The configure test for mktime (m4/mktime.m4) contains the following
code:
for (;;)
{
t = (time_t_max << 1) + 1;
if (t <= time_t_max)
break;
time_t_max = t;
}
This code has undefined behavior on signed integer overflow; at least
some versions of gcc, and any sane compiler, will optimize out the
exit condition since algebraically 2x+1>x for any nonnegative x. The
result is an infinite loop and failure of the test after the 60-second
timeout.
Finding the max possible value for a signed integer type is actually a
very hard problem in C. As far as I know it's impossible at
compile-time and might even be impossible at runtime unless you make
some assumptions (either the absence of padding bits, or the
well-definedness of converting larger/unsigned types to signed types).
The approach I would take is just:
time_t_max = (time_t)1 << 8*sizeof(time_t)-2;
If this test comes from higher-up (gnulib?) please forward my bug
report to the relevant upstream.
