From 1e34852f074e9d8afdd6b63590ef0b22bb0bf174 Mon Sep 17 00:00:00 2001
From: Garret Rieger <grieger@google.com>
Date: Sat, 11 Jun 2022 01:27:33 +0000
Subject: [PATCH] [subset] Fix undefined behaviour.

Don't memcpy if there's nothing to copy.
---
 src/hb-ot-post-table-v2subset.hh | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/src/hb-ot-post-table-v2subset.hh b/src/hb-ot-post-table-v2subset.hh
index 9d651cca8..3456c9883 100644
--- a/src/hb-ot-post-table-v2subset.hh
+++ b/src/hb-ot-post-table-v2subset.hh
@@ -61,7 +61,8 @@ HB_INTERNAL bool postV2Tail::serialize (hb_serialize_context_t *c,
     HBUINT8 *o = c->allocate_size<HBUINT8> (HBUINT8::static_size * (s.length + 1));
     if (unlikely (!o)) return_trace (false);
     if (!c->check_assign (o[0], s.length, HB_SERIALIZE_ERROR_INT_OVERFLOW)) return_trace (false);
-    memcpy (o+1, s.arrayZ, HBUINT8::static_size * s.length);
+    if (s.length)
+      memcpy (o+1, s.arrayZ, HBUINT8::static_size * s.length);
   }
 
   return_trace (true);