Associated objects bugs

[rfm]

I think there are two bugs in the associated objects implementation as follows:

1. it looks like retained/copied values are not released when the object they are associated with is deallocated, causing leaks.
2. it looks like the atomic policy is not fully implemented ... when getting an associated value it is not retained/autoreleased, so another thread can destroy it before the calling thread gets to retain it.

These issues are demonstrated in the gnustep-base tests (marked as hopeful) in Tests/base/Functions/runtime.m
These tests pass on OSX

[hmelder]

it looks like retained/copied values are not released when the object they are associated with is deallocated, causing leaks

#import <Foundation/Foundation.h>
#import <objc/runtime.h>

static void *AssociatedObjectKey = &AssociatedObjectKey;

void testAssociatedObjectMemoryLeak() {
    __weak id weakObject;

    @autoreleasepool {
		NSObject *testObj = [NSObject new];
        NSString *associatedValue = [NSString stringWithFormat:@"TestValue %p", AssociatedObjectKey]; // Force an allocated string

        objc_setAssociatedObject(testObj, AssociatedObjectKey, associatedValue, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
        weakObject = associatedValue;

        assert(weakObject != nil && "Associated object should be retained inside autoreleasepool");
    }

    // After the autoreleasepool block, testObj should be deallocated, and so should the associated object.
    assert(weakObject == nil && "Associated object should be released after the owner is deallocated");
}

int main() {
    testAssociatedObjectMemoryLeak();
    printf("Test passed: No memory leak detected.\n");
    return 0;
}

This passes on both macOS and Ubuntu 24.10 with libobjc2 master. It would be great to have a minimal test case to reproduce this.

[hmelder]

These issues are demonstrated in the gnustep-base tests (marked as hopeful) in Tests/base/Functions/runtime.m

Ah nvm

[hmelder]

All tests in runtime.m pass with this PR #331. Behaviour is now aligned with Apple's objc4.