[1.6] Fix: FileDescriptor.duplicate(as:) returns an invalid file descriptor on Windows #260
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…riptor on Windows FileDescriptor.duplicate(as:) is backed by dup2 on Unix, and _dup2 on Windows. On Unix, dup2 returns its second argument. On Windows, _dup2 instead returns 0 on success and -1 on error. This results in the newly returned FileDescriptor object always containing a '0' file descriptor rather than the newly created file descriptor, in violation of the documented behavior. Account for the platform difference in the syscall wrapper to fix this. Closes #192 (cherry picked from commit b2711a8)
jakepetroules
requested review from
glessard,
lorentey and
milseman
as code owners
glessard
approved these changes
Sep 15, 2025
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FileDescriptor.duplicate(as:) is backed by dup2 on Unix, and _dup2 on Windows. On Unix, dup2 returns its second argument. On Windows, _dup2 instead returns 0 on success and -1 on error. This results in the newly returned FileDescriptor object always containing a '0' file descriptor rather than the newly created file descriptor, in violation of the documented behavior.
Account for the platform difference in the syscall wrapper to fix this.
Closes #192
(cherry picked from commit b2711a8)