title: Automatically register new derived class / creator method
body: <p>I guess it'll be easiest if I give an example of what I'm trying to achieve.</p>
  
  <p>Let's say I'd like to implement a unit testing environment, in which implementing a new unit test would involve deriving from a given base class and (possibly) following guidlines involving putting additional macros. Such new test would then be automatically added to list of tests, ran one after another at some point. Two things however:</p>
  
  <ol>
  <li><p>I'm trying to make creating each new test as quick and easy as possible, especially when it comes to modifying files other than the files with the test itself. A perfect situation would be such, that implementing a new test wouldn't require touching any other files in the project. This is achievable with singletons and possibly CRTP, but now comes point number 2,</p></li>
  <li><p>The target is an MCU with limited amount of RAM (ROM in general is not a problem) and I'd like to be able to run the tests directly on the target platform. Because of this, static objects occupying memory throughout the entire application lifetime are not acceptable. Instead, I'd like to be able to create and delete each test separately only at the time it needs to be ran.</p></li>
  </ol>
  
  <p>Basically, the problem comes down to a way of automatically registering derived types - or creator methods - to a factory with minimum RAM overhead (I'm assuming there will be some, i.e. at least pointers to said methods).</p>
  
  <p>Sorry for no code samples, but there's really nothing to show here without already committing to one given implementation.</p>