How do I add a debug option to Makefile

Question

I've got the below simple Makefile which I use for compiling a C program:

all:
    gcc -Wall -o myfile myfile.c lol_dht22/dht22.c lol_dht22/locking.c -lwiringPi -lcurl -lm

I want to add in a debug option so I can compile with -DDEBUG, so if I run

make

it compiles as normal. and if I run

make debug

it compliles with the debug flag.

I have read through a few tutorial but seems to be getting more and more confused.

Answer 1

Here's an example makefile that has the two options you are looking for.

all:
    gcc -Wall -o myfile myfile.c lol_dht22/dht22.c lol_dht22/locking.c -lwiringPi -lcurl -lm
debug:
    gcc -DDEBUG -Wall -o myfile myfile.c lol_dht22/dht22.c lol_dht22/locking.c -lwiringPi -lcurl -lm

You just needed to add a debug option, which is done in similar fashion to the 'all' option you had already declared.

Answer 2

If you want to know how to do it well, here it is. You don't do make debug, instead, you should call

>make

or

>make DEFS=DEBUG

or

>make DEFS='ANY DEFINES YOU WANT'

In addition to normal Make rebuild criteria, the following Makefile recognizes rebuilds based on DEFS.

define DEPENDABLE_VAR

.PHONY: phony
$1: phony
    @if [[ `cat $1 2>&1` != '$($1)' ]]; then \
        echo -n $($1) > $1 ; \
    fi

endef

$(eval $(call DEPENDABLE_VAR,DEFS))


.PHONY: all
all: myfile

SRCS := myfile.c lol_dht22/dht22.c lol_dht22/locking.c
myfile: $(SRCS) Makefile DEFS
    gcc $(addprefix -D, $(DEFS)) -Wall -o $@ $(SRCS) -lwiringPi -lcurl -lm