On Wed, 28 Oct 2020, Patrick Palka wrote:
> The conversion function year_month_weekday::operator sys_days computes
> the number of days to offset from the first weekday of the month with:
>
> days{(index()-1)*7}
> ^~~~~~~~~~~~~ type 'unsigned'
>
> We'd like the above to yield -7d when index() is 0u, but our 'days'
> alias is based on long instead of int, so the conversion from unsigned
> to long instead yields a large positive quantity.
>
> This patch fixes this by casting the result of index() to int so that
> the initializer is sign-extended in the conversion to long. The added
> testcase also verifies that we do the right thing when index() == 5.
>
> Tested on x86_64-pc-linux-gnu, does this look OK for trunk?
>
> libstdc++-v3/ChangeLog:
>
> PR libstdc++/96713
> * include/std/chrono (year_month_weekday::operator sys_days):
> Cast the result of index() to int so that the initializer for
> days{} is sign-extended when it's converted to the underlying
> type.
> * testsuite/std/time/year_month_weekday/3.cc: New test.
> ---
> libstdc++-v3/include/std/chrono | 3 +-
> .../std/time/year_month_weekday/3.cc | 66 +++++++++++++++++++
> 2 files changed, 68 insertions(+), 1 deletion(-)
> create mode 100644 libstdc++-v3/testsuite/std/time/year_month_weekday/3.cc
>
> diff --git a/libstdc++-v3/include/std/chrono b/libstdc++-v3/include/std/chrono
> index 7539d7184ea..7c35b78fe59 100644
> --- a/libstdc++-v3/include/std/chrono
> +++ b/libstdc++-v3/include/std/chrono
> @@ -2719,7 +2719,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
> operator sys_days() const noexcept
> {
> auto __d = sys_days{year() / month() / 1};
> - return __d + (weekday() - chrono::weekday(__d) + days{(index()-1)*7});
> + return __d + (weekday() - chrono::weekday(__d)
> + + days{((int)index()-1)*7});
On second thought, for consistency with the rest of the header, I guess
we should use a functional cast instead of a C-style cast here:
-- >8 --
libstdc++-v3/ChangeLog:
PR libstdc++/96713
* include/std/chrono (year_month_weekday::operator sys_days):
Cast the result of index() to int so that the initializer for
days{} is sign-extended when it's converted to the underlying
type.
* testsuite/std/time/year_month_weekday/3.cc: New test.
---
libstdc++-v3/include/std/chrono | 3 +-
.../std/time/year_month_weekday/3.cc | 65 +++++++++++++++++++
2 files changed, 67 insertions(+), 1 deletion(-)
create mode 100644 libstdc++-v3/testsuite/std/time/year_month_weekday/3.cc
diff --git a/libstdc++-v3/include/std/chrono b/libstdc++-v3/include/std/chrono
index 7539d7184ea..f947082c528 100644
--- a/libstdc++-v3/include/std/chrono
+++ b/libstdc++-v3/include/std/chrono
@@ -2719,7 +2719,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
operator sys_days() const noexcept
{
auto __d = sys_days{year() / month() / 1};
- return __d + (weekday() - chrono::weekday(__d) + days{(index()-1)*7});
+ return __d + (weekday() - chrono::weekday(__d)
+ + days{(int(index())-1)*7});
}
explicit constexpr
diff --git a/libstdc++-v3/testsuite/std/time/year_month_weekday/3.cc
b/libstdc++-v3/testsuite/std/time/year_month_weekday/3.cc
new file mode 100644
index 00000000000..cccaccef211
--- /dev/null
+++ b/libstdc++-v3/testsuite/std/time/year_month_weekday/3.cc
@@ -0,0 +1,65 @@
+// { dg-options "-std=gnu++2a" }
+// { dg-do compile { target c++2a } }
+
+// 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/>.
+
+// PR libstdc++/97613
+// Test year_month_weekday to sys_days conversion for extreme values of
index().
+
+#include <chrono>
+
+void
+test01()
+{
+ using namespace std::chrono;
+ using ymd = year_month_day;
+
+ static_assert(ymd{sys_days{2020y/January/Sunday[0]}} == 2019y/December/29);
+ static_assert(ymd{sys_days{2020y/January/Monday[0]}} == 2019y/December/30);
+ static_assert(ymd{sys_days{2020y/January/Tuesday[0]}} == 2019y/December/31);
+ static_assert(ymd{sys_days{2020y/January/Wednesday[0]}} ==
2019y/December/25);
+ static_assert(ymd{sys_days{2020y/January/Thursday[0]}} == 2019y/December/26);
+ static_assert(ymd{sys_days{2020y/January/Friday[0]}} == 2019y/December/27);
+ static_assert(ymd{sys_days{2020y/January/Saturday[0]}} == 2019y/December/28);
+
+ static_assert((2020y).is_leap());
+ static_assert(ymd{sys_days{2020y/March/Sunday[0]}} == 2020y/February/23);
+ static_assert(ymd{sys_days{2020y/March/Monday[0]}} == 2020y/February/24);
+ static_assert(ymd{sys_days{2020y/March/Tuesday[0]}} == 2020y/February/25);
+ static_assert(ymd{sys_days{2020y/March/Wednesday[0]}} == 2020y/February/26);
+ static_assert(ymd{sys_days{2020y/March/Thursday[0]}} == 2020y/February/27);
+ static_assert(ymd{sys_days{2020y/March/Friday[0]}} == 2020y/February/28);
+ static_assert(ymd{sys_days{2020y/March/Saturday[0]}} == 2020y/February/29);
+
+ static_assert(!(2019y).is_leap());
+ static_assert(ymd{sys_days{2019y/March/Sunday[0]}} == 2019y/February/24);
+ static_assert(ymd{sys_days{2019y/March/Monday[0]}} == 2019y/February/25);
+ static_assert(ymd{sys_days{2019y/March/Tuesday[0]}} == 2019y/February/26);
+ static_assert(ymd{sys_days{2019y/March/Wednesday[0]}} == 2019y/February/27);
+ static_assert(ymd{sys_days{2019y/March/Thursday[0]}} == 2019y/February/28);
+ static_assert(ymd{sys_days{2019y/March/Friday[0]}} == 2019y/February/22);
+ static_assert(ymd{sys_days{2019y/March/Saturday[0]}} == 2019y/February/23);
+
+ static_assert(ymd{sys_days{2020y/December/Sunday[5]}} == 2021y/January/3);
+ static_assert(ymd{sys_days{2020y/December/Monday[5]}} == 2021y/January/4);
+ static_assert(ymd{sys_days{2020y/December/Tuesday[5]}} == 2020y/December/29);
+ static_assert(ymd{sys_days{2020y/December/Wednesday[5]}} ==
2020y/December/30);
+ static_assert(ymd{sys_days{2020y/December/Thursday[5]}} ==
2020y/December/31);
+ static_assert(ymd{sys_days{2020y/December/Friday[5]}} == 2021y/January/1);
+ static_assert(ymd{sys_days{2020y/December/Saturday[5]}} == 2021y/January/2);
+}
--
2.29.0.rc0
