Re: Y2K38 bug (January 19, 2038)

Keith Thompson wrote:

"Mr. Man-wai Chang" <toylet.toylet@gmail.com> writes:

On 9/3/2024 3:51 am, Keith Thompson wrote:

I'm a little disappointed that POSIX doesn't require time_t to be
signed.  64 bits is enough to represent a range of about 584 billion
years.  An unsigned time_t makes it impossible to represent times before
1970.

>
Could we roll our own signed time_t? :)

 
I see the smiley, but I don't get the joke.
 
If you're creating your own implementation, you can do anything you
like.  If not, and you're using an implementation that makes time_t an
unsigned type, there's not much you can do to treat it as signed.  For
example, localtime() would presumably treat a time_t value of -2 as a
very large unsigned value.
 
I don't know of any implementations that make time_t an unsigned type.

QNX is one.

See www.qnx.net/developers/docs/6.4.0/neutrino/sys_arch/kernel.html
which says:

    Valid dates on a QNX Neutrino system range from January 1970 to at
    least 2038. The time_t data type is an unsigned 32-bit number, which
    extends this range for many applications through 2106.

Also, having signed time_t doesn't necessarily mean that dates before
Jan 1970 are supported.  I seem to recall that MS Windows has signed
time_t but does not support negative values.

--
Geoff Clare <netnews@gclare.org.uk>