Fixes the bug of ecma_date_make_day() (#1836) & ecma_date_week_day(). (#1466)

The ecma_date_make_day() handled any date in October on leap years incorrectly,
which was mentioned in issue #1836. The ecma_date_week_day() returned minus values
when return week_day before 1970 years which was also incorrect.

This change solves these bugs. In addition, this enhances the algorithm of accessing 'the ym-mn-1'
by replacing binary search to simple computation at ecma_date_make_day().

JerryScript-DCO-1.0-Signed-off-by: Hayun Lee lhy920806@gmail.com

Author: LeeHayun

jerry-core/ecma/builtin-objects/ecma-builtin-helpers-date.c

@@ -432,7 +432,8 @@ ecma_date_week_day (ecma_number_t time) /**< time value */
     return time; /* time is NaN */
   }
 
-  return (ecma_number_t) fmod ((ecma_date_day (time) + 4), 7);
+  ecma_number_t week_day = (ecma_number_t) fmod ((ecma_date_day (time) + 4), 7);
+  return (week_day < 0) ? 7 + week_day : week_day;
 } /* ecma_date_week_day */
 
 /**
@@ -752,45 +753,19 @@ ecma_date_make_day (ecma_number_t year, /**< year value */
 
   /* 7. */
   ecma_number_t time = ecma_date_time_from_year (ym);
-  int32_t step = 182;
-  int32_t delta = step;
 
   /**
    * The algorithm below searches the following date: ym-mn-1
    * To find this time it starts from the beggining of the year (ym)
-   * then increase it by ECMA_DATE_MS_PER_DAY until it reaches the
-   * right date.
+   * then find the first day of the month.
    */
   if (ecma_date_year_from_time (time) == ym)
   {
-    /**
-     * Binary search to get the closest day in the previous month.
-     * It has to use integer days so sometimes the found time
-     * needs some more increasing which is done day by day below.
-     */
-    while (delta)
-    {
-      if (ecma_date_month_from_time (time + step * ECMA_DATE_MS_PER_DAY) < mn)
-      {
-        step += delta;
-      }
-      else
-      {
-        step -= delta;
-      }
-      delta = delta / 2;
-    }
-
-    if (ecma_date_month_from_time (time + step) < mn)
-    {
-      time += step * ECMA_DATE_MS_PER_DAY;
-    }
+    /* Get the month */
+    time += 31 * mn * ECMA_DATE_MS_PER_DAY;
 
     /* Get the month's first day */
-    while (ecma_date_month_from_time (time) < mn)
-    {
-      time += ECMA_DATE_MS_PER_DAY;
-    }
+    time += ((ecma_number_t) 1.0 - ecma_date_date_from_time (time)) * ECMA_DATE_MS_PER_DAY;
 
     if (ecma_date_month_from_time (time) == mn && ecma_date_date_from_time (time) == 1)
     {

tests/jerry/regression-test-issue-1386.js

@@ -0,0 +1,24 @@
+// Copyright 2016 Hayun Lee (lhy920806@gmail.com)
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+for (var y = 1950; y < 2050; y++) {
+  for (var m = 0; m < 12; m++) {
+    var last_date = new Date(y, m, 1).getDay ();
+    assert (!isNaN (last_date));
+    for (var d = 1; d < 32; d++) {
+      assert (last_date == new Date(y, m, d).getDay ());
+      last_date = (last_date + 1) % 7;
+    }
+  }
+}

tests/unit/test-date-helpers.c

@@ -162,6 +162,8 @@ main ()
   TEST_ASSERT (ecma_date_make_day (1970, 1, 35) == 65);
   TEST_ASSERT (ecma_date_make_day (1970, 13, 35) == 430);
   TEST_ASSERT (ecma_date_make_day (2016, 2, 1) == 16861);
+  TEST_ASSERT (ecma_date_make_day (2016, 8, 31) == 17075);
+  TEST_ASSERT (ecma_date_make_day (2016, 9, 1) == 17075);
 
   /* ecma_number_t ecma_date_make_date (day, time) */