How to check if a file exists in a makefile

Question

I have a makefile template to compile a single DLL (for a plugin system). The makefile of the user looks like this:

EXTRA_SRCS=file1 file2
include makefile.in
         


        

Answer 1

You didn't specify what compiler(s) you are using, but if you have access to gcc/g++ you can use the -MM option.

What I do is create a file with the extension of .d for every .c or .cpp file, and then "include" the .d files. I use something like this in my Makefile:

%.d: %.c
        gcc $(INCS) $(CFLAGS) -MM $< -MF $@

%.d: %.cpp
        g++ $(INCS) $(CXXFLAGS) -MM $< -MF $@

I then create the dependencies like this:

C_DEPS=$(C_SRCS:.c=.d)
CPP_DEPS=$(CPP_SRCS:.cpp=.d)
DEPS=$(C_DEPS) $(CPP_DEPS)

and this at the bottom of the Makefile:

include $(DEPS)

Is this the kind of behavior you're going for? The beauty of this method is that even if you're using a non-GNU compiler for actual compiling, the GNU compilers do a good job of calculating the dependencies.