refactor: ensure all stack allocations happen on every find_day run

to keep stack size consistent between runs with and without flags

Author: Kniggebrot

ccronexpr.c

@@ -618,20 +618,20 @@ find_next_day(struct tm *calendar, const uint8_t *cron_dom, unsigned int day_of_
     // Copy cron_dom to add days determined by L- and W- flags
     uint8_t cur_doms[4];
     memcpy(cur_doms, cron_dom, 4);
+    // Copy calendar to move day independently searching for L/W-Days; timezone MUST not be touched
+    // find_{L,W}_days() will not alter the original tm struct
+    struct tm searcher;
     if (lw_flags) {
-        // Copy calendar to move day independently searching for L/W-Days; timezone MUST not be touched
-        // find_{L,W}_days() will not alter the tm struct
-        struct tm searcher;
         memcpy(&searcher, calendar, sizeof searcher);
         // Add L days and W days of current month to cur_doms
         find_l_days(&searcher, cur_doms, l_dow_flags, l_dom_offset, lw_flags, res_out);
         if (*res_out) {
-            // something went wrong; return 0
+            // something went wrong; keep res_out value, return 0
             return 0;
         }
         find_w_days(&searcher, cur_doms, w_flags, res_out);
         if (*res_out) {
-            // something went wrong; return 0
+            // something went wrong; keep res_out value, return 0
             return 0;
         }
         // Get last day of current month: 0th day of next month

ccronexpr_test.c

@@ -530,6 +530,9 @@ void test_expr() {
     assert(check_next("0 0 12 1W,15W * ?","2025-05-01_11:00:00", "2025-05-01_12:00:00"));
     assert(check_next("0 0 12 1W,15W * ?","2025-05-01_13:01:00", "2025-05-15_12:00:00"));
     assert(check_next("0 0 12 1W,15W * ?","2025-05-15_12:01:00", "2025-06-02_12:00:00"));
+    // check 1st february 2025
+    assert(check_next("0 0 12 1,15 * ?", "2025-01-31_12:00:00", "2025-02-01_12:00:00"));
+    assert(check_next("0 0 12 1W,15W * ?", "2025-01-31_12:00:00", "2025-02-03_12:00:00"));
 }
 
 void test_parse() {