libstdc++/70762 fix fallback implementation of nonexistent_path

	PR libstdc++/70762
	* testsuite/util/testsuite_fs.h (__gnu_test::nonexistent_path): Use
	static counter to return a different path on every call.

From-SVN: r235395

libstdc++-v3/ChangeLog

+2016-04-24  Jonathan Wakely  <jwakely@redhat.com>
+
+	PR libstdc++/70762
+	* testsuite/util/testsuite_fs.h (__gnu_test::nonexistent_path): Use
+	static counter to return a different path on every call.
+
 2016-04-22  Tim Shen  <timshen@google.com>
 
 	PR libstdc++/70745

libstdc++-v3/testsuite/util/testsuite_fs.h

@@ -83,11 +83,13 @@ namespace __gnu_test
     p = tmp;
 #else
     char buf[64];
+    static int counter;
 #if _GLIBCXX_USE_C99_STDIO
-    std::snprintf(buf, 64, "filesystem-ts-test.%lu", (unsigned long)::getpid());
+    std::snprintf(buf, 64,
 #else
-    std::sprintf(buf, "filesystem-ts-test.%lu", (unsigned long)::getpid());
+    std::sprintf(buf,
 #endif
+      "filesystem-ts-test.%d.%lu", counter++, (unsigned long) ::getpid());
     p = buf;
 #endif
     return p;