Build C++ based packages using C++11

Michael Gmelin freebsd at grem.de
Tue Oct 29 12:34:26 UTC 2013


On Tue, 29 Oct 2013 00:16:17 +0100
Dimitry Andric <dim at FreeBSD.org> wrote:

> On 28 Oct 2013, at 19:57, Michael Gmelin <freebsd at grem.de> wrote:
> > Now that most ports build ok with clang, are there any steps planned
> > towards supporting C++11 and libc++ in the ports tree? I'm thinking
> > of flags like NEEDS_CPP98, NEEDS_CPP11 etc. With C++14 at the
> > horizon I expect more problems with ports depending on C++11 and
> > even though mixing standard libraries and language revisions might
> > build in many cases, it can lead to terrible problems at run time.
> 
> Aren't the Mozilla ports already doing something like this now?  (See
> https://developer.mozilla.org/en-US/docs/Using_CXX_in_Mozilla_code for
> their specific needs.)
> 
> -Dimitry
> 

I was thinking more of building the entire stack using C++11 (libc++
requires it anyway). To give you an example I know personally, the port
devel/ice provides a bigger feature set if C++11 is available. If it's
used, it's advised to also build dependencies (e.g. databases/db5)
using C++11 as well, to make sure symbols and exception handling works
properly.

So if developing a software that uses Ice and C++11 features, which in
turn requires to build all C++ port dependencies (including Ice and
others commonly used like boost-libs) using C++11, it really trickles
down to be able to build all ports using the current version of the
standard. This is a lot of work (many ports have minor issues that can
be corrected easily, some are more complicated).

The way I would approach this is to set up poudriere to build the
entire tree using clang++ -std=c++11 -stdlib=libc++ and then start
dealing with the fallout, fixing smaller problems immediately (or make
the maintainers fix them) and mark ports that are to hard to fix as
"NEEDS_CPP98" or something like this.

Comments?

-- 
Michael Gmelin


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