Fix race condition in dup2 when duplicating to same fd #60
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Per POSIX, dup2(fd, fd) should return fd immediately without modifying anything. The previous implementation would close_read()/close_write() and then add_reader()/add_writer() in separate operations, temporarily setting the pipe reference count to zero. A concurrent write during this window would see readers == 0 and incorrectly return EPIPE. Added early return when old_fd == new_fd to avoid this race. 🤖 Generated with [Claude Code](https://claude.com/claude-code) Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
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Summary
dup2(fd, fd)should returnfdimmediately without modifying anythingclose_read()/close_write()and thenadd_reader()/add_writer()in separate operations, temporarily setting the pipe reference count to zeroreaders == 0and incorrectly return EPIPEold_fd == new_fdto avoid this raceTest plan
dup2(fd, fd)returns immediately without affecting pipe state🤖 Generated with Claude Code