Re: [PATCH] t4212: handle systems with post-apocalyptic gmtime

On Tue, Apr 01, 2014 at 12:07:22PM -0700, Junio C Hamano wrote:

Jeff King [off-list ref] writes:

quoted

On Fri, Mar 28, 2014 at 12:30:02PM -0700, Junio C Hamano wrote:

quoted

Let's just deal with a simple known cases (like FreeBSD) in the real
code that everybody exercises at runtime, and have the new test only
check we do not segfault on a value we used to segfault upon seeing.

OK. Here it is, with the other option as an "alt" patch for reference.

  [1/2]: date: recognize bogus FreeBSD gmtime output
  [2/2]: t4212: loosen far-in-future test for AIX
  [2alt/2]: work around unreliable gmtime errors on AIX

-Peff

Thanks.  2alt does not look too bad, but on the other hand, we are
replacing a value that can produce the right result on correctly
implemented gmtime with a completely bogus value only because we
know there exists one broken implementation---which does not sound a
very good trade-off, given that we would get a result that does not
correspond to the input anyway with or without the change on the
broken implementation.

One other option is to push _all_ callers through a git_gmtime()
wrapper, and then use Makefile knobs to turn on specific quirks, like:

    struct tm *git_gmtime_r(const time_t *timep, struct tm *result)
    {
    #ifdef GMTIME_OVERFLOWS_32BIT
              if (*timep > 999999999999999)
                        return NULL;
    #endif

              ret = gmtime_r(timep, result);

    #ifdef GMTIME_ERROR_BLANK
              if (ret && !ret->tm_mday)
                        return NULL;
    #endif

              return ret;
    }

and then each platform can turn the knobs as appropriate.

-Peff