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f434ba03 | 1 | # memchr.m4 serial 8 |
7b6bb8da | 2 | dnl Copyright (C) 2002-2004, 2009-2011 Free Software Foundation, Inc. |
f6ea5628 DJ |
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 | ||
f434ba03 | 7 | AC_DEFUN_ONCE([gl_FUNC_MEMCHR], |
f6ea5628 | 8 | [ |
f434ba03 PA |
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_CHECK_FUNCS_ONCE([memchr]) | |
17 | if test $ac_cv_func_memchr = yes; then | |
18 | # Detect platform-specific bugs in some versions of glibc: | |
19 | # memchr should not dereference anything with length 0 | |
20 | # http://bugzilla.redhat.com/499689 | |
21 | # memchr should not dereference overestimated length after a match | |
22 | # http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=521737 | |
23 | # http://sourceware.org/bugzilla/show_bug.cgi?id=10162 | |
24 | # Assume that memchr works on platforms that lack mprotect. | |
25 | AC_CACHE_CHECK([whether memchr works], [gl_cv_func_memchr_works], | |
26 | [AC_RUN_IFELSE([AC_LANG_PROGRAM([[ | |
27 | #include <string.h> | |
28 | #if HAVE_SYS_MMAN_H | |
29 | # include <fcntl.h> | |
30 | # include <unistd.h> | |
31 | # include <sys/types.h> | |
32 | # include <sys/mman.h> | |
33 | # ifndef MAP_FILE | |
34 | # define MAP_FILE 0 | |
35 | # endif | |
36 | #endif | |
37 | ]], [[ | |
38 | char *fence = NULL; | |
39 | #if HAVE_SYS_MMAN_H && HAVE_MPROTECT | |
40 | # if HAVE_MAP_ANONYMOUS | |
41 | const int flags = MAP_ANONYMOUS | MAP_PRIVATE; | |
42 | const int fd = -1; | |
43 | # else /* !HAVE_MAP_ANONYMOUS */ | |
44 | const int flags = MAP_FILE | MAP_PRIVATE; | |
45 | int fd = open ("/dev/zero", O_RDONLY, 0666); | |
46 | if (fd >= 0) | |
47 | # endif | |
48 | { | |
49 | int pagesize = getpagesize (); | |
50 | char *two_pages = | |
51 | (char *) mmap (NULL, 2 * pagesize, PROT_READ | PROT_WRITE, | |
52 | flags, fd, 0); | |
53 | if (two_pages != (char *)(-1) | |
54 | && mprotect (two_pages + pagesize, pagesize, PROT_NONE) == 0) | |
55 | fence = two_pages + pagesize; | |
56 | } | |
57 | #endif | |
58 | if (fence) | |
59 | { | |
60 | if (memchr (fence, 0, 0)) | |
61 | return 1; | |
62 | strcpy (fence - 9, "12345678"); | |
63 | if (memchr (fence - 9, 0, 79) != fence - 1) | |
64 | return 2; | |
65 | } | |
66 | return 0; | |
67 | ]])], [gl_cv_func_memchr_works=yes], [gl_cv_func_memchr_works=no], | |
68 | [dnl Be pessimistic for now. | |
69 | gl_cv_func_memchr_works="guessing no"])]) | |
70 | if test "$gl_cv_func_memchr_works" != yes; then | |
71 | REPLACE_MEMCHR=1 | |
72 | fi | |
73 | else | |
74 | HAVE_MEMCHR=0 | |
75 | fi | |
76 | if test $HAVE_MEMCHR = 0 || test $REPLACE_MEMCHR = 1; then | |
77 | AC_LIBOBJ([memchr]) | |
f6ea5628 DJ |
78 | gl_PREREQ_MEMCHR |
79 | fi | |
80 | ]) | |
81 | ||
82 | # Prerequisites of lib/memchr.c. | |
83 | AC_DEFUN([gl_PREREQ_MEMCHR], [ | |
f434ba03 | 84 | AC_CHECK_HEADERS([bp-sym.h]) |
f6ea5628 | 85 | ]) |