xfreopen: new module, from coreutils

[gnulib.git] / m4 / memmem.m4

diff --git a/m4/memmem.m4 b/m4/memmem.m4
index 383ed4b..9e3d3d9 100644 (file)
--- a/m4/memmem.m4
+++ b/m4/memmem.m4
@@ -1,5 +1,5 @@
-# memmem.m4 serial 10
-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.
@@ -11,8 +11,8 @@ AC_DEFUN([gl_FUNC_MEMMEM_SIMPLE],
   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 $ac_cv_have_decl_memmem = no; then
     HAVE_DECL_MEMMEM=0
   fi
@@ -27,6 +27,7 @@ AC_DEFUN([gl_FUNC_MEMMEM],
     AC_CACHE_CHECK([whether memmem works in linear time],
       [gl_cv_func_memmem_works],
       [AC_RUN_IFELSE([AC_LANG_PROGRAM([[
+#include <signal.h> /* for signal */
 #include <string.h> /* for memmem */
 #include <stdlib.h> /* for malloc */
 #include <unistd.h> /* for alarm */
@@ -36,6 +37,7 @@ AC_DEFUN([gl_FUNC_MEMMEM],
     void *result = 0;
     /* Failure to compile this test due to missing alarm is okay,
        since all such platforms (mingw) also lack memmem.  */
+    signal (SIGALRM, SIG_DFL);
     alarm (5);
     /* Check for quadratic performance.  */
     if (haystack && needle)
@@ -49,9 +51,27 @@ AC_DEFUN([gl_FUNC_MEMMEM],
     /* Check for empty needle behavior.  */
     return !result || !memmem ("a", 1, 0, 0);]])],
        [gl_cv_func_memmem_works=yes], [gl_cv_func_memmem_works=no],
-       [dnl pessimistically assume the worst, since even glibc 2.6.1
-        dnl has quadratic complexity in its memmem
-        gl_cv_func_memmem_works="guessing no"])])
+       [dnl Only glibc >= 2.9 and cygwin >= 1.7.0 are known to have a
+        dnl memmem that works in linear time.
+        AC_EGREP_CPP([Lucky user],
+          [
+#include <features.h>
+#ifdef __GNU_LIBRARY__
+ #if (__GLIBC__ == 2 && __GLIBC_MINOR__ >= 9) || (__GLIBC__ > 2)
+  Lucky user
+ #endif
+#endif
+#ifdef __CYGWIN__
+ #include <cygwin/version.h>
+ #if CYGWIN_VERSION_DLL_MAJOR >= 1007
+  Lucky user
+ #endif
+#endif
+          ],
+          [gl_cv_func_memmem_works=yes],
+          [gl_cv_func_memmem_works="guessing no"])
+       ])
+      ])
     if test "$gl_cv_func_memmem_works" != yes; then
       REPLACE_MEMMEM=1
       AC_LIBOBJ([memmem])