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[gnulib.git] / m4 / memchr.m4

diff --git a/m4/memchr.m4 b/m4/memchr.m4
index bcfe869..ab773b8 100644 (file)
--- a/m4/memchr.m4
+++ b/m4/memchr.m4
@@ -1,10 +1,10 @@
-# memchr.m4 serial 6
-dnl Copyright (C) 2002, 2003, 2004, 2009 Free Software Foundation, Inc.
+# memchr.m4 serial 8
+dnl Copyright (C) 2002-2004, 2009-2010 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([gl_FUNC_MEMCHR],
+AC_DEFUN_ONCE([gl_FUNC_MEMCHR],
 [
   dnl Check for prerequisites for memory fence checks.
   gl_FUNC_MMAP_ANON
@@ -13,18 +13,14 @@ AC_DEFUN([gl_FUNC_MEMCHR],
 
   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
-
+  AC_CHECK_FUNCS_ONCE([memchr])
   if test $ac_cv_func_memchr = yes; then
     # Detect platform-specific bugs in some versions of glibc:
     # memchr should not dereference anything with length 0
     #   http://bugzilla.redhat.com/499689
     # memchr should not dereference overestimated length after a match
     #   http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=521737
+    #   http://sourceware.org/bugzilla/show_bug.cgi?id=10162
     # Assume that memchr works on platforms that lack mprotect.
     AC_CACHE_CHECK([whether memchr works], [gl_cv_func_memchr_works],
       [AC_RUN_IFELSE([AC_LANG_PROGRAM([[
@@ -52,11 +48,11 @@ AC_DEFUN([gl_FUNC_MEMCHR],
     {
       int pagesize = getpagesize ();
       char *two_pages =
-       (char *) mmap (NULL, 2 * pagesize, PROT_READ | PROT_WRITE,
-                      flags, fd, 0);
+        (char *) mmap (NULL, 2 * pagesize, PROT_READ | PROT_WRITE,
+                       flags, fd, 0);
       if (two_pages != (char *)(-1)
-         && mprotect (two_pages + pagesize, pagesize, PROT_NONE) == 0)
-       fence = two_pages + pagesize;
+          && mprotect (two_pages + pagesize, pagesize, PROT_NONE) == 0)
+        fence = two_pages + pagesize;
     }
 #endif
   if (fence)
@@ -72,10 +68,14 @@ AC_DEFUN([gl_FUNC_MEMCHR],
       [dnl Be pessimistic for now.
        gl_cv_func_memchr_works="guessing no"])])
     if test "$gl_cv_func_memchr_works" != yes; then
-      gl_PREREQ_MEMCHR
       REPLACE_MEMCHR=1
-      AC_LIBOBJ([memchr])
     fi
+  else
+    HAVE_MEMCHR=0
+  fi
+  if test $HAVE_MEMCHR = 0 || test $REPLACE_MEMCHR = 1; then
+    AC_LIBOBJ([memchr])
+    gl_PREREQ_MEMCHR
   fi
 ])