Re: [boost] [thread] A simply static initializeable mutex

From: Anthony Williams (anthony_w.geo_at_[hidden])
Date: 2006-10-30 16:29:15

Roland Schwarz <roland.schwarz_at_[hidden]> writes:

> Anthony Williams wrote:
>> I posted some MSVC-specific code a short time ago that overcame these problems
>> (see the thread on once init stuff).
>
> I remember those. You said that the solution however is highly
> compiler/platform dependent, didn't you?

Yes. I wouldn't want to commit to it working with anything other than MSVC. Of
course, if someone can verify it with other compilers, that would be good.

> So if the mutex ctor cannot be hidden from the public user interface,
> how should we ever hope to be able to manage this in an compiler
> independent way? Any ideas?

We could have a separate static mutex, which was POD and relied on
zero-initialization, and a dynamic mutex, which wrapped the static mutex with
a constructor.

> In a private discussion we had, I got the impression, that you were
> interested in the idea of a POD mutex. Do you still think this is an
> idea we should pursue?

Yes.

I think it is worth pursuing any and all avenues of finding a mutex which can
safely be used with either static or dynamic storage duration.

In discussions on the C++ Standards committee reflector, it seemed that people
were leaning towards an "it just works" interface for std::mutex, which allows
it to be declared with any storage duration, without an explicit
initializer. This was predicated on the idea that the various library
implementers each knew platform- and compiler- specific ways of doing this, so
we should specify the most user-friendly interface.

Therefore, I think that boost should try and provide this interface as far as
we are able. POD mutexes is one way. Named mutexes is another.

Anthony
-- 
Anthony Williams
Software Developer
Just Software Solutions Ltd
http://www.justsoftwaresolutions.co.uk