Panic if an OwnedFd carried a bad file descriptor

[tbu-]

This should never happen, notify the user if it did happen anyway.

[rustbot]

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[rust-log-analyzer]

The job x86_64-gnu-llvm-17 failed! Check out the build log: (web) (plain)

Click to see the possible cause of the failure (guessed by this bot)

#16 exporting to docker image format
#16 sending tarball 29.5s done
#16 DONE 35.2s
##[endgroup]
Setting extra environment values for docker:  --env ENABLE_GCC_CODEGEN=1 --env GCC_EXEC_PREFIX=/usr/lib/gcc/
[CI_JOB_NAME=x86_64-gnu-llvm-17]
---
sccache: Starting the server...
##[group]Configure the build
configure: processing command line
configure: 
configure: build.configure-args := ['--build=x86_64-unknown-linux-gnu', '--llvm-root=/usr/lib/llvm-17', '--enable-llvm-link-shared', '--set', 'rust.thin-lto-import-instr-limit=10', '--set', 'change-id=99999999', '--enable-verbose-configure', '--enable-sccache', '--disable-manage-submodules', '--enable-locked-deps', '--enable-cargo-native-static', '--set', 'rust.codegen-units-std=1', '--set', 'dist.compression-profile=balanced', '--dist-compression-formats=xz', '--disable-dist-src', '--release-channel=nightly', '--enable-debug-assertions', '--enable-overflow-checks', '--enable-llvm-assertions', '--set', 'rust.verify-llvm-ir', '--set', 'rust.codegen-backends=llvm,cranelift,gcc', '--set', 'llvm.static-libstdcpp', '--enable-new-symbol-mangling']
configure: target.x86_64-unknown-linux-gnu.llvm-config := /usr/lib/llvm-17/bin/llvm-config
configure: llvm.link-shared     := True
configure: rust.thin-lto-import-instr-limit := 10
configure: change-id            := 99999999
---
   Compiling std_detect v0.1.5 (/checkout/library/stdarch/crates/std_detect)
   Compiling miniz_oxide v0.7.2
   Compiling object v0.32.2
   Compiling addr2line v0.21.0
error: expected one of `.`, `=>`, `?`, or an operator, found `{`
    |
    |
180 |                     Err(err) if err.raw_os_error() == Some(libc::EBADF) {
    |                                                                         ^ expected one of `.`, `=>`, `?`, or an operator
error: could not compile `std` (lib) due to 1 previous error
Build completed unsuccessfully in 0:00:15
  local time: Mon Apr 29 13:10:30 UTC 2024
  network time: Mon, 29 Apr 2024 13:10:30 GMT

[bjorn3]

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.

[tbu-]

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.

[the8472]

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.