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linux: Improve panic message for out-of-range fds in FD_* functions - #5528

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danielcanencia:I_1401
Oct 1, 2026
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linux: Improve panic message for out-of-range fds in FD_* functions#5528
tgross35 merged 1 commit into
rust-lang:mainfrom
danielcanencia:I_1401

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@danielcanencia danielcanencia commented Sep 13, 2026 •
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Part of #1401

Fixes the out-of-bounds FD_SET/FD_CLR/FD_ISSET panic for Linux
(linux_like). The issue also calls for the same clear panic message in
other platforms; those remain a follow-up (cygwin, haiku, solaris, etc).

Note:

  • FD_ZERO needs no change — it takes no fd and fills the set, so there
    is nothing to range-check.

tgross35
tgross35 requested changes Sep 15, 2026
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Thanks for putting this together!

The issue also calls for the same clear panic message in other platforms; those remain a follow-up (cygwin, haiku, solaris, etc).

I'd prefer to get them all done at the same time.

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Comment thread src/unix/linux_like/mod.rs Outdated
Comment thread src/unix/linux_like/mod.rs Outdated
Comment thread src/unix/linux_like/mod.rs
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Reminder, once the PR becomes ready for a review, use @rustbot ready.

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rustbot commented Sep 27, 2026

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Some changes occurred in a solarish module

cc @jclulow, @pfmooney

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@danielcanencia

danielcanencia commented Sep 27, 2026

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@tgross35 All three review points are addressed: let-else style, panic! in the prelude, and coverage of all platforms. Ready for another look.

@rustbot ready

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One followup that came with the new changes, otherwise LGTM

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Comment thread src/fuchsia/mod.rs

f! {
pub unsafe fn FD_CLR(fd: c_int, set: *mut fd_set) -> () {
let fd = fd as usize;

@tgross35 tgross35 Sep 29, 2026

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Can you keep the single let fd = fd as usize; and use that? Since all other uses of fd are currently doing the same cast.

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Done, sorry about that. All functions now keep the single upfront cast.

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This PR was rebased onto a different main commit. Here's a range-diff highlighting what actually changed.

Rebasing is a normal part of keeping PRs up to date, so no action is needed—this note is just to help reviewers.

@danielcanencia
Improve panic message for out-of-range fds in FD_* functions
b4851cc 
Passing a file descriptor that is negative or >= FD_SETSIZE to FD_SET,
FD_CLR or FD_ISSET is undefined behavior per POSIX, and the previous
"index out of bounds" panic gave no hint of the required range. Panic
with a message that states the valid 0..FD_SETSIZE range instead.

Applies the fix across all platforms: linux_like, bsd, solarish, redox,
nto, newlib, fuchsia, haiku, cygwin, hurd, aix (bitmask via get/get_mut
+ let-else) and wasi (explicit range check). FD_ZERO is unchanged (takes
no fd). WASI has no FD_CLR.

Also adds panic! and Option::{self, None, Some} to the prelude so the
new code resolves under no_core (rustc-dep-of-std) builds.

Part of rust-lang#1401
@danielcanencia

danielcanencia commented Sep 29, 2026

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@rustbot ready

tgross35
tgross35 approved these changes Oct 1, 2026
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Thanks!

View changes since this review

@tgross35
tgross35 added this pull request to the merge queue Oct 1, 2026
Merged via the queue into rust-lang:main with commit 5b6e5a6 Oct 1, 2026
60 checks passed
@tgross35 tgross35 added the stable-nominated This PR should be considered for cherry-pick to libc's stable release branch label Oct 1, 2026
tgross35 pushed a commit to tgross35/rust-libc that referenced this pull request Oct 1, 2026
@danielcanencia @tgross35
Improve panic message for out-of-range fds in FD_* functions
05c67bd 
Passing a file descriptor that is negative or >= FD_SETSIZE to FD_SET,
FD_CLR or FD_ISSET is undefined behavior per POSIX, and the previous
"index out of bounds" panic gave no hint of the required range. Panic
with a message that states the valid 0..FD_SETSIZE range instead.

Applies the fix across all platforms: linux_like, bsd, solarish, redox,
nto, newlib, fuchsia, haiku, cygwin, hurd, aix (bitmask via get/get_mut
+ let-else) and wasi (explicit range check). FD_ZERO is unchanged (takes
no fd). WASI has no FD_CLR.

Also adds panic! and Option::{self, None, Some} to the prelude so the
new code resolves under no_core (rustc-dep-of-std) builds.

Part of rust-lang#1401

(backport <rust-lang#5528>)
(cherry picked from commit 5b6e5a6)
tgross35 pushed a commit to tgross35/rust-libc that referenced this pull request Oct 1, 2026
@danielcanencia @tgross35
Improve panic message for out-of-range fds in FD_* functions
22a2c9f 
Passing a file descriptor that is negative or >= FD_SETSIZE to FD_SET,
FD_CLR or FD_ISSET is undefined behavior per POSIX, and the previous
"index out of bounds" panic gave no hint of the required range. Panic
with a message that states the valid 0..FD_SETSIZE range instead.

Applies the fix across all platforms: linux_like, bsd, solarish, redox,
nto, newlib, fuchsia, haiku, cygwin, hurd, aix (bitmask via get/get_mut
+ let-else) and wasi (explicit range check). FD_ZERO is unchanged (takes
no fd). WASI has no FD_CLR.

Also adds panic! and Option::{self, None, Some} to the prelude so the
new code resolves under no_core (rustc-dep-of-std) builds.

Part of rust-lang#1401

(backport <rust-lang#5528>)
(cherry picked from commit 5b6e5a6)
tgross35 pushed a commit to tgross35/rust-libc that referenced this pull request Oct 1, 2026
@danielcanencia @tgross35
Improve panic message for out-of-range fds in FD_* functions
0bcf990 
Passing a file descriptor that is negative or >= FD_SETSIZE to FD_SET,
FD_CLR or FD_ISSET is undefined behavior per POSIX, and the previous
"index out of bounds" panic gave no hint of the required range. Panic
with a message that states the valid 0..FD_SETSIZE range instead.

Applies the fix across all platforms: linux_like, bsd, solarish, redox,
nto, newlib, fuchsia, haiku, cygwin, hurd, aix (bitmask via get/get_mut
+ let-else) and wasi (explicit range check). FD_ZERO is unchanged (takes
no fd). WASI has no FD_CLR.

Also adds panic! and Option::{self, None, Some} to the prelude so the
new code resolves under no_core (rustc-dep-of-std) builds.

Part of rust-lang#1401

(backport <rust-lang#5528>)
(cherry picked from commit 5b6e5a6)
tgross35 pushed a commit to tgross35/rust-libc that referenced this pull request Oct 1, 2026
@danielcanencia @tgross35
Improve panic message for out-of-range fds in FD_* functions
66ca15d 
Passing a file descriptor that is negative or >= FD_SETSIZE to FD_SET,
FD_CLR or FD_ISSET is undefined behavior per POSIX, and the previous
"index out of bounds" panic gave no hint of the required range. Panic
with a message that states the valid 0..FD_SETSIZE range instead.

Applies the fix across all platforms: linux_like, bsd, solarish, redox,
nto, newlib, fuchsia, haiku, cygwin, hurd, aix (bitmask via get/get_mut
+ let-else) and wasi (explicit range check). FD_ZERO is unchanged (takes
no fd). WASI has no FD_CLR.

Also adds panic! and Option::{self, None, Some} to the prelude so the
new code resolves under no_core (rustc-dep-of-std) builds.

Part of rust-lang#1401

(backport <rust-lang#5528>)
(cherry picked from commit 5b6e5a6)

[ needed to add an extra cast on WASI for the 0.2 branch - Trevor ]
tgross35 pushed a commit to tgross35/rust-libc that referenced this pull request Oct 1, 2026
@danielcanencia @tgross35
Improve panic message for out-of-range fds in FD_* functions
0861b92 
Passing a file descriptor that is negative or >= FD_SETSIZE to FD_SET,
FD_CLR or FD_ISSET is undefined behavior per POSIX, and the previous
"index out of bounds" panic gave no hint of the required range. Panic
with a message that states the valid 0..FD_SETSIZE range instead.

Applies the fix across all platforms: linux_like, bsd, solarish, redox,
nto, newlib, fuchsia, haiku, cygwin, hurd, aix (bitmask via get/get_mut
+ let-else) and wasi (explicit range check). FD_ZERO is unchanged (takes
no fd). WASI has no FD_CLR.

Also adds panic! and Option::{self, None, Some} to the prelude so the
new code resolves under no_core (rustc-dep-of-std) builds.

Part of rust-lang#1401

(backport <rust-lang#5528>)
(cherry picked from commit 5b6e5a6)

[ needed to add an extra cast on WASI for the 0.2 branch - Trevor ]
tgross35 pushed a commit to tgross35/rust-libc that referenced this pull request Oct 1, 2026
@danielcanencia @tgross35
Improve panic message for out-of-range fds in FD_* functions
c9c05f6 
Passing a file descriptor that is negative or >= FD_SETSIZE to FD_SET,
FD_CLR or FD_ISSET is undefined behavior per POSIX, and the previous
"index out of bounds" panic gave no hint of the required range. Panic
with a message that states the valid 0..FD_SETSIZE range instead.

Applies the fix across all platforms: linux_like, bsd, solarish, redox,
nto, newlib, fuchsia, haiku, cygwin, hurd, aix (bitmask via get/get_mut
+ let-else) and wasi (explicit range check). FD_ZERO is unchanged (takes
no fd). WASI has no FD_CLR.

Also adds panic! and Option::{self, None, Some} to the prelude so the
new code resolves under no_core (rustc-dep-of-std) builds.

Part of rust-lang#1401

(backport <rust-lang#5528>)
(cherry picked from commit 5b6e5a6)

[ needed to add an extra cast on WASI for the 0.2 branch - Trevor ]
@tgross35 tgross35 mentioned this pull request Oct 1, 2026
Merged
renovate-bot pushed a commit to renovate-bot/rust-lang-_-libc that referenced this pull request Oct 1, 2026
@danielcanencia @tgross35
Improve panic message for out-of-range fds in FD_* functions
8270aa1 
Passing a file descriptor that is negative or >= FD_SETSIZE to FD_SET,
FD_CLR or FD_ISSET is undefined behavior per POSIX, and the previous
"index out of bounds" panic gave no hint of the required range. Panic
with a message that states the valid 0..FD_SETSIZE range instead.

Applies the fix across all platforms: linux_like, bsd, solarish, redox,
nto, newlib, fuchsia, haiku, cygwin, hurd, aix (bitmask via get/get_mut
+ let-else) and wasi (explicit range check). FD_ZERO is unchanged (takes
no fd). WASI has no FD_CLR.

Also adds panic! and Option::{self, None, Some} to the prelude so the
new code resolves under no_core (rustc-dep-of-std) builds.

Part of rust-lang#1401

(backport <rust-lang#5528>)
(cherry picked from commit 5b6e5a6)

[ needed to add an extra cast on WASI for the 0.2 branch - Trevor ]
@tgross35 tgross35 added stable-applied This PR has been cherry-picked to libc's stable release branch and removed stable-nominated This PR should be considered for cherry-pick to libc's stable release branch labels Oct 1, 2026
This was referenced Oct 9, 2026
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