Mark public ObjC APIs as explicitly visible.

webrtc/base/objc/RTCLogging.h

 /*
  *  Copyright 2015 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.
  */
 
 #import <Foundation/Foundation.h>
 
+#import "webrtc/base/objc/RTCMacros.h"
+
 // Subset of rtc::LoggingSeverity.
 typedef NS_ENUM(NSInteger, RTCLoggingSeverity) {
   RTCLoggingSeverityVerbose,
   RTCLoggingSeverityInfo,
   RTCLoggingSeverityWarning,
   RTCLoggingSeverityError,
 };
 
-#if defined(__cplusplus)
-extern "C" void RTCLogEx(RTCLoggingSeverity severity, NSString* log_string);
-extern "C" void RTCSetMinDebugLogLevel(RTCLoggingSeverity severity);
-extern "C" NSString* RTCFileName(const char* filePath);
-#else
-
 // Wrapper for C++ LOG(sev) macros.
 // Logs the log string to the webrtc logstream for the given severity.
-extern void RTCLogEx(RTCLoggingSeverity severity, NSString* log_string);
+RTC_EXTERN void RTCLogEx(RTCLoggingSeverity severity, NSString* log_string);
 
 // Wrapper for rtc::LogMessage::LogToDebug.
 // Sets the minimum severity to be logged to console.
-extern void RTCSetMinDebugLogLevel(RTCLoggingSeverity severity);
+RTC_EXTERN void RTCSetMinDebugLogLevel(RTCLoggingSeverity severity);
 
 // Returns the filename with the path prefix removed.
-extern NSString* RTCFileName(const char* filePath);
-
-#endif
+RTC_EXTERN NSString* RTCFileName(const char* filePath);
 
 // Some convenience macros.
 
 #define RTCLogString(format, ...)                    \
   [NSString stringWithFormat:@"(%@:%d %s): " format, \
       RTCFileName(__FILE__),                         \
       __LINE__,                                      \
       __FUNCTION__,                                  \
       ##__VA_ARGS__]
 
@@ skipping 17 matching lines @@
 
 #if !defined(NDEBUG)
 #define RTCLogDebug(format, ...) RTCLogInfo(format, ##__VA_ARGS__)
 #else
 #define RTCLogDebug(format, ...) \
   do {                           \
   } while (false)
 #endif
 
 #define RTCLog(format, ...) RTCLogInfo(format, ##__VA_ARGS__)