[cmake-developers] C++11 and target_compiler_feature proposal

[Stephen Kelly]

Brad King wrote:

> * Using try_compile to detect feature support may be unreliable in the
> case of partially implemented features.  It is better to test the current
> compiler version against that documented by the vendor to support given
> features. The test case added in the cxx11 topic already does this to
> determine expected results.

I think there is a remaining issue with features and buggy-ness.

The new VS release has broken variadic templates support:

 http://thread.gmane.org/gmane.comp.lib.boost.devel/244986/focus=245333

That was worked around with a patch to boost. How do we determine if a bug 
is severe enough that we should consider it not enabled for the compiler?

It also has broken initializer_lists, which leads to the same question:

 http://thread.gmane.org/gmane.comp.lib.boost.devel/245202/focus=245221

For 'broken' things like cxx_initializer_lists and cxx_variadic_templates, I 
recommend that we enable the feature if the compiler vendor says it is 
available. 

Downstreams can define 

* Foo_BROKEN_VARIADIC_OVERLOADS (VS 2013)
* Foo_BROKEN_INITIALIZER_LIST_OVERLOADS (VS 2013)

if they wish in a wrapper around our generated header. 

We can even list such brokenness in the CMAKE_CXX_KNOWN_FEATURES 
documentation entry for it.

Comments?

Thanks,

Steve.