From c2dd686e96c7c4ff6a84bd43b68d3c28369e1f95 Mon Sep 17 00:00:00 2001
From: Nick Terrell <terrelln@fb.com>
Date: Fri, 5 Jan 2018 14:30:49 -0800
Subject: [PATCH] [lz4f] Skip memcpy() on empty dictionary

---
 lib/lz4frame.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/lib/lz4frame.c b/lib/lz4frame.c
index ebd1089..488ab75 100644
--- a/lib/lz4frame.c
+++ b/lib/lz4frame.c
@@ -1631,7 +1631,8 @@ size_t LZ4F_decompress(LZ4F_dctx* dctx,
             if (dctx->tmpOutSize > 64 KB) copySize = 0;
             if (copySize > preserveSize) copySize = preserveSize;
 
-            memcpy(dctx->tmpOutBuffer + preserveSize - copySize, oldDictEnd - copySize, copySize);
+            if (copySize > 0)
+                memcpy(dctx->tmpOutBuffer + preserveSize - copySize, oldDictEnd - copySize, copySize);
 
             dctx->dict = dctx->tmpOutBuffer;
             dctx->dictSize = preserveSize + dctx->tmpOutStart;
@@ -1639,7 +1640,8 @@ size_t LZ4F_decompress(LZ4F_dctx* dctx,
             const BYTE* const oldDictEnd = dctx->dict + dctx->dictSize;
             size_t const newDictSize = MIN(dctx->dictSize, 64 KB);
 
-            memcpy(dctx->tmpOutBuffer, oldDictEnd - newDictSize, newDictSize);
+            if (newDictSize > 0)
+                memcpy(dctx->tmpOutBuffer, oldDictEnd - newDictSize, newDictSize);
 
             dctx->dict = dctx->tmpOutBuffer;
             dctx->dictSize = newDictSize;