[buffer-verify] Error handling

src/hb-buffer-verify.cc

@@ -185,6 +185,8 @@ buffer_verify_unsafe_to_break (hb_buffer_t  *buffer,
   }
 
   bool ret = true;
+  if (likely (reconstruction->successful))
+  {
     hb_buffer_diff_flags_t diff = hb_buffer_diff (reconstruction, buffer, (hb_codepoint_t) -1, 0);
     if (diff & ~HB_BUFFER_DIFF_FLAG_GLYPH_FLAGS_MISMATCH)
     {
@@ -195,6 +197,7 @@ buffer_verify_unsafe_to_break (hb_buffer_t  *buffer,
       hb_buffer_set_length (buffer, 0);
       hb_buffer_append (buffer, reconstruction, 0, -1);
     }
+  }
 
   hb_buffer_destroy (reconstruction);
   hb_buffer_destroy (fragment);
@@ -377,6 +380,8 @@ buffer_verify_unsafe_to_concat (hb_buffer_t        *buffer,
     hb_buffer_reverse (reconstruction);
   }
 
+  if (likely (reconstruction->successful))
+  {
     /*
      * Diff results.
      */
@@ -390,7 +395,7 @@ buffer_verify_unsafe_to_concat (hb_buffer_t        *buffer,
       hb_buffer_set_length (buffer, 0);
       hb_buffer_append (buffer, reconstruction, 0, -1);
     }
-
+  }
 
 out:
   hb_buffer_destroy (reconstruction);