On Thu, Aug 22, 2024 at 09:57:39PM GMT, Paul Eggert wrote:
> On 2024-08-22 16:49, Alejandro Colomar wrote:
> > t = mktime(tp);
> > if (t == -1 && errno == EOVERFLOW)
> > return -1;
>
> This isn't right, for the same reason similar code wasn't right earlier. A
> successful call to mktime can return -1 and set errno to whatever value it
> likes.
Is mktime(3) allowed to return -1 and set EOVERFLOW on a successful
call?
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 and set errno to indicate the error.
ERRORS
The mktime() function shall fail if:
EOVERFLOW
The result cannot be represented.
The following sections are informative.
Then I think the API is completely broken. How should we check for
errors after a mktime(3) call?
If this is so, let me file a glibc bug requesting a fix of the API,
adding a promise that on success, errno will remain unset.
> This is just the first problem I found with the code (and I found it quickly
> because I remembered the earlier problem). I would expect there to be
> others.
>
> How about if we omit the sample code and make the minimal changes I
> suggested earlier?
Because I'm being very careful writing that code, and still I'm having
trouble doing that, I think we must provide some example of a correct
call, to prevent many other programmers from doing it wrong.
Cheers,
Alex
--
<https://www.alejandro-colomar.es/>
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