user/sven/glibc.git/stdlib/stdlib.h, branch master

Update copyright dates with scripts/update-copyrights

2026-01-01T21:42:29Z

Define C23 header version macros

2025-11-27T19:32:49Z

C23 defines library macros __STDC_VERSION_

_H__ to indicate that a header has support for new / changed features from C23. Now that all the required library features are implemented in glibc, define these macros. I'm not sure this is sufficiently much of a user-visible feature to be worth a mention in NEWS. Tested for x86_64. There are various optional C23 features we don't yet have, of which I might look at the Annex H ones (floating-point encoding conversion functions and _Float16 functions) next. * Optional time bases TIME_MONOTONIC, TIME_ACTIVE, TIME_THREAD_ACTIVE. See - we need to review / update that patch. (I think patch 2/2, inventing new names for all the nonstandard CLOCK_* supported by the Linux kernel, is rather more dubious.) * Updating conform/ tests for C23. * Defining the rounding mode macro FE_TONEARESTFROMZERO for RISC-V (as far as I know, the only architecture supported by glibc that has hardware support for this rounding mode for binary floating point) and supporting it throughout glibc and its tests (especially the string/numeric conversions in both directions that explicitly handle each possible rounding mode, and various tests that do likewise). * Annex H floating-point encoding conversion functions. (It's not entirely clear which are optional even given support for Annex H; there's some wording applied inconsistently about only being required when non-arithmetic interchange formats are supported; see the comments I raised on the WG14 reflector on 23 Oct 2025.) * _Float16 functions (and other header and testcase support for this type). * Decimal floating-point support. * Fully supporting __int128 and unsigned __int128 as integer types wider than intmax_t, as permitted by C23. Would need doing in coordination with GCC, see GCC bug 113887 for more discussion of what's involved.

Implement C23 const-preserving standard library macros

2025-11-20T19:31:04Z

C23 makes various standard library functions, that return a pointer into an input array, into macros that return a pointer to const when the relevant argument passed to the macro is a pointer to const. (The requirement is for macros, with the existing function types applying when macro expansion is suppressed. When a null pointer constant is passed, such as integer 0, that's the same as a pointer to non-const.) Implement this feature. This only applies to C, not C++, since such macros are not an appropriate way of doing this for C++ and all the affected functions other than bsearch have overloads to implement an equivalent feature for C++ anyway. Nothing is done to apply such a change to any non-C23 functions with the same property of returning a pointer into an input array. The feature is also disabled when _LIBC is defined, since there are various places in glibc that either redefine these identifiers as macros, or define the functions themselves, and would need changing to work in the presence of these macro definitions. A natural question is whether we should in fact change those places and not disable the macro definitions for _LIBC. If so, we'd need a solution for the places in glibc that define the macro *before* including the relevant header (in order in effect to disable the header declaration of the function by renaming that declaration). One testcase has #undef added to avoid conflicting with this feature and another has const added; -Wno-discarded-qualifiers is added for building zic (but could be removed once there's a new upstream tzcode release that's const-safe with this C23 change and glibc has updated to code from that new release). Probably other places in glibc proper would need const added if we remove the _LIBC conditionals. Another question would be whether some GCC extension should be added to support this feature better with macros that only expand each argument once (as well as reducing duplication of diagnostics for bad usages such as non-pointer and pointer-to-volatile-qualfied arguments). Tested for x86_64.

malloc: add free_sized and free_aligned_sized from C23

2025-11-19T16:47:53Z

Signed-off-by: Justin King Reviewed-by: Adhemerval Zanella

stdlib: Do not define once_flag, ONCE_FLAG_INIT for C++

2025-11-11T17:20:10Z

The definition of once_flag conflicts with std::once_flag in if “using namespace std;” is active. Updates commit a7ddbf456d97ac8d1aa7afd735e196a1488bd874 ("Add once_flag, ONCE_FLAG_INIT and call_once to stdlib.h for C23"). Suggested-by: Jonathan Wakely Reviewed-by: Collin Funk

Implement C23 memalignment

2025-10-17T16:56:59Z

Add the C23 memalignment function (query the alignment of a pointer) to glibc. Given how simple this operation is, it would make sense for compilers to inline calls to this function, but I'm treating that as a compiler matter (compilers should add it as a built-in function) rather than adding an inline version to glibc headers (although such an inline version would be reasonable as well). I've filed https://gcc.gnu.org/bugzilla/show_bug.cgi?id=122117 for this feature in GCC. Tested for x86_64 and x86.

Add once_flag, ONCE_FLAG_INIT and call_once to stdlib.h for C23

2025-10-01T15:15:15Z

C23 adds once_flag, ONCE_FLAG_INIT and call_once to stdlib.h (in C11 they were only in threads.h, in C23 they are in both headers; this change came from N2840). Implement this change, with a bits/types/once_flag.h header for the common type and initializer definitions. Note that there's an omnibus bug (bug 33001) that covers more than just these missing definitions. This doesn't seem a significant enough feature to be worth mentioning in NEWS. ISO C is not concerned with whether functions are in libc or libpthread, but POSIX links this to what header they are declared in, so functions declared in stdlib.h are supposed to be in libc. However, the current edition of POSIX is based on C17; hopefully Hurd glibc will have completed the merge of libpthread into libc (in particular, moving call_once) well before a future edition of POSIX based on C23 (or a later version of ISO C) is released. Tested for x86_64 and x86.

stdlib: Implement C2Y uabs, ulabs, ullabs and uimaxabs

2025-04-08T12:51:51Z

C2Y adds unsigned versions of the abs functions (see C2Y draft N3467 and proposal N3349). Tested for x86_64. Signed-off-by: Lenard Mollenkopf

Update copyright dates with scripts/update-copyrights

2025-01-01T19:22:09Z

stdlib: Mark `abort` as `cold`

2024-07-31T06:26:00Z

This helps HotColdSplitting in GCC/LLVM. Thought about doing `exit` as well since its only called once per process, but since its easy to imagine a hot path leading into `exit(0)`, its less clear if its profitable. Reviewed-by: Carlos O'Donell