libstdc++: Reset filesystem::recursive_directory_iterator on error

The standard requires directory iterators to become equal to the end
iterator value if they report an error. Some members functions of
filesystem::recursive_directory_iterator fail to do that.

libstdc++-v3/ChangeLog:

	* src/c++17/fs_dir.cc (recursive_directory_iterator::increment):
	Reset state to past-the-end iterator on error.
	(fs::recursive_directory_iterator::pop(error_code&)): Likewise.
	(fs::recursive_directory_iterator::pop()): Check _M_dirs before
	it might get reset.
	* src/filesystem/dir.cc (recursive_directory_iterator): Likewise,
	for the TS implementation.
	* testsuite/27_io/filesystem/iterators/error_reporting.cc: New test.
	* testsuite/experimental/filesystem/iterators/error_reporting.cc: New test.

1 files changed, 135 insertions, 0 deletions

diff --git a/libstdc++-v3/testsuite/27_io/filesystem/iterators/error_reporting.cc b/libstdc++-v3/testsuite/27_io/filesystem/iterators/error_reporting.cc
new file mode 100644
index 00000000000..81ef1069367
--- /dev/null
+++ b/libstdc++-v3/testsuite/27_io/filesystem/iterators/error_reporting.cc
@@ -0,0 +1,135 @@
+// Copyright (C) 2020-2022 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-do run { target { c++17 } } }
+// { dg-require-filesystem-ts "" }
+
+#include <filesystem>
+#include <cerrno>
+#include <stdio.h>
+#include <stdlib.h>
+#include <dirent.h>
+#include <testsuite_hooks.h>
+#include <testsuite_fs.h>
+
+int choice;
+
+struct dirent global_dirent;
+
+extern "C" struct dirent* readdir(DIR*)
+{
+  switch (choice)
+  {
+  case 1:
+    global_dirent.d_ino = 999;
+    global_dirent.d_type = DT_REG;
+    global_dirent.d_reclen = 0;
+    std::char_traits<char>::copy(global_dirent.d_name, "file", 5);
+    choice = 0;
+    return &global_dirent;
+  case 2:
+    global_dirent.d_ino = 111;
+    global_dirent.d_type = DT_DIR;
+    global_dirent.d_reclen = 60;
+    std::char_traits<char>::copy(global_dirent.d_name, "subdir", 7);
+    choice = 1;
+    return &global_dirent;
+  default:
+    errno = EIO;
+    return nullptr;
+  }
+  return &global_dirent;
+}
+
+void
+test01()
+{
+  namespace fs = std::filesystem;
+  std::error_code ec;
+  choice = 1;
+  fs::recursive_directory_iterator it(".", ec);
+  if (choice == 0) // custom readdir was called
+  {
+    it.increment(ec);
+    VERIFY( ec.value() == EIO );
+    VERIFY( it == end(it) );
+  }
+  else
+  {
+    puts("Custom readdir not used, cannot test error handling");
+    exit(0);
+  }
+
+#if __cpp_exceptions
+  choice = 1;
+  fs::recursive_directory_iterator it2(".", ec);
+  if (choice == 0)
+  {
+    try {
+      ++it2;
+      VERIFY( false );
+    } catch (const fs::filesystem_error& e) {
+      VERIFY( e.code().value() == EIO );
+      VERIFY( it2 == end(it2) );
+    }
+  }
+#endif
+}
+
+void
+test02()
+{
+  namespace fs = std::filesystem;
+  auto dir = __gnu_test::nonexistent_path();
+  fs::create_directories(dir/"subdir");
+
+  std::error_code ec;
+  choice = 2;
+  fs::recursive_directory_iterator it(dir, ec);
+  if (choice == 1)
+  {
+    ++it;
+    it.pop(ec);
+    VERIFY( ec.value() == EIO );
+    VERIFY( it == end(it) );
+  }
+
+#if __cpp_exceptions
+  choice = 2;
+  fs::recursive_directory_iterator it2(dir, ec);
+  if (choice == 1)
+  {
+    ++it2;
+    try {
+      it2.pop();
+      VERIFY( false );
+    } catch (const fs::filesystem_error& e) {
+      VERIFY( e.code().value() == EIO );
+      VERIFY( it2 == end(it2) );
+    }
+  }
+#endif
+
+  fs::remove_all(dir, ec);
+}
+
+int
+main()
+{
+  test01();
+  test02();
+}