From cc01dedc656e77f2b81902fe703537e39776a6ca Mon Sep 17 00:00:00 2001
From: "Yukihiro \"Matz\" Matsumoto" <matz@ruby-lang.org>
Date: Wed, 5 Jul 2017 03:07:44 +0900
Subject: Avoid undefined behavior of left shifting negative integer; #3728

---
 src/numeric.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

(limited to 'src')

diff --git a/src/numeric.c b/src/numeric.c
index 6c9875719..41c4678d3 100644
--- a/src/numeric.c
+++ b/src/numeric.c
@@ -962,16 +962,16 @@ lshift(mrb_state *mrb, mrb_int val, mrb_int width)
         (val   > (MRB_INT_MAX >> width))) {
       goto bit_overflow;
     }
+    return mrb_fixnum_value(val << width);
   }
   else {
     if ((width > NUMERIC_SHIFT_WIDTH_MAX) ||
         (val   < (MRB_INT_MIN >> width))) {
       goto bit_overflow;
     }
+    return mrb_fixnum_value(val * (1u << width));
   }
 
-  return mrb_fixnum_value(val << width);
-
 bit_overflow:
   {
     mrb_float f = (mrb_float)val;
-- 
cgit v1.2.3