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Re: [Patch, fortran] PR 56919 SYSTEM_CLOCK on Windows

Janne Blomqvist wrote:
Attached is an updated patch which uses GetTickCount for system_clock_4; this should be fine as system_clock_4 wraps around in ~25 days anyways. For system_clock_8 it uses QueryPerformance{Counter,Frequency}.

The patch also adds an additional check for _POSIX_MONOTONIC_CLOCK.
Ok for trunk?

Regarding the documentation, I wonder whether one should do the following additional changes: - Explicitly suggest to use a kind=8 argument fÃr system_clock (for higher resolution and to avoid overflows). - To change the system_clock example to use an integer(8) argument. Possibly, via iso_fortran_env's int64 or via selected_int_kind(18)


I'd add
as POSIX states: "If a symbolic constant is defined with the value -1, the option is not supported."

+      uint32_t cnt = GetTickCount ();

I wonder whether a comment stating that GetTickCount instead of QueryPerformanceCounter is used as the extra precision and 49.7-days overflow do not matter with the 32bit system_clock - and as QueryPerformanceCounter has issues on some (very few) systems.

Otherwise, it looks fine to me.


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