On 7/31/2014 1:37 AM, Antonio Mancina wrote:

Hi Gaetano and all,

Gaetano Mendola writes:

...

The following snippet seems to generate non monotonic local_date.

I'm using boost 1.55 on linux. [CUT] Am I missing something ?

some further investigation on this issue seemed to show that the problem is the following:

The

static time_type local_time(shared_ptr tz_ptr)

function, computes the local time by executing, in short sequence, these two instructions

utc_time_type utc_time = second_clock::universal_time(); time_duration_type utc_offset = second_clock::local_time() - utc_time;

Both the local_time() and universal_time() calls get a time information

static time_type local_time() { ::std::time_t t; ::std::time(&t); ::std::tm curr, *curr_ptr; //curr_ptr = ::std::localtime(&t); curr_ptr = c_time::localtime(&t, &curr); return create_time(curr_ptr); }

static time_type universal_time() {

::std::time_t t; ::std::time(&t); ::std::tm curr, *curr_ptr; //curr_ptr = ::std::gmtime(&t); curr_ptr = c_time::gmtime(&t, &curr); return create_time(curr_ptr); }

and finally invoke the create_time() function.

static time_type create_time(::std::tm* current) { date_type d(static_cast<unsigned short>(current->tm_year + 1900), static_cast<unsigned short>(current->tm_mon + 1), static_cast<unsigned short>(current->tm_mday)); time_duration_type td(current->tm_hour, current->tm_min, current->tm_sec); return time_type(d,td); }

create_time() simply builds a time information with a sec granularity (ms are NOT considered).

So, let's assume that

universal_time() gets called at PM 1:00:00_989ms UTC local_time() gets called at PM 3:00:01_002ms UTC+2 (so actually 13 ms later)

Then, create_time() truncates the milliseconds information and the utc_offset gets a +1 seconds offset with respect to the correct value.

Please file a bug in our tracker: https://svn.boost.org/trac/boost/. Thanks. -- Eric Niebler Boost.org http://www.boost.org