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Panic if an OwnedFd carried a bad file descriptor #124518

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Panic if an OwnedFd carried a bad file descriptor #124518

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19 changes: 13 additions & 6 deletions library/std/src/os/fd/owned.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -170,17 +170,24 @@ impl Drop for OwnedFd {
#[inline]
fn drop(&mut self) {
unsafe {
// Note that errors are ignored when closing a file descriptor. The
// reason for this is that if an error occurs we don't actually know if
// the file descriptor was closed or not, and if we retried (for
// something like EINTR), we might close another valid file descriptor
// opened after we closed ours.
#[cfg(not(target_os = "hermit"))]
{
#[cfg(unix)]
crate::sys::fs::debug_assert_fd_is_open(self.fd);

let _ = libc::close(self.fd);
match cvt(libc::close(self.fd)) {
Ok(_) => {},
Err(err) if err.raw_os_error() == Some(libc::EBADF) {
panic!("`OwnedFd` held an invalid file descriptor");
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debug_assert_fd_is_open (added in #124210) checks if the file descriptor actually existed. The reason that PR doesn't just check the result of close is because a FUSE filesystem can return EBADF from close even if the fd actually exists.

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Hmmmmm. I see.

It's sad that there's no way to return an error here, would be nice if the user could somehow be alerted to this problem even in release mode.

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@the8472 the8472 Apr 29, 2024 •
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the right way to do that is to add an explicit fn close(self) -> Result method. Whether everyone is onboard with that is a separate question.

}
// Note that errors are ignored when closing a file
// descriptor. The reason for this is that if an error
// occurs we don't actually know if the file descriptor was
// closed or not, and if we retried (for something like
// EINTR), we might close another valid file descriptor
// opened after we closed ours.
Err(_) => {}
}
}
#[cfg(target_os = "hermit")]
let _ = hermit_abi::close(self.fd);
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