Re: [PATCH] string: Declare POSIX.1-2024 string functions [BZ #34466]

On 13/08/26 00:13, Gao Xiang wrote:
> From: Xiang Gao <[email protected]>
> 
> POSIX.1-2024 adds memmem, strlcpy and strlcat to string.h.
> glibc already implements these functions. but their public
> declarations are currently only exports by __USE_MISC.
> Applications built in POSIX.1-2024 mode with _POSIX_C_SOURCE=
> 202405L will fail with implicit function declaration errors.
> 
> Using existed feature macro to expose the declarations required
> by POSIX.1-2024.
> 
> Add string/tst-posix2024 to verify strict POSIX.1-2024 header
> visibility.
> 
> Tested on x86_64 Fedora 42.
> 
> The following tests passed without regressions:
>   make test t=string/tst-posix2024
>   make check subdirs=string
>   make check subdirs=conform
> 
> Signed-off-by: Xiang Gao <[email protected]>

We already have a similar patch [1], already approved by DJ. Does this add
or fix something else?

[1] https://patchwork.sourceware.org/project/glibc/patch/[email protected]/

> ---
>  conform/data/string.h-data |  7 ++++++
>  string/Makefile            |  2 ++
>  string/string.h            |  6 ++++--
>  string/tst-posix2024.c     | 44 ++++++++++++++++++++++++++++++++++++++
>  4 files changed, 57 insertions(+), 2 deletions(-)
>  create mode 100644 string/tst-posix2024.c
> 
> diff --git a/conform/data/string.h-data b/conform/data/string.h-data
> index abc6b12b5d..c9526e06d0 100644
> --- a/conform/data/string.h-data
> +++ b/conform/data/string.h-data
> @@ -13,6 +13,9 @@ function int memcmp (const void*, const void*, size_t)
>  function {void*} memcpy (void*, const void*, size_t)
>  function {void*} memmove (void*, const void*, size_t)
>  function {void*} memset (void*, int, size_t)
> +#if defined XOPEN2K24 || defined POSIX2024
> +function {void*} memmem (const void*, size_t, const void*, size_t)
> +#endif
>  #if defined XOPEN2K8 || defined XOPEN2K24 || defined POSIX2008 || defined POSIX2024
>  function {char*} stpcpy (char*, const char*)
>  function {char*} stpncpy (char*, const char*, size_t)
> @@ -38,6 +41,10 @@ function int strerror_r (int, char*, size_t)
>  function {char*} strerror_l (int, locale_t)
>  #endif
>  function size_t strlen (const char*)
> +#if defined XOPEN2K24 || defined POSIX2024
> +function size_t strlcat (char*, const char*, size_t)
> +function size_t strlcpy (char*, const char*, size_t)
> +#endif
>  function {char*} strncat (char*, const char*, size_t)
>  function int strncmp (const char*, const char*, size_t)
>  function {char*} strncpy (char*, const char*, size_t)
> diff --git a/string/Makefile b/string/Makefile
> index aa0b0c2f57..a968994fcb 100644
> --- a/string/Makefile
> +++ b/string/Makefile
> @@ -201,6 +201,7 @@ tests := \
>    tst-endian \
>    tst-inlcall \
>    tst-memmove-overflow \
> +  tst-posix2024 \
>    tst-strerror-fail \
>    tst-strfry \
>    tst-strlcat \
> @@ -270,6 +271,7 @@ CFLAGS-tst-inlcall.c += -fno-builtin
>  CFLAGS-tst-xbzero-opt.c += -O3
>  CFLAGS-tst-xmemset-opt.c += -O3
>  CFLAGS-test-endian-sign-conversion.c += -Werror -Wsign-conversion
> +CFLAGS-tst-posix2024.c += -std=c17 -Werror=implicit-function-declaration
>  # BZ 21006: Resolve all functions but at least explicit_bzero at startup.
>  # Otherwise the test fails on s390x as the memcpy in prepare_test_buffer is
>  # done by loading r4 / r5 with the test_pattern and using store multiple
> diff --git a/string/string.h b/string/string.h
> index 743395b3e3..15959356a2 100644
> --- a/string/string.h
> +++ b/string/string.h
> @@ -414,7 +414,7 @@ extern char *strcasestr (const char *__haystack, const char *__needle)
>  # endif
>  #endif
>  
> -#ifdef __USE_MISC
> +#if defined __USE_MISC || defined __USE_XOPEN2K24
>  /* Find the first occurrence of NEEDLE in HAYSTACK.
>     NEEDLE is NEEDLELEN bytes long;
>     HAYSTACK is HAYSTACKLEN bytes long.  */
> @@ -423,7 +423,9 @@ extern void *memmem (const void *__haystack, size_t __haystacklen,
>       __THROW __attribute_pure__ __nonnull ((1, 3))
>      __attr_access ((__read_only__, 1, 2))
>      __attr_access ((__read_only__, 3, 4));
> +#endif
>  
> +#ifdef __USE_MISC
>  /* Copy N bytes of SRC to DEST, return pointer to bytes after the
>     last written byte.  */
>  extern void *__mempcpy (void *__restrict __dest,
> @@ -533,7 +535,7 @@ extern char *stpncpy (char *__restrict __dest,
>       __THROW __nonnull ((1, 2));
>  #endif
>  
> -#ifdef __USE_MISC
> +#if defined __USE_MISC || defined __USE_XOPEN2K24
>  /* Copy at most N - 1 characters from SRC to DEST.  */
>  extern size_t strlcpy (char *__restrict __dest,
>  		       const char *__restrict __src, size_t __n)
> diff --git a/string/tst-posix2024.c b/string/tst-posix2024.c
> new file mode 100644
> index 0000000000..0e25d0770f
> --- /dev/null
> +++ b/string/tst-posix2024.c
> @@ -0,0 +1,44 @@
> +/* Test POSIX.1-2024 <string.h> declarations.
> +   Copyright (C) 2026 Free Software Foundation, Inc.
> +   This file is part of the GNU C Library.
> +
> +   The GNU C Library is free software; you can redistribute it and/or
> +   modify it under the terms of the GNU Lesser General Public
> +   License as published by the Free Software Foundation; either
> +   version 2.1 of the License, or (at your option) any later version.
> +
> +   The GNU C Library is distributed in the hope that it will be useful,
> +   but WITHOUT ANY WARRANTY; without even the implied warranty of
> +   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> +   Lesser General Public License for more details.
> +
> +   You should have received a copy of the GNU Lesser General Public
> +   License along with the GNU C Library; if not, see
> +   <https://www.gnu.org/licenses/>.  */
> +
> +/* Undo _GNU_SOURCE define before the first public header is included so that
> +   this test checks strict POSIX.1-2024 visibility.  */
> +
> +#undef _GNU_SOURCE
> +#define _POSIX_C_SOURCE 202405L
> +
> +#include <string.h>
> +#include <support/check.h>
> +
> +static int
> +do_test (void)
> +{
> +  char buffer[8];
> +
> +  TEST_COMPARE (strlcpy (buffer, "abc", sizeof buffer), 3);
> +  TEST_COMPARE_STRING (buffer, "abc");
> +
> +  TEST_COMPARE (strlcat (buffer, "defgh", sizeof buffer), 8);
> +  TEST_COMPARE_STRING (buffer, "abcdefg");
> +
> +  TEST_VERIFY (memmem (buffer, strlen (buffer), "cde", 3) == buffer + 2);
> +
> +  return 0;
> +}
> +
> +#include <support/test-driver.c>