unix: add HOST_NAME_MAX - #5531
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Yasser-Ameur wants to merge 2 commits into
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POSIX requires HOST_NAME_MAX in <limits.h> for use with gethostname, and it was missing everywhere except Fuchsia. Added it per family, glibc and uclibc at 64 and the musl-derived and BSD-ish libcs at 255, skipping FreeBSD, NetBSD, DragonFly, Apple, Solaris/illumos and Hurd, which deliberately leave it undefined for sysconf instead. glibc 64: https://github.com/bminor/glibc/blob/04e750e75b73957cf1c791535a3f4319534a52fc/sysdeps/unix/sysv/linux/bits/local_lim.h#L93 uclibc-ng 64: https://github.com/kraj/uclibc-ng/blob/f6f9f40cb17ae95610c4fe36f6ee77cfbcf05df1/libc/sysdeps/linux/common/bits/local_lim.h#L93 musl 255: https://git.musl-libc.org/cgit/musl/tree/include/limits.h?id=5e9972eaef08ccf55dabe254ac829a30329793d3#n56 android bionic 255: https://github.com/aosp-mirror/platform_bionic/blob/731631f300090436d7f5df80d50b6275c8c60a93/libc/include/bits/posix_limits.h#L135 openbsd 255: https://github.com/openbsd/src/blob/78e3ccc2aa1724882faaab7fa2366e535f039976/sys/sys/syslimits.h#L76 haiku 255: https://github.com/haiku/haiku/blob/89141b6857474342330f6205850b59435165187b/headers/posix/limits.h#L35 redox 255: https://github.com/redox-os/relibc/blob/381772ec81fced6d055f0f0ba6fa92c7f3256fbb/src/header/limits/mod.rs#L145 emscripten 255: https://github.com/emscripten-core/emscripten/blob/06e8b0d84d8b409b1b5ee59832948877bda6137e/system/lib/libc/musl/include/limits.h#L63 wasi 255: https://github.com/WebAssembly/wasi-libc/blob/06513b9ae0c1b14ca3010924939c007ed27628a1/libc-top-half/musl/include/limits.h#L56 cygwin 255: https://github.com/cygwin/cygwin/blob/00208dc31e790b8c130f32c4a0528c781fc07328/winsup/cygwin/include/cygwin/limits.h#L22
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tgross35
requested changes
Sep 17, 2026
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| pub const _SC_GETGR_R_SIZE_MAX: c_int = 100; | ||
| pub const _SC_GETPW_R_SIZE_MAX: c_int = 101; | ||
| pub const _SC_LOGIN_NAME_MAX: c_int = 102; | ||
| /// Constants may change across releases. See the [usage guidelines](crate#usage-guidelines) | ||
| /// for details. | ||
| pub const HOST_NAME_MAX: c_int = 255; | ||
| pub const _SC_THREAD_SAFE_FUNCTIONS: c_int = 103; | ||
| pub const _SC_TRACE_NAME_MAX: c_int = 104; |
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Move this to either side of the existing _SC group
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| pub const _SC_HOST_NAME_MAX: c_int = 180; | ||
| /// Constants may change across releases. See the [usage guidelines](crate#usage-guidelines) | ||
| /// for details. | ||
| pub const HOST_NAME_MAX: c_int = 255; | ||
| pub const _SC_TRACE: c_int = 181; |
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| /// Constants may change across releases. See the [usage guidelines](crate#usage-guidelines) | ||
| /// for details. |
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You can drop these comments, this isn't quite as volatile as other _MAX constants that change every time we get a new one
| GLOB_TILDE | ||
| GLOB_TILDE_CHECK | ||
| HOSTFS_SUPER_MAGIC | ||
| HOST_NAME_MAX |
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Put this in linux.txt rather than linux-gnu and linux-musl since it's present on all environments
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Reminder, once the PR becomes ready for a review, use |
…emver entry Review cleanups: the OpenBSD and WASI constants sit after their _SC groups instead of inside them, the volatility comments are dropped since this value does not change between releases, and the semver entry lives in linux.txt rather than in both linux-gnu.txt and linux-musl.txt.
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Done: OpenBSD and WASI moved after their @rustbot ready |
tgross35
approved these changes
Sep 17, 2026
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@rustbot author for squash |
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Sep 17, 2026
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Adds
HOST_NAME_MAXwhere the platform's own limits header defines it: 64 for glibc and uclibc-ng, 255 for musl, Android, OpenBSD, Haiku, Redox, Emscripten, WASI and Cygwin. Not added for FreeBSD, NetBSD, DragonFly, Apple, illumos and Hurd, whose headers leave it undefined on purpose (sysconf only). Header sources for each value are in the commit message.ctest passes for x86_64-unknown-linux-gnu and x86_64-unknown-linux-musl, with the constant present in the generated test source for both.
Closes #5511