title: NSThread leak with NSString
body: <p>I just struggling with memory leak introduced by <code>NSString</code> in <code>NSThread</code>. Please see below.</p>
  
  <pre><code>NSThread* myThread = [[NSThread alloc] initWithTarget:self selector:@selector(testSomething) object:nil];
  
  [myThread start];
  
  - (void)testSomething
  {
     while (1) {
          @autoreleasepool
          {
             NSString *str = [NSString stringWithFormat:@"%@", [NSDate date]];
             // NSLog(@"%@", str);
          }
          [NSThread sleepForTimeInterval:.1];
      }
  }
  </code></pre>
  
  <p>This leak provokes by <code>NSString *str</code> but how to fix it in ARC? </p>
  
  <p>I have no idea. I've checked with Profiler; but if I use <code>CFStringRef hello = CFSTR("Hello, world."); CFRelease(hello);</code> There are no leaks...</p>