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
