Re: [boost] boost::posix_time::time_duration greater than 24 hours

From: Jeff Garland (jeff_at_[hidden])
Date: 2007-12-11 22:34:57

Mark Van Dijk wrote:
> My apologies for not specifing this earlier - i just assumed that many
> people had previously run into it.  Michael Mathews is correct about the
> operator<<() and strftime.c being the cause of this issue.

Thx for the detail. I don't normally develop on Windows -- unless I'm paid 
that is ;-)

> operator<<(ostream&, time_duration const&) basically converts the
> time_duration object to a tm struct using the function
> boost::posix_time::to_tm(time_duration const&).  At this point, the tm
> structure contains an hours value of 24 - which Microsoft considers to
> be out-of-range.  Further down the stack the _Strftime_l() function
> verifies the tm structure and everything comes to a crashing halt at
> this point.

Yeah that clears up the mystery.

> The MSDN docs for _Strftime_l() states that this function will check the
> tm struct for invalid and out-of-range values and will call the invalid
> parameter handler in this case.
 >
> Hope that helps  :-)

While my initial reaction is that I'm not inclined to fix this problem since 
this seems like another case of an over-zealous 'safety cleanup' on MS part 
(The previous example was when MS disallowed tm from having negative years 
early in VC8 -- thus not correctly handling output for any date less than 
1/1/1900 breaking working code - someone submitted a bug report and I believe 
they've changed it back now).  Anyway, on my Linux machine with gcc4 things 
operate pretty much does what you might expect:

   time_duration td1(300,0,0);
   std::cout << td1 << std::endl;  300:00:00

That said, I am compelled by the open group spec for strftime saying that %H 
has a range of 00-23.  So this seems like an ugly specification flaw in the 
date-time i/o concept for durations.  Basically a really nasty problem for 
long time durations that depend on output of larger than 2 digit hours 
quantities.  The quick hack would be to change time_facet.hpp to override the 
%H output.  However, %H input is also broken because it only looks for 2 
digits.   So, I'm afraid this isn't a super quick issue to resolve...

Note I'm guessing the reason this doesn't come up to much is that most people 
use time_duration output in the context of ptime which normalizes the day 
count on construction:

  date d(...);
  ptime t(d, hours(24)); //d+1 at 00:00::00
  std::cout << t << std::endl; //fine...hours will be 0

Jeff