Enable the -Wundef warning for clang

webrtc/base/logging.cc

 /*
  *  Copyright 2004 The WebRTC Project Authors. All rights reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
@@ skipping 132 matching lines @@
   if (file != NULL)
     print_stream_ << "(" << FilenameFromPath(file)  << ":" << line << "): ";
 
   if (err_ctx != ERRCTX_NONE) {
     std::ostringstream tmp;
     tmp << "[0x" << std::setfill('0') << std::hex << std::setw(8) << err << "]";
     switch (err_ctx) {
       case ERRCTX_ERRNO:
         tmp << " " << strerror(err);
         break;
-#if WEBRTC_WIN
+#ifdef WEBRTC_WIN
       case ERRCTX_HRESULT: {
         char msgbuf[256];
         DWORD flags = FORMAT_MESSAGE_FROM_SYSTEM;
         HMODULE hmod = GetModuleHandleA(module);
         if (hmod)
           flags |= FORMAT_MESSAGE_FROM_HMODULE;
         if (DWORD len = FormatMessageA(
             flags, hmod, err,
             MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
             msgbuf, sizeof(msgbuf) / sizeof(msgbuf[0]), NULL)) {
@@ skipping 384 matching lines @@
   }
 
   if (state) {
     state->unprintable_count_[input] = consecutive_unprintable;
   }
 }
 
 //////////////////////////////////////////////////////////////////////
 
 }  // namespace rtc