From 2e7c716511e8b2cfcd059fa2a2ed4cdd48b351bf Mon Sep 17 00:00:00 2001
From: Behdad Esfahbod <behdad@behdad.org>
Date: Tue, 16 Oct 2018 18:35:03 -0700
Subject: [PATCH] [buffer] Add an assert

See if it helps debugging https://bugs.chromium.org/p/chromium/issues/detail?id=895117
---
 src/hb-buffer.cc | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/src/hb-buffer.cc b/src/hb-buffer.cc
index 1d3b602b4..00e7e149c 100644
--- a/src/hb-buffer.cc
+++ b/src/hb-buffer.cc
@@ -359,6 +359,8 @@ hb_buffer_t::replace_glyphs (unsigned int num_in,
 {
   if (unlikely (!make_room_for (num_in, num_out))) return;
 
+  assert (idx + num_in <= len);
+
   merge_clusters (idx, idx + num_in);
 
   hb_glyph_info_t orig_info = info[idx];