Question

I am using a variation of GCC that is specific to ARM microprocessors, and I am trying to figure out what this macro is doing in stdint.h.

   #if defined(__GNUC__) && \
    ( (__GNUC__ >= 4) || \
    ( (__GNUC__ >= 3) && defined(__GNUC_MINOR__) && (__GNUC_MINOR__ > 2) ) )
    /* gcc > 3.2 implicitly defines the values we are interested */ 
    #define __STDINT_EXP(x) __##x##__
    #else
    #define __STDINT_EXP(x) x
    #include <limits.h>
    #endif

__GNUC__ is an implementation specific macro, but how would you find out what the compiler is using for this? Printf() wouldn’t work for this compiler because it’s output is for an embedded system.

Answer 1

gcc’s option -dM spits you all macros that are defined internally. Something like

gcc -xc -dM -E /dev/null | sort | less

should do the trick.