iphone - 调试构建工作得很好，临时构建很难崩溃

Question

我正在使用 EXIF 库 http://code.google.com/p/iphone-exif/我遇到了一个真正令人头疼的错误。当我在调试版本中实现该库时，一切都运行良好，但当我编译用于临时 beta 测试时，应用程序会严重崩溃。

我收到以下错误:

Exception Type:  EXC_BAD_ACCESS (SIGBUS)
Exception Codes: KERN_PROTECTION_FAILURE at 0x00000000
Crashed Thread:  5

使用线程 5:

0   Gaia GPS                       0x000494e4 -[EXFJpeg scanImageData:] (EXFJpeg.m:372)
1   Gaia GPS                       0x0000524c -[MyAppDelegate saveImage:] (MyAppDelegate.m:935)
2   Foundation                     0x317fef32 0x317ad000 + 335666
3   Foundation                     0x317ae09a 0x317ad000 + 4250
4   libSystem.B.dylib              0x329c892a 0x329a4000 + 149802

我怀疑调试构建处理内存的方式与临时构建处理内存的方式有所不同。在我看来，从错误来看，这段代码正在尝试写入它无权访问的内存块，当它这样做时，Ad-hoc iPhone 操作系统会关闭该进程。

什么会在临时发行版中导致此行为，但在调试版本中不会？即使手机断开连接且调试器关闭，调试构建也能正常工作。

提前非常感谢。

代码:

我的实现库的代码(第 935 行是该 block 的第一行，即 alloc 语句)

:

EXFJpeg* jpegScanner = [[EXFJpeg alloc] init]; 
  [jpegScanner scanImageData:imgData];   

  CLLocation *location = self.gps.lastReading ? self.gps.lastReading : [self.gps.locationManager location];
  [location retain];


  NSMutableArray* locArray = [self createLocArray:location.coordinate.latitude]; 
  EXFGPSLoc* gpsLoc = [[EXFGPSLoc alloc] init]; 
  [self populateGPS: gpsLoc :locArray]; 
  [jpegScanner.exifMetaData addTagValue:gpsLoc forKey:[NSNumber numberWithInt:EXIF_GPSLatitude]; 
  [gpsLoc release]; 

  locArray = [self createLocArray:location.coordinate.longitude]; 
  gpsLoc = [[EXFGPSLoc alloc] init]; 
  [self populateGPS: gpsLoc :locArray];
  [locArray release]; 

  [jpegScanner.exifMetaData addTagValue:gpsLoc forKey:[NSNumber numberWithInt:EXIF_GPSLongitude]; 
  [gpsLoc release]; 

  NSString *ref = (location.coordinate.latitude <0.0)?ref = @"S": @"N";  
  [jpegScanner.exifMetaData addTagValue: ref forKey:[NSNumber numberWithInt:EXIF_GPSLatitudeRef] ];
  ref = (location.coordinate.longitude <0.0)? @"W": @"E";
  [jpegScanner.exifMetaData addTagValue: ref forKey:[NSNumber numberWithInt:EXIF_GPSLongitudeRef]];
  [jpegScanner.exifMetaData addTagValue: @"Apple" forKey:[NSNumber numberWithInt:EXIF_Make];
  [jpegScanner.exifMetaData addTagValue: @"iPhone" forKey:NSNumber numberWithInt:EXIF_Model];  
  [jpegScanner.exifMetaData addTagValue:[NSNumber numberWithInt:0] forKey:[NSNumber numberWithInt:EXIF_GPSAltitudeRef] ];

  NSArray *arr = [[NSArray alloc] initWithObjects:[NSNumber numberWithInt:0], NSNumber numberWithInt:0], [NSNumber numberWithInt:2], [NSNumber numberWithInt:2], nil];
  [jpegScanner.exifMetaData addTagValue: arr forKey:[NSNumber numberWithInt:EXIF_GPSVersion] ];
  [arr release];

  long numDenumArray[2]; 
  long* arrPtr = numDenumArray; 
  [EXFUtils convertRationalToFraction:&arrPtr: [NSNumber numberWithDouble:location.altitude]]; 
  EXFraction *fract = [[EXFraction alloc] initWith:numDenumArray[0] :numDenumArray[1]]; 
  [jpegScanner.exifMetaData addTagValue:fract forKey:[NSNumber 
                                           numberWithInt:EXIF_GPSAltitude] ]; 

  NSMutableData *newData = [[NSMutableData alloc] init];
  [jpegScanner populateImageData:newData];
  [jpegScanner release];

最后但并非最重要的是库本身的函数:

-(void) scanImageData: (NSData*) jpegData {

    Debug(@"Starting scan headers");

    // pointer to the end of the EXIF Data and the start of the rest of the image
    ByteArray* endOfEXFPtr;

    imageLength = CFDataGetLength((CFDataRef)jpegData);

   // CFRetain(&imageLength);

    Debug(@"Length of image %i", imageLength);

    imageBytePtr = (UInt8 *) CFDataGetBytePtr((CFDataRef)jpegData);
    imageStartPtr = imageBytePtr;

    // check if a valid jpeg file
    UInt8 val = [self readNextbyte];

    if (val != M_BEG){
         Debug(@"Not a valid JPEG File");
        return;
    }

    val = [self readNextbyte];

    if (val != M_SOI){
        Debug(@"Not a valid start of image JPEG File");
        return;
    }


    // increment this to position after second byte
    BOOL finished =FALSE;

    while(!finished){
        // increment the marker

        val = [self nextMarker];

        Debug(@"Got next marker %x at byte count %i", val, (imageBytePtr - imageStartPtr));

        switch(val){
                case M_SOF0:  /* Baseline */
                case M_SOF1:  /* Extended sequential, Huffman */
                case M_SOF2:  /* Progressive, Huffman */
                case M_SOF3:  /* Lossless, Huffman */
                case M_SOF5:  /* Differential sequential, Huffman */
                case M_SOF6:  /* Differential progressive, Huffman */
                case M_SOF7:  /* Differential lossless, Huffman */
                case M_SOF9:  /* Extended sequential, arithmetic */
                case M_SOF10:  /* Progressive, arithmetic */
                case M_SOF11:  /* Lossless, arithmetic */
                case M_SOF13:  /* Differential sequential, arithmetic */
                case M_SOF14:  /* Differential progressive, arithmetic */
                case M_SOF15:  /* Differential lossless, arithmetic */
                    // Remember the kind of compression we saw
                    {
                      int compression = *imageBytePtr;   // <-----------LINE 372
                        self.exifMetaData.compression = compression;

                        // Get the intrinsic properties fo the image
                        [self readImageInfo];
                    }
                    break;

               case M_SOS:  /* stop before hitting compressed data */
                Debug(@"Found SOS at %i", imageBytePtr - imageStartPtr);
              //  [self skipVariable];

                // Update the EXIF
             //  updateExif();
                    finished = TRUE;
                    break;
               case M_EOI:  /* in case it's a tables-only JPEG stream */
                    Debug(@"End of Image reached at %i ", imageBytePtr - imageStartPtr);
                    finished =TRUE;
                    break;
               case M_COM: 
                    Debug(@"Got com  at %i",imageBytePtr - imageStartPtr);
                    break;

               case M_APP0:
               case M_APP1:
               case M_APP2:
               case M_APP3:
               case M_APP4:
               case M_APP5:
               case M_APP6:
               case M_APP7:
               case M_APP8:
               case M_APP9:
               case M_APP10:
               case M_APP11:
               case M_APP12:
               case M_APP13:
               case M_APP14:
               case M_APP15:
               // Some digital camera makers put useful textual
               // information into APP1 and APP12 markers, so we print
               // those out too when in -verbose mode.
                {
                    Debug(@"Found app %x at %i", val, imageBytePtr - imageStartPtr);


                    NSData* commentData = [self processComment];
                    NSNumber* key = [[NSNumber alloc]initWithInt:val];

                    // add comments to dictionary
                    [self.keyedHeaders  setObject:commentData forKey:key];
                    [key release];
                    // will always mark the end of the app_x block
                    endOfEXFPtr = imageBytePtr;

                    // we pass a pointer to the NSData pointer here
                    if (val == M_APP0){
                         Debug(@"Parsing JFIF APP_0 at %i", imageBytePtr - imageStartPtr);
                        [self parseJfif:(CFDataRef*)&commentData];
                    } else if (val == M_APP1){
                        [self parseExif:(CFDataRef*)&commentData];
                        Debug(@"Finished App1 at %i", endOfEXFPtr - imageStartPtr);
                    } else if (val == M_APP2){
                        Debug(@"Finished APP2 at %i", imageBytePtr - imageStartPtr);
                    }else{
                        Debug(@"Finished App &x at %i", val, imageBytePtr - imageStartPtr);
                    }

                }


               break;
            case M_SOI:
                Debug(@"SOI encountered at %i",imageBytePtr - imageStartPtr);

                break;
               default:           // Anything else just gets skipped
                Debug(@"NOt handled %x skipping at %i",val, imageBytePtr - imageStartPtr);
                [self skipVariable];  // we assume it has a parameter count...
               break;
               }     

        }



    // add in the bytes after the exf block
    NSData* theRemainingdata = [[NSData alloc] initWithBytes:endOfEXFPtr length:imageLength - (endOfEXFPtr - imageStartPtr)];
    self.remainingData = theRemainingdata;
    [theRemainingdata release];

    endOfEXFPtr = NULL;
    imageStartPtr = NULL;
    imageBytePtr = NULL;

}

Answer 1

我不久前遇到了同样的问题，并找到了 2 个解决方案(或解决方法):

1. 使用 http://code.google.com/p/iphone-exif/downloads/list 中的预编译库而不是从源代码编译

2. 将 EXFMetaData.m 的第 1270 行更改为:

   CFDataGetBytes(*exifData, CFRangeMake(6,2), order);

按照此处的建议:http://code.google.com/p/iphone-exif/issues/detail?id=4&can=1