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cgdbclangc-preprocessor

Can C macros be expanded in gdb when the program was compiled using clang?

I have a macro that fetch's the J-th bit of an integer: 

#define TWO_TO_THE(POWER) (1 << POWER)

#define JTH_BIT(BITS, J)  ((TWO_TO_THE((J-1)) & BITS) != 0)

However, I can't use it from gdb by issuing the command print JTH_BIT(i,j), can macros in C even be used while debugging?

Solution

  • Macros are handled by the pre-processor. The compiler doesn't even know about them.

    However, if lucky, GCC's option -g3 would do the job and generate code allowing gdb to expand a macro.

    From the gdb documentation (emphasis by me):

    -glevel

    [...] Level 3 includes extra information, such as all the macro definitions present in the program. Some debuggers support macro expansion when you use -g3.