cloned from:

• SR-3536 Memory leak with String.range(options: .regularExpression)

Issue Description:

NSCache's implementation on Linux only works when the keys are statically defined keys, such as globally defined static constants.

  open class NSCache ... {
    private var _entries = Dictionary<UnsafeRawPointer, NSCacheEntry<KeyType, ObjectType>>()
    open func object(forKey key: KeyType) -> ObjectType? {
        var object: ObjectType?
        
        let keyRef = unsafeBitCast(key, to: UnsafeRawPointer.self)
        
        _lock.lock()
        if let entry = _entries[keyRef] {
            object = entry.value
        }
        _lock.unlock()
        
        return object
    }
  }

As a result, when using dynamically created keys (such as the result of String interpolation) this implementation fails and results in excessive growth; in addition, it does not seem to respect the countLimit. So any Linux code using NSCache directly or indirectly with non-static keys will experience unconstrained memory growth as items are added.