Block runtime argument not retaining local variables (32-bit architecture only)

[novixon]

Hello, guys! I found a problem.

I want to make a factory method with Typhoon. My TyphoonAssembly is OK - I checked it. The problem is though that I get "exc_bad_access" crash when using the client's code below.

MyClass localVariable = [MyClass new];
[concreteAssembly factoryMethodWithBlockRuntimeArgument:^(id data, NSError *error) {
    if (localVariable) {
        //
    }
}];

I found that this crash happens when localVariable is released (e.g. in the end of the method). I thought that it has to be retained by the block. The crash will not appear if I make the localVariable static, for example.

If I don't use some kind of local variables inside block - my code works fine. Do you have any ideas on this problem?

Thanks!

[vasilenkoigor]

Hello @novixon! Can you give me some more details about your implementation a factory method with block?

[novixon]

Hi @spbvasilenko! Here it is. It not the exact production code, but it is pretty identical. As I said before there is no crash and the code works fine If I don't use localVariable inside a runtime-injected block.

typedef void(^ResultBlock)(id data, NSError *error);
- (void)configureWithResultBlock:(ResultBlock)resultBlock;

- (id)factoryMethodWithBlockRuntimeArgument:(ResultBlock)resultBlock {

    return [TyphoonDefinition withClass:[SomeClass class]
                          configuration:^(TyphoonDefinition *definition) {

                              [definition useInitializer:@selector(defaultInitializer)];

                              SEL configSel = @selector(configureWithResultBlock:);
                              [definition injectMethod:configSel
                                            parameters:^(TyphoonMethod *method) {

                                                [method injectParameterWith:resultBlock];
                                            }];
                          }];
}

[vasilenkoigor]

@novixon hmm..it is strange behaviour. I'm written test code like your example and make some few tests, this work fine with local variables. Local variable is retained into block scope.

[novixon]

@spbvasilenko Check it with iPhone 4/4s/5 simulator/device (32-bit architecture). We've found that problem is hidden there.

[vasilenkoigor]

@novixon Yep, Im reproduce this issue on 32-bit architecture. I have noticed interested behaviour...if result block is NSMallocBlock, code work fine without crashes. If block is NSStackBlock, we have a crash.

NSObject *object = [NSObject new];
 __weak typeof(object) weakObject = object;
void (^block)(id data, NSError *error) = ^(id data, NSError *error) {
      __weak typeof(object) strongObject = weakObject;
        if (strongObject) {
            NSLog(@"");
        }
};
[_assembly factoryMethodWithBlockRuntimeArgument:[block copy]];

NSLog(@"%@", object);

This slice example code work without crash.

[novixon]

@spbvasilenko Yep, I got the same result - no crash when defining the result block before passing it as a parameter.

[vasilenkoigor]

@novixon, I'm want to fix this issue and make the MR

[novixon]

@spbvasilenko It's great, thanks! I will research this a little bit on weekends if needed.

[alexgarbarev]

Reviewed. Looks cool! Thanks, guys!