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

在 2026/8/13 19:46, Adhemerval Zanella Netto 写道:
> 
> 
> 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>
> 

Thanks for pointing this out.

No, my patch does not fix anything beyound Matthias' s patch. I misssed 
that earlier patch thread when I started looking at BZ#34466.

Plase disregard my patch, Matthias' s version is more complete because 
it also covers the fortify path.