localhost sendmail: (null): time_to_text: bsnprintf

[timmydo]

I'm seeing the following log when trying to run opensmtpd on GNU Guix:

localhost sendmail: (null): time_to_text: bsnprintf

Looking at the code, it is print here:

const char *
time_to_text(time_t when)
{
	struct tm *lt;
	static char buf[40];
	char *day[] = {"Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat"};
	char *month[] = {"Jan","Feb","Mar","Apr","May","Jun",
			 "Jul","Aug","Sep","Oct","Nov","Dec"};
	const char *tz;
	long offset;

	lt = localtime(&when);
	if (lt == NULL || when == 0)
		fatalx("time_to_text: localtime");

#if HAVE_STRUCT_TM_TM_GMTOFF
	offset = lt->tm_gmtoff;
	tz = lt->tm_zone;
#elif defined HAVE_DECL_ALTZONE && defined HAVE_DECL_TIMEZONE
	offset = lt->tm_isdst > 0 ? altzone : timezone;
	tz = lt->tm_isdst > 0 ? tzname[1] : tzname[0];
#endif

	/* We do not use strftime because it is subject to locale substitution*/
	if (!bsnprintf(buf, sizeof(buf),
	    "%s, %d %s %d %02d:%02d:%02d %c%02d%02d (%s)",
	    day[lt->tm_wday], lt->tm_mday, month[lt->tm_mon],
	    lt->tm_year + 1900,
	    lt->tm_hour, lt->tm_min, lt->tm_sec,
	    offset >= 0 ? '+' : '-',
	    abs((int)offset / 3600),
	    abs((int)offset % 3600) / 60,
	    tz))
		fatalx("time_to_text: bsnprintf");

	return buf;
}

I don't see where HAVE_STRUCT_TM_TM_GMTOFF or HAVE_DECL_* are defined, so I'm assuming they're undefined. Which means that offset and tz are uninitialized. If tz is null, then printf will print something like this:

Wed, 31 Dec 1969 16:20:34 +0000 ((null))

which is 40 characters, or the exact size of the buffer, causing bsnprintf to fail and print that error. I haven't verified that is happening, but what would be the recommended fix?