Re: [boost] [atomic] Bikeshedding over address-free waiting/notifying operation names

On 2020-06-02 17:28, Hans Dembinski via Boost wrote:

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On 2. Jun 2020, at 11:21, Alexander Grund via Boost wrote:

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boost::interprocess::atomic.

That name cannot be used in Boost.Atomic as it is reserved for Boost.Interprocess.

Atomics that are lock-free can already be used for inter-process communication, so a hypothetical boost::interprocess::atomic would largely duplicate boost::atomic. However, I'm open to the idea, if it is significantly different from boost::atomic.

The obvious solution then is to use boost::atomic::interprocess ;-)

... I was going to suggest the same :)

The problem with this is that the resulting name will be long and have the potential of name clash with Boost.Interprocess. Boost.Atomic types are currently defined in namespace boost::atomics and then imported into namespace boost (so that people can use boost::atomic<int> instead of boost::atomics::atomic<int>). Adding namespace boost::atomics::interprocess would make it impossible to import it into namespace boost as it would conflict with Boost.Interprocess. So people will have to spell boost::atomics::interprocess::atomic<int>, which is unfortunate. There is an alternative to name the type differently, e.g. boost::atomics::interprocess_atomic<int> or boost::atomics::pshared_atomic<int>, though I'm not sure I like it either. Or use a different name for the nested namespace instead of interprocess (ipc? other suggestions?).

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I do see value in having 2 different atomic types in different namespaces as the use case is different: The "regular" atomic usually works. Once you need interprocess communication you use another type, not another member function.

Agreed, having two different types has benefits: - you can prevent people to pass a boost::atomic where a boost::atomic::interprocess is needed (if that makes any sense..., do atomics ever appear in interfaces?) - you can make the intent clear in the implementation of a class or function

Yes, I can see the potential benefit of having a separate type for inter-process. That would allow writing generic algorithms over process-local and inter-process atomics. It's those naming details I'm not quite happy about. Also, and more importantly, given that atomics may potentially use runtime detection of availability of lock-free operations, it isn't clear what behavior should inter-process atomics have if the required operations turn out to be unavailable in run time. This is not a problem in the current implementation, as it always uses compile-time detection, but I wouldn't want to prohibit runtime detection in the future.