Relevance of platfrom-specific shared_ptr implementations

From: Peter Dimov (pdimov_at_[hidden])
Date: 2020-05-31 15:18:02

Greetings,

shared_ptr has a number of platform-specific implementations for its control 
block, specifically the atomic reference count manipulation:

https://github.com/boostorg/smart_ptr/blob/develop/include/boost/smart_ptr/detail/sp_counted_base.hpp

Those have been accumulated over the years and I'd like to clean them up, 
remove the unused ones and fold as many of them as possible into a few 
generic implementations using either std::atomic, GCC atomic intrinsics 
(https://gcc.gnu.org/onlinedocs/gcc-10.1.0/gcc/_005f_005fatomic-Builtins.html) 
or GCC/intel sync intrinsics 
(https://gcc.gnu.org/onlinedocs/gcc-10.1.0/gcc/_005f_005fsync-Builtins.html).

But I have no experience with non-x86 platforms and don't know where 
boost::shared_ptr is still used and which of the platform-specific 
implementations are still needed. (Neither do I know on which platforms the 
atomic and the sync intrinsics actually work, as opposed to just compile and 
then fail to link.)

Any information along these lines is welcome. If you know of a platform 
where boost::shared_ptr is still used, but which supports none of the 
"modern" ways to implement atomic ops, please let me know. If you would like 
some of the plaform-specific files to be retained, please let me know. 
Thanks in advance.