Guide to predefined macros in C++ compilers (gcc, clang, msvc etc.)

https://blog.kowalczyk.info/article/j/guide-to-predefined-macros-in-c-compilers-gcc-clang-msvc-etc..html

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When writing portable C++ code you need to write conditional code that depends on compiler used or the OS for which the code is written.

Here’s a typical case:

#if defined (_MSC_VER)
// code specific to Visual Studio compiler
#endif      

To perform those checks you need to check pre-processor macros that various compilers set.

It can eihter be binary is defined vs. is not defined check (e.g. 

__APPLE__

) or checking a value of the macro (e.g. 

_MSC_VER

 defines version of Visual Studio compiler).

This document describes macros set by various compilers.

Other documentations:

• predefined macros in Visual Studio
• https://sourceforge.net/p/predef/wiki/Compilers/
• to list clang’s pre-defined macros: 

  clang -x c /dev/null -dM -E

• to list gcc’s pre-defined macros: 

  gcc -x c /dev/null -dM -E

   (not that on mac gcc is actually clang that ships with XCode)
• the 

  -x c /dev/null -dM -E

   also works for mingw (which is based on gcc)
• listing predefined macros for other compilers

Checking for OS (platform)

To check for which OS the code is compiled:

Linux and Linux-derived           __linux__
Android                           __ANDROID__ (implies __linux__)
Linux (non-Android)               __linux__ && !__ANDROID__
Darwin (Mac OS X and iOS)         __APPLE__
Akaros (http://akaros.org)        __ros__
Windows                           _WIN32
Windows 64 bit                    _WIN64 (implies _WIN32)
NaCL                              __native_client__
AsmJS                             __asmjs__
Fuschia                           __Fuchsia__      

Checking the compiler:

To check which compiler is used:

Visual Studio       _MSC_VER
gcc                 __GNUC__
clang               __clang__
emscripten          __EMSCRIPTEN__ (for asm.js and webassembly)
MinGW 32            __MINGW32__
MinGW-w64 32bit     __MINGW32__
MinGW-w64 64bit     __MINGW64__      

Checking compiler version

gcc

__GNUC__

 (e.g. 5) and 

__GNUC_MINOR__

 (e.g. 1).

To check that this is gcc compiler version 5.1 or greater:

#if defined(__GNUC__) && (__GNUC___ > 5 || (__GNUC__ == 5 && __GNUC_MINOR__ >= 1))
// this is gcc 5.1 or greater
#endif      

Notice the chack has to be: 

major > 5 || (major == 5 && minor >= 1)

. If you only do 

major == 5 && minor >= 1

, it won’t work for version 6.0.

clang

__clang_major__

, 

__clang_minor__

, 

__clang_patchlevel__

Visual Studio

_MSC_VER

 and 

_MSC_FULL_VER

:

VS                        _MSC_VER   _MSC_FULL_VER
1                         800
3                         900
4                         1000
4                         1020
5                         1100
6                         1200
6 SP6                     1200    12008804
7                         1300    13009466
7.1 (2003)                1310    13103077
8 (2005)                  1400    140050727
9 (2008)                  1500    150021022
9 SP1                     1500    150030729
10 (2010)                 1600    160030319
10 (2010) SP1             1600    160040219
11 (2012)                 1700    170050727
12 (2013)                 1800    180021005
14 (2015)                 1900    190023026
14 (2015 Update 1)        1900    190023506
14 (2015 Update 2)        1900    190023918
14 (2015 Update 3)        1900    190024210
15 (2017 Update 1 & 2)    1910    191025017
15 (2017 Update 3 & 4)    1911
15 (2017 Update 5)        1912      

More information:

• https://blogs.msdn.microsoft.com/vcblog/2016/10/05/visual-c-compiler-version/
• https://blogs.msdn.microsoft.com/vcblog/2017/11/15/side-by-side-minor-version-msvc-toolsets-in-visual-studio-2017/#comment-467525

MinGW

MinGW (aka MinGW32) and MinGW-w64 32bit: 

__MINGW32_MAJOR_VERSION

 and 

__MINGW32_MINOR_VERSION

MinGW-w64 64bit: 

__MINGW64_VERSION_MAJOR

 and 

__MINGW64_VERSION_MINOR

Checking processor architecture

gcc

The meaning of those should be self-evident:

• __i386__

• __x86_64__

• __arm__

  . If defined, you can further check:

  • __ARM_ARCH_5T__

  • __ARM_ARCH_7A__

• __powerpc64__

• __aarch64__

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Written on Nov 7 2017. Topics: programming, c++ .

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