WOFF2: avoid a Msan error use-of-uninitialized-value in woff2_dec.cc

third_party/woff2/src/woff2_dec.cc

 // Copyright 2014 Google Inc. All Rights Reserved.
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
 // You may obtain a copy of the License at
 //
 // http://www.apache.org/licenses/LICENSE-2.0
 //
 // Unless required by applicable law or agreed to in writing, software
 // distributed under the License is distributed on an "AS IS" BASIS,
@@ skipping 585 matching lines @@
     }
 
     // TODO(user) Old code aligned glyphs ... but do we actually need to?
     if (PREDICT_FALSE(!Pad4(out))) {
       return FONT_COMPRESSION_FAILURE();
     }
 
     *glyf_checksum += ComputeULongSum(glyph_buf.get(), glyph_size);
 
     // We may need x_min to reconstruct 'hmtx'
-    Buffer x_min_buf(glyph_buf.get() + 2, 2);
-    int16_t x_min;
-    if (PREDICT_FALSE(!x_min_buf.ReadS16(&x_min))) {
-      return FONT_COMPRESSION_FAILURE();
+    if (n_contours > 0) {
+      Buffer x_min_buf(glyph_buf.get() + 2, 2);
+      if (PREDICT_FALSE(!x_min_buf.ReadS16(&info->x_mins[i]))) {
+        return FONT_COMPRESSION_FAILURE();
+      }
     }
-
-    info->x_mins[i] = n_contours != 0 ? x_min : 0;
   }
 
   // glyf_table dst_offset was set by ReconstructFont
   glyf_table->dst_length = out->Size() - glyf_table->dst_offset;
   loca_table->dst_offset = out->Size();
   // loca[n] will be equal the length of the glyph data ('glyf') table
   loca_values[info->num_glyphs] = glyf_table->dst_length;
   if (PREDICT_FALSE(!StoreLoca(loca_values, info->index_format, loca_checksum,
       out))) {
     return FONT_COMPRESSION_FAILURE();
@@ skipping 733 matching lines @@
                                        hdr.uncompressed_size,
                                        &metadata, &hdr, i, out))) {
       return FONT_COMPRESSION_FAILURE();
     }
   }
 
   return true;
 }
 
 } // namespace woff2