commit 23c3b47b453b8796bbdb75abede5305b1a5435f3
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Sat Jan 12 00:02:07 2019 +0000

    PR libstdc++/88811 fix typo introduced in r266569
    
            PR libstdc++/88811
            PR libstdc++/83306
            * src/filesystem/path.cc: Fix typo. If first path is empty, show []
            before second path.
            * testsuite/experimental/filesystem/filesystem_error/cons.cc: New
            test.

diff --git a/libstdc++-v3/src/filesystem/path.cc b/libstdc++-v3/src/filesystem/path.cc
index 048c5617668..92def10e33e 100644
--- a/libstdc++-v3/src/filesystem/path.cc
+++ b/libstdc++-v3/src/filesystem/path.cc
@@ -494,7 +494,7 @@ fs::filesystem_error::_M_gen_what()
   const std::string pstr2 = _M_path2.u8string();
   experimental::string_view s = this->system_error::what();
   const size_t len = 18 + s.length()
-    + (pstr1.length() ? pstr1.length() + 3 : 0)
+    + (pstr1.length() || pstr2.length() ? pstr1.length() + 3 : 0)
     + (pstr2.length() ? pstr2.length() + 3 : 0);
   std::string w;
   w.reserve(len);
@@ -506,8 +506,10 @@ fs::filesystem_error::_M_gen_what()
       w += pstr1;
       w += ']';
     }
-  if (!pstr1.empty())
+  if (!pstr2.empty())
     {
+      if (pstr1.empty())
+	w += " []";
       w += " [";
       w += pstr2;
       w += ']';
diff --git a/libstdc++-v3/testsuite/experimental/filesystem/filesystem_error/cons.cc b/libstdc++-v3/testsuite/experimental/filesystem/filesystem_error/cons.cc
new file mode 100644
index 00000000000..a08852df1e3
--- /dev/null
+++ b/libstdc++-v3/testsuite/experimental/filesystem/filesystem_error/cons.cc
@@ -0,0 +1,90 @@
+// Copyright (C) 2018-2019 Free Software Foundation, Inc.
+//
+// This file is part of the GNU ISO C++ Library.  This library is free
+// software; you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the
+// Free Software Foundation; either version 3, or (at your option)
+// any later version.
+
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License along
+// with this library; see the file COPYING3.  If not see
+// <http://www.gnu.org/licenses/>.
+
+// { dg-options "-std=gnu++17 -lstdc++fs" }
+// { dg-do run { target c++11 } }
+// { dg-require-filesystem-ts "" }
+
+#include <experimental/filesystem>
+#include <testsuite_hooks.h>
+
+using std::experimental::filesystem::filesystem_error;
+using std::experimental::filesystem::path;
+
+bool contains(std::string what_str, std::string expected)
+{
+  return what_str.find(expected) != std::string::npos;
+}
+
+void
+test01()
+{
+  const char* const str = "error test";
+  const std::error_code ec = make_error_code(std::errc::is_a_directory);
+  const path p1 = "test/path/one";
+  const path p2 = "/test/path/two";
+
+  const filesystem_error e1(str, ec);
+  VERIFY( contains(e1.what(), str) );
+  VERIFY( !contains(e1.what(), "[]") ); // no "empty path" in the string
+  VERIFY( e1.path1().empty() );
+  VERIFY( e1.path2().empty() );
+  VERIFY( e1.code() == ec );
+
+  const filesystem_error e2(str, p1, ec);
+  VERIFY( e2.path1() == p1 );
+  VERIFY( e2.path2().empty() );
+  VERIFY( contains(e2.what(), str) );
+  VERIFY( contains(e2.what(), p1.string()) );
+  VERIFY( e2.code() == ec );
+
+  const filesystem_error e3(str, path{}, ec);
+  VERIFY( e3.path1().empty() );
+  VERIFY( e3.path2().empty() );
+  VERIFY( contains(e3.what(), str) );
+  VERIFY( e3.code() == ec );
+
+  const filesystem_error e4(str, p1, p2, ec);
+  VERIFY( e4.path1() == p1 );
+  VERIFY( e4.path2() == p2 );
+  VERIFY( contains(e4.what(), str) );
+  VERIFY( contains(e4.what(), p1.string()) );
+  VERIFY( contains(e4.what(), p2.string()) );
+  VERIFY( !contains(e4.what(), "[]") );
+  VERIFY( e4.code() == ec );
+
+  const filesystem_error e5(str, p1, path{}, ec);
+  VERIFY( e5.path1() == p1 );
+  VERIFY( e5.path2().empty() );
+  VERIFY( contains(e5.what(), str) );
+  VERIFY( contains(e5.what(), p1.string()) );
+  VERIFY( e5.code() == ec );
+
+  const filesystem_error e6(str, path{}, p2, ec);
+  VERIFY( e6.path1().empty() );
+  VERIFY( e6.path2() == p2 );
+  VERIFY( contains(e6.what(), str) );
+  VERIFY( contains(e6.what(), "[]") );
+  VERIFY( contains(e6.what(), p2.string()) );
+  VERIFY( e6.code() == ec );
+}
+
+int
+main()
+{
+  test01();
+}