xcode tool to find memory issues, access of a pointer to a location of another variable ecc

i'm using cocos2d, however the question is general. i have a class

CCNode *scaleLayer

in touchesMoved event i set

scaleLayer.scale=(some calculation)

if i compile in device the pr开发者_运维知识库ogram crashes, on simulator works well. if i put nslogs before the precedent instruction, works well even in device. could be some memory, pointer or what could it be? however, exist a tool of xcode that can make me find or understand where to point my eye? thanks

here is the code:

- (void)ccTouchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
NSSet *allTouches = [event allTouches];
//NSLog(@"comincio");
switch ([allTouches count]) {
    case 2: { //Double Touch
        UITouch *t1 = [[allTouches allObjects] objectAtIndex:0];
        UITouch *t2 = [[allTouches allObjects] objectAtIndex:1];
        CGPoint p1=[self convertTouchToNodeSpace: t1];
        CGPoint p2=[self convertTouchToNodeSpace: t2];                  

        initialDistance = [self distanceBetweenTwoPoints:p1 B:p2];
        oldScale=scaleLayer.scale;
        NSLog(@"distanza iniz %f",initialDistance);
    } break;
            default:
        break;
}
}

-(void)ccTouchesMoved:(NSSet *)touches withEvent:(UIEvent *)event{
    CGPoint location;   
    UITouch *t1,*t2;    
    CGPoint p1,p2;

    NSSet *allTouces=[event allTouches];
    switch ([allTouces count]) {
case 2:
            //NSLog(@"2 tocchi");
            t1=[[allTouces allObjects] objectAtIndex:0];
            t2=[[allTouces allObjects] objectAtIndex:1];
            p1=[self convertTouchToNodeSpace: t1];
            p2=[self convertTouchToNodeSpace: t2];
            CGFloat finalDistance=[self distanceBetweenTwoPoints:p1 B:p2];
//if i put here NSLog("%f %f %f",oldScale,finalDistance,initialDistance); all goes well
            scaleLayer.scale=oldScale*finalDistance/initialDistance;
            NSLog(@"scala %f",scaleLayer.scale);//finalDistance/initialDistance);
//this nslog give me error if i not put that nslog before
            break;

        default:
            break;
    }
}

-(CGFloat)distanceBetweenTwoPoints:(CGPoint)A B:(CGPoint)B{
    float x=B.x-A.x;
    float y=B.y-A.y;
    return sqrt(x*x+y*y);
}

Try building with the static analyzer (Shift-Command-A)

Try watching the memory address. Here are some links to get you started: scottmpeak.com and SO discussion

One option you can use is zombies, it is already explained in stackoverflow, so I am not going to do it here.

But if you are getting EXC_BAD_ACCESS kind of errors you can add an exception breakpoint. That also helps sometimes. These are the steps to do so

1. In the bottom left corner of the breakpoint navigator click the plus button.
2. In the pop up, select "Add exception breakpoint"
3. Choose the type of exception. I normally select "All" exception
4. Click done.

Apple explained this here.