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-rw-r--r--m4/memchr.m4106
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diff --git a/m4/memchr.m4 b/m4/memchr.m4
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+# memchr.m4 serial 18
+dnl Copyright (C) 2002-2004, 2009-2022 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])
+
+ AC_REQUIRE([gl_STRING_H_DEFAULTS])
+ # Detect platform-specific bugs in some versions of glibc:
+ # memchr should not dereference anything with length 0
+ # https://bugzilla.redhat.com/show_bug.cgi?id=499689
+ # memchr should not dereference overestimated length after a match
+ # https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=521737
+ # https://sourceware.org/bugzilla/show_bug.cgi?id=10162
+ # memchr should cast the second argument to 'unsigned char'.
+ # This bug exists in Android 4.3.
+ # 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
+]], [[
+ int result = 0;
+ 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)
+ {
+ /* Test against bugs on glibc systems. */
+ if (memchr (fence, 0, 0))
+ result |= 1;
+ strcpy (fence - 9, "12345678");
+ if (memchr (fence - 9, 0, 79) != fence - 1)
+ result |= 2;
+ if (memchr (fence - 1, 0, 3) != fence - 1)
+ result |= 4;
+ /* Test against bug on AIX 7.2. */
+ if (memchr (fence - 4, '6', 16) != fence - 4)
+ result |= 8;
+ }
+ /* Test against bug on Android 4.3. */
+ {
+ char input[3];
+ input[0] = 'a';
+ input[1] = 'b';
+ input[2] = 'c';
+ if (memchr (input, 0x789abc00 | 'b', 3) != input + 1)
+ result |= 16;
+ }
+ return result;
+]])],
+ [gl_cv_func_memchr_works=yes],
+ [gl_cv_func_memchr_works=no],
+ [case "$host_os" in
+ # Guess no on Android.
+ linux*-android*) gl_cv_func_memchr_works="guessing no" ;;
+ # Guess yes on native Windows.
+ mingw*) gl_cv_func_memchr_works="guessing yes" ;;
+ # If we don't know, obey --enable-cross-guesses.
+ *) gl_cv_func_memchr_works="$gl_cross_guess_normal" ;;
+ esac
+ ])
+ ])
+ case "$gl_cv_func_memchr_works" in
+ *yes) ;;
+ *) REPLACE_MEMCHR=1 ;;
+ esac
+])
+
+# Prerequisites of lib/memchr.c.
+AC_DEFUN([gl_PREREQ_MEMCHR], [
+ AC_CHECK_HEADERS([bp-sym.h])
+])