Question

OK, I’m hitting a wall here.

I don’t know why my Xcode 4.5.2 is saying I am using 4.16 GB of memory before crashing:

ExampleEngine(11672,0xac70f2c0) malloc: *** mmap(size=4160753664) failed (error code=12)
*** error: can't allocate region
*** set a breakpoint in malloc_error_break to debug

I ran my OpenGL ES application using Instruments – Leaks & Allocations. It shows that the total amount of allocation memory I used was 1.46 MB Live Bytes.

I am trying to follow an OpenGL ES tutorial by Ian Terrel:

http://games.ianterrell.com/how-to-draw-2d-shapes-with-glkit-part-2/

I am stuck of the last part the EERegularPolygon class (all the previous shapes like Triangle, Rectangle, Elipse worked fine). My code is like this (slightly different to his because I am using Xcode 4.5.2’s auto @synthesize):

// EERegularPolygon.h file
#import "EEShape.h"

@interface EERegularPolygon : EEShape

@property (readonly) int numSides;
@property (nonatomic) float radius;

-(id)initWithNumSides:(int)numSides;

@end


// EERegularPolygon.m file
#import "EERegularPolygon.h"

#define M_TAU (2 * M_PI)

@implementation EERegularPolygon

-(id)initWithNumSides:(int)numSides
{
    self = [super init];

    if(self)
    {
        _numSides = numSides;
    }

    return self;
}

-(void)updateVertices
{    
    for(int i = 0; i < self.numSides; i++)
    {
        float theta = ((float) i) / self.numSides * M_TAU;
        self.vertices[i] = GLKVector2Make(cos(theta) * self.radius, sin(theta) * self.radius);
    }
}

-(void)setRadius:(float)radius
{
    _radius = radius;

    [self updateVertices];
}

@end


// HexagonScene.h file
#import "EEScene.h"
#import "EERegularPolygon.h"

@interface HexagonScene : EEScene
{
    EERegularPolygon *polygon;
}

@end



// HexagonScene.m file
#import "HexagonScene.h"

@implementation HexagonScene

-(id)init
{
    self = [super init];

    if(self)
    {
        polygon = [[EERegularPolygon alloc] initWithNumSides:6];
        polygon.radius = 1;
    }

    return self;
}

-(void)render
{
    [super render];

    [polygon render];
}

@end



// AppDelegate DidFinishLaunchingWithOptions: method
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
    EAGLContext *context = [[EAGLContext alloc] initWithAPI:kEAGLRenderingAPIOpenGLES2];
    [EAGLContext setCurrentContext:context];

    GLKView *view = [[GLKView alloc] initWithFrame:[[UIScreen mainScreen] bounds] context:context];
    view.delegate = self;

    GLKViewController *controller = [[GLKViewController alloc] init];
    controller.delegate = self;
    controller.view = view;

    self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];
    self.window.rootViewController = controller;
    [self.window makeKeyAndVisible];

    scene = [[HexagonScene alloc] init];
    scene.left = -3;
    scene.right = 3;
    scene.bottom = -2;
    scene.top = 2;
    scene.clearColor = GLKVector4Make(0.25, 0.25, 0.25, 1.0);


    return YES;
}

Anyone got any ideas why Xcode is reporting 4.16 GB of memory was trying to be allocated ?

I tried manually writing the get and set method for the EERegularPolygon class too but that also didn’t work.

Answer 1

OK, I have magically stumbled upon the solution after trying to debug the problem.

First and foremost, the two changes:

1) I forgot to override the following method:

-(int)numVertices 
{ 
    return self.numSides 
}

2) The one single line that stopped the app from crashing and show the hexagon shape was this NSLog() line:

-(id)initWithNumSides:(int)numSides
{
    self = [super init];

    if(self)
    {
        _numSides = numSides;

        // ---------------------------------
        // IF THIS LINE IS COMMENTED OUT,
        // THE APP CRASHES, 
        //
        // BUT IF THE LINE IS NOT COMMENTED
        // THE APP WORKS, THE HEXAGON IS
        // RENDERED TO SCREEN AS DESIRED
        //
        // I WANT TO KNOW WHY :(
        // ---------------------------------
        NSLog(@"M_TAU = %lf", M_TAU);
    }

    return self;
}

There must be something I don’t understand about #define preprocessor directive not defined until it’s actually called in the above line of code.

Can any C or Objective C guru please explain ?

I’ll dig Google too to see if I can get an understanding why a #define fails to work until a NSLog is called in my above code.

Unless it’s a bug with the compiler or Xcode, otherwise it seems absurd.

EDIT

OK, further discovery, it’s not that the #define was broken and that I needed to call the M_TAU constant like so in the init:

NSLog(@"M_TAU = %lf", M_TAU);

It seems I need to have a line of NSLog inside my init function for some odd reason, anything.