Makefile debug target

StevenR · 01-11-2009, 05:01 PM

Hello,

I'm having a problem with a makefile script i'm trying to write.
I want to compile a C++ program in two possible ways: "make"
(default target, main) and "make debug". When i supply the debug
target, exactly the same as main should be built, but then with the
DEBUG flag (-g -D DEBUG).

This sounds really logical, but i can't find the answer anywhere
in the forums.

This is the script:

CXX=g++
CXXFLAGS=-ansi -std=c++98 -Wall -W
DEBUG=-g -D DEBUG
OBJS=main.o NgramCreator.o

main: $(OBJS)
$(CXX) $(OBJS) -o $@
$(OBJS): NgramCreator.h
$(CXX) $(CXXFLAGS) $(DEBUG) -c $*.cpp

clean:
rm -f *~ *.o main *.gch

I don't have a clue how to do this, can anybody help me?

Thanks

Steven

ntubski · 01-11-2009, 07:47 PM

If you don't mind running make clean when you switch between debug and normal builds the following should suffice. The main trick is Target Specific Variables.

Code:

CXX=g++
CC=g++ # CC is used for linking
CXXFLAGS=-ansi -std=c++98 -Wall -W
DEBUG=-g -D DEBUG
OBJS=main.o NgramCreator.o

main: $(OBJS)
debug: CXXFLAGS += $(DEBUG)
debug: main
$(OBJS): NgramCreator.h

clean:
        rm -f *~ *.o main *.gch

If you are going to be switching back and forth a lot, I would recommend keeping things in separate directories, like this:

Code:

CXX=g++
CC=g++
CXXFLAGS=-ansi -std=c++98 -Wall -W
DEBUG=-g -D DEBUG
OBJS=main.o NgramCreator.o
SRC=$(OBJS:.o=.cpp)
DEBUG_OBJS = $(addprefix debug/, $(OBJS))

main: $(OBJS)
debug: CXXFLAGS += $(DEBUG)
debug: main
$(OBJS): NgramCreator.h

clean:  
        rm -f *~ *.o main *.gch debug/*.o debug/main

$(DEBUG_OBJS) : $(SRC) NgramCreator.h

debug : debug/main
debug/main : $(DEBUG_OBJS)
        $(CXX) $(DEBUG_OBJS) -o debug/main

debug/%.o : %.cpp
        $(CXX) $(CXXFLAGS) $(DEBUG) -c $< -o $@