Programming :: Tell Makefile Not To Compile Debug Code?

I've been trying to work out a way to stop chunks of code being compiled using a variable in my makefile but can't work it out. What I mean is for example in my code I might have.

/****output comms portdata********/
printf("
debug comms port %d",ReadPort("ttys1);

I only wish this code to be compiled when I'm debugging. What I've tried is using #ifdef with

#ifdef COMM_PORT_DEBUG
printf("
debug comms port %d",ReadPort("ttys1);
#endif

Then in my make file I set COMM_PORT_DEBUG to 1 so

DEBUG_DEFS = COMM_PORT_DEBUG=1

I then thought I could put it into my in my link line

all: $(CC) $(CPFLAGS) $(DEBUG_DEFS) $(INC_PATHS) $(SOURCE) -o $(PROGRAM) $(LIB_DIRS) $(GAME_LIBS)

but this gives a

gcc: COMM_PORT_DEBUG=1: No such file or directory

is there a way to do this sort of thing? Or am I barking up the wrong tree?