Question

I have a project with 50+ .h files and 50+ .cpp files. I’m using make to build a project, which looks something like this (it’s just a piece of an entire file):

HEADERS := $(shell find $(INCLUDE) -name "*.h")
%.obj: %.cpp $(HEADERS)
    $(CPP) $(CPPFLAGS) -fPIC -o $@ -g -c $<

When I’m making changes to one .h file, the whole project has to be re-compiled. It’s annoying and time-consuming. But I don’t want to hard-code file dependencies inside Makefile, since it’s even more time-consuming. I would like to have some make-like tool, which will find dependencies right inside my .cpp/.h files, automatically. Any suggestions? Thanks in advance!

Answer 1

Simplest way:

depend:
    g++ -M *.cpp >.depends

-include .depends

Better way:

SRC=foo.cpp bar.cpp ...
OBJ=$(patsubst %.cpp,%.o,$(SRC))
DEPS=$(patsubst %.o,.deps/%.o.dep,$(OBJ))

all: .deps

.deps: 
     mkdir -p .deps

.cpp.o:
    $(CXX) $(CXXFLAGS) -MD -MF .deps/$@.dep -c -o $@ $<

-include $(DEPS)

So compiler will generate all dependencies for each file during build automatically.

Or even better: use Autotools, CMake or other build system that does this job for you.