Precise GC state

[Ola Fosheim Grostad]

On Monday, 27 November 2017 at 06:47:00 UTC, Dmitry Olshansky 
wrote:
> Last time I check shared_ptr can be safely shared across 
> threads, hence RC is takling synchronization and most likely 
> atomics since locks won’t be any better.

The controlblock can, but it is crazy to use shared_ptr for 
anything more than high level ownership. It is a general solution 
with weak pointers and extra indirection, not a typical RC 
implementation for datastructures.

>> In C++ sync is manual, which is the only efficient way to do
>
> ??? shared_ptr is nowhere manual.

There is an upcoming atomic_shared_ptr, but it is not in the 
standard yet.

> My post is about particular primitive in C++ std, what could be 
> done instead or in addition to is not important.

Oh, but it is.

1. D currently does not provide what you says it does.

2. Sane C++ programmers rarely use shared_ptr for more than 
exchsnging ownership (suitable for sharing things like bitmap 
textures). There are plenty of other RC implementations for 
tracking memory. So you compare apples and oranges.