Beman Dawes wrote:
On Sat, Oct 8, 2011 at 7:08 AM, Vicente J. Botet Escriba <vicente.botet@> wrote:
... Discussion of alternatives ...
I see three alternatives:
A- Standard Clock::now() noexcept;
B- Standard+Hybrid Clock::now() noexcept; Clock::now(system::error_code&); // takes care of boost::throw()
C-Standard+EC+TOE Clock::now() noexcept; Clock::now(system::error_code&) noexcept; Clock::now(throw_on_error_t&); ... Which way do you prefer? What do you think?
D - Standard with additional behavior:
* Return a special time_point value when an error occurs. Do this by having time_point provide "static constexpr time_point error();" in addition to min() and max(). Add something like this to the docs: "Since most programs will run in only in environments where clocks never fail, most programmers can safely ignore the possibility of this value being returned."
I don't like the addition of not_a_time_point value as the result of the standard prototype, as it forces the user to check any call to now(). If we think that in some platforms clock::now could result in an error that the user can do something about, we should use either an error code or an exception, but not an invalid value. If the user couldn't do anything, as this is an internal error, the standard behavior is enough. Well this is my opinion ;-)
(You might consider on Windows doing a fall-back if the Win32 high resolution timer fails, by the way.)
What do you mean by doing a fallback?
* At compile time, detect platforms (such as tiny embedded systems) that never support the Clock, and issue an #error. Perhaps folks on the list could help identifying such systems. They are probably rare.
The library provides already macros to check for the availability of all the clocks expect system_clock, which is mandatory. I will check if I have generated a #error for platforms other than win, posix or mac. Best, Vicente -- View this message in context: http://boost.2283326.n4.nabble.com/chrono-system-Make-possible-to-don-t-prov... Sent from the Boost - Dev mailing list archive at Nabble.com.