time: time_t is signed, and mktime() is happy to return negative time

Passing a year such as 1960 to mktime() will result in a negative return
value. This is quite confusing, as the man page claims that on failure
the call will return -1...

Given that our own usec_t type is unsigned, and we can't express times
before 1970 hence, let's consider all negative times returned by
mktime() as invalid, regardless if just -1, or anything else negative.

1 files changed, 4 insertions, 4 deletions

diff --git a/src/basic/calendarspec.c b/src/basic/calendarspec.c
index 2e5622699d..35dfb6a3db 100644
--- a/src/basic/calendarspec.c
+++ b/src/basic/calendarspec.c
@@ -1020,7 +1020,7 @@ static int find_end_of_month(struct tm *tm, bool utc, int day) {
         t.tm_mon++;
         t.tm_mday = 1 - day;
 
-        if (mktime_or_timegm(&t, utc) == (time_t) -1 ||
+        if (mktime_or_timegm(&t, utc) < 0 ||
             t.tm_mon != tm->tm_mon)
                 return -1;
 
@@ -1086,7 +1086,7 @@ static bool tm_out_of_bounds(const struct tm *tm, bool utc) {
 
         t = *tm;
 
-        if (mktime_or_timegm(&t, utc) == (time_t) -1)
+        if (mktime_or_timegm(&t, utc) < 0)
                 return true;
 
         /*
@@ -1115,7 +1115,7 @@ static bool matches_weekday(int weekdays_bits, const struct tm *tm, bool utc) {
                 return true;
 
         t = *tm;
-        if (mktime_or_timegm(&t, utc) == (time_t) -1)
+        if (mktime_or_timegm(&t, utc) < 0)
                 return false;
 
         k = t.tm_wday == 0 ? 6 : t.tm_wday - 1;
@@ -1238,7 +1238,7 @@ int calendar_spec_next_usec(const CalendarSpec *spec, usec_t usec, usec_t *next)
                 return r;
 
         t = mktime_or_timegm(&tm, spec->utc);
-        if (t == (time_t) -1)
+        if (t < 0)
                 return -EINVAL;
 
         *next = (usec_t) t * USEC_PER_SEC + tm_usec;