std/sys/fd: Relax READ_LIMIT on Darwin
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Darwin's `read`/`write` syscalls emit `EINVAL` only when `nbyte > INT_MAX`. The case `nbyte == INT_MAX` is valid, so the subtraction can be removed.
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- 1 from READ_LIMIT on DarwinREAD_LIMIT on Darwin
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Thanks for testing this! @bors r+ rollup |
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…, r=ChrisDenton
std/sys/fd: Relax `READ_LIMIT` on Darwin
Darwin's `read`/`write` syscalls emit `EINVAL` only when `nbyte > INT_MAX`. The case `nbyte == INT_MAX` is valid, so the subtraction (`- 1`) in
```rust
const READ_LIMIT: usize = if cfg!(target_vendor = "apple") {
libc::c_int::MAX as usize - 1 // <- HERE
} else {
libc::ssize_t::MAX as usize
};
```
can be removed.
I tested that the case `nbyte == INT_MAX` is valid on various versions of macOS, including old one like Mac OS X 10.5.
The man page says:
- read() and pread() will fail if the parameter nbyte exceeds INT_MAX (link: https://keith.github.io/xcode-man-pages/read.2.html)
- write() and pwrite() will fail if the parameter nbyte exceeds INT_MAX (link: https://keith.github.io/xcode-man-pages/write.2.html)
Here are links to Darwin's code:
- [macOS 15.5] https://github.com/apple-oss-distributions/xnu/blob/e3723e1f17661b24996789d8afc084c0c3303b26/bsd/kern/sys_generic.c#L307
- [Mac OS X 10.2] https://github.com/apple/darwin-xnu/blob/d738f900846ed2d5f685e18bf85ce63b0176f61a/bsd/kern/sys_generic.c#L220
Related PR: rust-lang#38622.
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Aug 23, 2025
Rollup of 7 pull requests Successful merges: - #144452 (std/sys/fd: Relax `READ_LIMIT` on Darwin) - #145307 (Fix `LazyLock` poison panic message) - #145515 (Optimize `char::encode_utf8`) - #145540 (interpret/allocation: get_range on ProvenanceMap) - #145774 (Remove default opts from config) - #145780 (Do not warn about missing change ID in tarball builds) - #145781 (Remove profile section from Clippy) r? `@ghost` `@rustbot` modify labels: rollup
samueltardieu
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Aug 23, 2025
…, r=ChrisDenton
std/sys/fd: Relax `READ_LIMIT` on Darwin
Darwin's `read`/`write` syscalls emit `EINVAL` only when `nbyte > INT_MAX`. The case `nbyte == INT_MAX` is valid, so the subtraction (`- 1`) in
```rust
const READ_LIMIT: usize = if cfg!(target_vendor = "apple") {
libc::c_int::MAX as usize - 1 // <- HERE
} else {
libc::ssize_t::MAX as usize
};
```
can be removed.
I tested that the case `nbyte == INT_MAX` is valid on various versions of macOS, including old one like Mac OS X 10.5.
The man page says:
- read() and pread() will fail if the parameter nbyte exceeds INT_MAX (link: https://keith.github.io/xcode-man-pages/read.2.html)
- write() and pwrite() will fail if the parameter nbyte exceeds INT_MAX (link: https://keith.github.io/xcode-man-pages/write.2.html)
Here are links to Darwin's code:
- [macOS 15.5] https://github.com/apple-oss-distributions/xnu/blob/e3723e1f17661b24996789d8afc084c0c3303b26/bsd/kern/sys_generic.c#L307
- [Mac OS X 10.2] https://github.com/apple/darwin-xnu/blob/d738f900846ed2d5f685e18bf85ce63b0176f61a/bsd/kern/sys_generic.c#L220
Related PR: rust-lang#38622.
samueltardieu
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Aug 23, 2025
…, r=ChrisDenton
std/sys/fd: Relax `READ_LIMIT` on Darwin
Darwin's `read`/`write` syscalls emit `EINVAL` only when `nbyte > INT_MAX`. The case `nbyte == INT_MAX` is valid, so the subtraction (`- 1`) in
```rust
const READ_LIMIT: usize = if cfg!(target_vendor = "apple") {
libc::c_int::MAX as usize - 1 // <- HERE
} else {
libc::ssize_t::MAX as usize
};
```
can be removed.
I tested that the case `nbyte == INT_MAX` is valid on various versions of macOS, including old one like Mac OS X 10.5.
The man page says:
- read() and pread() will fail if the parameter nbyte exceeds INT_MAX (link: https://keith.github.io/xcode-man-pages/read.2.html)
- write() and pwrite() will fail if the parameter nbyte exceeds INT_MAX (link: https://keith.github.io/xcode-man-pages/write.2.html)
Here are links to Darwin's code:
- [macOS 15.5] https://github.com/apple-oss-distributions/xnu/blob/e3723e1f17661b24996789d8afc084c0c3303b26/bsd/kern/sys_generic.c#L307
- [Mac OS X 10.2] https://github.com/apple/darwin-xnu/blob/d738f900846ed2d5f685e18bf85ce63b0176f61a/bsd/kern/sys_generic.c#L220
Related PR: rust-lang#38622.
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Aug 23, 2025
Rollup of 14 pull requests Successful merges: - #143898 (opt-dist: rebuild rustc when doing static LLVM builds) - #144452 (std/sys/fd: Relax `READ_LIMIT` on Darwin) - #145234 (match exhaustiveness diagnostics: show a trailing comma on singleton tuple consructors in witness patterns (and clean up a little)) - #145515 (Optimize `char::encode_utf8`) - #145540 (interpret/allocation: get_range on ProvenanceMap) - #145670 (port `sanitize` attribute to the new parsing infrastructure) - #145713 (next-solver: fix `feature(const_trait_impl)` bootstrap) - #145729 (Remove two duplicated crates) - #145744 (miri: also detect aliasing of in-place argument and return place) - #145774 (Remove default opts from config) - #145781 (Remove profile section from Clippy) - #145782 (rustdoc: make attributes render consistently) - #145787 (citool: cleanup `mismatched_lifetime_syntaxes` warnings) - #145791 (Fix ICE when validating transmuting ZST to inhabited enum) r? `@ghost` `@rustbot` modify labels: rollup
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Rollup merge of #144452 - morinmorin:apple/update_read_limit, r=ChrisDenton std/sys/fd: Relax `READ_LIMIT` on Darwin Darwin's `read`/`write` syscalls emit `EINVAL` only when `nbyte > INT_MAX`. The case `nbyte == INT_MAX` is valid, so the subtraction (`- 1`) in ```rust const READ_LIMIT: usize = if cfg!(target_vendor = "apple") { libc::c_int::MAX as usize - 1 // <- HERE } else { libc::ssize_t::MAX as usize }; ``` can be removed. I tested that the case `nbyte == INT_MAX` is valid on various versions of macOS, including old one like Mac OS X 10.5. The man page says: - read() and pread() will fail if the parameter nbyte exceeds INT_MAX (link: https://keith.github.io/xcode-man-pages/read.2.html) - write() and pwrite() will fail if the parameter nbyte exceeds INT_MAX (link: https://keith.github.io/xcode-man-pages/write.2.html) Here are links to Darwin's code: - [macOS 15.5] https://github.com/apple-oss-distributions/xnu/blob/e3723e1f17661b24996789d8afc084c0c3303b26/bsd/kern/sys_generic.c#L307 - [Mac OS X 10.2] https://github.com/apple/darwin-xnu/blob/d738f900846ed2d5f685e18bf85ce63b0176f61a/bsd/kern/sys_generic.c#L220 Related PR: #38622.
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Rollup of 14 pull requests Successful merges: - rust-lang/rust#143898 (opt-dist: rebuild rustc when doing static LLVM builds) - rust-lang/rust#144452 (std/sys/fd: Relax `READ_LIMIT` on Darwin) - rust-lang/rust#145234 (match exhaustiveness diagnostics: show a trailing comma on singleton tuple consructors in witness patterns (and clean up a little)) - rust-lang/rust#145515 (Optimize `char::encode_utf8`) - rust-lang/rust#145540 (interpret/allocation: get_range on ProvenanceMap) - rust-lang/rust#145670 (port `sanitize` attribute to the new parsing infrastructure) - rust-lang/rust#145713 (next-solver: fix `feature(const_trait_impl)` bootstrap) - rust-lang/rust#145729 (Remove two duplicated crates) - rust-lang/rust#145744 (miri: also detect aliasing of in-place argument and return place) - rust-lang/rust#145774 (Remove default opts from config) - rust-lang/rust#145781 (Remove profile section from Clippy) - rust-lang/rust#145782 (rustdoc: make attributes render consistently) - rust-lang/rust#145787 (citool: cleanup `mismatched_lifetime_syntaxes` warnings) - rust-lang/rust#145791 (Fix ICE when validating transmuting ZST to inhabited enum) r? `@ghost` `@rustbot` modify labels: rollup
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Darwin's
read/writesyscalls emitEINVALonly whennbyte > INT_MAX. The casenbyte == INT_MAXis valid, so the subtraction (- 1) incan be removed.
I tested that the case
nbyte == INT_MAXis valid on various versions of macOS, including old one like Mac OS X 10.5.The man page says:
Here are links to Darwin's code:
Related PR: #38622.