GC for noobs

[Szymon Gatner]

On Thursday, 27 February 2014 at 11:13:17 UTC, bearophile wrote:
> Szymon Gatner:
>
>>I just want them to do their cleanup first as they should.
>
> Why? Perhaps if you explain what's behind your needs better, 
> people can help better.
>
> Bye,
> bearophile

In my specific example I am creating OpenGL Renderer. Renderer 
class instance holds GLContext instance. After context creation 
GL objects are created like textures and vertex buffers. Those 
are Texture and VertexBuffer class instances too. It is critical 
that those child resources are freed before GL context is 
destroyed. Thing is, even tho Renderer keeps list of Textures , 
VertexBuffers and  Context object, order of their destruction is 
completely undefined making Context d-tor called first and then 
child resources d-tors which ends in catastrophe.

In C++ (which has a LOT of problems) this is a no-brainer. Order 
of d-tors is fully defined. Sub-objects are destroyed before 
parent d-tor is called so only thing to worry about is the order 
of definition of members.

This is just an example but I would think that it is something 
rather important to have... What about child objects 
un-registering themselves in d-tors from a list that parent 
object holds and parent is destroyed first? What about 
asynchronous completion handler object that should notify some 
other object that it finished/not finished a job but a notifee is 
already destroyed because application is being shut-down? I 
honestly can't imagine how to reason about object graph lifetimes 
in GC world and I am sure I am missing something very basic. 
Probably a very different mindset.