On Thu, 20 Jul 2017 14:33:58 -0700, Charles Mills wrote: >Yes, negative UNIX times are legal and generally work. > I had understood that negative time_t values are illegal but generally work.
The closest I can find in POSIX is: http://pubs.opengroup.org/onlinepubs/9699919799/functions/mktime.html#tag_16_329_04 RETURN VALUE The mktime() function shall return the specified time since the Epoch encoded as a value of type time_t. If the time since the Epoch cannot be represented, the function shall return the value (time_t)-1 [CX] [Option Start] and set errno to indicate the error. Should I assume that mktime( 1969-12-31 23:59:59 ) returns (time_t)-1 and does not set ERRNO? I had understood that the z/OS XLC standard time functions report an error on an input negative time_t. >But a shift -- arithmetic, not logical! -- of a negative number works, except >it sometimes ends up off by one, which is not going to be a huge problem here, >right? One microsecond. It truncates correctly toward -∞, not toward 0. "Off by" is in the eye of the beholder, and irrelevant because TOD values are unsigned. -- gil ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
