swatt (08/13/82)
Many people have worried about C and UNIX portability to new machine
hosts, but it seems everyone has missed a widespread bug that will
affect portability of UNIX into the next century.
in /usr/include/sys/types.h (4.1bsd) the type "time_t" is declared as
"int", which is the same as "long int". Now UNIX keeps time as the
number of seconds since midnight January 1, 1975. What will happen as
time marches on and eventually becomes negative? Well, "make" for one
will break. I bet all the news software will collapse, or at least
fail to expire articles. "readnews -a april 1" will not do anything
reasonable.
The list of things that will go wrong is probably only limited by:
"grep -c time_t /usr/src/cmd/*.[cy] /usr/src/cmd/*/*.[cy]"
How soon will this disaster hit us? The program:
unsigned int breakdate = (1<<31)-1;
main ()
{
printf ("everything breaks %s\n", ctime (&breakdate));
}
run on our machine gives:
everything breaks Mon Jan 18 22:14:07 2038
This leaves us enough time to ammend the C language standard to include
type "unsigned long", which will stave off the inevitable disaster
for another 63 years, when the number of seconds since midnight January
1, 1975 will no longer fit in 32 bits. Sometime in 2101 UNIX will run
out of time completely.
One day that year, people all over the world will come to their
automated offices (or stay at home and work on their workstation
connected to their office via a Wide Area Network), and find themselves
living in their great-great-grandfather's time. By then, every piece
of silicon in the world (solar system, galaxy, universe?????) will be
running some adaptation of UNIX(tm) 68.0, which will be portable to all
digital, analog, fluidic, and optical computers. All over the
UNIXverse, time will jump backwards 126 years! Talk about computer time
bombs!
Credit goes to Mack Endres for first noticing this serious bug.
- Alan S. Watt