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c++gcc

Detect gcc as opposed to msvc / clang with macro

I am working on a project that has been built with both gcc and msvc so far. We recently started building with clang as well.

There are some parts in the code, where platform-specific things are done:

#ifndef _WIN32
// ignore this in msvc
#endif

Since gcc has previously been the only non-windows build, this was equivalent to saying "do this only for gcc". But now it means "do this only for gcc and clang".

However there are still situations, where I would like to handle something specifically for gcc, and not for clang. Is there a simple and robust way to detect gcc, i.e.

#ifdef ???
// do this *only* for gcc
#endif
Solution 
  • __GNUC__
__GNUC_MINOR__
__GNUC_PATCHLEVEL__

    These macros are defined by all GNU compilers that use the C preprocessor: C, C++, Objective-C and Fortran. Their values are the major version, minor version, and patch level of the compiler, as integer constants. For example, GCC 3.2.1 will define __GNUC__ to 3, __GNUC_MINOR__ to 2, and __GNUC_PATCHLEVEL__ to 1. These macros are also defined if you invoke the preprocessor directly.

    Also:

    __GNUG__

    The GNU C++ compiler defines this. Testing it is equivalent to testing (__GNUC__ && __cplusplus).

    Source

    Apparently, clang uses them too. However it also defines:

    __clang__
__clang_major__
__clang_minor__
__clang_patchlevel__

    So you can do:

    #ifdef __GNUC__
    #ifndef __clang__
...

    Or even better (note the order):

    #if defined(__clang__)
....
#elif defined(__GNUC__) || defined(__GNUG__)
....
#elif defined(_MSC_VER)
....