From 2c652768a878dd951385f48df450b2a1dc12dc12 Mon Sep 17 00:00:00 2001
From: naruse <naruse@b2dd03c8-39d4-4d8f-98ff-823fe69b080e>
Date: Sun, 25 Nov 2018 16:23:18 +0000
Subject: [PATCH] Normalize month-mday before finding epoch

Especially over the year 2038, 30 Feb and so on may cause odd behavior
on validating found epoch with given year-month-day [Bug #15340]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@65974 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
---
 test/ruby/test_time.rb | 23 +++++++++++++++++++++++
 time.c                 | 23 +++++++++++++++++++++++
 2 files changed, 46 insertions(+)

diff --git a/test/ruby/test_time.rb b/test/ruby/test_time.rb
index 0aac07b05d..7c5ee5466d 100644
--- a/test/ruby/test_time.rb
+++ b/test/ruby/test_time.rb
@@ -1056,6 +1056,29 @@ class TestTime < Test::Unit::TestCase
       assert_equal(min, t.min)
       assert_equal(sec, t.sec)
     }
+    assert_equal(Time.local(2038,3,1), Time.local(2038,2,29))
+    assert_equal(Time.local(2038,3,2), Time.local(2038,2,30))
+    assert_equal(Time.local(2038,3,3), Time.local(2038,2,31))
+    assert_equal(Time.local(2040,2,29), Time.local(2040,2,29))
+    assert_equal(Time.local(2040,3,1), Time.local(2040,2,30))
+    assert_equal(Time.local(2040,3,2), Time.local(2040,2,31))
+    n = 2 ** 64
+    n += 400 - n % 400 # n is over 2^64 and multiple of 400
+    assert_equal(Time.local(n,2,29),Time.local(n,2,29))
+    assert_equal(Time.local(n,3,1), Time.local(n,2,30))
+    assert_equal(Time.local(n,3,2), Time.local(n,2,31))
+    n += 100
+    assert_equal(Time.local(n,3,1), Time.local(n,2,29))
+    assert_equal(Time.local(n,3,2), Time.local(n,2,30))
+    assert_equal(Time.local(n,3,3), Time.local(n,2,31))
+    n += 4
+    assert_equal(Time.local(n,2,29),Time.local(n,2,29))
+    assert_equal(Time.local(n,3,1), Time.local(n,2,30))
+    assert_equal(Time.local(n,3,2), Time.local(n,2,31))
+    n += 1
+    assert_equal(Time.local(n,3,1), Time.local(n,2,29))
+    assert_equal(Time.local(n,3,2), Time.local(n,2,30))
+    assert_equal(Time.local(n,3,3), Time.local(n,2,31))
   end
 
   def test_future
diff --git a/time.c b/time.c
index 1c9f4e1833..0679f7e5ce 100644
--- a/time.c
+++ b/time.c
@@ -2876,6 +2876,29 @@ time_arg(int argc, const VALUE *argv, struct vtm *vtm)
 	vtm->mday = obj2ubits(v[2], 5);
     }
 
+    /* normalize month-mday */
+    switch (vtm->mon) {
+      case 2:
+        {
+            /* this drops higher bits but it's not a problem to calc leap year */
+            unsigned int mday2 = leap_year_v_p(vtm->year) ? 29 : 28;
+            if (vtm->mday > mday2) {
+                vtm->mday -= mday2;
+                vtm->mon++;
+            }
+        }
+        break;
+      case 4:
+      case 6:
+      case 9:
+      case 11:
+        if (vtm->mday == 31) {
+            vtm->mon++;
+            vtm->mday = 1;
+        }
+        break;
+    }
+
     vtm->hour = NIL_P(v[3])?0:obj2ubits(v[3], 5);
 
     vtm->min  = NIL_P(v[4])?0:obj2ubits(v[4], 6);