Creating Makefile with libraries

Question

How can I create a simple Makefile using the below command?

 g++ -Wall -I/usr/include/opencv -I/usr/include/opencv2 -L/usr/lib/ -g -o exe sourc1.cpp sourc2.cpp sourc3.cpp -lopencv_core -lopencv_imgproc -lopencv_highgui -lopencv_ml -lopencv_video -lopencv_features2d -lopencv_calib3d -lopencv_objdetect -lopencv_contrib -lopencv_legacy -lv4l1 -lv4l2 -lv4lconvert -pthread  

I referenced this link but I am getting confused.

Answer 1

Maybe something like

 # your Makefile

 #### variables
 RM= rm -vf
 CXX= g++
 CXXFLAGS= -Wall -g
 CPPFLAGS= -I/usr/include/opencv -I/usr/include/opencv2 
 LDLIBS= -lopencv_core -lopencv_imgproc -lopencv_highgui \
         -lopencv_ml -lopencv_video -lopencv_features2d \
         -lopencv_calib3d -lopencv_objdetect -lopencv_contrib \
         -lopencv_legacy -lv4l1 -lv4l2 -lv4lconvert 
 SOURCEFILES= sourc1.cpp sourc2.cpp sourc3.cpp 
 OBJECTFILES= $(patsubst %.cpp,%.o,$(SOURCEFILES))
 PROGNAME= yourexe

 ### rules
 .PHONY: all clean

 all: $(PROGNAME)
 $(PROGNAME): $(OBJECTFILES)
       $(LINK.cpp) $^ $(LOADLIBES) $(LDLIBS) -o $@

 clean:
       $(RM) $(OBJECTFILES) $(PROGNAME) 

Feel free to adapt. (You probably have header files, and you need to add dependencies of object files to source and to header files). Perhaps use pkg-config if it knows about opencv. Replace the initial many spaces in the rules with a tab. Read carefully GNU make documentation.

If you have sourc2.cpp and if you have two header files header1.hh and header2.hh which are #include-d by sourc2.cpp you'll need to add the dependency rule:

 sourc2.o: source2.cpp header1.hh header2.hh

and there is a way (by passing arguments like -M or -MD to gcc thru suitable rules) to get such dependencies automatically generated, see this question.

You may want to use remake to debug your Makefile-s (e.g. as remake -x). Run make -p to understand which rules are known to make