Memory Leaks

[BigBearStudios]

Hey, i switched from C++ to Object C a few weeks back. I ran the XCode memory leak tool and its telling me im getting leaks, i may be mis-understanding some difference between C++ and OC.

The first leak is in the following small class:

@interface ZombiePhoneInputProcessor : NSObject {
@private
	ZombiePhoneWorld *p_World;
}

-(ZombiePhoneInputProcessor*) initWithWorldRef: (ZombiePhoneWorld*) world;
-(void) processInputPress: (CGPoint) pointPress;

@end

@implementation ZombiePhoneInputProcessor

-(ZombiePhoneInputProcessor*) initWithWorldRef: (ZombiePhoneWorld*) world {
	self = [super init];
	
    if ( self ) {		
        p_World = world;
    }
	
    return self;
}

@end

The leaks coming from this class but i dont see how. Im passing a pointer to an object and setting another object to point to this object.

Its called as follows:

// Initialise input processor
	m_pInput = [[ZombiePhoneInputProcessor alloc] initWithWorldRef: self];
	if( m_pInput == nil )
	{
		#ifdef DEBUG
		NSLog(@"Failed to initialise zombie input manager.\n");
		#endif
		
		return false;
	}

m_pInput is a pointer variable inside this class. Where am i going wrong?

[BigBearStudios]

Originally Posted by BigBearStudios

Hey, i switched from C++ to Object C a few weeks back. I ran the XCode memory leak tool and its telling me im getting leaks, i may be mis-understanding some difference between C++ and OC.

The first leak is in the following small class:

@interface ZombiePhoneInputProcessor : NSObject {
@private
	ZombiePhoneWorld *p_World;
}

-(ZombiePhoneInputProcessor*) initWithWorldRef: (ZombiePhoneWorld*) world;
-(void) processInputPress: (CGPoint) pointPress;

@end

@implementation ZombiePhoneInputProcessor

-(ZombiePhoneInputProcessor*) initWithWorldRef: (ZombiePhoneWorld*) world {
	self = [super init];
	
    if ( self ) {		
        p_World = world;
    }
	
    return self;
}

@end

The leaks coming from this class but i dont see how. Im passing a pointer to an object and setting another object to point to this object.

Its called as follows:

// Initialise input processor
	m_pInput = [[ZombiePhoneInputProcessor alloc] initWithWorldRef: self];
	if( m_pInput == nil )
	{
		#ifdef DEBUG
		NSLog(@"Failed to initialise zombie input manager.\n");
		#endif
		
		return false;
	}

m_pInput is a pointer variable inside this class. Where am i going wrong?

Does the leak detetctor work properly? Its telling me theres leaks even when i just initialise a MutableArray like so:

m_entityArray = [[NSMutableArray alloc] initWithCapacity: (int)(MAX_WEAK_ZOMBIES + MAX_CHUNK_ZOMBIES )];

Im not adding anything after that, just reserving space.

[Kalimba]

Originally Posted by BigBearStudios

Does the leak detetctor work properly? Its telling me theres leaks even when i just initialise a MutableArray like so:

m_entityArray = [[NSMutableArray alloc] initWithCapacity: (int)(MAX_WEAK_ZOMBIES + MAX_CHUNK_ZOMBIES )];

Im not adding anything after that, just reserving space.

What you're describing makes sense to me. Maybe you don't fully understand what Instruments is telling you when it "reports" a leak? It is essentially saying: "I've found a chunk of memory that you have allocated, but nothing in your code is referencing (pointing to) this chunk, and here's the line of code that allocated the chunk." When you alloc/init an NSMutableArray, even though the array itself is empty, there is space (memory) allocated for the array container itself. That's what is leaking in this case, according to Instruments.

I suspect your leaks are occurring when you reassign variables that are currently pointing at something else, without first properly cleaning up the existing value. That's a classic coding "leak", and not unique to Obj-C, illustrated by this simple C code:

    unsigned char * buffer;

    buffer = malloc( 1024 * 1024 ); // allocate a buffer

    // do something with buffer

    buffer = malloc( 5 * 1024 * 1024 ); // allocate another buffer
    // Oops, just reassigned buffer without first cleaning it up. That's a 1MB leak.