From b9e52db28398c5a792ae16730243af764c869bcd Mon Sep 17 00:00:00 2001
From: Nobuyoshi Nakada <nobu@ruby-lang.org>
Date: Sat, 4 May 2019 22:00:22 +0900
Subject: [PATCH] Add a pathologic check

---
 time.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/time.c b/time.c
index 2630f735bf..2086dcd22e 100644
--- a/time.c
+++ b/time.c
@@ -4627,6 +4627,9 @@ time_isdst(VALUE time)
 
     GetTimeval(time, tobj);
     MAKE_TM(time, tobj);
+    if (tobj->vtm.isdst == VTM_ISDST_INITVAL) {
+        rb_raise(rb_eRuntimeError, "isdst is not set yet");
+    }
     return tobj->vtm.isdst ? Qtrue : Qfalse;
 }