ios - xcode 无法理解的异常

Question

我正在编写 ios 应用程序，它从网络摄像机接收帧并使用 UIImage 和计时器显示它们。但是时不时会遇到无法理解的异常。
这是一个堆栈

thread #1: tid = 0x72198, 0x0553a240 vImage`vConvert_RGB888toBGRA8888 + 1760, queue = 'com.apple.main-thread', stop reason = EXC_BAD_ACCESS (code=1, address=0xe429000)

frame #0: 0x0553a240 vImage`vConvert_RGB888toBGRA8888 + 1760  
frame #1: 0x05523280 vImage`vImageConvert_RGB888toBGRA8888 + 96
frame #2: 0x01f2f1aa CoreGraphics`CGSConvertBGR888toRGBA8888 + 165  
frame #3: 0x01f5a83e CoreGraphics`argb32_image + 4830
frame #4: 0x0ae007ad libRIP.A.dylib`ripl_Mark + 38  
frame #5: 0x0ae101e1 libRIP.A.dylib`RIPLayerBltImage + 1187
frame #6: 0x0adfcc59 libRIP.A.dylib`ripc_RenderImage + 258  
frame #7: 0x0adfb0cb libRIP.A.dylib`ripc_DrawImage + 1051
frame #8: 0x01fe4865 CoreGraphics`CGContextDrawImage + 435  
frame #9: 0x01657498 QuartzCore`CA::Render::(anonymous namespace)::create_image_by_rendering(CGImage*, CGColorSpace*, unsigned int) + 708
frame #10: 0x01656f31 QuartzCore`CA::Render::create_image(CGImage*, CGColorSpace*, unsigned int) + 2261  
frame #11: 0x0165784d QuartzCore`CA::Render::copy_image(CGImage*, CGColorSpace*, unsigned int, double) + 430
frame #12: 0x01738d10 QuartzCore`-[CALayer(CALayerPrivate) _copyRenderLayer:layerFlags:commitFlags:] + 557  
frame #13: 0x0173a031 QuartzCore`CA::Layer::copy_render_layer(CA::Transaction*, unsigned int, unsigned int*) + 57
frame #14: 0x0168fc9d QuartzCore`CA::Context::commit_layer(CA::Layer*, unsigned int, unsigned int, void*) + 119  
frame #15: 0x0172a727 QuartzCore`CA::Layer::commit_if_needed(CA::Transaction*, void (*)(CA::Layer*, unsigned int, unsigned int, void*), void*) + 317
frame #16: 0x0172a6a7 QuartzCore`CA::Layer::commit_if_needed(CA::Transaction*, void (*)(CA::Layer*, unsigned int, unsigned int, void*), void*) + 189  
frame #17: 0x0172a6a7 QuartzCore`CA::Layer::commit_if_needed(CA::Transaction*, void (*)(CA::Layer*, unsigned int, unsigned int, void*), void*) + 189
frame #18: 0x01690dd6 QuartzCore`CA::Context::commit_transaction(CA::Transaction*) + 1794  
frame #19: 0x01691b85 QuartzCore`CA::Transaction::commit() + 393
frame #20: 0x0174f5b0 QuartzCore`+[CATransaction flush] + 52  
frame #21: 0x021909b6 UIKit`_UIWindowUpdateVisibleContextOrder + 232
frame #22: 0x02190825 UIKit`+[UIWindow _prepareWindowsPassingTestForAppResume:] + 28  
frame #23: 0x02190a0f UIKit`+[UIWindow _prepareWindowsForAppResume] + 41
frame #24: 0x02164972 UIKit`-[UIApplication _handleApplicationResumeEvent:] + 80  
frame #25: 0x0216593f UIKit`-[UIApplication handleEvent:withNewEvent:] + 1898
frame #26: 0x02166555 UIKit`-[UIApplication sendEvent:] + 85  
frame #27: 0x02153250 UIKit`_UIApplicationHandleEvent + 683
frame #28: 0x04c6bf02 GraphicsServices`_PurpleEventCallback + 776  
frame #29: 0x04c6ba0d GraphicsServices`PurpleEventCallback + 46
frame #30: 0x0368eca5 CoreFoundation`__CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE1_PERFORM_FUNCTION__ + 53  
frame #31: 0x0368e9db CoreFoundation`__CFRunLoopDoSource1 + 523
frame #32: 0x036b968c CoreFoundation`__CFRunLoopRun + 2156  
frame #33: 0x036b89d3 CoreFoundation`CFRunLoopRunSpecific + 467
frame #34: 0x036b87eb CoreFoundation`CFRunLoopRunInMode + 123  
frame #35: 0x04c6a5ee GraphicsServices`GSEventRunModal + 192
frame #36: 0x04c6a42b GraphicsServices`GSEventRun + 104  
frame #37: 0x02152f9b UIKit`UIApplicationMain + 1225
frame #38: 0x00009344 thin_client_v2`main(argc=1, argv=0xbfffee4c) + 164 at main.m:17  

但我认为它并没有多大帮助，那么我如何才能理解我的代码的哪一行引发了异常？我添加了所有异常断点和 this技巧，但对我没有帮助。

谢谢

附言
所以我在我的项目中添加了僵尸对象。据我了解，它将帮助我获得更正确的堆栈跟踪。
关于创建图像。这是我的代码

- (UIImage *)imageFromAVPicture:(AVPicture)pict width:(int)width height:(int)height    
{
    CGBitmapInfo bitmapInfo = kCGBitmapByteOrderDefault;
    CFDataRef data = CFDataCreateWithBytesNoCopy(kCFAllocatorDefault, pict.data[0], pict.linesize[0]*height,kCFAllocatorNull);
    CGDataProviderRef provider = CGDataProviderCreateWithCFData(data);
    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
    CGImageRef cgImage = CGImageCreate(width, 
                                       height, 
                                       8, 
                                       24, 
                                       pict.linesize[0], 
                                       colorSpace, 
                                       bitmapInfo, 
                                       provider, 
                                       NULL, 
                                       NO, 
                                       kCGRenderingIntentDefault);
    CGColorSpaceRelease(colorSpace);
    UIImage *image = [UIImage imageWithCGImage:cgImage];

    CGImageRelease(cgImage);
    CGDataProviderRelease(provider);
    CFRelease(data);

    return image;
}

但我认为如果问题出在这个方法中，它就会一直崩溃，对吗？但异常(exception)情况确实很少见。

Answer 1

这意味着您的应用正在崩溃，因为它触及了未映射的内存。

如果您使用未初始化的 CGDataProviderRef 创建 CGImageRef，然后在 CGImageRef 消失之前释放像素，则通常会发生这种情况。这会使 CGImageRef 指向垃圾，如果您尝试绘制它将会崩溃。如果您非常确定自己没有这样做并且可以想出一个可重现的示例案例，那么我建议向 Apple 提交错误:http://bugreporter.apple.com