3.7.2. Common Predefined Macros

3.7.2 Common Predefined Macros

The common predefined macros are GNU C extensions. They are available with the same meanings regardless of the machine or operating system on which you are using GNU C or GNU Fortran. Their names all start with double underscores.

__COUNTER__
This macro expands to sequential integral values starting from 0. In conjunction with the ## operator, this provides a convenient means to generate unique identifiers. Care must be taken to ensure that __COUNTER__ is not expanded prior to inclusion of precompiled headers which use it. Otherwise, the precompiled headers will not be used.
__GFORTRAN__
The GNU Fortran compiler defines this.
__GNUC__
__GNUC_MINOR__
__GNUC_PATCHLEVEL__
These macros are defined by all GNU compilers that use th