Re: [tz] mktime() clarification

Dag-Erling Smørgrav wrote:

Both the C standard and POSIX state that mktime() returns -1 on failure; POSIX additionally states that it sets errno. However, since -1 is also a valid result (representing 23:59:59 UTC on 1969-12-31) and POSIX never guarantees that a successful call does not modify errno, it seems to me that the only reliable way to determine whether mktime() succeeded...

I could be wrong, but I have the impression that there are or have been a very few library functions over the years that *did* guarantee not to modify errno on success. I wish mktime was or could be made one of them -- that would seem to be an ideal way to resolve the return value ambiguity here.