libstdc++: Use non-throwing increment in recursive_directory_iterator [PR 97731]

As described in the PR, the recursive_directory_iterator constructor
calls advance(ec), but ec is a pointer so it calls _Dir::advance(bool).
The intention was to either call advance() or advance(*ec) depending
whether the pointer is null or not.

This fixes the bug and renames the parameter to ecptr to make similar
mistakes less likely in future.

libstdc++-v3/ChangeLog:

	PR libstdc++/97731
	* src/filesystem/dir.cc (recursive_directory_iterator): Call the
	right overload of _Dir::advance.
	* testsuite/experimental/filesystem/iterators/97731.cc: New test.

(cherry picked from commit 2f93a2a03a343a29f614a530d7657f1ed6347ed5)

2 files changed, 60 insertions, 7 deletions

diff --git a/libstdc++-v3/src/filesystem/dir.cc b/libstdc++-v3/src/filesystem/dir.cc
index 8b1b98d..9db295d 100644
--- a/libstdc++-v3/src/filesystem/dir.cc
+++ b/libstdc++-v3/src/filesystem/dir.cc
@@ -181,16 +181,16 @@ struct fs::recursive_directory_iterator::_Dir_stack : std::stack<_Dir>
 
 fs::recursive_directory_iterator::
 recursive_directory_iterator(const path& p, directory_options options,
-                             error_code* ec)
+                             error_code* ecptr)
 : _M_options(options), _M_pending(true)
 {
-  if (ec)
-    ec->clear();
   if (DIR* dirp = ::opendir(p.c_str()))
     {
+      if (ecptr)
+	ecptr->clear();
       auto sp = std::make_shared<_Dir_stack>();
       sp->push(_Dir{ dirp, p });
-      if (sp->top().advance(ec))
+      if (ecptr ? sp->top().advance(*ecptr) : sp->top().advance())
 	_M_dirs.swap(sp);
     }
   else
@@ -198,14 +198,18 @@ recursive_directory_iterator(const path& p, directory_options options,
       const int err = errno;
       if (err == EACCES
 	  && is_set(options, fs::directory_options::skip_permission_denied))
-	return;
+	{
+	  if (ecptr)
+	    ecptr->clear();
+	  return;
+	}
 
-      if (!ec)
+      if (!ecptr)
 	_GLIBCXX_THROW_OR_ABORT(filesystem_error(
 	      "recursive directory iterator cannot open directory", p,
 	      std::error_code(err, std::generic_category())));
 
-      ec->assign(err, std::generic_category());
+      ecptr->assign(err, std::generic_category());
     }
 }
 
diff --git a/libstdc++-v3/testsuite/experimental/filesystem/iterators/97731.cc b/libstdc++-v3/testsuite/experimental/filesystem/iterators/97731.cc
new file mode 100644
index 0000000..c6a9d56
--- /dev/null
+++ b/libstdc++-v3/testsuite/experimental/filesystem/iterators/97731.cc
@@ -0,0 +1,49 @@
+// 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/>.
+
+// { dg-options "-DUSE_FILESYSTEM_TS -lstdc++fs" }
+// { dg-do run { target c++11 } }
+// { dg-require-filesystem-ts "" }
+
+#include <experimental/filesystem>
+#include <cerrno>
+#include <testsuite_hooks.h>
+
+bool used_custom_readdir = false;
+
+extern "C" void* readdir(void*)
+{
+  used_custom_readdir = true;
+  errno = EIO;
+  return nullptr;
+}
+
+void
+test01()
+{
+  using std::experimental::filesystem::recursive_directory_iterator;
+  std::error_code ec;
+  recursive_directory_iterator it(".", ec);
+  if (used_custom_readdir)
+    VERIFY( ec.value() == EIO );
+}
+
+int
+main()
+{
+  test01();
+}