[PATCH v2 2/2] timegm.3: Remove recommendation against use of timegm()

[Paul Eggert]

On 10/11/21 4:12 AM, Alejandro Colomar wrote:

> time_t portable_timegm(struct tm *tm)
> {
> 	tm->tm_isdst = 0;
> 	/*
> 	 * If another thread modifies the timezone during the
> 	 * execution of the line below, it will produce undefined
> 	 * behavior.
> 	 */
> 	return mktime(tm) - timezone;
> }

This doesn't work for multiple reasons: it's not thread-safe, mktime 
might set timezone even in a single-threaded app, and the subtraction 
might overflow.