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# strncpy.m4
# serial 1
dnl Copyright (C) 2002-2004, 2009-2025 Free Software Foundation, Inc.
dnl This file is free software; the Free Software Foundation
dnl gives unlimited permission to copy and/or distribute it,
dnl with or without modifications, as long as this notice is preserved.
dnl This file is offered as-is, without any warranty.
AC_DEFUN_ONCE([gl_FUNC_STRNCPY],
[
AC_REQUIRE([gl_STRING_H_DEFAULTS])
AC_REQUIRE([AC_PROG_CC])
AC_REQUIRE([AC_CANONICAL_HOST]) dnl for cross-compiles
dnl Check for prerequisites for memory fence checks.
gl_FUNC_MMAP_ANON
AC_CHECK_HEADERS_ONCE([sys/mman.h])
AC_CHECK_FUNCS_ONCE([mprotect])
dnl Detect bug in FreeBSD 15.0 on x86_64:
dnl strncpy should not dereference more than n bytes, but always dereferences
dnl n+1 bytes if the first n bytes don't contain a NUL byte.
dnl Assume that strncpy works on platforms that lack mprotect.
AC_CACHE_CHECK([whether strncpy works], [gl_cv_func_strncpy_works],
[AC_RUN_IFELSE([AC_LANG_PROGRAM([[
#include <string.h>
#if HAVE_SYS_MMAN_H
# include <fcntl.h>
# include <unistd.h>
# include <sys/types.h>
# include <sys/mman.h>
#endif
]GL_MDA_DEFINES],
[[
char *fence = NULL;
#if HAVE_SYS_MMAN_H && HAVE_MPROTECT
{
long int pagesize = sysconf (_SC_PAGESIZE);
char *two_pages =
(char *) mmap (NULL, 2 * pagesize, PROT_READ | PROT_WRITE,
MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
if (two_pages != (char *)(-1)
&& mprotect (two_pages + pagesize, pagesize, PROT_NONE) == 0)
fence = two_pages + pagesize;
}
#endif
if (fence)
{
char dest[8];
dest[0] = 'a';
dest[1] = 'b';
dest[2] = 'c';
dest[3] = 'd';
dest[4] = 'e';
dest[5] = 'f';
dest[6] = 'g';
*(fence - 3) = '7';
*(fence - 2) = '2';
*(fence - 1) = '9';
if (strncpy (dest + 1, fence - 3, 3) != dest + 1)
return 1;
if (dest[0] != 'a')
return 2;
if (dest[1] != '7' || dest[2] != '2' || dest[3] != '9')
return 3;
if (dest[4] != 'e')
return 4;
}
return 0;
]])], [gl_cv_func_strncpy_works=yes], [gl_cv_func_strncpy_works=no],
[
case "$host_os" in
# Guess no on FreeBSD.
freebsd* | dragonfly*) gl_cv_func_strncpy_works="guessing no" ;;
# Guess yes on native Windows.
mingw* | windows*) gl_cv_func_strncpy_works="guessing yes" ;;
# Guess yes otherwise.
*) gl_cv_func_strncpy_works="guessing yes" ;;
esac
])
])
case "$gl_cv_func_strncpy_works" in
*yes) ;;
*) REPLACE_STRNCPY=1 ;;
esac
])
# Prerequisites of lib/strncpy.c.
AC_DEFUN([gl_PREREQ_STRNCPY], [
:
])
|
