Let breakpad build with -Wall on OS X and Linux.

src/common/dwarf/dwarf2reader.cc

 // Copyright (c) 2010 Google Inc. All Rights Reserved.
 //
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 // notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 // copyright notice, this list of conditions and the following disclaimer
@@ skipping 499 matching lines @@
     if (abbrev.has_children) {
       die_stack.push(absolute_offset);
     } else {
       handler_->EndDIE(absolute_offset);
     }
   }
 }
 
 LineInfo::LineInfo(const char* buffer, uint64 buffer_length,
                    ByteReader* reader, LineInfoHandler* handler):
-    handler_(handler), reader_(reader), buffer_(buffer),
-    buffer_length_(buffer_length) {
+    handler_(handler), reader_(reader), buffer_(buffer) {
+#ifndef NDEBUG
+  buffer_length_ = buffer_length;
+#endif
   header_.std_opcode_lengths = NULL;
 }
 
 uint64 LineInfo::Start() {
   ReadHeader();
   ReadLines();
   return after_header_ - buffer_;
 }
 
 // The header for a debug_line section is mildly complicated, because
@@ skipping 1803 matching lines @@
                                               uint64 insn_offset) {
   fprintf(stderr,
           "%s: CFI %s at offset 0x%llx in section '%s':"
           " the DW_CFA_restore_state instruction at offset 0x%llx"
           " would clear the CFA rule in effect\n",
           filename_.c_str(), CallFrameInfo::KindName(kind), offset,
           section_.c_str(), insn_offset);
 }
 
 }  // namespace dwarf2reader