82030d5101
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. |
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| include | ||
| libsupc++ | ||
| po | ||
| python | ||
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| src | ||
| testsuite | ||
| acinclude.m4 | ||
| aclocal.m4 | ||
| ChangeLog | ||
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| config.h.in | ||
| configure | ||
| configure.ac | ||
| configure.host | ||
| crossconfig.m4 | ||
| fragment.am | ||
| linkage.m4 | ||
| Makefile.am | ||
| Makefile.in | ||
| README | ||
file: libstdc++-v3/README New users may wish to point their web browsers to the file index.html in the 'doc/html' subdirectory. It contains brief building instructions and notes on how to configure the library in interesting ways.