NSMutableArray EXC_BAD_EXCESS SIGBUS

Question

Hi, I've the following code which causes crashes after sometime as i've set the below code in a timer:

CGImageRef cgImage = UIGetScreenImage();
[array addObject:(id)cgImage];
CGImageRelease(cgImage);

Where initiallly i've declared array as:

array = [[NSMutableArray alloc] init];

The timer goes well till 10 seconds as timer is of 1/10 seconds after 10 seconds it crashes.

I think the application crashes because of EXC_BAD_EXCESS but dont know how to solve. Can anybody help in solving the problem?

Thanks in Adv.

Answer 1

addObject: will raise an exception if the object is nil. Try this:

array = [[NSMutableArray alloc] initWithCapacity:1]; //designated initializer
CGImageRef cgImage = UIGetScreenImage();
if(cgImage)
{
    [array addObject:cgImage];
    CGImageRelease(cgImage);
}

Answer 2

Are you sure you're supposed to be releasing cgImage?

I don't see documentation for UIGetScreenImage(), but if it follows the Create Rule, I would not expect you to need to release the object (because the function does not have "Create" or "Copy" in its name).

EDIT: I've since found several references that say that you do need to release the image, despite the name of the function. (Which has apparently been renamed UICreateScreenImage() in the 3.2 SDK.

Answer 3

From the Apple Developer Forum to UIGetScreenImage():

As you use this function, please note that it returns a retained CGImageRef and manage your memory accordingly.