* [Bug libstdc++/89102] 'common_type' of single abominable function should not have a nested typename
[not found] <bug-89102-4@http.gcc.gnu.org/bugzilla/>
@ 2020-08-27 21:40 ` cvs-commit at gcc dot gnu.org
2021-03-29 20:04 ` cvs-commit at gcc dot gnu.org
1 sibling, 0 replies; 2+ messages in thread
From: cvs-commit at gcc dot gnu.org @ 2020-08-27 21:40 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89102
--- Comment #9 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Jonathan Wakely <redi@gcc.gnu.org>:
https://gcc.gnu.org/g:82030d51017323c5706d58d8c8626324ece007e4
commit r11-2913-g82030d51017323c5706d58d8c8626324ece007e4
Author: Jonathan Wakely <jwakely@redhat.com>
Date: Thu Aug 27 22:36:03 2020 +0100
libstdc++: Make std::chrono::duration use reduced ratio for period
This implements the changes from P0548 "common_type and duration". That
was a change for C++17, but as it corrects some issues introduced by DRs
I'm also treating it as a DR and changing it for all modes from C++11
up.
The main change is that duration<R,P>::period no longer denotes P, but
rather P::type, the reduced ratio. The unary operator+ and operator-
members of duration should now return a duration using that reduced
ratio.
The requirement that common_type<T>::type is the same type as
common_type<T, T>::type (rather than simply T) was already implemented
for PR 89102.
The standard says that duration::operator+() and duration::operator-()
should return common_type_t<duration>, but that seems unnecessarily
expensive to compute. This change just uses duration<rep, period> which
is the same type, so we don't need to instantiate common_type.
As an optimization, this also adds partial specializations of
common_type for two durations of the same type, a single duration, two
time_points of the same type, and a single time_point. These
specializations avoid instantiating other specializations of common_type
and one or both of __duration_common_type or __timepoint_common_type for
the cases where the answer is trivial to obtain.
libstdc++-v3/ChangeLog:
* include/std/chrono (__duration_common_type): Ensure the
reduced ratio is used. Remove unused partial specialization
using __failure_type.
(common_type): Pass reduced ratios to __duration_common_type.
Add partial specializations for simple cases involving a single
duration or time_point type.
(duration::period): Use reduced ratio.
(duration::operator+(), duration::operator-()): Return duration
type using the reduced ratio.
* testsuite/20_util/duration/requirements/typedefs_neg2.cc:
Adjust expected errors.
* testsuite/20_util/duration/requirements/reduced_period.cc: New
test.
^ permalink raw reply [flat|nested] 2+ messages in thread* [Bug libstdc++/89102] 'common_type' of single abominable function should not have a nested typename
[not found] <bug-89102-4@http.gcc.gnu.org/bugzilla/>
2020-08-27 21:40 ` [Bug libstdc++/89102] 'common_type' of single abominable function should not have a nested typename cvs-commit at gcc dot gnu.org
@ 2021-03-29 20:04 ` cvs-commit at gcc dot gnu.org
1 sibling, 0 replies; 2+ messages in thread
From: cvs-commit at gcc dot gnu.org @ 2021-03-29 20:04 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89102
--- Comment #10 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-10 branch has been updated by Jonathan Wakely
<redi@gcc.gnu.org>:
https://gcc.gnu.org/g:7dea2f84f26d454331d34b8536c261b6e96205d7
commit r10-9608-g7dea2f84f26d454331d34b8536c261b6e96205d7
Author: Jonathan Wakely <jwakely@redhat.com>
Date: Thu Aug 27 22:36:03 2020 +0100
libstdc++: Make std::chrono::duration use reduced ratio for period
This implements the changes from P0548 "common_type and duration". That
was a change for C++17, but as it corrects some issues introduced by DRs
I'm also treating it as a DR and changing it for all modes from C++11
up.
The main change is that duration<R,P>::period no longer denotes P, but
rather P::type, the reduced ratio. The unary operator+ and operator-
members of duration should now return a duration using that reduced
ratio.
The requirement that common_type<T>::type is the same type as
common_type<T, T>::type (rather than simply T) was already implemented
for PR 89102.
The standard says that duration::operator+() and duration::operator-()
should return common_type_t<duration>, but that seems unnecessarily
expensive to compute. This uses duration<common_type_t<rep>, period>
which is the same type, so we avoid a common_type specialization.
As an optimization, this also adds partial specializations of
common_type for two durations of the same type, a single duration, two
time_points of the same type, and a single time_point. These
specializations avoid instantiating other specializations of common_type
and one or both of __duration_common_type or __timepoint_common_type for
the cases where the answer is trivial to obtain.
libstdc++-v3/ChangeLog:
* include/std/chrono (__duration_common_type): Ensure the
reduced ratio is used. Remove unused partial specialization
using __failure_type.
(common_type): Pass reduced ratios to __duration_common_type.
Add partial specializations for simple cases involving a single
duration or time_point type.
(duration::period): Use reduced ratio.
(duration::operator+(), duration::operator-()): Return duration
type using the reduced ratio.
* testsuite/20_util/duration/requirements/typedefs_neg2.cc:
Adjust expected errors.
* testsuite/20_util/duration/requirements/reduced_period.cc: New
test.
(cherry picked from commit 82030d51017323c5706d58d8c8626324ece007e4)
^ permalink raw reply [flat|nested] 2+ messages in thread