libstdc++: Fix filesystem::path pretty printer test failure

On some systems libstdc++-prettyprinters/cxx17.cc FAILs with this error:

skipping: Python Exception <type 'exceptions.AttributeError'> 'gdb.Type' object has no attribute 'name': ^M
got: $27 = filesystem::path "/dir/."^M
FAIL: libstdc++-prettyprinters/cxx17.cc print path2

The gdb.Type.name attribute isn't present in GDB 7.6, so we get an
exception from StdPathPrinter._iterator.__next__ trying to use it.
The StdPathPrinter._iterator is already passed the type's name in its
constructor, so we can just store that and use it instead of
gdb.Type.name.

libstdc++-v3/ChangeLog:

	* python/libstdcxx/v6/printers.py (StdExpPathPrinter): Store the
	name of the type and pass it to the iterator.
	(StdPathPrinter): Likewise.
	* testsuite/libstdc++-prettyprinters/filesystem-ts.cc: New test.

libstdc++-v3/python/libstdcxx/v6/printers.py

@@ -1294,6 +1294,7 @@ class StdExpPathPrinter:
 
     def __init__ (self, typename, val):
         self.val = val
+        self.typename = typename
         start = self.val['_M_cmpts']['_M_impl']['_M_start']
         finish = self.val['_M_cmpts']['_M_impl']['_M_finish']
         self.num_cmpts = int (finish - start)
@@ -1312,10 +1313,11 @@ class StdExpPathPrinter:
             t = self._path_type()
             if t:
                 path = '%s [%s]' % (path, t)
-        return "filesystem::path %s" % path
+        return "experimental::filesystem::path %s" % path
 
     class _iterator(Iterator):
-        def __init__(self, cmpts):
+        def __init__(self, cmpts, pathtype):
+            self.pathtype = pathtype
             self.item = cmpts['_M_impl']['_M_start']
             self.finish = cmpts['_M_impl']['_M_finish']
             self.count = 0
@@ -1331,13 +1333,13 @@ class StdExpPathPrinter:
             self.count = self.count + 1
             self.item = self.item + 1
             path = item['_M_pathname']
-            t = StdExpPathPrinter(item.type.name, item)._path_type()
+            t = StdExpPathPrinter(self.pathtype, item)._path_type()
             if not t:
                 t = count
             return ('[%s]' % t, path)
 
     def children(self):
-        return self._iterator(self.val['_M_cmpts'])
+        return self._iterator(self.val['_M_cmpts'], self.typename)
 
 class StdPathPrinter:
     "Print a std::filesystem::path"
@@ -1370,6 +1372,7 @@ class StdPathPrinter:
 
     class _iterator(Iterator):
         def __init__(self, impl, pathtype):
+            self.pathtype = pathtype
             if impl:
                 # We can't access _Impl::_M_size because _Impl is incomplete
                 # so cast to int* to access the _M_size member at offset zero,
@@ -1402,7 +1405,7 @@ class StdPathPrinter:
             self.count = self.count + 1
             self.item = self.item + 1
             path = item['_M_pathname']
-            t = StdPathPrinter(item.type.name, item)._path_type()
+            t = StdPathPrinter(self.pathtype, item)._path_type()
             if not t:
                 t = count
             return ('[%s]' % t, path)

libstdc++-v3/testsuite/libstdc++-prettyprinters/filesystem-ts.cc

@@ -0,0 +1,39 @@
+// { dg-options "-g -O0 -lstdc++fs" }
+// { dg-do run { target c++11 } }
+// { dg-require-filesystem-ts "" }
+
+// Copyright (C) 2020 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/>.
+
+#include <experimental/filesystem>
+#include <iostream>
+
+int
+main()
+{
+  std::experimental::filesystem::path path0;
+// { dg-final { note-test path0 {experimental::filesystem::path ""} } }
+  std::experimental::filesystem::path path1("filename");
+// { dg-final { note-test path1 {experimental::filesystem::path "filename"} } }
+  std::experimental::filesystem::path path2("/dir/.");
+// { dg-final { note-test path2 {experimental::filesystem::path "/dir/." = {[root-directory] = "/", [1] = "dir", [2] = "."}} } }
+
+  std::cout << "\n";
+  return 0;			// Mark SPOT
+}
+
+// { dg-final { gdb-test SPOT } }