PR78111 fix fallback code for filesystem::canonical

	PR libstdc++/78111
	* src/filesystem/ops.cc (canonical): Set error for non-existent path.

From-SVN: r241549

libstdc++-v3/ChangeLog

+2016-10-26  Jonathan Wakely  <jwakely@redhat.com>
+
+	PR libstdc++/78111
+	* src/filesystem/ops.cc (canonical): Set error for non-existent path.
+
 2016-10-26  Uros Bizjak  <ubizjak@gmail.com>
 
 	* acinclude.m4 (GLIBCXX_CHECK_FILESYSTEM_DEPS): Include <limits.h>

libstdc++-v3/src/filesystem/ops.cc

@@ -142,7 +142,11 @@ fs::canonical(const path& p, const path& base, error_code& ec)
 #endif
 
   if (!exists(pa, ec))
-    return result;
+    {
+      if (!ec)
+	ec = make_error_code(std::errc::no_such_file_or_directory);
+      return result;
+    }
   // else: we know there are (currently) no unresolvable symlink loops
 
   result = pa.root_path();