Re: [boost] Boost.Threads, N2178, N2184, et al

From: Peter Dimov (pdimov_at_[hidden])
Date: 2007-03-22 08:31:26

Anthony Williams wrote:

> OK. But that doesn't really address my initial point: implementing
> call_once in terms of the POSIX pthread_once is a bit pointless if
> you need to implement pthread_once separately anyway. If you don't
> have pthread_once, I would write call_once (or, equivalently
> pthread_once2_np), and implement pthread_once in terms of that.

This is tied to another issue, whether the implementation should be 
header-only. If one is committed to produce a header-only implementation, it 
makes sense to reuse your current call_once in the implementation of 
pthread_once (and possibly pthread_once2_np).

The N2178 pthread.h aims to support the scenario where one is to deliver a 
separately compiled pthread-win32.lib/dll (as part of the Platform SDK, say 
;-) ). This is why I've tried to make sure that the C++ templated layer is 
implementable without loss of performance or generality in terms of a 
non-templated API (which happens to be a slightly extended pthreads layer). 
With careful definitions of the pthread_* types, it's possible to achieve 
binary compatibility as well, that is, link the program against a newer 
version of pthread-win32.lib/dll and have it work without recompilation. 
This is not possible with header-only templates or inline functions, because 
they are burned into the application code at compile time.