[tz] mktime() clarification

[brian.inglis at systematicsw.ab.ca]

On 2024-03-25 19:52, Paul Eggert via tz wrote:
> On 3/25/24 12:16, Dag-Erling Smørgrav via tz wrote:
>> it seems to me
>> that the only reliable way to determine whether mktime() succeeded,
>> within the bounds of the aforementioned standards, is to set tm_wday or
>> tm_yday to an out-of-bounds value (e.g. -1) prior to calling mktime()
> 
> That's what I do, and it works portably on all platforms I know of. In contrast, 
> I doubt whether the errno=0 trick is portable.
> 
> I installed the attached proposed patch to the documentation.

> +To distinguish failure from a valid \-1 return,
> +you can set
> +.B tm_mday

    .B tm_wday?

> +or
> +.B tm_yday
> +to a negative value before calling

-- 
Take care. Thanks, Brian Inglis              Calgary, Alberta, Canada

La perfection est atteinte                   Perfection is achieved
non pas lorsqu'il n'y a plus rien à ajouter  not when there is no more to add
mais lorsqu'il n'y a plus rien à retirer     but when there is no more to cut
                                 -- Antoine de Saint-Exupéry