Merge pull request #15645 from poettering/calender-expression-doc-fix

some calendar expression fixes and documentation updates

src/shared/calendarspec.c

@@ -30,6 +30,9 @@
  * linked compenents anyway. */
 #define CALENDARSPEC_COMPONENTS_MAX 240
 
+/* Let's make sure that the microsecond component is safe to be stored in an 'int' */
+assert_cc(INT_MAX >= USEC_PER_SEC);
+
 static void chain_free(CalendarComponent *c) {
         CalendarComponent *n;
 
@@ -88,6 +91,16 @@ static void normalize_chain(CalendarComponent **c) {
                 if (i->stop > i->start && i->repeat > 0)
                         i->stop -= (i->stop - i->start) % i->repeat;
 
+                /* If a repeat value is specified, but it cannot even be triggered once, let's suppress
+                 * it.
+                 *
+                 * Similar, if the stop value is the same as the start value, then let's just make this a
+                 * non-repeating chain element */
+                if ((i->stop > i->start && i->repeat > 0 && i->start + i->repeat > i->stop) ||
+                    i->start == i->stop) {
+                        i->repeat = 0;
+                        i->stop = -1;
+                }
         }
 
         if (n <= 1)
@@ -162,7 +175,7 @@ int calendar_spec_normalize(CalendarSpec *c) {
         return 0;
 }
 
-_pure_ static bool chain_valid(CalendarComponent *c, int from, int to, bool end_of_month) {
+static bool chain_valid(CalendarComponent *c, int from, int to, bool end_of_month) {
         assert(to >= from);
 
         if (!c)
@@ -366,14 +379,13 @@ int calendar_spec_to_string(const CalendarSpec *c, char **p) {
         }
 
         r = fflush_and_check(f);
+        fclose(f);
+
         if (r < 0) {
                 free(buf);
-                fclose(f);
                 return r;
         }
 
-        fclose(f);
-
         *p = buf;
         return 0;
 }
@@ -643,6 +655,12 @@ static int prepend_component(const char **p, bool usec, unsigned nesting, Calend
 
                 if (repeat == 0)
                         return -ERANGE;
+        } else {
+                /* If no repeat value is specified for the µs component, then let's explicitly refuse ranges
+                 * below 1s because our default repeat granularity is beyond that. */
+
+                if (usec && stop >= 0 && start + repeat > stop)
+                        return -EINVAL;
         }
 
         if (!IN_SET(*e, 0, ' ', ',', '-', '~', ':'))

src/shared/calendarspec.h

@@ -19,9 +19,9 @@ typedef struct CalendarComponent {
 
 typedef struct CalendarSpec {
         int weekdays_bits;
-        bool end_of_month;
-        bool utc;
-        int dst;
+        bool end_of_month:1;
+        bool utc:1;
+        signed int dst:2;
         char *timezone;
 
         CalendarComponent *year;