X-Git-Url: http://erislabs.net/gitweb/?a=blobdiff_plain;f=m4%2Fmemmem.m4;h=9e3d3d956d4eb9914d4f6b24130ad86aa4f3a1c8;hb=ba4000b09804294e46373afb2003744612096a20;hp=9767354ad2827144335e0ed2294e538d3f245d82;hpb=e3adb96fc71c48e1d3e638e7e1afadcd3ac0d840;p=gnulib.git

diff --git a/m4/memmem.m4 b/m4/memmem.m4
index 9767354ad..9e3d3d956 100644
--- a/m4/memmem.m4
+++ b/m4/memmem.m4
@@ -1,33 +1,45 @@
-# memmem.m4 serial 7
-dnl Copyright (C) 2002, 2003, 2004, 2007, 2008 Free Software Foundation, Inc.
+# memmem.m4 serial 14
+dnl Copyright (C) 2002, 2003, 2004, 2007, 2008, 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([gl_FUNC_MEMMEM],
+dnl Check that memmem is present.
+AC_DEFUN([gl_FUNC_MEMMEM_SIMPLE],
 [
   dnl Persuade glibc <string.h> to declare memmem().
   AC_REQUIRE([AC_USE_SYSTEM_EXTENSIONS])
 
   AC_REQUIRE([gl_HEADER_STRING_H_DEFAULTS])
-  AC_REPLACE_FUNCS(memmem)
-  AC_CHECK_DECLS_ONCE(memmem)
+  AC_REPLACE_FUNCS([memmem])
+  AC_CHECK_DECLS_ONCE([memmem])
   if test $ac_cv_have_decl_memmem = no; then
     HAVE_DECL_MEMMEM=0
-  else
+  fi
+  gl_PREREQ_MEMMEM
+]) # gl_FUNC_MEMMEM_SIMPLE
+
+dnl Additionally, check that memmem is efficient and handles empty needles.
+AC_DEFUN([gl_FUNC_MEMMEM],
+[
+  AC_REQUIRE([gl_FUNC_MEMMEM_SIMPLE])
+  if test $ac_cv_have_decl_memmem = yes; then
     AC_CACHE_CHECK([whether memmem works in linear time],
       [gl_cv_func_memmem_works],
-      [AC_RUN_IFELSE([AC_LANG_PROGRAM([
+      [AC_RUN_IFELSE([AC_LANG_PROGRAM([[
+#include <signal.h> /* for signal */
 #include <string.h> /* for memmem */
 #include <stdlib.h> /* for malloc */
 #include <unistd.h> /* for alarm */
-], [[size_t m = 1000000;
+]], [[size_t m = 1000000;
     char *haystack = (char *) malloc (2 * m + 1);
     char *needle = (char *) malloc (m + 1);
     void *result = 0;
     /* Failure to compile this test due to missing alarm is okay,
        since all such platforms (mingw) also lack memmem.  */
+    signal (SIGALRM, SIG_DFL);
     alarm (5);
+    /* Check for quadratic performance.  */
     if (haystack && needle)
       {
 	memset (haystack, 'A', 2 * m);
@@ -36,18 +48,36 @@ AC_DEFUN([gl_FUNC_MEMMEM],
 	needle[m] = 'B';
 	result = memmem (haystack, 2 * m + 1, needle, m + 1);
       }
+    /* Check for empty needle behavior.  */
     return !result || !memmem ("a", 1, 0, 0);]])],
 	[gl_cv_func_memmem_works=yes], [gl_cv_func_memmem_works=no],
-	[dnl pessimistically assume the worst, since even glibc 2.6.1
-	 dnl has quadratic complexity in its memmem
-	 gl_cv_func_memmem_works=no])])
-    if test $gl_cv_func_memmem_works = no; then
+	[dnl Only glibc >= 2.9 and cygwin >= 1.7.0 are known to have a
+	 dnl memmem that works in linear time.
+	 AC_EGREP_CPP([Lucky user],
+	   [
+#include <features.h>
+#ifdef __GNU_LIBRARY__
+ #if (__GLIBC__ == 2 && __GLIBC_MINOR__ >= 9) || (__GLIBC__ > 2)
+  Lucky user
+ #endif
+#endif
+#ifdef __CYGWIN__
+ #include <cygwin/version.h>
+ #if CYGWIN_VERSION_DLL_MAJOR >= 1007
+  Lucky user
+ #endif
+#endif
+	   ],
+	   [gl_cv_func_memmem_works=yes],
+	   [gl_cv_func_memmem_works="guessing no"])
+	])
+      ])
+    if test "$gl_cv_func_memmem_works" != yes; then
       REPLACE_MEMMEM=1
       AC_LIBOBJ([memmem])
     fi
   fi
-  gl_PREREQ_MEMMEM
-])
+]) # gl_FUNC_MEMMEM
 
 # Prerequisites of lib/memmem.c.
 AC_DEFUN([gl_PREREQ_MEMMEM], [:])