CODEWITHSUNDEEP
visual-c++
WolfgangS
WolfgangS

Reputation: 164

Which values can _MSVC_LANG have?

I am using Visual Studio 2015 Update 3 and my _MSVC_LANG is defined as 201402L, regardless of whether I supply /std:c++14 as compiler parameter or not.

Does _MSVC_LANG have other values in later or earlier versions of visual-c++?

Upvotes: 2

Views: 5756

Answers (2)

W1M0R
W1M0R

Reputation: 3626

Another resource lists the possible values for _MSVC_LANG as 201402L, 201703L, 202002L, or a higher unspecified value, depending on the /std switch being used during compilation:

_MSVC_LANG Defined as an integer literal that specifies the C++ language standard targeted by the compiler. It's set only in code compiled as C++. The macro is the integer literal value 201402L by default, or when the /std:c++14 compiler option is specified. The macro is set to 201703L if the /std:c++17 compiler option is specified. The macro is set to 202002L if the /std:c++20 compiler option is specified. It's set to a higher, unspecified value when the /std:c++latest option is specified. Otherwise, the macro is undefined. The _MSVC_LANG macro and /std (Specify language standard version) compiler options are available beginning in Visual Studio 2015 Update 3.

Upvotes: 1

Mark Ingram
Mark Ingram

Reputation: 73673

Prior to Visual Studio 2015, the _MSVC_LANG macro didn't exist (internally they relied on the __cplusplus macro containing the equivalent version number).

In Visual Studio's yvals.h header, you can see the logic for C++ version macros (this is from Visual Studio 2017 15.3.3):

 #ifndef _HAS_CXX17
  #if defined(_MSVC_LANG) && !(defined(__EDG__) && defined(__clang__))  // TRANSITION, VSO#273681
   #if _MSVC_LANG > 201402
    #define _HAS_CXX17  1
   #else /* _MSVC_LANG > 201402 */
    #define _HAS_CXX17  0
   #endif /* _MSVC_LANG > 201402 */
  #else /* _MSVC_LANG etc. */
   #if __cplusplus > 201402
    #define _HAS_CXX17  1
   #else /* __cplusplus > 201402 */
    #define _HAS_CXX17  0
   #endif /* __cplusplus > 201402 */
  #endif /* _MSVC_LANG etc. */
 #endif /* _HAS_CXX17 */

The preprocessor definitions _HAS_CXX17 & _HAS_CXX14 control the inclusion of STL features.

Upvotes: 7

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