6. Representation of #define and #undef

This section describes the stabs support for macro define and undefine information, supported on some systems. (e.g., with `-g3' `-gstabs' when using GCC).

A #define macro-name macro-body is represented with an N_MAC_DEFINE stab with a string field of macro-name macro-body.

An #undef macro-name is represented with an N_MAC_UNDEF stabs with a string field of simply macro-name.

For both N_MAC_DEFINE and N_MAC_UNDEF, the desc field is the line number within the file where the corresponding #define or #undef occurred.

For example, the following C code:

#define NONE 42 #define TWO(a, b) (a + (a) + 2 * b) #define ONE(c) (c + 19) main(int argc, char *argv[]) { func(NONE, TWO(10, 11)); func(NONE, ONE(23)); #undef ONE #define ONE(c) (c + 23) func(NONE, ONE(-23)); return (0); } int global; func(int arg1, int arg2) { global = arg1 + arg2; }

produces the following stabs (as well as many others):

.stabs "NONE 42",54,0,1,0 .stabs "TWO(a,b) (a + (a) + 2 * b)",54,0,2,0 .stabs "ONE(c) (c + 19)",54,0,3,0 .stabs "ONE",58,0,10,0 .stabs "ONE(c) (c + 23)",54,0,11,0

NOTE: In the above example, 54 is N_MAC_DEFINE and 58 is N_MAC_UNDEF.