+++ /dev/null
-# memchr.m4 serial 7
-dnl Copyright (C) 2002, 2003, 2004, 2009 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],
-[
- 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 $ac_cv_func_memchr = yes; then
- # Detect platform-specific bugs in some versions of glibc:
- # memchr should not dereference anything with length 0
- # http://bugzilla.redhat.com/499689
- # memchr should not dereference overestimated length after a match
- # http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=521737
- # http://sourceware.org/bugzilla/show_bug.cgi?id=10162
- # Assume that memchr works on platforms that lack mprotect.
- AC_CACHE_CHECK([whether memchr works], [gl_cv_func_memchr_works],
- [AC_RUN_IFELSE([AC_LANG_PROGRAM([[
-#include <string.h>
-#if HAVE_SYS_MMAN_H
-# include <fcntl.h>
-# include <unistd.h>
-# include <sys/types.h>
-# include <sys/mman.h>
-# ifndef MAP_FILE
-# define MAP_FILE 0
-# endif
-#endif
-]], [[
- char *fence = NULL;
-#if HAVE_SYS_MMAN_H && HAVE_MPROTECT
-# if HAVE_MAP_ANONYMOUS
- const int flags = MAP_ANONYMOUS | MAP_PRIVATE;
- const int fd = -1;
-# else /* !HAVE_MAP_ANONYMOUS */
- const int flags = MAP_FILE | MAP_PRIVATE;
- int fd = open ("/dev/zero", O_RDONLY, 0666);
- if (fd >= 0)
-# endif
- {
- int pagesize = getpagesize ();
- char *two_pages =
- (char *) mmap (NULL, 2 * pagesize, PROT_READ | PROT_WRITE,
- flags, fd, 0);
- if (two_pages != (char *)(-1)
- && mprotect (two_pages + pagesize, pagesize, PROT_NONE) == 0)
- fence = two_pages + pagesize;
- }
-#endif
- if (fence)
- {
- if (memchr (fence, 0, 0))
- return 1;
- strcpy (fence - 9, "12345678");
- if (memchr (fence - 9, 0, 79) != fence - 1)
- return 2;
- }
- return 0;
-]])], [gl_cv_func_memchr_works=yes], [gl_cv_func_memchr_works=no],
- [dnl Be pessimistic for now.
- gl_cv_func_memchr_works="guessing no"])])
- if test "$gl_cv_func_memchr_works" != yes; then
- gl_PREREQ_MEMCHR
- REPLACE_MEMCHR=1
- AC_LIBOBJ([memchr])
- fi
- fi
-])
-
-# Prerequisites of lib/memchr.c.
-AC_DEFUN([gl_PREREQ_MEMCHR], [
- AC_CHECK_HEADERS([bp-sym.h])
-])