[Mxflib-developers] Smart Pointers

[Matt B. <ma...@be...>]

Guys,

A couple of issues regarding smart pointers...

Firstly I have been considering ways to reduce the overhead when using 
smart pointers and it seems that a lot of cycles can be saved by using 
references to pointers in function calls. This will save incrementing and 
decrementing the count with each call - there is no risk of the object 
needing to be deleted as the calling function will always hold a pointer to 
it.  This should be especially useful for in-lines as they will optimize 
out nicely.  The only things that are not safe (as far as I can tell) are 
storing references to smart pointers and passing references between threads 
- so don't do either.  I will gradually move functions to use references to 
pointers rather than pointers - this will not affect any calling code.

Secondly I have established how to safely use "polymorphic" smart 
pointers.  This can be done providing the base class derives from 
RefCount<> and none of the derived classes do.  Then a smart pointer to a 
base class can safely point to a derived class and the correct virtual 
functions will be called as expected.  However... if you do this please 
remember to include a virtual destructor or things can fall apart (as in 
normal c++).

On a related issue I have also added "SmartPtr_Cast" which allows you to 
cast a smart pointer to a pointer of a different type. Unfortunately it has 
to be a bit awkward as MSVC 6 doesn't cope well with template functions. 
Also both classes must be derived (directly or indirectly) from RefCount<> 
to ensure that the reference counting works.

Matt


P.S. All this is going on in the Develop-EssenceRead branch which will 
become 0.5-Beta at some stage.