Re: libobjc2 objc_setassociatedobject issue

[David Chisnall]

Ah, sorry, I was reading your example the other way around.  This seems to be 
because [[NSString alloc] init] returns a singleton on GNUstep.  I don't think 
this is necessarily a bug, as there's nothing in the contract for NSString that 
says that it needs to return a new instance for different immutable strings.

In general, using associated objects on immutable objects is a bad idea, 
because it breaks the assumption that you can use equal instances 
interchangeably.  

David

On 13 Dec 2013, at 14:03, David Chisnall <address@hidden> wrote:

> I've now added a test for this to the libobjc2 test suite, but it passes and 
> so does not appear to be the cause.  Your issue appears to be the dictionary 
> being over-retained.  I will investigate further.
> 
> David
> 
> P.S. When sending test cases, it helps to send them in the format of a test 
> suite for the thing you are testing, or as stand-alone programs.  I'd have 
> got to this a lot sooner if I didn't have to hack on the test to make it 
> compile.
> 
> On 19 Nov 2013, at 01:33, Doug Warren <address@hidden> wrote:
> 
>> Hi Guys,
>> 
>> Was tracking a memory leak in an existing app and tracked it down to 
>> objc_setassociatedobject not working as expected from the code being 
>> developed for the Apple Runtime.  The docs around objc_setassociatedobject 
>> seem to imply it follows the Apple Runtime but this simple gtest will pass 
>> on Apple but fail on libobjc/GNUStep Base:
>> 
>> static BOOL deallocCalled = NO;
>> static const char* objc_setAssociatedObjectKey = 
>> "objc_setAssociatedObjectKey";
>> 
>> @interface NSMutableDictionary(setAssociatedObjectTest)
>> @end
>> 
>> @implementation NSMutableDictionary(setAssociatedObjectTest)
>> 
>> -(void) dealloc
>> {
>>    deallocCalled = YES;
>>    [super dealloc];
>> }
>> 
>> @end
>> 
>> TEST(objc_setAssociatedObject, AssociatedObjectsAreReleased)
>> {
>>    @autoreleasepool {
>>        NSObject* object = [[NSString alloc] init];
>> 
>>        NSMutableDictionary *info = [NSMutableDictionary 
>> dictionaryWithCapacity:1];
>>        objc_setAssociatedObject(object, &objc_setAssociatedObjectKey, info, 
>> OBJC_ASSOCIATION_RETAIN);
>> 
>>        [object release];
>>    }
>> 
>>    ASSERT_TRUE(deallocCalled);
>> }
>> 
>> Adding calls to GSDebugAllocationList before/after the autorelease pool:
>> 1    NSDataMalloc
>> 1    GSMutableDictionary
>> 
>> Shows that the dictionary leaks.
>> 
>> Any thoughts?
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> 
> 
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