From 2d7ba6381876d9592bf804bb15e0037ebdec5800 Mon Sep 17 00:00:00 2001
From: Valentin Bartenev <vbart@nginx.com>
Date: Sun, 28 Jul 2019 17:19:51 +0300
Subject: [PATCH] Fixed undefined behaviour in left shift of negative numbers.

Now it's implementation defined.
---
 njs/njs_vmcode.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/njs/njs_vmcode.c b/njs/njs_vmcode.c
index fae0ca7f..f6068240 100644
--- a/njs/njs_vmcode.c
+++ b/njs/njs_vmcode.c
@@ -421,7 +421,8 @@ next:
                         i32 = njs_number_to_int32(num);
 
                         if (op == NJS_VMCODE_LEFT_SHIFT) {
-                            i32 <<= u32;
+                            /* Shifting of negative numbers is undefined. */
+                            i32 = (uint32_t) i32 << u32;
                         } else {
                             i32 >>= u32;
                         }
-- 
2.47.3