beginner GNU Makefile Error

Question

This is my first, attempt at a, Makefile after necessity from a previous post .

Anyway here's the code

SortLab.exe : SelectionSort.o Main.o  
        g++ -o $@ $^  
SelectionSort.o : SelectionSort.cpp SelectionSort.h  
Main.o : Main.cpp  

#-------------------------------------------------------------

run: SortLab.exe  
        ./SortLab.exe  

clean:  
    rm -f *.o  
    rm -f *.exe  

build: clean SortLab.exe  

%.o: %.cpp  
    g++ -c $<  

I intend to have SelectionSort.cpp & SelectionSort.h form an object file, and Main.cpp to form its own object file. Then finally create an executable. Main.cpp depends on SelectionSort.cpp , where do I go wrong?

Also where can I find what the different GNU commands mean, -o -c and such

Answer 1

1. You shouldn't need to define the %.o: %.cpp rule yourself, Make knows how to compile C++.
2. Indent with tabs, not spaces; Make is sensitive to the difference.
3. Every object file should depend on the headers included in the source files it depends on. You probably need Main.o : Main.cpp SelectionSort.h .
4. build shouldn't depend on clean , it defeats one of Make's main features (selectively recompilation when files have changed).
5. If you make build the first target, you can run Make without a target to get a full compile. It's customary to call the main target all .