Avoid quadratic strstr implementations.

[gnulib.git] / m4 / strndup.m4

diff --git a/m4/strndup.m4 b/m4/strndup.m4
index 80dfcc1..f7934ef 100644 (file)
--- a/m4/strndup.m4
+++ b/m4/strndup.m4
@@ -1,24 +1,53 @@
-# strndup.m4 serial 2
-dnl Copyright (C) 2002, 2003 Free Software Foundation, Inc.
-dnl This file is free software, distributed under the terms of the GNU
-dnl General Public License.  As a special exception to the GNU General
-dnl Public License, this file may be distributed as part of a program
-dnl that contains a configuration script generated by Autoconf, under
-dnl the same distribution terms as the rest of that program.
+# strndup.m4 serial 14
+dnl Copyright (C) 2002-2003, 2005-2007 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_STRNDUP],
 [
   dnl Persuade glibc <string.h> to declare strndup().
-  AC_REQUIRE([AC_GNU_SOURCE])
+  AC_REQUIRE([AC_USE_SYSTEM_EXTENSIONS])
 
-  AC_REPLACE_FUNCS(strndup)
-  if test $ac_cv_func_strndup = no; then
+  AC_REQUIRE([gl_HEADER_STRING_H_DEFAULTS])
+  AC_CHECK_DECLS_ONCE([strndup])
+  if test $ac_cv_have_decl_strndup = no; then
+    HAVE_DECL_STRNDUP=0
+  fi
+
+  # AIX 4.3.3, AIX 5.1 have a function that fails to add the terminating '\0'.
+  AC_CACHE_CHECK([for working strndup], gl_cv_func_strndup,
+    [AC_RUN_IFELSE([
+       AC_LANG_PROGRAM([#include <string.h>
+                       #include <stdlib.h>], [[
+#ifndef HAVE_DECL_STRNDUP
+  extern char *strndup (const char *, size_t);
+#endif
+  char *s;
+  s = strndup ("some longer string", 15);
+  free (s);
+  s = strndup ("shorter string", 13);
+  return s[13] != '\0';]])],
+       [gl_cv_func_strndup=yes],
+       [gl_cv_func_strndup=no],
+       [AC_CHECK_FUNC([strndup],
+          [AC_EGREP_CPP([too risky], [
+#ifdef _AIX
+               too risky
+#endif
+             ],
+             [gl_cv_func_strndup=no],
+             [gl_cv_func_strndup=yes])],
+          [gl_cv_func_strndup=no])])])
+  if test $gl_cv_func_strndup = yes; then
+    AC_DEFINE([HAVE_STRNDUP], 1,
+      [Define if you have the strndup() function and it works.])
+  else
+    HAVE_STRNDUP=0
+    AC_LIBOBJ([strndup])
     gl_PREREQ_STRNDUP
   fi
 ])
 
 # Prerequisites of lib/strndup.c.
-AC_DEFUN([gl_PREREQ_STRNDUP], [
-  AC_CHECK_DECLS(strnlen)
-])
-
+AC_DEFUN([gl_PREREQ_STRNDUP], [:])