|
434
|
1 # memchr.m4 serial 7
|
|
|
2 dnl Copyright (C) 2002-2004, 2009-2010 Free Software Foundation, Inc.
|
|
|
3 dnl This file is free software; the Free Software Foundation
|
|
|
4 dnl gives unlimited permission to copy and/or distribute it,
|
|
|
5 dnl with or without modifications, as long as this notice is preserved.
|
|
|
6
|
|
|
7 AC_DEFUN_ONCE([gl_FUNC_MEMCHR],
|
|
|
8 [
|
|
|
9 dnl Check for prerequisites for memory fence checks.
|
|
|
10 gl_FUNC_MMAP_ANON
|
|
|
11 AC_CHECK_HEADERS_ONCE([sys/mman.h])
|
|
|
12 AC_CHECK_FUNCS_ONCE([mprotect])
|
|
|
13
|
|
|
14 dnl These days, we assume memchr is present. But just in case...
|
|
|
15 AC_REQUIRE([gl_HEADER_STRING_H_DEFAULTS])
|
|
|
16 AC_REPLACE_FUNCS([memchr])
|
|
|
17 if test $ac_cv_func_memchr = no; then
|
|
|
18 gl_PREREQ_MEMCHR
|
|
|
19 REPLACE_MEMCHR=1
|
|
|
20 fi
|
|
|
21
|
|
|
22 if test $ac_cv_func_memchr = yes; then
|
|
|
23 # Detect platform-specific bugs in some versions of glibc:
|
|
|
24 # memchr should not dereference anything with length 0
|
|
|
25 # http://bugzilla.redhat.com/499689
|
|
|
26 # memchr should not dereference overestimated length after a match
|
|
|
27 # http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=521737
|
|
|
28 # http://sourceware.org/bugzilla/show_bug.cgi?id=10162
|
|
|
29 # Assume that memchr works on platforms that lack mprotect.
|
|
|
30 AC_CACHE_CHECK([whether memchr works], [gl_cv_func_memchr_works],
|
|
|
31 [AC_RUN_IFELSE([AC_LANG_PROGRAM([[
|
|
|
32 #include <string.h>
|
|
|
33 #if HAVE_SYS_MMAN_H
|
|
|
34 # include <fcntl.h>
|
|
|
35 # include <unistd.h>
|
|
|
36 # include <sys/types.h>
|
|
|
37 # include <sys/mman.h>
|
|
|
38 # ifndef MAP_FILE
|
|
|
39 # define MAP_FILE 0
|
|
|
40 # endif
|
|
|
41 #endif
|
|
|
42 ]], [[
|
|
|
43 char *fence = NULL;
|
|
|
44 #if HAVE_SYS_MMAN_H && HAVE_MPROTECT
|
|
|
45 # if HAVE_MAP_ANONYMOUS
|
|
|
46 const int flags = MAP_ANONYMOUS | MAP_PRIVATE;
|
|
|
47 const int fd = -1;
|
|
|
48 # else /* !HAVE_MAP_ANONYMOUS */
|
|
|
49 const int flags = MAP_FILE | MAP_PRIVATE;
|
|
|
50 int fd = open ("/dev/zero", O_RDONLY, 0666);
|
|
|
51 if (fd >= 0)
|
|
|
52 # endif
|
|
|
53 {
|
|
|
54 int pagesize = getpagesize ();
|
|
|
55 char *two_pages =
|
|
|
56 (char *) mmap (NULL, 2 * pagesize, PROT_READ | PROT_WRITE,
|
|
|
57 flags, fd, 0);
|
|
|
58 if (two_pages != (char *)(-1)
|
|
|
59 && mprotect (two_pages + pagesize, pagesize, PROT_NONE) == 0)
|
|
|
60 fence = two_pages + pagesize;
|
|
|
61 }
|
|
|
62 #endif
|
|
|
63 if (fence)
|
|
|
64 {
|
|
|
65 if (memchr (fence, 0, 0))
|
|
|
66 return 1;
|
|
|
67 strcpy (fence - 9, "12345678");
|
|
|
68 if (memchr (fence - 9, 0, 79) != fence - 1)
|
|
|
69 return 2;
|
|
|
70 }
|
|
|
71 return 0;
|
|
|
72 ]])], [gl_cv_func_memchr_works=yes], [gl_cv_func_memchr_works=no],
|
|
|
73 [dnl Be pessimistic for now.
|
|
|
74 gl_cv_func_memchr_works="guessing no"])])
|
|
|
75 if test "$gl_cv_func_memchr_works" != yes; then
|
|
|
76 gl_PREREQ_MEMCHR
|
|
|
77 REPLACE_MEMCHR=1
|
|
|
78 AC_LIBOBJ([memchr])
|
|
|
79 fi
|
|
|
80 fi
|
|
|
81 ])
|
|
|
82
|
|
|
83 # Prerequisites of lib/memchr.c.
|
|
|
84 AC_DEFUN([gl_PREREQ_MEMCHR], [
|
|
|
85 AC_CHECK_HEADERS([bp-sym.h])
|
|
|
86 ])
|
