[cfe-dev] How to test for std::move (intersection of Apple and Clang)

[Richard Smith]

On Jul 31, 2015 4:12 PM, "Jeffrey Walton" <noloader at gmail.com> wrote:
>
> I have the following code:
>
> // R-values: MS at VS2010 (16.00); GCC at 4.3; Clang at 2.9; and Intel
11.1.
> //   The extra tests on GCC are because Clang and ICC claims to be GCC 4.
> #if (_MSC_VER >= 1600)
> # define MY_CXX11_RVALUES 1
> #elif defined(__clang__)
> # if __has_feature(cxx_rvalue_references)
> #  define MY_CXX11_RVALUES 1
> # endif
> #elif (__INTEL_COMPILER >= 1110)
> # define MY_CXX11_RVALUES 1
> #elif (__GNUC__ >= 5 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 3))
> # define MY_CXX11_RVALUES 1
> #endif // R-value compilers
>
> Then guard the rvalue gear in the declaration and implementation:
>
> if MY_CXX11_RVALUES
> MyClass::MyClass(MyClass&& t)
>     : m_alloc(std::move(t.m_alloc)), m_size(t.m_size),
m_ptr(std::move(t.m_ptr))
>     {
>         t.m_alloc = A();
>         t.m_alloc = nullptr;
>         t.m_size = 0;
>     }
> }
> #endif
>
> Results in:
>
>     ./myclass.h:276:18: error: no member named 'move' in namespace 'std'
>                 : m_alloc(std::move(t.m_alloc)), m_size(t.m_size),
m_ptr...
>                           ~~~~~^
>     ./myclass.h:276:65: error: no member named 'move' in namespace 'std'
>       ...: m_alloc(std::move(t.m_alloc)), m_size(t.m_size),
> m_ptr(std::move(t.m_p...
>
> And the compiler:
>
>     $ c++ -v
>     Apple LLVM version 5.1 (clang-503.0.40) (based on LLVM 3.4svn)
>     Target: x86_64-apple-darwin12.6.0
>     Thread model: posix
>
> What is the proper way to guard to rvalues and std::move when using
> Clang on Apple?

You need to test the version of the standard library, not of the compiler,
to detect std::move. Or you could implement your own move function; it's
pretty trivial.
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