Availability of C++11 features

Question

Compiler vendors have been adopting C++11 features piecemeal, which was predictable, as many of them are not easily implemented.

The standard way for reporting which spec the compiler fully supports is via the __cplusplus predefined macro. However, major vendors are reporting __cplusplus = 199711L, meaning they are only fully supporting C++98 (eg. MSVC14). This (presumably) means that they do not fully support the C++11 spec, even though they may have implemented a lion's share of the functionality.

I would like to start using C++11 features, when they are available (and fallback to existing code when they are not). However, my code must support many compilers, including proprietary compilers which I may not have access to use. Is there any standard way to know which C++11 features are available from a compiler, without knowing specifically which compiler is being used? (if a compiler behaves in a non-standard way, then it is acceptable for the detection behavior to be incorrect).

NOTE: This question is a generalization of my question 'Availability of static_assert c++11', which was not very well received, because I think my motivation was misunderstood.

Answer 1

You might be interested in feature test macros, which enable you to test for specific C++11, C++14 or even C++17 features, such as __cpp_static_assert, __cpp_lib_make_unique or __cpp_variable_templates. Clang and GCC already support this, see a live demo.

Answer 2

g++/clang++ do not have C++11 enabled by default, not even the latest versions. Whenever you compile with g++ using -std=c++11, your macro __cplusplus will have the expected value.

VS seem to have all features enabled by default, thanks @Comic, but it is not updating the macro since it is not yet fully C++11 compliant.

As far as detecting "C++11 availability" for a generic compiler, I am not aware of any portable way of doing it, unless you check for the __cplusplus macro. But, as you observed, the macro may not be implemented for some compilers by default (as is the case for g++/clang++), or not implemented at all (VS). Your only choice at this stage seem to be an external tool like CMake, which can detect the compiler, and conditional on the compiler type CMake can then define some macro which you can check in your code to enable C++11.