CXXSTD=c++11

[Bryan Drewery]

On 3/24/2016 3:39 PM, Warner Losh wrote:
> 
>> On Mar 24, 2016, at 4:36 PM, Bryan Drewery <bdrewery at freebsd.org> wrote:
>>
>> Is there any problem with forcing -std=c++11 for all CXX/LIB_CXX builds
>> now?  We do this when using an external GCC since it doesn't default to
>> the c++11 standard quite yet.  As far as I understand, we require c++11
>> to build clang/libc++.
>>
>> It seems to be the problem at
>> https://lists.freebsd.org/pipermail/freebsd-toolchain/2015-October/001757.html
>> which I've fixed in an upcoming commit to properly pass -std=c++11 to
>> the lib32 build in CXXFLAGS.
> 
> Wouldn’t that break the spark and mips builds if we did it always? They are the
> last stragglers to not have a working, fully vetted clang in the tree.
> 

When building with external GCC we're forcing it to use libc++ which
uses static_assert which doesn't work without -std=c++11.  The external
GCC support now always forces -std=gnu++11 but I was testing with
removing it.

libatf blows up:

> In file included from /usr/obj/powerpc.powerpc64/root/git/freebsd/tmp/usr/include/c++/v1/ostream:137:0,
>                  from /root/git/freebsd/contrib/atf/atf-c++/detail/application.hpp:29,
>                  from /root/git/freebsd/contrib/atf/atf-c++/detail/application.cpp:26:
> /usr/obj/powerpc.powerpc64/root/git/freebsd/tmp/usr/include/c++/v1/memory: In member function 'void std::__1::default_delete<_Tp>::operator()(_Tp*) const':
> /usr/obj/powerpc.powerpc64/root/git/freebsd/tmp/usr/include/c++/v1/memory:2514:13: error: typedef '__t2514' locally defined but not used [-Werror=unused-local-typedefs]
>              static_assert(sizeof(_Tp) > 0, "default_delete can not delete incomplete type");

I stopped testing at this point.

We've fixed it by always passing -std=gnu++11 to the entire build but
then that ends up hiding other issues like that Static_assert in
libcxxrt being misused.

Not passing -std=c++11 to the lib32 build just happens to work because
we don't normally build c++ libraries in it that don't otherwise force
-std=c++11 (such as libc++ does now).

-- 
Regards,
Bryan Drewery

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