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-rw-r--r--gnulib-m4/memchr.m486
1 files changed, 86 insertions, 0 deletions
diff --git a/gnulib-m4/memchr.m4 b/gnulib-m4/memchr.m4
new file mode 100644
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+++ b/gnulib-m4/memchr.m4
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+# 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])
+])