[pool release]; Crash my app

Question

In my app i have a loop that move on array of UIImage and make stuff with this images. the loop work in the background Thread so in the start of the function i put :

NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];

and in the end

[pool release];

In the loop i create UIImage so i need to release it because it give me a memory warning if i am not make a release.

When the app finish the loop and get to the

[pool release];

it give me BAD_ACCESS error and crash the app.

Edit

---

This is the methods in the loop

        UIImage *tmp = [image rotate:UIImageOrientationRight];
        //do some stuff with this image
        [tmp release];

This is the rotate method:

    UIImage*           copy = nil;
    CGRect             bnds = CGRectZero;
    UIImage*           copy = nil;
    CGContextRef       ctxt = nil;
    CGImageRef         imag = self.CGImage;
    CGRect             rect = CGRectZero;
    CGAffineTransform  tran = CGAffineTransformIdentity;

    rect.size.width  = CGImageGetWidth(imag);
    rect.size.height = CGImageGetHeight(imag);

    bnds = rect;

    UIGraphicsBeginImageContext(bnds.size);
    ctxt = UIGraphicsGetCurrentContext();

switch (orient)
{
    case UIImageOrientationLeft:
    case UIImageOrientationLeftMirrored:
    case UIImageOrientationRight:
    case UIImageOrientationRightMirrored:
        CGContextScaleCTM(ctxt, -1.0, 1.0);
        CGContextTranslateCTM(ctxt, -rect.size.height, 0.0);
        break;

    default:
        CGContextScaleCTM(ctxt, 1.0, -1.0);
        CGContextTranslateCTM(ctxt, 0.0, -rect.size.height);
        break;
}

CGContextConcatCTM(ctxt, tran);
CGContextDrawImage(UIGraphicsGetCurrentContext(), rect, imag);

copy = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();

if (imag) {
    CFRelease(imag);
}

return copy;

Answer 1

You're over-releasing your image after rotating it.

    UIImage *tmp = [image rotate:UIImageOrientationRight];
    //do some stuff with this image
    [tmp release]; // Here

UIGraphicsGetImageFromCurrentImageContext() returns an autoreleased object, so you don't need to call release on it after you return it.

The crash happens when releasing the NSAutoreleasePool because the last -release is not sent until it gets drained and sends the correct release call to your object that was previously and wrongly released by you.

Answer 2

Probably you're releasing some objects you create and don't own between the time you create the pool and release it again.

NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];

NSString *s = [NSString stringWithFormat:@"%d", 2];
// Your string now has a retain count of one, but it's autoreleased. So when the pool
// gets released it'll release the string

[s release];
// You decrease the retain count to zero, so the object gets destroyed
// s now points to a deallocated object

[pool release];
// The pool gets destroyed, so it tries to send a release method to your string. However,
// the string doesn't exist anymore so an error occurs.

Answer 3

我认为您的崩溃可能与自动释放池何时释放UIImage有关，而不是与释放自动释放池有关。