libc++ differences between 9.2 and 10.0

[Michael Gmelin]

On Fri, 20 Sep 2013 15:01:58 +0930
Shane Ambler <FreeBSD at ShaneWare.Biz> wrote:

> I'm Starting to look at fixing my ports to build on 10.0 and there
> appears to be a difference between 9.2 and 10.0 when it comes to
> using libc++
> 
> The first port I am looking at is graphics/opencolorio. a patch was
> submitted (ports/182220) that works fine on 10.0 but it breaks 9.2
> build when using clang with -
> error: no type named 'shared_ptr' in namespace 'std'
> 
> The patch is simple, just adding -
> 
> #elif __cplusplus >= 199711
> #include <memory>
> #define OCIO_SHARED_PTR std::shared_ptr
> #define OCIO_DYNAMIC_POINTER_CAST std::dynamic_pointer_cast
> 
> As far as I can see both 10.0 and 9.2 use the same contrib/libc++
> contents but I don't see why 9.2 isn't finding std::shared_ptr
> 
> 
> The other thing is I don't think testing __cplusplus is the right way
> to go but don't see an alternative. __cplusplus is defined in clang
> irrespective of the library used so isn't really a reliable test.
> 
> Are there any defines to easily test for std::shared_ptr or is that a
> test I need to create for configure or cmake - has already been done?

Hi Shane,

I looks like you're using libstdc++ on 9.2 (the version that comes with
gcc 4.2). To build with libc++ you need to use

CXXFLAGS+= -std=c++11 -stdlib=libc++.

Checking for _cplusplus isn't enough, since this only checks for the
language standard, but not for standard c++ library used.

First you should check for a C++11 enabled compiled (you're checking
for C++98, which didn't standardize std::shared_ptr)

#elif __cplusplus >= 201103

Then you should also check which standard library is used (in the end
you can mix clang C++11 and an old C++ standard library):

#elif  _cplusplus >= 201103 && defined(_LIBCPP_VERSION)

This checks if libc++ is used.

Since all relevant version of libc++ support C++11 features like
shared_ptr this should be good enough.

If you want to stay compatible with newer versions of gcc and libstdc++
you'll have to figure out how to check for this as well (unfortunately
I can't tell the exact checks to use from the top of my head).

Cheers,
Michael

> 
> 
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-- 
Michael Gmelin