[PATCH] libstdc++/71320 Add or remove file permissions correctly

[Jonathan Wakely]

This adds the missing functionality to filesystem::permissions().

        PR libstdc++/71320
        * src/filesystem/ops.cc (permissions(const path&, perms, error_code&)):
        Add or remove permissions according to perms argument.
        * testsuite/experimental/filesystem/operations/permissions.cc: New
        test.

Tested x86_64-linux, committed to trunk, backports to follow.



commit bab71865ec13fff8dc212e6e538abe3cde7de6e8
Author: redi <redi@138bc75d-0d04-0410-961f-82ee72b054a4>
Date:   Mon Jun 6 15:50:01 2016 +0000

    libstdc++/71320 Add or remove file permissions correctly
    
        PR libstdc++/71320
        * src/filesystem/ops.cc (permissions(const path&, perms, error_code&)):
        Add or remove permissions according to perms argument.
        * testsuite/experimental/filesystem/operations/permissions.cc: New
        test.
    
    git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@237136 
138bc75d-0d04-0410-961f-82ee72b054a4

diff --git a/libstdc++-v3/src/filesystem/ops.cc 
b/libstdc++-v3/src/filesystem/ops.cc
index 5b82088..67ed8e6 100644
--- a/libstdc++-v3/src/filesystem/ops.cc
+++ b/libstdc++-v3/src/filesystem/ops.cc
@@ -1084,6 +1084,28 @@ fs::permissions(const path& p, perms prms)
 
 void fs::permissions(const path& p, perms prms, error_code& ec) noexcept
 {
+  const bool add = is_set(prms, perms::add_perms);
+  const bool remove = is_set(prms, perms::remove_perms);
+  if (add && remove)
+    {
+      ec = std::make_error_code(std::errc::invalid_argument);
+      return;
+    }
+
+  prms &= perms::mask;
+
+  if (add || remove)
+    {
+      auto st = status(p, ec);
+      if (ec)
+       return;
+      auto curr = st.permissions();
+      if (add)
+       prms |= curr;
+      else
+       prms = curr & ~prms;
+    }
+
 #if _GLIBCXX_USE_FCHMODAT
   if (::fchmodat(AT_FDCWD, p.c_str(), static_cast<mode_t>(prms), 0))
 #else
diff --git 
a/libstdc++-v3/testsuite/experimental/filesystem/operations/permissions.cc 
b/libstdc++-v3/testsuite/experimental/filesystem/operations/permissions.cc
new file mode 100644
index 0000000..e414860
--- /dev/null
+++ b/libstdc++-v3/testsuite/experimental/filesystem/operations/permissions.cc
@@ -0,0 +1,51 @@
+// Copyright (C) 2016 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++11 -lstdc++fs" }
+// { dg-require-filesystem-ts "" }
+
+// 15.26 Permissions [fs.op.permissions]
+
+#include <experimental/filesystem>
+#include <fstream>
+#include <testsuite_fs.h>
+#include <testsuite_hooks.h>
+
+void
+test01()
+{
+  bool test __attribute__((unused)) = true;
+  using perms = std::experimental::filesystem::perms;
+
+  auto p = __gnu_test::nonexistent_path();
+  std::ofstream{p.native()};
+  VERIFY( exists(p) );
+  permissions(p, perms::owner_all);
+  VERIFY( status(p).permissions() == perms::owner_all );
+  permissions(p, perms::group_read | perms::add_perms);
+  VERIFY( status(p).permissions() == (perms::owner_all | perms::group_read) );
+  permissions(p, perms::group_read | perms::remove_perms);
+  VERIFY( status(p).permissions() == perms::owner_all );
+
+  remove(p);
+}
+
+int
+main()
+{
+  test01();
+}