makefile automatic src file detection and dependency generation

Question

I have the following setup for my c++ project:

in the src-folder, there are *.cpp and corresponding *.h files and in the obj-folders I want to have my .o-files.

Answer 1

All right, you asked for it.

1: Your collect_sources:... include sources is glorious Rube Goldberg hackery. Just do this:

SRCS = $(wildcard ./src/*.cpp)

And if you want to confirm it by eye, you can do this:

$(info $(SRCS))

2:

clear_dependencies:
    echo "" > $(DEP);

Just for the sake of aesthetics, let's fix this.

clear_dependencies:
    $(RM) $(DEP);

3:

$(SRCDIR)/%.cpp:
    @$(CXX) $(DEPFLAGS) -MT \
  "$(subst $(SRCDIR),$(OBJDIR),$(subst $(EXT_SRC),$(EXT_OBJ),$$file))" \
  $(addprefix ,$$file) >> $(DEP);

This will take some work. First the immediate problem: the target is a real file which exists, and the rule has no prerequisites. Therefore the rule will not be run (I have no idea why it worked for you in a previous version, maybe something else was different). As a temporary fix I suggest we switch to a static pattern rule and PHONY targets:

.PHONY:$(SRCS)
$(SRCS) : $(SRCDIR)/%.cpp:
    @$(CXX) $(DEPFLAGS) -MT \
   ...

See if all that works, then we can tackle the big stuff.