On 19/09/20 11:37 +0100, Mike Crowe wrote:
On Friday 11 September 2020 at 19:59:36 +0100, Jonathan Wakely wrote:
commit 53ad6b1979f4bd7121e977c4a44151b14d8a0147
Author: Jonathan Wakely <jwak...@redhat.com>
Date: Fri Sep 11 19:59:11 2020
libstdc++: Fix chrono::__detail::ceil to work with C++11
In C++11 constexpr functions can only have a return statement, so we
need to fix __detail::ceil to make it valid in C++11. This can be done
by moving the comparison and increment into a new function, __ceil_impl,
and calling that with the result of the duration_cast.
This would mean the standard C++17 std::chrono::ceil function would make
two further calls, which would add too much overhead when not inlined.
For C++17 and later use a using-declaration to add chrono::ceil to
namespace __detail. For C++11 and C++14 define chrono::__detail::__ceil
as a C++11-compatible constexpr function template.
libstdc++-v3/ChangeLog:
* include/std/chrono [C++17] (chrono::__detail::ceil): Add
using declaration to make chrono::ceil available for internal
use with a consistent name.
(chrono::__detail::__ceil_impl): New function template.
(chrono::__detail::ceil): Use __ceil_impl to compare and
increment the value. Remove SFINAE constraint.
This change introduces a new implementation of ceil that, as far as I can
tell, has no tests. A patch is attached to add the equivalent of the
existing chrono::ceil tests for chrono::__detail::ceil. The tests fail to
compile if I run them without 53ad6b1979f4bd7121e977c4a44151b14d8a0147 as
expected due to the previous non-C++11-compliant implementation.
Pushed to master, thanks.
From b9dffbf4f1bc05a887269ea95a3b86d5a611e720 Mon Sep 17 00:00:00 2001
From: Mike Crowe <m...@mcrowe.com>
Date: Wed, 16 Sep 2020 15:31:28 +0100
Subject: [PATCH 1/2] libstdc++: Test C++11 implementation of
std::chrono::__detail::ceil
Commit 53ad6b1979f4bd7121e977c4a44151b14d8a0147 split the implementation
of std::chrono::__detail::ceil so that when compiling for C++17 and
later std::chrono::ceil is used but when compiling for earlier versions
a separate implementation is used to comply with C++11's limited
constexpr rules. Let's run the equivalent of the existing
std::chrono::ceil test cases on std::chrono::__detail::ceil too to make
sure that it doesn't get broken.
libstdc++-v3/ChangeLog:
* testsuite/20_util/duration_cast/rounding_c++11.cc: Copy
rounding.cc and alter to support compilation for C++11 and to
test std::chrono::__detail::ceil.
---
.../20_util/duration_cast/rounding_c++11.cc | 43 +++++++++++++++++++
1 file changed, 43 insertions(+)
create mode 100644
libstdc++-v3/testsuite/20_util/duration_cast/rounding_c++11.cc
diff --git a/libstdc++-v3/testsuite/20_util/duration_cast/rounding_c++11.cc
b/libstdc++-v3/testsuite/20_util/duration_cast/rounding_c++11.cc
new file mode 100644
index 00000000000..f10d27fd082
--- /dev/null
+++ b/libstdc++-v3/testsuite/20_util/duration_cast/rounding_c++11.cc
@@ -0,0 +1,43 @@
+// Copyright (C) 2016-2020 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 "-std=gnu++11" }
+// { dg-do compile { target c++11 } }
+
+#include <chrono>
+
+using std::chrono::seconds;
+using std::chrono::milliseconds;
+
+using fp_seconds = std::chrono::duration<float>;
+
+static_assert( std::chrono::__detail::ceil<seconds>(milliseconds(1000))
+ == seconds(1) );
+static_assert( std::chrono::__detail::ceil<seconds>(milliseconds(1001))
+ == seconds(2) );
+static_assert( std::chrono::__detail::ceil<seconds>(milliseconds(1500))
+ == seconds(2) );
+static_assert( std::chrono::__detail::ceil<seconds>(milliseconds(1999))
+ == seconds(2) );
+static_assert( std::chrono::__detail::ceil<seconds>(milliseconds(2000))
+ == seconds(2) );
+static_assert( std::chrono::__detail::ceil<seconds>(milliseconds(2001))
+ == seconds(3) );
+static_assert( std::chrono::__detail::ceil<seconds>(milliseconds(2500))
+ == seconds(3) );
+static_assert( std::chrono::__detail::ceil<fp_seconds>(milliseconds(500))
+ == fp_seconds{0.5f} );
--
2.28.0
