[MacRuby-devel] copied Proc objects cause crash when used as Objective-C blocks

[Alan Skipp]

Whoops, sorry about that. I find that I can get away without assigning to self in 'init' when doing a quick hack, but certainly not the recommended approach, especially when attempting to track down another bug.
I've amended the initializer now and I still encounter the same problem.

Al

On 19 Nov 2010, at 10:53, Thibault Martin-Lagardette wrote:

> Hi Alan,
> 
> I didn't look in further details yet, but clearly your initWithBlock method is wrong, it should be:
> 
> - (id)initWithBlock:(void (^)())aBlock;
> {
> 	if ((self = [super init])) {
> 		block = [aBlock copy];
> 		NSLog(@"Block: %@", block);
> 		block();
> 	}
> 	return self;
> }
> 
> You are not assigning `self` to be equal to what `[super init]` returns, and this is, even without macruby or blocks, prone to crashes :-)
> 
> Can you try to fix this and then tell us if it's still crashing?
> 
> -- 
> Thibault Martin-Lagardette
> 
> 
> 
> On Nov 19, 2010, at 10:14, Alan Skipp wrote:
> 
>> I've been attempting to get an objective-c framework to work with macruby and I believe I've found a bug in the way ruby Proc objects are copied when used as objective-c blocks.
>> The copied block doesn't seem to persist correctly beyond the scope in which it was copied. It isn't deallocated, but calling it results in a crash. Typical error messages are:
>>  wrong type NSCFSet (expected Proc) (TypeError)
>>  wrong type NSRectSet (expected Proc) (TypeError)
>> I'm guessing that there's a pointer to the wrong memory location?
>> 
>> Here's the Objective-C implementation:
>> 
>> @implementation TestBlock
>> 
>> - (id)initWithBlock:(void (^)())aBlock;
>> {
>> 	[super init];
>> 	block = [aBlock copy];
>> 	NSLog(@"Block: %@", block);
>> 	block();
>> 	return self;
>> }
>> 
>> - (void)callBlock;
>> {
>> 	NSLog(@"block: %@", block);
>> 	block();
>> }
>> 
>> @end
>> 
>> 
>> Within 'initWithBlock:', the copied block can be invoked without error. Attempting to do so from 'callBlock', results in a crash. The test framework can be used without error when using objective-c.
>> 
>> Here's the ruby controller code:
>> 
>> @b = TestBlock.alloc.initWithBlock Proc.new { puts "hello from ruby"} 
>> 
>> # this next line is called from a different scope and causes the crash
>> @b.callBlock
>> 
>> 
>> 2010-11-19 08:41:06.620 CallObjectiveCBlocks[7046:a0f] Block: <__NSAutoBlock__: 0x200be74a0>
>> hello from ruby
>> 
>> 2010-11-19 08:41:20.011 CallObjectiveCBlocks[7046:a0f] block: <__NSAutoBlock__: 0x200be74a0>
>> 2010-11-19 08:41:20.012 CallObjectiveCBlocks[7046:a0f] /Users/alan/Documents/programming/macruby/CallObjectiveCBlocks/build/Debug/CallObjectiveCBlocks.app/Contents/Resources/Controller.rb:21:in `call:': wrong type Array (expected Proc) (TypeError)
>> 	from /Users/alan/Documents/programming/macruby/CallObjectiveCBlocks/build/Debug/CallObjectiveCBlocks.app/Contents/Resources/rb_main.rb:23:in `<main>'
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