Change the implementation, in the way that mismatch in return
type of the from/to_sys/utc functions (not returning time_point,
or returning time_point with inappropriate clock) leads to
hard error.
Added appropariate fail test for to_sys function, including:
* returning an int
* returning time_point of wrong clock
* reutrning reference to time_point
Added an clock_time_conversion trait, that should be specialized
with SourceClock and DestClock respectively and provide an function
that convert time_point in SourceClock to equivalent time_point
in DestClock.
This function has following specializations:
1) <sys_clock, utc_clock> - convert sys_time to utc_time
2) <utc_clock, sys_clock> - convert utc_time to sys_time
3) <Clock, sys_clock> - calls Clock::to_sys if it returns sys_time
4) <Clock, utc_clock> - calls Clock::to_utc if it returns utc_time
5) <sys_clock, Clock> - calls Clock::from_sys if it returns time_point<Clock>
5) <utc_clock, Clock> - calls Clock::from_utc if it returns time_point<Clock>
Implemented an clock_cast<DestClock>(time_point<SourceClock, Dur> st), that
works as follow:
1) If DestClock is same as SourceClock, returns std
2) Otherwise, if clock_conversion<SourceClock, DestClock> available, uses it
3) Otherwise, if tries using clock_conversion<SourceClock, CommClock>
and clock_conversion<CommClock, DestClock> for CommClock being utc_time
or sys_time
4) Otherwise, tries using clock_conversion<SourceClock, utc_clock>
and clock_conversion<sys_clock, DestinationClock> or reversed (firstly
convert to sys_clock, then to utc_clock) to convert.
All the calls to `std::time_get::get` had `0` as end-of-range iterator.
E.g.
auto& f = use_facet<time_get<CharT>>(is.getloc());
// ...
f.get(is, 0, is, err, &tm, command, fmt+1);
^
Using `nullptr` instead of `0` doesn't trigger the GCC 5.x warning:
> warning: zero as null pointer constant [-Wzero-as-null-pointer-constant]
tm variable is not initialized in to_stream(), and valgrind warns about
"Conditional jump or move depends on uninitialised value(s)".
This is a false positive, as strftime always reads tm_hour, even if it
ends up never using it. To silence the warnings, initialize tm to zero.
Tomasz Kamiński
Howard Hinnant
Tullio Menga
Alexander Karatarakis
Pavel Davydov
Manlio Morini
Tomi Valkeinen
Markus Werle