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

[Alan Skipp]

Hi Laurent,
The work around you suggested works.
Also, after a clean build the automatic loading of framework and bridgeSupport file worked as well.
Thanks very much,

Alan


On 22 Nov 2010, at 02:55, Laurent Sansonetti wrote:

> Hi Alan,
> 
> Thanks for reporting that problem in the tracker. In the meantime, keeping a reference to the Proc object in the Ruby side might work around the problem (as I suspect that the proc here is being garbage-collected prematurely).
> 
> 	@b = TestBlock.alloc.initWithBlock (@tmp ||= Proc.new { puts "hello from ruby"})
> 
> Laurent
> 
> On Nov 19, 2010, at 3:25 AM, Alan Skipp wrote:
> 
>> 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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>>> 
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>> 
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