Re: [boost] [thread] semaphore

Subject: Re: [boost] [thread] semaphore
From: Niall Douglas (s_sourceforge_at_[hidden])
Date: 2013-09-19 11:54:16

On 18 Sep 2013 at 12:33, Tim Blechmann wrote:

> condition_variables have their use, but stating that other
> synchronization primitives are more error-prone to use is just wrong!

A CAS lock + CV is very straightforward.

> semaphores and win32-style events do have a well-defined semantics,
> which is more suited in many use cases. of course, they can be emulated
> with cvs, if you don't care about performance

I have a soft spot for win32-style events because I think they fill a 
certain useful niche where rolling your own implementation is hard to 
get race condition free and performant under contention. I tried 
persuading WG14 to adopt one for C11, but they felt it needed to go 
through the AWG and POSIX, and libc maintainers weren't interested so 
I got nowhere.

A C++11 future is effectively a one shot win32 pulse event object 
however, while a C++11 shared_future is effectively a one shot win32 
event object. I have been known to use them with <int> and me writing 
1 to the promise as a quick and dirty event object ...

Niall

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