Question

我现在看起来像是无法解决的EXC_BAD_ACCESS问题。我已经尝试过启用NSZombie，因为在许多帖子中似乎都是建议但是我正在处理c指针而不是obj c对象所以我没有得到任何有用的调试信息。

我的代码工作的方式是，在它需要来自磁盘的一些音频之前，我分离一个新的posix线程，传递一个指向我想要的音频信息的指针。然后我读了一些样品。我选择posix而不是NSThread或NSOperation的原因是因为它似乎表现得更快。我的音频非常密集，所以我需要尽可能快地读取音频。

如何修复此错误的访问错误？它不会一直发生。有时它似乎发生在应用程序非常繁忙时。偶尔它根本不会发生。

无论如何，我可以试着快速解决这个问题吗？我怎么能调查这种情况的原因呢？

修改这是我提出的单独问题的链接，但它与同一问题有关

[线索强烈的io] [1]

//detachnewthread gets called from remoteio callback

void detachnewthread(AudioSourceOBJ str)
{

    //..... code removed for brevity
    if(str)
    {

        int rc;

        rc = pthread_create(&str->thread, NULL, FetchAudio, (void *)str);
        if (rc){
            printf("ERROR; return code from pthread_create() is %d\n", rc);
            exit(-1);
        }

    }

}


void *FetchAudio(void *threadid)

{ AudioSourceOBJ soundptr = threadid;

AudioUnitSampleType *outSamplesChannelLeft;
AudioUnitSampleType *outSamplesChannelRight;

outSamplesChannelLeft                 = (AudioUnitSampleType *) soundptr->queuebuffer->ABL->mBuffers[0].mData;
outSamplesChannelRight  = (AudioUnitSampleType *)soundptr->queuebuffer->ABL->mBuffers[0].mData;
// ExtAudioFileRef audioFileRef;



// result=  ExtAudioFileOpenURL(str->path, &str->audioFileObject);

AudioStreamBasicDescription importFormat = {0};

size_t bytesPerSample = sizeof (AudioUnitSampleType);

// Fill the application audio format struct's fields to define a linear PCM, 
//        stereo, noninterleaved stream at the hardware sample rate.
importFormat.mFormatID          = kAudioFormatLinearPCM;
importFormat.mFormatFlags       = kAudioFormatFlagsAudioUnitCanonical;
importFormat.mBytesPerPacket    = bytesPerSample;
importFormat.mFramesPerPacket   = 1;
importFormat.mBytesPerFrame     = bytesPerSample;
importFormat.mChannelsPerFrame  = 2;                    // 2 indicates stereo
importFormat.mBitsPerChannel    = 8 * bytesPerSample;
importFormat.mSampleRate        = 44100;


ExtAudioFileSetProperty (
                                     engineDescribtion.audiofilerefs[soundptr->audioindex],
                                     kExtAudioFileProperty_ClientDataFormat,
                                     sizeof (importFormat),
                                     &importFormat
                                     );

UInt32 numberofframestoread=(soundptr->amounttoread);
AudioBufferList *bufferList;

bufferList = (AudioBufferList *) malloc (
                                         sizeof (AudioBufferList) + sizeof (AudioBuffer) * (1)
                                         );


// initialize the mNumberBuffers member
bufferList->mNumberBuffers = 2;

// initialize the mBuffers member to 0
AudioBuffer emptyBuffer = {0};
size_t arrayIndex;
for (arrayIndex = 0; arrayIndex < 2; arrayIndex++) {
    bufferList->mBuffers[arrayIndex] = emptyBuffer;
}

// set up the AudioBuffer structs in the buffer list
bufferList->mBuffers[0].mNumberChannels  = 1;
bufferList->mBuffers[0].mDataByteSize    = numberofframestoread * sizeof (AudioUnitSampleType);
bufferList->mBuffers[0].mData            = (AudioUnitSampleType*)calloc(numberofframestoread, sizeof(AudioUnitSampleType));

    bufferList->mBuffers[1].mNumberChannels  = 1;
    bufferList->mBuffers[1].mDataByteSize    = numberofframestoread * sizeof (AudioUnitSampleType);
    bufferList->mBuffers[1].mData            = (AudioUnitSampleType*)calloc(numberofframestoread, sizeof(AudioUnitSampleType));




AudioUnitSampleType *inSamplesChannelLeft=bufferList->mBuffers[0].mData;
AudioUnitSampleType *inSamplesChannelRight=bufferList->mBuffers[1].mData;



// UInt32 read=(UInt32)soundptr->fetchsample;
UInt32 read_plus_half_buffer=soundptr->fetchsample;

UInt32 readdestination= read_plus_half_buffer+numberofframestoread;
UInt32 actualsamplesread=0;

actualsamplesread=numberofframestoread;


if (readdestination>soundptr->perfectframecount) {


    UInt32 readinpt1=0;
    UInt32 readoutpt1=0;
    UInt32 readinpt2=0;
    UInt32 readoutpt2=0;
    Float32 readtillendamount=0;

    readinpt1=read_plus_half_buffer;
    readoutpt1=soundptr->perfectframecount;
    readinpt2=0;



    if(read_plus_half_buffer>soundptr->perfectframecount)
    {
        readtillendamount=numberofframestoread;
        readinpt1=read_plus_half_buffer-soundptr->perfectframecount;

    }else
    {

        readtillendamount=soundptr->perfectframecount - readinpt1;
        readoutpt2=numberofframestoread-readtillendamount;




    }
    actualsamplesread= readtillendamount;
    ExtAudioFileSeek(engineDescribtion.audiofilerefs[soundptr->audioindex], readinpt1);
    ExtAudioFileRead(engineDescribtion.audiofilerefs[soundptr->audioindex],&actualsamplesread , bufferList);

    int writeposition=soundptr->queuebuffer->position;

    for (int i=0; i<actualsamplesread; i++) {


        outSamplesChannelLeft[writeposition]=inSamplesChannelLeft[i];
        outSamplesChannelRight[writeposition]=inSamplesChannelRight[i];



        writeposition++;

    }

    if (actualsamplesread!=readtillendamount) {

        UInt32 newzeroamount= readtillendamount-actualsamplesread;

        for (int j=0; j<newzeroamount; j++) {

            outSamplesChannelLeft[writeposition]=0;
            outSamplesChannelRight[writeposition]=0;
            writeposition++;

        }

    }       
    bufferList->mBuffers[1].mDataByteSize    = readoutpt2 * sizeof (AudioUnitSampleType);
    bufferList->mBuffers[0].mDataByteSize    = readoutpt2 * sizeof (AudioUnitSampleType);


    ExtAudioFileSeek(engineDescribtion.audiofilerefs[soundptr->audioindex], 0);
    ExtAudioFileRead(engineDescribtion.audiofilerefs[soundptr->audioindex],&readoutpt2 , bufferList);


    for (int k=0; k<readoutpt2; k++) {

        outSamplesChannelLeft[writeposition]=inSamplesChannelLeft[k];
        outSamplesChannelRight[writeposition]=inSamplesChannelRight[k];
        writeposition++;

    }


}else if(readdestination<=soundptr->perfectframecount){

    ExtAudioFileSeek(engineDescribtion.audiofilerefs[soundptr->audioindex], read_plus_half_buffer);

    bufferList->mBuffers[1].mDataByteSize    = actualsamplesread * sizeof (AudioUnitSampleType);
    bufferList->mBuffers[0].mDataByteSize    = actualsamplesread * sizeof (AudioUnitSampleType);
    // crash happens here

    if(bufferList)
    {
   assert( ExtAudioFileRead(engineDescribtion.audiofilerefs[soundptr->audioindex],&actualsamplesread , bufferList));
    }else

    {
        printf("NO BUFFER");
    }



    int writeposition=soundptr->queuebuffer->position;
    for (int i=0; i<actualsamplesread; i++) {

        outSamplesChannelLeft[writeposition]=inSamplesChannelLeft[i];
        outSamplesChannelRight[writeposition]=inSamplesChannelRight[i];
        writeposition++;

    }

    if (actualsamplesread!=numberofframestoread) {
        int zerosamples=0;

        zerosamples=numberofframestoread-actualsamplesread;

        for (int j=0; j<zerosamples; j++) {
            outSamplesChannelLeft[writeposition]=0;
            outSamplesChannelRight[writeposition]=0;
            writeposition++;


        }

    }                

}else
{
    printf("unknown condition");

}





free(bufferList->mBuffers[0].mData); 
free(bufferList->mBuffers[1].mData); 
free(bufferList);
bufferList=nil;

soundptr->queuebuffer->isreading=NO;

// pthread_detach(soundptr->thread);  
// free(&soundptr->m_lock);
return 0;
// pthread_exit(NULL);

}

修改2

O.K我已经想出了如何使用malloc历史。我有一个很大的跟踪声明。这是我第一次见过这样的事情。我不知道如何使用它来帮助自己。

    ALLOC 0x6c67000-0x6c67fd7 [size=4056]: thread_a019c540 |start | main | UIApplicationMain | GSEventRun | GSEventRunModal | CFRunLoopRunInMode | CFRunLoopRunSpecific | __CFRunLoopRun | __CFRunLoopDoSource1 | __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE1_PERFORM_FUNCTION__ | migHelperRecievePortCallout | _XReceivedStatusBarDataAndActions | _UIStatusBarReceivedStatusBarDataAndActions | -[UIStatusBarServer _receivedStatusBarData:actions:] | -[UIStatusBarForegroundView setStatusBarData:actions:animated:] | -[UIStatusBarLayoutManager updateItemsWithData:actions:animated:] | -[UIStatusBarLayoutManager _updateItemView:withData:actions:animated:] | -[UIStatusBarItemView updateContentsAndWidth] | -[UIStatusBarTimeItemView contentsImageForStyle:] | -[UIStatusBarItemView drawText:forStyle:] | -[UIStatusBarItemView drawText:forStyle:forWidth:lineBreakMode:letterSpacing:] | -[NSString(UIStringDrawing) drawAtPoint:forWidth:withFont:lineBreakMode:letterSpacing:] | -[NSString(UIStringDrawing) drawAtPoint:forWidth:withFont:lineBreakMode:letterSpacing:includeEmoji:] | -[NSString(WebStringDrawing) _web_drawAtPoint:forWidth:withFont:ellipsis:letterSpacing:includeEmoji:] | -[NSString(WebStringDrawing) __web_drawAtPoint:forWidth:withFont:ellipsis:letterSpacing:includeEmoji:measureOnly:] | -[NSString(WebStringDrawing) __web_drawAtPoint:forWidth:withFont:ellipsis:letterSpacing:includeEmoji:measureOnly:renderedStringOut:] | drawAtPoint(unsigned short const*, int, WebCore::FloatPoint const&, WebCore::Font const&, WebCore::GraphicsContext*, WebCore::BidiStatus*, int) | WebCore::Font::drawSimpleText(WebCore::GraphicsContext*, WebCore::TextRun const&, WebCore::FloatPoint const&, int, int) const | WebCore::Font::drawGlyphBuffer(WebCore::GraphicsContext*, WebCore::GlyphBuffer const&, WebCore::TextRun const&, WebCore::FloatPoint&) const | WebCore::Font::drawGlyphs(WebCore::GraphicsContext*, WebCore::SimpleFontData const*, WebCore::GlyphBuffer const&, int, int, WebCore::FloatPoint const&, bool) const | WebCore::showGlyphsWithAdvances(WebCore::FontPlatformData const&, CGContext*, unsigned short const*, CGSize const*, unsigned long) | CGContextShowGlyphsWithAdvances | draw_glyphs | ripc_DrawGlyphs | ripc_RenderGlyphs | CGGlyphLockLockGlyphBitmaps | create_missing_bitmaps | CGFontCreateGlyphBitmap8 | aa_create | malloc | malloc_zone_malloc 
----
FREE  0x6c67000-0x6c67fd7 [size=4056]: thread_a019c540 |start | main | UIApplicationMain | GSEventRun | GSEventRunModal | CFRunLoopRunInMode | CFRunLoopRunSpecific | __CFRunLoopRun | __CFRunLoopDoSource1 | __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE1_PERFORM_FUNCTION__ | migHelperRecievePortCallout | _XReceivedStatusBarDataAndActions | _UIStatusBarReceivedStatusBarDataAndActions | -[UIStatusBarServer _receivedStatusBarData:actions:] | -[UIStatusBarForegroundView setStatusBarData:actions:animated:] | -[UIStatusBarLayoutManager updateItemsWithData:actions:animated:] | -[UIStatusBarLayoutManager _updateItemView:withData:actions:animated:] | -[UIStatusBarItemView updateContentsAndWidth] | -[UIStatusBarTimeItemView contentsImageForStyle:] | -[UIStatusBarItemView drawText:forStyle:] | -[UIStatusBarItemView drawText:forStyle:forWidth:lineBreakMode:letterSpacing:] | -[NSString(UIStringDrawing) drawAtPoint:forWidth:withFont:lineBreakMode:letterSpacing:] | -[NSString(UIStringDrawing) drawAtPoint:forWidth:withFont:lineBreakMode:letterSpacing:includeEmoji:] | -[NSString(WebStringDrawing) _web_drawAtPoint:forWidth:withFont:ellipsis:letterSpacing:includeEmoji:] | -[NSString(WebStringDrawing) __web_drawAtPoint:forWidth:withFont:ellipsis:letterSpacing:includeEmoji:measureOnly:] | -[NSString(WebStringDrawing) __web_drawAtPoint:forWidth:withFont:ellipsis:letterSpacing:includeEmoji:measureOnly:renderedStringOut:] | drawAtPoint(unsigned short const*, int, WebCore::FloatPoint const&, WebCore::Font const&, WebCore::GraphicsContext*, WebCore::BidiStatus*, int) | WebCore::Font::drawSimpleText(WebCore::GraphicsContext*, WebCore::TextRun const&, WebCore::FloatPoint const&, int, int) const | WebCore::Font::drawGlyphBuffer(WebCore::GraphicsContext*, WebCore::GlyphBuffer const&, WebCore::TextRun const&, WebCore::FloatPoint&) const | WebCore::Font::drawGlyphs(WebCore::GraphicsContext*, WebCore::SimpleFontData const*, WebCore::GlyphBuffer const&, int, int, WebCore::FloatPoint const&, bool) const | WebCore::showGlyphsWithAdvances(WebCore::FontPlatformData const&, CGContext*, unsigned short const*, CGSize const*, unsigned long) | CGContextShowGlyphsWithAdvances | draw_glyphs | ripc_DrawGlyphs | ripc_RenderGlyphs | CGGlyphLockLockGlyphBitmaps | create_missing_bitmaps | CGFontCreateGlyphBitmap8 | aa_destroy | free 

ALLOC 0x6c67000-0x6c67fff [size=4096]: thread_b024f000 |thread_start | _pthread_start | __NSThread__main__ | -[NSThread main] | -[FirstViewController checkstate:] | CALayer_setter_kCAValueFloat | CALayer_setter | CA::Transaction::ensure_compat() | CA::Transaction::create() | malloc | malloc_zone_malloc 
----
FREE  0x6c67000-0x6c67fff [size=4096]: thread_b024f000 |thread_start | _pthread_start | __NSThread__main__ | -[NSString compare:options:] | _pthread_exit | _pthread_tsd_cleanup | free 

ALLOC 0x6c67000-0x6c67fff [size=4096]: thread_b0353000 |thread_start | _pthread_start | __NSThread__main__ | -[NSThread main] | -[FirstViewController checkstate:] | CALayer_setter_kCAValueFloat | CALayer_setter | CA::Transaction::ensure_compat() | CA::Transaction::create() | malloc | malloc_zone_malloc 
----
FREE  0x6c67000-0x6c67fff [size=4096]: thread_b0353000 |thread_start | _pthread_start | __NSThread__main__ | -[NSString compare:options:] | _pthread_exit | _pthread_tsd_cleanup | free 

ALLOC 0x6c67000-0x6c67fff [size=4096]: thread_b0763000 |thread_start | _pthread_start | FetchAudio | ExtAudioFileRead | ExtAudioFile::Read(unsigned long, unsigned long&, AudioBufferList*) | AudioConverterFillComplexBuffer | BufferedAudioConverter::FillBuffer(unsigned long&, AudioBufferList&, AudioStreamPacketDescription*) | AudioConverterChain::RenderOutput(CABufferList*, unsigned long, unsigned long&, AudioStreamPacketDescription*) | BufferedAudioConverter::FillBuffer(unsigned long&, AudioBufferList&, AudioStreamPacketDescription*) | CBRConverter::RenderOutput(CABufferList*, unsigned long, unsigned long&, AudioStreamPacketDescription*) | BufferedAudioConverter::GetInputBytes(unsigned long, unsigned long&, CABufferList const*&) | CABufferList::AllocateBuffers(unsigned long) | operator new[](unsigned long) | operator new(unsigned long) | malloc | malloc_zone_malloc 
----
FREE  0x6c67000-0x6c67fff [size=4096]: thread_b0763000 |thread_start | _pthread_start | FetchAudio | ExtAudioFileRead | ExtAudioFile::Read(unsigned long, unsigned long&, AudioBufferList*) | AudioConverterFillComplexBuffer | BufferedAudioConverter::FillBuffer(unsigned long&, AudioBufferList&, AudioStreamPacketDescription*) | AudioConverterChain::RenderOutput(CABufferList*, unsigned long, unsigned long&, AudioStreamPacketDescription*) | BufferedAudioConverter::FillBuffer(unsigned long&, AudioBufferList&, AudioStreamPacketDescription*) | CBRConverter::RenderOutput(CABufferList*, unsigned long, unsigned long&, AudioStreamPacketDescription*) | BufferedAudioConverter::GetInputBytes(unsigned long, unsigned long&, CABufferList const*&) | free 

ALLOC 0x6c67000-0x6c67fff [size=4096]: thread_b0a6f000 |thread_start | _pthread_start | FetchAudio | ExtAudioFileRead | ExtAudioFile::Read(unsigned long, unsigned long&, AudioBufferList*) | AudioConverterFillComplexBuffer | BufferedAudioConverter::FillBuffer(unsigned long&, AudioBufferList&, AudioStreamPacketDescription*) | AudioConverterChain::RenderOutput(CABufferList*, unsigned long, unsigned long&, AudioStreamPacketDescription*) | BufferedAudioConverter::FillBuffer(unsigned long&, AudioBufferList&, AudioStreamPacketDescription*) | CBRConverter::RenderOutput(CABufferList*, unsigned long, unsigned long&, AudioStreamPacketDescription*) | BufferedAudioConverter::GetInputBytes(unsigned long, unsigned long&, CABufferList const*&) | CABufferList::AllocateBuffers(unsigned long) | operator new[](unsigned long) | operator new(unsigned long) | malloc | malloc_zone_malloc 
----
FREE  0x6c67000-0x6c67fff [size=4096]: thread_b0a6f000 |thread_start | _pthread_start | FetchAudio | ExtAudioFileRead | ExtAudioFile::Read(unsigned long, unsigned long&, AudioBufferList*) | AudioConverterFillComplexBuffer | BufferedAudioConverter::FillBuffer(unsigned long&, AudioBufferList&, AudioStreamPacketDescription*) | AudioConverterChain::RenderOutput(CABufferList*, unsigned long, unsigned long&, AudioStreamPacketDescription*) | BufferedAudioConverter::FillBuffer(unsigned long&, AudioBufferList&, AudioStreamPacketDescription*) | CBRConverter::RenderOutput(CABufferList*, unsigned long, unsigned long&, AudioStreamPacketDescription*) | BufferedAudioConverter::GetInputBytes(unsigned long, unsigned long&, CABufferList const*&) | free 

ALLOC 0x6c67000-0x6c67fff [size=4096]: thread_b0081000 |thread_start | _pthread_start | __NSThread__main__ | -[NSThread main] | -[FirstViewController checkstate:] | CALayer_setter_kCAValueFloat | CALayer_setter | CA::Transaction::ensure_compat() | CA::Transaction::create() | malloc | malloc_zone_malloc 
----
FREE  0x6c67000-0x6c67fff [size=4096]: thread_b0081000 |thread_start | _pthread_start | __NSThread__main__ | -[NSString compare:options:] | _pthread_exit | _pthread_tsd_cleanup | free

Answer 1

我注意到代码中有以下几行：

bufferList = (AudioBufferList *) malloc (
                                         sizeof (AudioBufferList) + sizeof (AudioBuffer) * (1)
                                         );
// initialize the mNumberBuffers member
bufferList->mNumberBuffers = 2;

你正在使用AudioBufferList来获得一个AudioBuffer的容量，但后来表明它实际上有两个。尝试将“*（1）”更改为“*（2）”。

除此之外，你不应该在线程中执行malloc或ExtAudioFileOpen，因为这会占用时间。如果您可以设置预先执行malloc和ExtAudioFileOpen并将它们保存在文件的结构数组中，您可能会发现性能/稳定性有所提高。

我可能没有完全正确地阅读代码，因为它看起来格式有些混乱，但我希望这会有所帮助。

Answer 2

你可以通过找到它并找出错误的原因来解决这个问题，而不是通过try / catch来解决这个问题。

Guard Malloc可以帮助您识别程序中的许多问题。它是一个诊断选项，您可以在Xcode中启用它。当您尝试读取或写入您不拥有的内存时，该选项的目的是失败，使得程序的哪个部分导致问题比通常更清晰。完整详情：man guardmalloc。第一步是纠正所有问题，guardmalloc指出。您应该能够在没有这些问题的情况下运行您的应用数小时。

如果您希望异常和运行时检查可以帮助您更早地识别这些问题（值得您考虑），请考虑使用C ++而不是C来实现。

<强>更新

如果它是有问题的分配的堆分配，那么malloc日志记录可能会对您有所帮助。启用malloc日志记录并且调试器暂停执行时，只需使用malloc_history查看分配的调用堆栈。 malloc_history将查找日志中的地址并转储alloc创建的callstack。从那里，你只需按照你的程序中的分配流程找到你错了。

Answer 3

我最终找到了解决这个问题的方法。每次我需要音频时，我都会创建一个新线程来获取音频。在线程为特定缓冲区获取音频时，同一缓冲区将再次请求数据，导致同时访问相同的缓冲区，因此exc_bad_access。

我通过只有一个线程等待并通过posix条件发出信号来获取数据来解决这个问题。

这里的所有答案都很有用，并帮助我学习了很多关于调试的知识。谢谢你们..

Answer 4

这个问题几乎肯定会发生，因为你的阅读记忆是你不应该的。因此EXC_BAD_ACCESS。重要的是缓冲区的大小和您正在读取的内存量都是正确的。例如，如果您尝试读取超过缓冲区的值，则会收到错误。

在ExtAudioFileRead中，&readoutpt2处的值应指定帧数。你确定这个值是否正确？ bufferList大到足以存储该帧数吗？当您读取数据时，您是否正在通过bufferList推进指针，并且您推进的数量是否正确？

您是否根据基础类型正确分配内存？例如，您的音频数据是整数还是浮点格式？

基本上，一切都需要正确加起来，否则你会在某个地方放一个缓冲区！

尝试追踪内存问题的另一个工具是guard malloc。您可以在此处找到更多信息Enabling the Malloc Debugging Features

间歇性的extaudiofileread exc_bad_access

4 个答案: