GCCG with C++11

Martin Sebor msebor@redhat.com
Thu May 28 15:51:00 GMT 2015


On 05/28/2015 09:24 AM, Hotmail (ArbolOne) wrote:
> If I am not mistaken _MSC_VER >= 1600 is the version that started
> implementing C++11. So, I test for that version of the compiler in my
> code, i.e.
> #ifdef _MSC_VER >= 1600
>     ....
> #endif
> I would like to do the same for __GNUG__, but what version of g++
> started implementing C++11?

The standard specifies that implementations conforming to C++
11 must define the __cplusplus macro to 201103L, and recommends
that non-conforming compilers (presumably those that aim to be
C++11 conforming but whose support is incomplete) should use
a value with at most five decimal digits.

C++ 98 defines __cplusplus to 199711L, and C++ 14 to 201402L.

With that, the following should cover past and future cases:

   #if __cplusplus == 199711L
     // C++ 98 conforming implementation
   #elif __cplusplus == 201103L
     // C++ 11 conforming implementation
   #elif __cplusplus == 201402L
     // C++ 14 conforming implementation
   #elif __cplusplus > 201402L
     // future C++ implementation
   #elif 0 < __cplusplus && __cplusplus < 100000L
     // non-conforming C++ implementation
   #else
     // not C++ or a non-conforming C++ implementation
   #endif

Though it seems to me that the recommendation in the footnote
below quoted from 16.8 Predefined Macros, blurs the distinction
between incomplete C++ implementations targeting C++ 11 and 14
(and 17).

   157) It is intended that future versions of this standard
   will replace the value of this macro with a greater value.
   Non-conforming compilers should use a value with at most
   five decimal digits.

Martin



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