On 2024-08-23 14:28:13 +0200, Alejandro Colomar wrote: [about mktime] > tm_wday is guaranteed to be left unmodified on a failed call. Where did you see that? I cannot see any guarantee in case of a failed call, so that I would say that tm_wday could have been modified, e.g. if the values are set before checking whether the calendar time can be represented. > This provides a way to determine if the call failed. The example in C17 does not use the above claim that "tm_wday is guaranteed to be left unmodified on a failed call" to determine whether the call failed. Instead, it uses if (mktime(&time_str) == (time_t)(-1)) which is not 100% correct, since -1 can be a valid value (as already noticed). > Indeed, this is the only way to determine if the call failed: > > tm.tm_wday = INT_MAX; > mktime(&tm); > if (tm.tm_wday == INT_MAX) > err(1, "mktime"); Because of my above remark, I think that a mktime(&tm) == (time_t)(-1) test is needed *in addition to* the tm.tm_wday == INT_MAX test. -- Vincent Lefèvre <vincent@xxxxxxxxxx> - Web: <https://www.vinc17.net/> 100% accessible validated (X)HTML - Blog: <https://www.vinc17.net/blog/> Work: CR INRIA - computer arithmetic / AriC project (LIP, ENS-Lyon)
