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[gnulib.git] / m4 / strstr.m4

diff --git a/m4/strstr.m4 b/m4/strstr.m4
index 9f08b7f..0f17a6b 100644 (file)
--- a/m4/strstr.m4
+++ b/m4/strstr.m4
@@ -1,25 +1,39 @@
-# strstr.m4 serial 1
-dnl Copyright (C) 2008 Free Software Foundation, Inc.
+# strstr.m4 serial 6
+dnl Copyright (C) 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.
 
-dnl Check that strstr is efficient.
-AC_DEFUN([gl_FUNC_STRSTR],
+dnl Check that strstr works.
+AC_DEFUN([gl_FUNC_STRSTR_SIMPLE],
 [
   AC_REQUIRE([gl_HEADER_STRING_H_DEFAULTS])
-  AC_CACHE_CHECK([whether strstr works in linear time],
-    [gl_cv_func_strstr_linear],
-    [AC_RUN_IFELSE([AC_LANG_PROGRAM([
+  AC_REQUIRE([gl_FUNC_MEMCHR])
+  if test "$gl_cv_func_memchr_works" != yes; then
+    REPLACE_STRSTR=1
+    AC_LIBOBJ([strstr])
+  fi
+]) # gl_FUNC_STRSTR_SIMPLE
+
+dnl Additionally, check that strstr is efficient.
+AC_DEFUN([gl_FUNC_STRSTR],
+[
+  AC_REQUIRE([gl_FUNC_STRSTR_SIMPLE])
+  if test $REPLACE_STRSTR = 0; then
+    AC_CACHE_CHECK([whether strstr works in linear time],
+      [gl_cv_func_strstr_linear],
+      [AC_RUN_IFELSE([AC_LANG_PROGRAM([[
+#include <signal.h> /* for signal */
 #include <string.h> /* for memmem */
 #include <stdlib.h> /* for malloc */
 #include <unistd.h> /* for alarm */
-], [[size_t m = 1000000;
+]], [[size_t m = 1000000;
     char *haystack = (char *) malloc (2 * m + 2);
     char *needle = (char *) malloc (m + 2);
     void *result = 0;
     /* Failure to compile this test due to missing alarm is okay,
        since all such platforms (mingw) also have quadratic strstr.  */
+    signal (SIGALRM, SIG_DFL);
     alarm (5);
     /* Check for quadratic performance.  */
     if (haystack && needle)
@@ -33,12 +47,31 @@ AC_DEFUN([gl_FUNC_STRSTR],
        result = strstr (haystack, needle);
       }
     return !result;]])],
-      [gl_cv_func_strstr_linear=yes], [gl_cv_func_strstr_linear=no],
-      [dnl pessimistically assume the worst, since even glibc 2.6.1
-       dnl has quadratic complexity in its strstr
-       gl_cv_func_strstr_linear="guessing no"])])
-  if test "$gl_cv_func_strstr_linear" != yes; then
-    REPLACE_STRSTR=1
-    AC_LIBOBJ([strstr])
+        [gl_cv_func_strstr_linear=yes], [gl_cv_func_strstr_linear=no],
+        [dnl Only glibc >= 2.9 and cygwin >= 1.7.0 are known to have a
+         dnl strstr 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_strstr_linear=yes],
+           [gl_cv_func_strstr_linear="guessing no"])
+        ])
+      ])
+    if test "$gl_cv_func_strstr_linear" != yes; then
+      REPLACE_STRSTR=1
+      AC_LIBOBJ([strstr])
+    fi
   fi
 ]) # gl_FUNC_STRSTR