-foundation exit tests still work when running with this branch of swift-testing on Ubuntu 20.04 |
…ntly the case though)
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stmontgomery
approved these changes
Jun 10, 2025
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On FreeBSD, OpenBSD, Android, and Glibc ≥ 2.29,
posix_spawn_file_actions_adddup2()automatically clearsFD_CLOEXECif the file descriptors passed to it are equal. Relying on this behaviour eliminates a race condition when spawning child processes. This functionality is standardized in POSIX.1-2024 thanks to Austin Group Defect #411.Some older Linuxes (Amazon Linux 2 in particular) don't have this functionality, so we do a runtime check of the Glibc version.
This PR is a follow-up to #1145.
Resolves #1140.
Checklist: