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.
Antonio
