From 55446b8967ed0a7f66502424d309f0b8fa74919f Mon Sep 17 00:00:00 2001
From: Zufu Liu <unknown>
Date: Sat, 29 Jun 2019 11:57:11 +1000
Subject: Backport: Bug [#2115]. Fix undefined behaviour of shifting negative
 values.

Backport of changeset 7612:d70ccc4f172a.
---
 src/PositionCache.cxx | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

(limited to 'src')

diff --git a/src/PositionCache.cxx b/src/PositionCache.cxx
index 8910a2955..03393536d 100644
--- a/src/PositionCache.cxx
+++ b/src/PositionCache.cxx
@@ -615,10 +615,11 @@ bool PositionCacheEntry::Retrieve(unsigned int styleNumber_, const char *s_,
 }
 
 unsigned int PositionCacheEntry::Hash(unsigned int styleNumber_, const char *s, unsigned int len_) noexcept {
-	unsigned int ret = s[0] << 7;
+	const unsigned char *us = reinterpret_cast<const unsigned char *>(s);
+	unsigned int ret = us[0] << 7;
 	for (unsigned int i=0; i<len_; i++) {
 		ret *= 1000003;
-		ret ^= s[i];
+		ret ^= us[i];
 	}
 	ret *= 1000003;
 	ret ^= len_;
-- 
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