【发布时间】：2011-10-28 16:59:16
【问题描述】：
目前我遇到了一个似乎无法解决的 EXC_BAD_ACCESS 问题。 我已经尝试启用 NSZombie，这似乎是许多帖子中的建议，但我处理的是 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。
我的代码的工作方式是，在它需要一些来自磁盘的音频之前，我分离了一个新的 posix 线程，向它传递一个指向我想要的音频信息的指针。然后我读了一些样本。 我之所以选择 posix 而不是 NSThread 或 NSOperation 是因为它似乎执行得更快。我的音频占用大量 CPU，因此我需要尽快读取音频。
如何解决这个错误的访问错误？它不会一直发生。有时它似乎发生在应用程序非常繁忙的时候。偶尔它根本不会发生。
无论如何我可以尝试解决这个问题作为快速解决方案吗？我还能如何调查造成这种情况的原因？
编辑这是我提出的一个单独问题的链接，但它与同一个问题有关
[密集 io 线程][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);
}
编辑 2
好的，我已经弄清楚了如何使用 malloc 历史记录。我有一个很大的跟踪声明。这是我以前第一次看到这样的东西，我不知道如何用它来帮助自己。
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
【问题讨论】：
-
'似乎执行得更快' - 除非您非常快速地创建线程，否则我非常怀疑用于创建线程的方法会影响它们的性能。但是，请用一些基准证明我错了；）
-
您认为快速多快？我每秒分离大约 16 - 24 个线程。是不是太过分了？
-
我认为这有点过分，是的。我会考虑重新考虑架构——有这么多线程，创建线程的成本将开始超过它们的好处。您可以按顺序执行什么操作，从而减少创建的线程数？
-
感谢您的意见。好吧，我有 0 到 20 个音频文件需要随时读取。 Prehaps 我可以尝试只使用 1 个单一的生产者线程并从中为它们提供服务。我担心它不会足够快地执行。或者也许我可以让一个线程不断地为每一位音频运行，并使用标志来指示他们是否应该休眠或获取音频？你认为有这么多线程可能与我的内存访问问题有关吗？
标签： iphone ios exc-bad-access