Re: [Boost-users] Signals2 benchmark

Subject: Re: [Boost-users] Signals2 benchmark
From: Gavin Lambert (gavinl_at_[hidden])
Date: 2015-02-22 18:48:31

On 11/02/2015 11:22, Gottlob Frege wrote:
> It sounds like Nigel has convinced Nevin that for a hypothetical
> thread-safe + non-thread-safe "Signals3", we could/would do it the
> right way.

FWIW, existing Signals2 already does it the "right way", if I'm 
following the conversation properly.

By default Signals2 gives you thread-safe signals, but if you want 
non-thread-safe signals you merely need to supply a dummy mutex template 
parameter.  Thus both implementations can co-exist without any ODR 
violations or magic #defines.  (And you can use some alternate mutex 
type if you wish, which I have found useful on occasion.)

It's possible that this limits some further performance optimisations 
that could be done if you know that the mutex is a no-op -- but if 
someone cared to make those optimisations it could be done easily enough 
as a template specialisation without affecting anything else.

(Having said that, it could be an interesting exercise to make a 
Signals3 that uses non-blocking atomic operations instead of mutexes 
where feasible.  I'm not sure how much benefit there would be in 
real-world software though.)