From 7171917b52880728b513168d946196331b7707d1 Mon Sep 17 00:00:00 2001
From: Behdad Esfahbod <behdad@behdad.org>
Date: Sat, 15 Jan 2022 17:16:40 -0700
Subject: [PATCH] [vector] Construct items when enlarging

---
 src/hb-vector.hh | 23 +++++++++++++++++++++--
 1 file changed, 21 insertions(+), 2 deletions(-)

diff --git a/src/hb-vector.hh b/src/hb-vector.hh
index a474a7ba5..636e125c5 100644
--- a/src/hb-vector.hh
+++ b/src/hb-vector.hh
@@ -232,6 +232,26 @@ struct hb_vector_t
     return new_array;
   }
 
+  template <typename T = Type,
+	    hb_enable_if (std::is_trivially_copy_assignable<T>::value)>
+  void
+  grow_vector (unsigned size)
+  {
+    memset (arrayZ + length, 0, (size - length) * sizeof (*arrayZ));
+    length = size;
+  }
+  template <typename T = Type,
+	    hb_enable_if (!std::is_trivially_copy_assignable<T>::value)>
+  void
+  grow_vector (unsigned size)
+  {
+    while (length < size)
+    {
+      length++;
+      new (std::addressof (arrayZ[length - 1])) Type ();
+    }
+  }
+
   template <typename T = Type,
 	    hb_enable_if (std::is_trivially_copy_assignable<T>::value)>
   void
@@ -294,8 +314,7 @@ struct hb_vector_t
       return false;
 
     if (size > length)
-      // XXX construct objects.
-      memset (arrayZ + length, 0, (size - length) * sizeof (*arrayZ));
+      grow_vector (size);
     else if (size < length)
       shrink_vector (size);