tor/changes/gmtime_null

  o Minor bugfixes
    - On some platforms, gmtime and localtime can return NULL under
      certain circumstances even for well-defined values of time_t.
      Try to detect and make up for this deficiency.  Possible fix for
      bug 2077.  Bugfix on all versions of Tor.  Found by boboper.
Detect and handle NULL returns from (gm/local)time_r These functions can return NULL for otherwise-valid values of time_t. Notably, the glibc gmtime manpage says it can return NULL if the year if greater than INT_MAX, and the windows MSDN gmtime page says it can return NULL for negative time_t values. Also, our formatting code is not guaranteed to correctly handle years after 9999 CE. This patch tries to correct this by detecting NULL values from gmtime/localtime_r, and trying to clip them to a reasonable end of the scale. If they are in the middle of the scale, we call it a downright error. Arguably, it's a bug to get out-of-bounds dates like this to begin with. But we've had bugs of this kind in the past, and warning when we see a bug is much kinder than doing a NULL-pointer dereference. Boboper found this one too. 2010-12-07 20:37:50 +01:00			`o Minor bugfixes`
			`- On some platforms, gmtime and localtime can return NULL under`
			`certain circumstances even for well-defined values of time_t.`
			`Try to detect and make up for this deficiency. Possible fix for`
			`bug 2077. Bugfix on all versions of Tor. Found by boboper.`