Re: [boost] BOOST_NO_CXX11_ATOMIC?

Subject: Re: [boost] BOOST_NO_CXX11_ATOMIC?
From: John Maddock (john_at_[hidden])
Date: 2013-12-03 13:21:58

> Beman says that we often define a header macro which says that the header 
> doesn't exist when the header exists, but is incomplete. This is correct.
>
> You then - apparently - suggested that we do that (pretend that the header 
> doesn't exist), but in addition, supply other macros that signify that the 
> header exists and provides some feature. I disagree that we should do 
> that. (I say apparently because I wasn't sure that you did, hence my "if" 
> qualifier above.)
>
> I think that in such a situation we should provide the feature macros, 
> without a header macro. Any positive claim that a feature X exists and 
> works implies the existence of the header. The header macro is - in this 
> case - redundant.

Right, that's basically what we've always done:

BOOST_NO_HEADER : when not defined, header exists and mostly (usefully) 
works.
BOOST_NO_HEADER_FEATURE : when not defined then some "advanced" feature not 
covered by the above also works.

Of course deciding what you class as advanced vs usefully works is always 
troublesome.

John.