Re: [PATCH] Implement LWG 2686, hash<error_condition>

[Jonathan Wakely <jwakely at redhat dot com>]

On 04/05/19 15:36 +0100, Jonathan Wakely wrote:
> On 03/05/19 23:42 +0100, Jonathan Wakely wrote:
> > On 23/03/17 17:49 +0000, Jonathan Wakely wrote:
> > > On 12/03/17 13:16 +0100, Daniel Krügler wrote:
> > > > The following is an *untested* patch suggestion, please verify.
> > > >
> > > > Notes: My interpretation is that hash<error_condition> should be
> > > > defined outside of the _GLIBCXX_COMPATIBILITY_CXX0X block, please
> > > > double-check that course of action.
> > >
> > > That's right.
> > >
> > > > I noticed that the preexisting hash<error_code> did directly refer to
> > > > the private members of error_code albeit those have public access
> > > > functions. For consistency I mimicked that existing style when
> > > > implementing hash<error_condition>.
> > >
> > > I see no reason for that, so I've removed the friend declaration and
> > > used the public member functions.
> >
> > I'm going to do the same for hash<error_code> too. It can also use the
> > public members instead of being a friend.
> >
> >
> > > Although this is a DR, I'm treating it as a new C++17 feature, so I've
> > > adjusted the patch to only add the new specialization for C++17 mode.
> > > We're too close to the GCC 7 release to be adding new things to the
> > > default mode, even minor things like this. After GCC 7 is released we
> > > can revisit it and decide if we want to enable it for all modes.
> >
> > We never revisited that, and it's still only enabled for C++17 and up.
> > I guess that's OK, but we could enabled it for C++11 and 14 on trunk
> > if we want. Anybody care enough to argue for that?
> >
> > > Here's what I've tested and will be committing.
> >
> > > commit 90ca0fd91f5c65af370beb20af06bdca257aaf63
> > > Author: Jonathan Wakely <jwakely@redhat.com>
> > > Date:   Thu Mar 23 11:47:39 2017 +0000
> > >
> > >  Implement LWG 2686, std::hash<error_condition>, for C++17
> > >  2017-03-23  Daniel Kruegler  <daniel.kruegler@gmail.com>
> > >  	Implement LWG 2686, Why is std::hash specialized for error_code,
> > >  	but not error_condition?
> > >  	* include/std/system_error (hash<error_condition>): Define for C++17.
> > >  	* testsuite/20_util/hash/operators/size_t.cc (hash<error_condition>):
> > >  	Instantiate test for error_condition.
> > >  	* testsuite/20_util/hash/requirements/explicit_instantiation.cc
> > >  	(hash<error_condition>): Instantiate hash<error_condition>.

I'm adding a similar test for hash<error_code> too.

Tested powerpc64le-linux, committing to trunk shortly.


commit 4034dddf0dbfc20ff9069602a419a95b09de20f6
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Tue May 7 11:09:00 2019 +0100

    Add test for std::hash<std::error_code>
    
    Copied from 19_diagnostics/error_condition/hash.cc added recently.
    
            * testsuite/19_diagnostics/error_code/hash.cc: New test.

diff --git a/libstdc++-v3/testsuite/19_diagnostics/error_code/hash.cc b/libstdc++-v3/testsuite/19_diagnostics/error_code/hash.cc
new file mode 100644
index 00000000000..2014e676878
--- /dev/null
+++ b/libstdc++-v3/testsuite/19_diagnostics/error_code/hash.cc
@@ -0,0 +1,50 @@
+// Copyright (C) 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-do run { target c++11 } }
+
+#include <system_error>
+#include <testsuite_hooks.h>
+
+struct error_cat : std::error_category
+{
+  error_cat(std::string s) : _name(s) { }
+  std::string _name;
+  const char* name() const noexcept override { return _name.c_str(); }
+  std::string message(int) const override { return "error"; }
+};
+
+void
+test01()
+{
+  std::hash<std::error_code> h;
+  error_cat kitty("kitty"), moggy("moggy");
+  std::error_code cond1(99, kitty);
+  VERIFY( h(cond1) == h(cond1) );
+  std::error_code cond2(99, kitty);
+  VERIFY( h(cond1) == h(cond2) );
+  std::error_code cond3(88, kitty);
+  VERIFY( h(cond1) != h(cond3) );
+  std::error_code cond4(99, moggy);
+  VERIFY( h(cond1) != h(cond4) );
+}
+
+int
+main()
+{
+  test01();
+}