crash course - Page 73 - Developer IT

EXC_BAD_ACCESS in CFAttributedStringSetAttribute and NSNumber?

- by RichardR

Hi all, I am getting an infuriating EXC_BAD_ACCESS error in an objective c app I am working on. Any help you could offer would be much appreciated. I have tried the normal debug methods for this error (turning on NSZombieEnabled, checking retain/release/autorelease to make sure I'm not trying to access a deallocated object, etc.) and it hasn't seemed to help. Basically, the error always occurs in this function: ` void op_TJ(CGPDFScannerRef scanner, void *info) { PDFPage *self = info; CGPDFArrayRef array; NSMutableString *tempString = [NSMutableString stringWithCapacity:1]; NSMutableArray *kernArray = [[NSMutableArray alloc] initWithCapacity:1]; if(!CGPDFScannerPopArray(scanner, &array)) { [kernArray release]; return; } for(size_t n = 0; n < CGPDFArrayGetCount(array); n += 2) { if(n >= CGPDFArrayGetCount(array)) continue; CGPDFStringRef pdfString; // if we get a PDF string if (CGPDFArrayGetString(array, n, &pdfString)) { //get the actual string const unsigned char *charstring = CGPDFStringGetBytePtr(pdfString); //add this string to our temp string [tempString appendString:[NSString stringWithCString:(const char*)charstring encoding:[self pageEncoding]]]; //NSLog(@"string: %@", tempString); //get the space after this string CGPDFReal r = 0; if (n+1 < CGPDFArrayGetCount(array)) { CGPDFArrayGetNumber(array, n+1, &r); // multiply by the font size CGFloat k = r; k = -k/1000 * self.tmatrix.a * self.fontSize; CGFloat kKern = self.kern * self.tmatrix.a; k = k + kKern; // add the location and kern to the array NSNumber *tempKern = [NSNumber numberWithFloat:k]; NSLog(@"tempKern address: %p", tempKern); [kernArray addObject:[NSArray arrayWithObjects:[NSNumber numberWithInt:[tempString length] - 1], tempKern, nil]]; } } } // create an attribute string CFMutableAttributedStringRef attString = CFAttributedStringCreateMutable(kCFAllocatorDefault, 10); CFAttributedStringReplaceString(attString, CFRangeMake(0, 0), (CFStringRef)tempString); //apply overall kerning NSNumber *tkern = [NSNumber numberWithFloat:self.kern * self.tmatrix.a * self.fontSize]; CFAttributedStringSetAttribute(attString, CFRangeMake(0, CFAttributedStringGetLength(attString)), kCTKernAttributeName, (CFNumberRef)tkern); //apply individual kern attributes for (NSArray *kernLoc in kernArray) { NSLog(@"kern location: %i, %i", [[kernLoc objectAtIndex:0] intValue],[[kernLoc objectAtIndex:1] floatValue]); CFAttributedStringSetAttribute(attString, CFRangeMake([[kernLoc objectAtIndex:0] intValue], 1), kCTKernAttributeName, (CFNumberRef)[kernLoc objectAtIndex:1]); } CFAttributedStringReplaceAttributedString([self cfAttString], CFRangeMake(CFAttributedStringGetLength([self cfAttString]), 0), attString); //release CFRelease(attString); [kernArray release]; } ` The program always crashes because of line CFAttributedStringSetAttribute(attString, CFRangeMake([[kernLoc objectAtIndex:0] intValue], 1), kCTKernAttributeName, (CFNumberRef)[kernLoc objectAtIndex:1]) And it seems to depend on a few things: if [kernLoc objectAtIndex:1] refers to an [NSNumber numberWithFloat:k] where k = 0 (in other words, if k = 0 above where I populate kernArray) then the program crashes almost immediately If I comment out the line k = k + kKern, it takes longer for the program to crash, but does eventually (why would the crash depend on this value?) If I change the length of CFRangeMake from 1 to 0, it takes a lot longer for the program to crash, but still eventually does. (I don't think I am trying to access beyond the bounds of attString, but am I missing something?) When it crashes, I get something similar to: #0 0x942c7ed7 in objc_msgSend () #1 0x00000013 in ?? () #2 0x0285b827 in CFAttributedStringSetAttribute () #3 0x0000568f in op_TJ (scanner=0x472a590, info=0x4a32320) at /Users/Richard/Desktop/AppTest/PDFHighlight 2/PDFScannerOperators.m:251 Any ideas? It seems like somewhere along the way I am overwriting memory or trying to access memory that has been changed, but I have no idea. If there's anymore information I can provide, please let me know. Thanks, Richard

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