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authorTavian Barnes <tavianator@tavianator.com>2020-11-04 11:36:47 -0500
committerTavian Barnes <tavianator@tavianator.com>2020-11-04 11:36:47 -0500
commit726d78019593d5b5f192d2962f5bc975bfe85785 (patch)
tree88cbdef159df912a3ecd5e18ba16be470da1b77b /bar.h
parent9b34fc831eec048ee34d99250c240115f74b1bfa (diff)
downloadbfs-726d78019593d5b5f192d2962f5bc975bfe85785.tar.xz
spawn: Fix error pipe write failure handling
A short history lesson: this code (from exec.c) used to just be write(...); In 649d85b, an empty if block was added to placate _FORTIFY_SOURCE's warn_unused_result: if (write(...) != sizeof(error)) { // ... } This is fine since the parent doesn't rely on receiving those writes (e.g. the child could die before writing), and the small write to a pipe won't fail anyway. But when bfs_spawn() was created, the implementation changed to this: while (write(...) < sizeof(error)); The while loop was presumably added to mirror musl's posix_spawn() implementation, which handles EINTR. But musl's is actually correct: while (write(...) < 0); whereas mine has a subtle bug: since sizeof(error) is unsigned, the bfs code did an unsigned comparison, meaning -1 from write() would *not* restart the loop. Fix it by comparing with 0 like musl, since short writes are impossible here. Perhaps it's time for -Wsign-compare, despite the other 18 instances being false positives.
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