-# memchr.m4 serial 7
-dnl Copyright (C) 2002-2004, 2009-2010 Free Software Foundation, Inc.
+# memchr.m4 serial 13
+dnl Copyright (C) 2002-2004, 2009-2018 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.
AC_DEFUN_ONCE([gl_FUNC_MEMCHR],
[
+ 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 These days, we assume memchr is present. But just in case...
AC_REQUIRE([gl_HEADER_STRING_H_DEFAULTS])
- AC_REPLACE_FUNCS([memchr])
- if test $ac_cv_func_memchr = no; then
- gl_PREREQ_MEMCHR
- REPLACE_MEMCHR=1
- fi
-
- if test $ac_cv_func_memchr = yes; then
+ m4_ifdef([gl_FUNC_MEMCHR_OBSOLETE], [
+ dnl These days, we assume memchr is present. But if support for old
+ dnl platforms is desired:
+ AC_CHECK_FUNCS_ONCE([memchr])
+ if test $ac_cv_func_memchr = no; then
+ HAVE_MEMCHR=0
+ fi
+ ])
+ if test $HAVE_MEMCHR = 1; then
# Detect platform-specific bugs in some versions of glibc:
# memchr should not dereference anything with length 0
- # http://bugzilla.redhat.com/499689
+ # https://bugzilla.redhat.com/show_bug.cgi?id=499689
# memchr should not dereference overestimated length after a match
- # http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=521737
- # http://sourceware.org/bugzilla/show_bug.cgi?id=10162
+ # https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=521737
+ # https://sourceware.org/bugzilla/show_bug.cgi?id=10162
# Assume that memchr works on platforms that lack mprotect.
AC_CACHE_CHECK([whether memchr works], [gl_cv_func_memchr_works],
[AC_RUN_IFELSE([AC_LANG_PROGRAM([[
# endif
#endif
]], [[
+ int result = 0;
char *fence = NULL;
#if HAVE_SYS_MMAN_H && HAVE_MPROTECT
# if HAVE_MAP_ANONYMOUS
if (fence)
{
if (memchr (fence, 0, 0))
- return 1;
+ result |= 1;
strcpy (fence - 9, "12345678");
if (memchr (fence - 9, 0, 79) != fence - 1)
- return 2;
+ result |= 2;
+ if (memchr (fence - 1, 0, 3) != fence - 1)
+ result |= 4;
}
- return 0;
-]])], [gl_cv_func_memchr_works=yes], [gl_cv_func_memchr_works=no],
- [dnl Be pessimistic for now.
- gl_cv_func_memchr_works="guessing no"])])
- if test "$gl_cv_func_memchr_works" != yes; then
- gl_PREREQ_MEMCHR
- REPLACE_MEMCHR=1
- AC_LIBOBJ([memchr])
- fi
+ return result;
+]])],
+ [gl_cv_func_memchr_works=yes],
+ [gl_cv_func_memchr_works=no],
+ [case "$host_os" in
+ # Guess yes on native Windows.
+ mingw*) gl_cv_func_memchr_works="guessing yes" ;;
+ # Be pessimistic for now.
+ *) gl_cv_func_memchr_works="guessing no" ;;
+ esac
+ ])
+ ])
+ case "$gl_cv_func_memchr_works" in
+ *yes) ;;
+ *) REPLACE_MEMCHR=1 ;;
+ esac
fi
])