Re: [boost] [Config] Support for switching between std:: andboost:: equivalents.

Subject: Re: [boost] [Config] Support for switching between std:: andboost:: equivalents.
From: Edward Diener (eldiener_at_[hidden])
Date: 2015-06-07 14:50:51

On 6/7/2015 1:29 PM, Peter Dimov wrote:
> John Maddock wrote:
>
>> Right.  But if lib X prefers/needs to use the Boost version always,
>> they don't have to use this mechanism.
>
> What I'm saying is more like lib X has a dual interface, but _the user_
> of lib X wants to use the boost:: version, whereas lib X detects C++11
> and provides the std:: version.
>
> Lib X is
>
> #if CXX11
>
> void libx_f( std::regex const & rx );
>
> #else
>
> void libx_f( boost::regex const & rx );
>
> #endif
>
> but the user wants to continue using boost::regex under C++11.
>
> This could in principle be addressed in some way by giving the user the
> option to override libX's decision to go with std::regex.

I have thought of letting the end-user override libX's decision. For a 
currently supported XXX library in my macro system I could allow a 
BOOST_CPP_XXX_USE_BOOST be defined by the user which would force the use 
of the Boost library even in C++11 mode. I have also contemplated a 
convenient BOOST_CPP_USE_BOOST macro being defined by the end-user which 
would force the use of a Boost library for any XXX library in C++11 
mode. Programming this idea into my macro system is trivial.

But suppose compiling in C++11 mode one TU has BOOST_CPP_XXX_USE_BOOST 
defined and another TU does not and both include some interface affected 
by this decision.

I think in this case KISS is better than the kiss of death <g>.