The Annoying C-Preprocessor Macros

• By default, gdb is not aware of C pre-processor macros, which is very annoying.
• To solve this on Linux, compile the code like this:

  gcc -gdwarf-2 -g3 prog.c -o prog

• Inside gdb:

  Breakpoint 1, main () at c_preprocessor_macros.c:14
  14		int state = STATE_BAD;
  (gdb) p STATE_BAD
  $1 = 1
  (gdb) info macro STATE_BAD
  Defined at /home/choo/work/lin-club/gdb_-_customize_it/gdb_source_examples/c_preprocessor_macros.c:4
  #define STATE_BAD 1
       

  Breakpoint 2, main () at c_preprocessor_macros.c:19
  19		int person2_qualities = FLAG_SMART | FLAG_TALL | FLAG_HEAVY;
  (gdb) macro expand  FLAG_SMART | FLAG_TALL | FLAG_HEAVY
  expands to: 2 | 4 | 8
       

Originally written by guy keren