CODEWITHSUNDEEP
iosobjective-cexc-bad-access
Lneuner
Lneuner

Reputation: 1100

How to reproduce EXC_BAD_ACCESS in generic case

I've been playing around in Objective-C and was trying to purposefully get a EXC_BAD_ACCESS crash. What are some sure ways to achieve this?

I read that Whenever you encounter EXC_BAD_ACCESS, it means that you are sending a message to an object that has already been released. What is meant by the phrase "sending a message to an object"?

Something that I tried to achieve the crash but did not succeed:

 __weak NSMutableArray *array;
    NSLog(@"%@", array)
    [array insertObject:@2 atIndex:0];
    NSLog(@"%@", array.firstObject)

Upvotes: 1

Views: 186

Answers (1)

vadian
vadian

Reputation: 285072

You are sending insert:atIndex: to array.

The code does not crash because in Objective-C it's allowed to send a message to nil.

array is nil because it's declared but not initialized (yet).

You can reproduce a crash by declaring an object property with assign attibute

@property (assign) NSMutableArray *array;

Then create a method

- (void)insertSomething {
    self.array = [NSMutableArray array];
    [self.array insertObject:@2 atIndex:0];
}

and call it

[self insertSomething];
NSLog(@"%@", self.array.firstObject);

Due to the assign attribute array is a weak reference and gets released right after leaving the insertSomething method.

Upvotes: 1

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