Crash using [UIBezierPath CGPath] with CAShapeLayer under ARC

Question

I'm getting a BAD ACCESS error using [UIBezierPath CGPath] with CAShapeLayer under ARC. I've tried bridging in various ways but I'm not clear if that is the problem. I have isolated the crash to using the result of the makeToPath method:

 maskLayer = [CAShapeLayer layer];
 maskLayer.path = [self makeToPath];

But this doesn't crash:

 maskLayer = [CAShapeLayer layer];
 maskLayer.path = [self makeFromPath];

Is there something invalid with the path created by makeToPath? I'm planning to use the from and to paths with a CABasicAnimation once I sort this crash out. What is the correct ARC bridging for CGPathRefs from UIBezierPath?

-(CGPathRef)makeToPath
{
    UIBezierPath* triangle = [UIBezierPath bezierPath];
    [triangle moveToPoint:CGPointZero];
    [triangle addLineToPoint:CGPointMake(self.view.frame.size.width,0)];
    [triangle addLineToPoint:CGPointMake(0, self.view.frame.size.height)];
    [triangle closePath];
    return [triangle CGPath];
}

-(CGPathRef)makeFromPath
{
    UIBezierPath*rect = [UIBezierPath bezierPathWithRect:self.view.frame];
    return [rect CGPath];
}

UPDATE So I changed my .h file per an answer below but I am still getting the crash

-(CGPathRef)makeToPath CF_RETURNS_RETAINED;
-(CGPathRef)makeFromPath CF_RETURNS_RETAINED;

I also tried making my methods return a UIBezierPath instance per the answer here (shown below). Still no success. Anyone want to give me the longform explanation on how to fix this?

maskLayer.path = [[self makeToPath] CGPath];// CRASHES
morph.toValue =  CFBridgingRelease([[self makeToPath] CGPath]);// CRASHES

---

-(UIBezierPath*)makeToPath
{
    UIBezierPath* triangle = [UIBezierPath bezierPath];
    [triangle moveToPoint:CGPointZero];
    [triangle addLineToPoint:CGPointMake(self.view.frame.size.width,0)];
    [triangle addLineToPoint:CGPointMake(0, self.view.frame.size.height)];
    [triangle closePath];
    return triangle;
}

Answer 1

The problem is with returning the CGPath. The value returned is a CGPathRef which is not covered by ARC. The UIBezierPath you create is released after the method ends. Thus also freeing the CGPathRef. You can specify a source annotation to let ARC know your intent:

In the .h file:

-(CGPathRef)makeToPath CF_RETURNS_RETAINED;
-(CGPathRef)makeFromPath CF_RETURNS_RETAINED;

Answer 2

As the other poster pointed out, you are returning a CGPath reference taken from a UIBezierPath object that goes out of scope at the end of the method. As the docs on the UIBezierPath CGPath property say:

The path object itself is owned by the UIBezierPath object and is valid only until you make further modifications to the path.

You need to create a copy of your CGPath and return that:

-(CGPathRef)makeToPath
{
    UIBezierPath* triangle = [UIBezierPath bezierPath];
    [triangle moveToPoint:CGPointZero];
    [triangle addLineToPoint:CGPointMake(self.view.frame.size.width,0)];
    [triangle addLineToPoint:CGPointMake(0, self.view.frame.size.height)];
    [triangle closePath];
    CGPathRef theCGPath = [triangle CGPath];
    return CGPathCreateCopy(theCGPath);
}

The way I read the link to the llvm project, I think that the cf_returns_retained qualifier is intended to tell the caller the memory management policy for the returned value, rather than doing the retain for you.

Thus I think you would both need to create a copy of the path AND add the cf_returns_retained qualifier. I'm not clear on the syntax of that qualifier, however. (Never used it before.)

Assuming the other poster had the right syntax, it would look something like this:

-(CGPathRef)makeToPath CF_RETURNS_RETAINED;
{
    UIBezierPath* triangle = [UIBezierPath bezierPath];
    [triangle moveToPoint:CGPointZero];
    [triangle addLineToPoint:CGPointMake(self.view.frame.size.width,0)];
    [triangle addLineToPoint:CGPointMake(0, self.view.frame.size.height)];
    [triangle closePath];
    CGPathRef theCGPath = [triangle CGPath];
    return CGPathCreateCopy(theCGPath);
}