我最近将一个c文件导入到我想要使用的obj项目中.在我想要使用它的类中,我将文件名从MyClass.m更改为MyClass.mm.
这样做会给我20个左右的错误.这些错误到底意味着什么？如何将MyClass更改为目标c类以方便我想要使用的新c类,而不会出现这些错误？
Undefined symbols for architecture i386: "setAudioInputIsStereo(audiosourceobj*,bool)",referenced from: -[Engine extractMp3Audio:withChannelId:withPadId:] in Engine.o "setAudioInputFrameCount(audiosourceobj*,int)",referenced from: -[Engine extractMp3Audio:withChannelId:withPadId:] in Engine.o "setAudioInputSendValue(audiosourceobj*,referenced from: -[Engine extractMp3Audio:withChannelId:withPadId:] in Engine.o "getPointerToAudioLeftBuffer(audiosourceobj*)",referenced from: -[Engine extractMp3Audio:withChannelId:withPadId:] in Engine.o "getPointerToAudioRightBuffer(audiosourceobj*)",referenced from: -[Engine extractMp3Audio:withChannelId:withPadId:] in Engine.o "freeAudioBuffers(audiosourceobj*)",referenced from: -[Engine extractMp3Audio:withChannelId:withPadId:] in Engine.o -[Engine clearAudioInput:pid:] in Engine.o -[Engine reset] in Engine.o "setAudioInputReadPoint(audiosourceobj*,referenced from: -[Engine extractMp3Audio:withChannelId:withPadId:] in Engine.o "setAudioInputHasAudio(audiosourceobj*,referenced from: -[Engine extractMp3Audio:withChannelId:withPadId:] in Engine.o -[Engine reset] in Engine.o -[Engine setAudioPath:channel:pad:] in Engine.o "setAudioInputState(audiosourceobj*,referenced from: -[Engine extractMp3Audio:withChannelId:withPadId:] in Engine.o -[Engine clearAudioInput:pid:] in Engine.o -[Engine reset] in Engine.o -[Engine setAudioPath:channel:pad:] in Engine.o "initAudioInputHasAudio(audiosourceobj*,signed char)",referenced from: -[Engine clearAudioInput:pid:] in Engine.o -[Engine reset] in Engine.o "initAudioInputReadPoint(audiosourceobj*,referenced from: -[Engine clearAudioInput:pid:] in Engine.o -[Engine reset] in Engine.o "initAudioInputFrameCount(audiosourceobj*,referenced from: -[Engine clearAudioInput:pid:] in Engine.o -[Engine reset] in Engine.o "initAudioInputSampleToAction(audiosourceobj*,referenced from: -[Engine clearAudioInput:pid:] in Engine.o -[Engine reset] in Engine.o "newChannelOBJ()",referenced from: setUpChannels(int,int)in Engine.o "setVolume(channelobj*,float)",int)in Engine.o "setMute(channelobj*,int)in Engine.o "setNumberOfInputs(channelobj*,int)in Engine.o "setChannelID(channelobj*,int)in Engine.o "createInputs(channelobj*,int)in Engine.o "setBufferSize(channelobj*,int)in Engine.o "createChannelEQS(channelobj*)",int)in Engine.o "actionupdatecomplete(audiosourceobj*,objc_object*)",referenced from: channelMixerCallback(void*,unsigned long*,AudioTimeStamp const*,unsigned long,AudioBufferList*)in Engine.o
解决方法
听起来你的函数有C链接,但你没有在它们的标题中正确声明.因此.mm文件(Objective-C)将会看到它们并假设C链接.最简单的解决方法是将#include语句包装在适当的extern块中：
extern "C" {
#include "..."
}
更好的解决方案是在标头本身内执行此操作：
#if defined(__cplusplus)
extern "C" {
#endif /* defined(__cplusplus) */
extern void whatever(void);
extern int foobar(double);
...
#if defined(__cplusplus)
}
#endif /* defined(__cplusplus) */
Apple为此使用宏,名为__BEGIN_DECLS和__END_DECLS,但它们是非标准的,因此您无法直接在跨平台共享的文件中使用它们.
