id	summary	reporter	owner	description	type	status	milestone	component	version	severity	resolution	keywords	cc
3471	microseconds constructor overflows	Andrey Semashev	Andrey Semashev	"From the users ML: [http://lists.boost.org/boost-users/2008/10/41763.php]

The boost::date_time::microseconds(...) constructor overflows the int64 size
limits in intermediary calculations. The code below will reproduce the error
(using VC++ 2008 and boost 1.36).

{{{
ptime start(boost::gregorian::date(2000, 1, 1));
ptime end(boost::gregorian::date(2000, 5, 1));
time_duration td = end - start;

ptime wrongEnd = start + microseconds(td.total_microseconds());
BOOST_CHECK_EQUAL(end, wrongEnd);
}}}

The microseconds constructor takes an int64 as input and the
total_microseconds is well within its range. Inside the
date_time::subsecond_duration<time_duration, 1000000> the internal duration
is calculated as

{{{
ss*traits_type::res_adjust()/frac_of_second
}}}

Since the both res_adjust() and frac_of_second have the value 1000000, the
result should be ss*1 but... the intermediary value ss*res_adjust overflows
the int64 causing a negative number to be returned.

Question is, is this by design or is it a bug? I'm rather new to
boost::date_time and was hoping to replace our current datetime types with
it. We are using millisecond timestamped data over long time series (years).

I guess the simple solution would be to add parentheses around
(res_adjust()/frac_of_second) assuming frac_of_second always divides
res_adjust. However, there are similar issues when adding 200 years worth of
seconds which overflows the int32 argument (but that's not of my immediate
concern)."	Patches	closed	Boost 1.43.0	date_time	Boost 1.40.0	Problem	fixed	microseconds