date: avoid crash on invalid time

[emaste]

Summary

localtime(3) returns NULL when passed an invalid time_t but date(1) previously did not handle it. Exit with an error in that case.

PR:             220828
Reported by:    Vinícius Zavam

[cem]

bin/date/date.c

177–180 ↗

(On Diff #30966)

This changes the behavior of the code in the success case. Previously we copied the struct tm and modified the local copy. Now we're modifying whatever localtime() gave us, which I suspect is some global storage?

[emaste]

bin/date/date.c

177–180 ↗

(On Diff #30966)

Yes. Note that setthetime() already modifies the returned struct tm.

[cem]

bin/date/date.c

169 ↗

(On Diff #30966)

This path can also dereference the pointer returned from localtime() without checking for NULL.

177–180 ↗

(On Diff #30966)

Ok.

214–215 ↗

(On Diff #30966)

(See here.)

[emaste]

check an additional localtime for NULL return

[cem]

bin/date/date.c

215 ↗

(On Diff #30973)

Syntax seems wrong and ld not lt.

[emaste]

correct retypeo from previous upload