C++ SDL 项目的 Makefile

Question

I'm still learning how to set up a Makefile and I'm kind of lost here. I'm using windows and currently trying to fire up my Makefile for small C++ SDL project.

I have 3 .cpp files:

main.cpp
window.cpp
rect.cpp

As well as 2 extra header files:

Window.h
rect.h

So having trouble setting up everything on a Makefile This is what i currently have:

CXXFLAGS = -Ideps/include -std=c++0x
LXXFLAGS = -Ldeps/lib -lmingw32 -lSDL2main -lSDL2

cup: main.o
    g++ main.o -o cup $(LXXFLAGS) 

main.o: main.cpp
    g++ main.cpp -c $(CXXFLAGS) 

window.o: window.cpp 
    g++ window.cpp -c 

rect.o: rect.cpp 
    g++ rect.cpp -c  

But I'm getting a bunch of undefined reference errors for my constructors on my command prompt. Help please!

Answer 1

From the Makefile contents I read that cup binary is only created from main.o and it does not link window.o nor rect.o , which is where probably those missing references are defined. At the very least I would update the primary rule to say:

cup: main.o window.o rect.o
    g++ $(LXXFLAGS) -o cup $^

Thus said, you could make even more use from implicit rules that are built into make , and, if following the standard naming for linking flags, the Makefile could be reduced even further to just a linking line (as compilation rules are implicit), eg:

$ cat Makefile
CXXFLAGS = -Ideps/include -std=c++0x
LDFLAGS = -Ldeps/lib
LDLIBS = -lmingw32 -lSDL2main -lSDL2

cup: main.o window.o rect.o
        $(LINK.cc) $^ $(LDLIBS) -o $@

Output:

$ make
g++ -Ideps/include -std=c++0x   -c -o main.o main.cpp
g++ -Ideps/include -std=c++0x   -c -o window.o window.cpp
g++ -Ideps/include -std=c++0x   -c -o rect.o rect.cpp
g++ -Ideps/include -std=c++0x  -Ldeps/lib  main.o window.o rect.o -lmingw32 -lSDL2main -lSDL2 -o cup