time_t when used as timedelta

[Erik Cederstrand]

Hi list,

I'm looking at this possible divide-by zero in dhclient: http://scan.freebsd.your.org/freebsd-head/WORLD/2012-10-07-amd64/report-nBhqE2.html.gz#EndPath

In this specific case, it's obvious from the intention of the code that ip->client->interval is always >0, but it's not obvious to me in the code. I could add an assert before the possible divide-by-zero:

assert(ip->client->interval > 0);

But looking at the code, I'm not sure it's very elegant. ip->client->interval is defined as time_t (see src/sbin/dhclient/dhcpd.h), which is a signed integer type, if I'm correct. However, some time_t members of struct client_state and struct client_config (see said header file) are assumed in the code to be positive and possibly non-null. Instead of plastering the code with asserts, is there something like an utime_t type? Or are there better ways to enforce the invariant?

Thanks,
Erik