A quick fix for Mac GCC.

net/base/crl_set.cc

 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "base/base64.h"
 #include "base/json/json_reader.h"
 #include "base/logging.h"
 #include "base/stl_util.h"
 #include "base/values.h"
 #include "crypto/sha2.h"
@@ skipping 392 matching lines @@
 
   *out_crl_set = crl_set;
   return true;
 }
 
 CRLSet::Result CRLSet::CheckCertificate(
     const base::StringPiece& serial_number,
     const base::StringPiece& parent_spki) const {
   base::StringPiece serial(serial_number);
 
-  if (!serial.empty() && serial[0] >= 0x80) {
+  if (!serial.empty() && static_cast<unsigned char>(serial[0]) >= 0x80) {

[wtc, 2011/11/01 04:02:51]

It may be better to use bit testing:
  (serial[0] & 0x80) != 0

[Hironori Bono, 2011/11/01 07:57:52]

Done. Thanks for your suggestion. It also fixes the bot.

     // This serial number is negative but the process which generates CRL sets
     // will reject any certificates with negative serial numbers as invalid.
     return UNKNOWN;
   }
 
   // Remove any leading zero bytes.
   while (serial.size() > 1 && serial[0] == 0x00)
     serial.remove_prefix(1);
 
   std::map<std::string, size_t>::const_iterator i =
@@ skipping 21 matching lines @@
 
 uint32 CRLSet::sequence() const {
   return sequence_;
 }
 
 const CRLSet::CRLList& CRLSet::crls() const {
   return crls_;
 }
 
 }  // namespace net