Re: [boost] Curiousity question

Subject: Re: [boost] Curiousity question
From: Sylvester-Bradley, Gareth (Gareth.Sylvester-Bradley_at_[hidden])
Date: 2016-10-13 11:17:33

On 13 October 2016 15:33, Edward Diener wrote:
> I understand that and I think that is the general consensus. But what might happen,
> not that it seems to bother anyone much but me <g>, is that your library, which supports
> C++03, is nevertheless "compiled" by some programmer(s) using C++11 in their own
> project. Then their normal use of std::shared_ptr ( because it's there and naturally
> supported by their compiler implementation in C++11 mode ) doesn't really "play well"
> with your own use of boost::shared_ptr. Of course you may well say "what's the big deal,
> when you interface with my library you will use boost::shared_ptr and have a
> dependency on it, while otherwise you have chosen to use std::shared_ptr and have a
> dependency on your compiler's implementation. I see no problem with that." And
> technically you would be right, but practically the user of your library might feel differently about it.

I think you've summarised nicely how I feel about it - our need to support C++03 users while not making C++11 users uncomfortable.

We do it using-declarations in namespace bst (I pronounce it 'best'!), in headers called "bst/xxx.hpp", which default to symbols from std, but can be instructed to use Boost. No auto-detection.
There's the ABI issue that Gavin Lambert mentioned earlier. Otherwise seems to work well for us.
Sometimes (like bst::placeholders), there's a tiny bit of extra work to put the Boost names in the right places, but not often.
We also sometimes switch a bunch of symbols together where that makes sense (e.g. having consistent std or boost function/thread/chrono).
I agree with Peter Dimov that "bst" or "cxx_dual" would seem to live best outside of the main Boost distrib though.

#ifndef BST_XXX_HPP
#define BST_XXX_HPP
#ifndef BST_XXX_BOOST
#include <xxx>
namespace bst
{
    using std::xxx1;
    using std::xxx2;
}
#else
namespace bst
#include <boost/xxx/xxx1.hpp>
#include <boost/xxx/xxx2.hpp>
namespace bst
{
    using boost::xxx1;
    using boost::xxx2;
}
#endif
#endif

Cheers,
Gareth