Add `io::ErrorKind::TooManyOpenFiles` by valentynkit · Pull Request #158326 · rust-lang/rust

valentynkit · 2026-06-23T19:07:51Z

Adds an unstable io::ErrorKind::TooManyOpenFiles for the open-file-limit condition.

EMFILE and ENFILE currently decode to ErrorKind::Uncategorized, so stable code cannot tell that an operation failed because the process or the system ran out of file descriptors without inspecting raw_os_error() and a platform-specific libc/windows-sys constant.

Implements the accepted ACP rust-lang/libs-team#818, including its decision to collapse EMFILE and ENFILE into a single variant. Finer-grained handling stays available through raw_os_error().

The variant maps:

EMFILE / ENFILE on Unix and WASI
ERROR_TOO_MANY_OPEN_FILES / WSAEMFILE on Windows
FR_TOO_MANY_OPEN_FILES on VEXos

Tracking issue: #158319

r? libs

`EMFILE` and `ENFILE` decoded to `ErrorKind::Uncategorized`, so running out of file descriptors could only be detected through `raw_os_error()`. Map them, and the equivalent codes on Windows (`ERROR_TOO_MANY_OPEN_FILES`, `WSAEMFILE`) and VEXos (`FR_TOO_MANY_OPEN_FILES`), to a new unstable `TooManyOpenFiles` variant.

rust-log-analyzer · 2026-06-23T19:10:49Z

A job failed! Check out the build log: (web) (plain enhanced) (plain)

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

  IMAGE: x86_64-gnu-tools
##[endgroup]
    Updating crates.io index
error: failed to get `adler2` as a dependency of package `miniz_oxide v0.8.8`
    ... which satisfies dependency `miniz_oxide = "^0.8.5"` of package `flate2 v1.1.9`
    ... which satisfies dependency `flate2 = "^1.1.9"` of package `citool v0.1.0 (/home/runner/work/rust/rust/src/ci/citool)`

Caused by:
  failed to load source for dependency `adler2`

Caused by:
  unable to update registry `crates-io`

Caused by:
  download of ad/le/adler2 failed

Caused by:
  curl failed

Caused by:

jhpratt · 2026-06-24T03:47:21Z

@bors r+ rollup

PR CI failure is spurious

rust-bors · 2026-06-24T03:47:24Z

📌 Commit 9261852 has been approved by jhpratt

It is now in the queue for this repository.

🌲 The tree is currently closed for pull requests below priority 5. This pull request will be tested once the tree is reopened.

Rollup of 35 pull requests Successful merges: - #158315 (`rust-analyzer` subtree update) - #158336 (Stop excluding `stdarch` test crates from `rust-src`) - #155739 (Add temporary scope to assert_eq and assert_ne) - #156885 (Fix misattributed type inference error span for index expressions) - #157271 (simplify some `proc_macro` things) - #157419 (move rustc_type_ir Term things to term_kind.rs) - #157883 (Remove strict invariant node_type on hir_type during ty privacy visit) - #157921 (trait solver: Resolve region vars in max universe) - #157960 (delegation: add support for infers in generics) - #157983 (Lift the same-signature restriction for `extern "tail"`) - #158053 (Optimize network address parser) - #158105 (Extract all instance shim variants into new `ShimKind` enum) - #158207 (Resolver: local/external split of `resolve_ident_in_module_non_globs_unadjusted` ) - #158279 (Follow goto and drop when linting unreachable code) - #157527 (Move derive tests into their dedicated folder) - #157807 (don't ice on non-lifetime binders under `-Zassumptions-on-binders`) - #157939 (Reorganize `tests/ui/issues` [8/N]) - #157946 (Make `char::is_private_use` and `char::is_assigned` unstably public) - #158003 (Reorganize `tests/ui/issues` [9/N]) - #158020 (Update mingw-w64 C toolchain) - #158039 (c-variadic: test that we use equality up to free lifetimes) - #158060 (Reorganize `tests/ui/issues` [10/N]) - #158222 (format: ignore println newline in foreign format hints) - #158223 (Move target checking for #[lang] to the attribute parser) - #158252 (Use `cfg_select` in `std::os`) - #158263 (Only load the feature list once in the entire resolver) - #158267 (FromUtf8Error::into_utf8_lossy better example and suggest use) - #158272 (Reorganize `tests/ui/issues` [13/N]) - #158274 (triagebot: Stop pinging myself) - #158282 (slice_split_once: bounds check optimization note) - #158300 (Improve unknown crate_type diagnostic suggestions) - #158304 (mailmap: update mu001999) - #158309 (Update `rustc-literal-escaper` version to `0.0.8`) - #158314 (Fix incorrect unsafe debug assertion in unchecked_div_exact) - #158326 (Add `io::ErrorKind::TooManyOpenFiles`)

…-files, r=jhpratt Add `io::ErrorKind::TooManyOpenFiles` Adds an unstable `io::ErrorKind::TooManyOpenFiles` for the open-file-limit condition. `EMFILE` and `ENFILE` currently decode to `ErrorKind::Uncategorized`, so stable code cannot tell that an operation failed because the process or the system ran out of file descriptors without inspecting `raw_os_error()` and a platform-specific `libc`/`windows-sys` constant. Implements the accepted ACP rust-lang/libs-team#818, including its decision to collapse `EMFILE` and `ENFILE` into a single variant. Finer-grained handling stays available through `raw_os_error()`. The variant maps: - `EMFILE` / `ENFILE` on Unix and WASI - `ERROR_TOO_MANY_OPEN_FILES` / `WSAEMFILE` on Windows - `FR_TOO_MANY_OPEN_FILES` on VEXos Tracking issue: rust-lang#158319 r? libs

Rollup of 35 pull requests Successful merges: - #158315 (`rust-analyzer` subtree update) - #158336 (Stop excluding `stdarch` test crates from `rust-src`) - #155739 (Add temporary scope to assert_eq and assert_ne) - #156885 (Fix misattributed type inference error span for index expressions) - #157271 (simplify some `proc_macro` things) - #157419 (move rustc_type_ir Term things to term_kind.rs) - #157883 (Remove strict invariant node_type on hir_type during ty privacy visit) - #157921 (trait solver: Resolve region vars in max universe) - #157960 (delegation: add support for infers in generics) - #157983 (Lift the same-signature restriction for `extern "tail"`) - #158053 (Optimize network address parser) - #158105 (Extract all instance shim variants into new `ShimKind` enum) - #158207 (Resolver: local/external split of `resolve_ident_in_module_non_globs_unadjusted` ) - #158279 (Follow goto and drop when linting unreachable code) - #157527 (Move derive tests into their dedicated folder) - #157807 (don't ice on non-lifetime binders under `-Zassumptions-on-binders`) - #157939 (Reorganize `tests/ui/issues` [8/N]) - #157946 (Make `char::is_private_use` and `char::is_assigned` unstably public) - #158003 (Reorganize `tests/ui/issues` [9/N]) - #158020 (Update mingw-w64 C toolchain) - #158039 (c-variadic: test that we use equality up to free lifetimes) - #158060 (Reorganize `tests/ui/issues` [10/N]) - #158222 (format: ignore println newline in foreign format hints) - #158223 (Move target checking for #[lang] to the attribute parser) - #158252 (Use `cfg_select` in `std::os`) - #158263 (Only load the feature list once in the entire resolver) - #158267 (FromUtf8Error::into_utf8_lossy better example and suggest use) - #158272 (Reorganize `tests/ui/issues` [13/N]) - #158274 (triagebot: Stop pinging myself) - #158282 (slice_split_once: bounds check optimization note) - #158300 (Improve unknown crate_type diagnostic suggestions) - #158304 (mailmap: update mu001999) - #158309 (Update `rustc-literal-escaper` version to `0.0.8`) - #158314 (Fix incorrect unsafe debug assertion in unchecked_div_exact) - #158326 (Add `io::ErrorKind::TooManyOpenFiles`)

Rollup merge of #158326 - valentynkit:io-error-too-many-open-files, r=jhpratt Add `io::ErrorKind::TooManyOpenFiles` Adds an unstable `io::ErrorKind::TooManyOpenFiles` for the open-file-limit condition. `EMFILE` and `ENFILE` currently decode to `ErrorKind::Uncategorized`, so stable code cannot tell that an operation failed because the process or the system ran out of file descriptors without inspecting `raw_os_error()` and a platform-specific `libc`/`windows-sys` constant. Implements the accepted ACP rust-lang/libs-team#818, including its decision to collapse `EMFILE` and `ENFILE` into a single variant. Finer-grained handling stays available through `raw_os_error()`. The variant maps: - `EMFILE` / `ENFILE` on Unix and WASI - `ERROR_TOO_MANY_OPEN_FILES` / `WSAEMFILE` on Windows - `FR_TOO_MANY_OPEN_FILES` on VEXos Tracking issue: #158319 r? libs

JonathanBrouwer · 2026-06-25T10:57:39Z

@rust-timer build 125395d
Perf run for #158342

rust-timer · 2026-06-25T22:08:01Z

Finished benchmarking commit (125395d): comparison URL.

Overall result: ❌✅ regressions and improvements - no action needed

Benchmarking means the PR may be perf-sensitive. Consider adding rollup=never if this change is not fit for rolling up.

@rustbot label: -S-waiting-on-perf -perf-regression

Instruction count

Our most reliable metric. Used to determine the overall result above. However, even this metric can be noisy.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	1.0%	[0.8%, 1.2%]	6
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-0.2%	[-0.2%, -0.2%]	1
All ❌✅ (primary)	-	-	0

Max RSS (memory usage)

Results (primary 4.9%)

A less reliable metric. May be of interest, but not used to determine the overall result above.

	mean	range	count
Regressions ❌ (primary)	4.9%	[3.9%, 5.8%]	2
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	4.9%	[3.9%, 5.8%]	2

Cycles

Results (primary 1.6%, secondary 2.4%)

A less reliable metric. May be of interest, but not used to determine the overall result above.

	mean	range	count
Regressions ❌ (primary)	1.6%	[1.6%, 1.6%]	1
Regressions ❌ (secondary)	2.4%	[2.4%, 2.4%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	1.6%	[1.6%, 1.6%]	1

Binary size

Results (secondary 0.1%)

A less reliable metric. May be of interest, but not used to determine the overall result above.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	0.1%	[0.1%, 0.1%]	3
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-	-	0

Bootstrap: 503.101s -> 505.347s (0.45%)
Artifact size: 353.51 MiB -> 353.43 MiB (-0.02%)

Rollup of 35 pull requests Successful merges: - rust-lang/rust#158315 (`rust-analyzer` subtree update) - rust-lang/rust#158336 (Stop excluding `stdarch` test crates from `rust-src`) - rust-lang/rust#155739 (Add temporary scope to assert_eq and assert_ne) - rust-lang/rust#156885 (Fix misattributed type inference error span for index expressions) - rust-lang/rust#157271 (simplify some `proc_macro` things) - rust-lang/rust#157419 (move rustc_type_ir Term things to term_kind.rs) - rust-lang/rust#157883 (Remove strict invariant node_type on hir_type during ty privacy visit) - rust-lang/rust#157921 (trait solver: Resolve region vars in max universe) - rust-lang/rust#157960 (delegation: add support for infers in generics) - rust-lang/rust#157983 (Lift the same-signature restriction for `extern "tail"`) - rust-lang/rust#158053 (Optimize network address parser) - rust-lang/rust#158105 (Extract all instance shim variants into new `ShimKind` enum) - rust-lang/rust#158207 (Resolver: local/external split of `resolve_ident_in_module_non_globs_unadjusted` ) - rust-lang/rust#158279 (Follow goto and drop when linting unreachable code) - rust-lang/rust#157527 (Move derive tests into their dedicated folder) - rust-lang/rust#157807 (don't ice on non-lifetime binders under `-Zassumptions-on-binders`) - rust-lang/rust#157939 (Reorganize `tests/ui/issues` [8/N]) - rust-lang/rust#157946 (Make `char::is_private_use` and `char::is_assigned` unstably public) - rust-lang/rust#158003 (Reorganize `tests/ui/issues` [9/N]) - rust-lang/rust#158020 (Update mingw-w64 C toolchain) - rust-lang/rust#158039 (c-variadic: test that we use equality up to free lifetimes) - rust-lang/rust#158060 (Reorganize `tests/ui/issues` [10/N]) - rust-lang/rust#158222 (format: ignore println newline in foreign format hints) - rust-lang/rust#158223 (Move target checking for #[lang] to the attribute parser) - rust-lang/rust#158252 (Use `cfg_select` in `std::os`) - rust-lang/rust#158263 (Only load the feature list once in the entire resolver) - rust-lang/rust#158267 (FromUtf8Error::into_utf8_lossy better example and suggest use) - rust-lang/rust#158272 (Reorganize `tests/ui/issues` [13/N]) - rust-lang/rust#158274 (triagebot: Stop pinging myself) - rust-lang/rust#158282 (slice_split_once: bounds check optimization note) - rust-lang/rust#158300 (Improve unknown crate_type diagnostic suggestions) - rust-lang/rust#158304 (mailmap: update mu001999) - rust-lang/rust#158309 (Update `rustc-literal-escaper` version to `0.0.8`) - rust-lang/rust#158314 (Fix incorrect unsafe debug assertion in unchecked_div_exact) - rust-lang/rust#158326 (Add `io::ErrorKind::TooManyOpenFiles`)

…, r=joboet std: treat ENFILE as transient in the pidfd support probe The pidfd support probe special-cases `EMFILE` from `pidfd_open`: it returns the error without caching anything, so the next spawn re-probes. `ENFILE` falls through instead, into the fallback arm, so the probe caches pidfd as unsupported for the rest of the process, even after descriptors free up. Both errnos come from the same `pidfd_open` call and mean the same thing: the process is out of file descriptors, just per-process (`EMFILE`) vs system-wide (`ENFILE`). I don't see a reason to treat them differently here, so this handles `ENFILE` the same way: ```rust Err(e) if matches!(e.raw_os_error(), Some(libc::EMFILE | libc::ENFILE)) => { ``` I kept the raw `raw_os_error()` check rather than `ErrorKind::TooManyOpenFiles` (rust-lang#158326, which maps both) to match the rest of this probe, but can switch if you'd prefer. I didn't add a test, since triggering it needs real fd exhaustion during the probe, which isn't practical to reproduce. The `EMFILE` arm isn't tested either. r? libs

std: treat ENFILE as transient in the pidfd support probe The pidfd support probe special-cases `EMFILE` from `pidfd_open`: it returns the error without caching anything, so the next spawn re-probes. `ENFILE` falls through instead, into the fallback arm, so the probe caches pidfd as unsupported for the rest of the process, even after descriptors free up. Both errnos come from the same `pidfd_open` call and mean the same thing: the process is out of file descriptors, just per-process (`EMFILE`) vs system-wide (`ENFILE`). I don't see a reason to treat them differently here, so this handles `ENFILE` the same way: ```rust Err(e) if matches!(e.raw_os_error(), Some(libc::EMFILE | libc::ENFILE)) => { ``` I kept the raw `raw_os_error()` check rather than `ErrorKind::TooManyOpenFiles` (#158326, which maps both) to match the rest of this probe, but can switch if you'd prefer. I didn't add a test, since triggering it needs real fd exhaustion during the probe, which isn't practical to reproduce. The `EMFILE` arm isn't tested either. r? libs

Rollup merge of #158486 - valentynkit:pidfd-enfile-transient, r=joboet std: treat ENFILE as transient in the pidfd support probe The pidfd support probe special-cases `EMFILE` from `pidfd_open`: it returns the error without caching anything, so the next spawn re-probes. `ENFILE` falls through instead, into the fallback arm, so the probe caches pidfd as unsupported for the rest of the process, even after descriptors free up. Both errnos come from the same `pidfd_open` call and mean the same thing: the process is out of file descriptors, just per-process (`EMFILE`) vs system-wide (`ENFILE`). I don't see a reason to treat them differently here, so this handles `ENFILE` the same way: ```rust Err(e) if matches!(e.raw_os_error(), Some(libc::EMFILE | libc::ENFILE)) => { ``` I kept the raw `raw_os_error()` check rather than `ErrorKind::TooManyOpenFiles` (#158326, which maps both) to match the rest of this probe, but can switch if you'd prefer. I didn't add a test, since triggering it needs real fd exhaustion during the probe, which isn't practical to reproduce. The `EMFILE` arm isn't tested either. r? libs

Rollup of 35 pull requests Successful merges: - rust-lang/rust#158315 (`rust-analyzer` subtree update) - rust-lang/rust#158336 (Stop excluding `stdarch` test crates from `rust-src`) - rust-lang/rust#155739 (Add temporary scope to assert_eq and assert_ne) - rust-lang/rust#156885 (Fix misattributed type inference error span for index expressions) - rust-lang/rust#157271 (simplify some `proc_macro` things) - rust-lang/rust#157419 (move rustc_type_ir Term things to term_kind.rs) - rust-lang/rust#157883 (Remove strict invariant node_type on hir_type during ty privacy visit) - rust-lang/rust#157921 (trait solver: Resolve region vars in max universe) - rust-lang/rust#157960 (delegation: add support for infers in generics) - rust-lang/rust#157983 (Lift the same-signature restriction for `extern "tail"`) - rust-lang/rust#158053 (Optimize network address parser) - rust-lang/rust#158105 (Extract all instance shim variants into new `ShimKind` enum) - rust-lang/rust#158207 (Resolver: local/external split of `resolve_ident_in_module_non_globs_unadjusted` ) - rust-lang/rust#158279 (Follow goto and drop when linting unreachable code) - rust-lang/rust#157527 (Move derive tests into their dedicated folder) - rust-lang/rust#157807 (don't ice on non-lifetime binders under `-Zassumptions-on-binders`) - rust-lang/rust#157939 (Reorganize `tests/ui/issues` [8/N]) - rust-lang/rust#157946 (Make `char::is_private_use` and `char::is_assigned` unstably public) - rust-lang/rust#158003 (Reorganize `tests/ui/issues` [9/N]) - rust-lang/rust#158020 (Update mingw-w64 C toolchain) - rust-lang/rust#158039 (c-variadic: test that we use equality up to free lifetimes) - rust-lang/rust#158060 (Reorganize `tests/ui/issues` [10/N]) - rust-lang/rust#158222 (format: ignore println newline in foreign format hints) - rust-lang/rust#158223 (Move target checking for #[lang] to the attribute parser) - rust-lang/rust#158252 (Use `cfg_select` in `std::os`) - rust-lang/rust#158263 (Only load the feature list once in the entire resolver) - rust-lang/rust#158267 (FromUtf8Error::into_utf8_lossy better example and suggest use) - rust-lang/rust#158272 (Reorganize `tests/ui/issues` [13/N]) - rust-lang/rust#158274 (triagebot: Stop pinging myself) - rust-lang/rust#158282 (slice_split_once: bounds check optimization note) - rust-lang/rust#158300 (Improve unknown crate_type diagnostic suggestions) - rust-lang/rust#158304 (mailmap: update mu001999) - rust-lang/rust#158309 (Update `rustc-literal-escaper` version to `0.0.8`) - rust-lang/rust#158314 (Fix incorrect unsafe debug assertion in unchecked_div_exact) - rust-lang/rust#158326 (Add `io::ErrorKind::TooManyOpenFiles`)

rustbot assigned jhpratt Jun 23, 2026

rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. T-libs Relevant to the library team, which will review and decide on the PR/issue. labels Jun 23, 2026

rust-bors Bot added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Jun 24, 2026

This was referenced Jun 24, 2026

Tracking Issue for io_error_too_many_open_files #158319

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Rollup of 35 pull requests #158342

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JonathanBrouwer mentioned this pull request Jun 24, 2026

[CI] Rollup of 35 pull requests #158354

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rust-bors Bot merged commit 81526af into rust-lang:main Jun 25, 2026
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rustbot added this to the 1.98.0 milestone Jun 25, 2026

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This was referenced Jun 27, 2026

std: treat ENFILE as transient in the pidfd support probe #158486

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std: per-platform decode_error_kind copies have drifted (wasi/teeos missing arms) #158490

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Add `io::ErrorKind::TooManyOpenFiles`#158326

Add `io::ErrorKind::TooManyOpenFiles`#158326
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rust-timer commented Jun 25, 2026

Overall result: ❌✅ regressions and improvements - no action needed

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valentynkit commented Jun 23, 2026 •

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