commit 723e928b84b0adac84cc11ec5c075a45e1a79903
author Mark Adler <zlib@madler.net> Thu Oct 12 19:44:01 2017 -0700
committer Mark Adler <zlib@madler.net> Thu Oct 12 19:44:01 2017 -0700
tree 5090ac2d115e17a71528780ad8efe70b74f907fa
parent b25d5fcdcf4723ca3da8bc69ecc6c52010778f7c

Avoid an undefined behavior of memcpy() in _tr_stored_block().

Allegedly the behavior of memcpy() is undefined if the source
pointer is NULL, even if the number of bytes to copy is zero.

trees.c

diff --git a/trees.c b/trees.c
index 50cf4b4..1321548 100644
--- a/trees.c
+++ b/trees.c
@@ -870,7 +870,8 @@
     bi_windup(s);        /* align on byte boundary */
     put_short(s, (ush)stored_len);
     put_short(s, (ush)~stored_len);
-    zmemcpy(s->pending_buf + s->pending, (Bytef *)buf, stored_len);
+    if (stored_len)
+        zmemcpy(s->pending_buf + s->pending, (Bytef *)buf, stored_len);
     s->pending += stored_len;
 #ifdef ZLIB_DEBUG
     s->compressed_len = (s->compressed_len + 3 + 7) & (ulg)~7L;