Re: How to adding pathes to dependencies in rules of `.d` files

Can you please give me suggestions to improve it.

1. In thie out of source version, I can not omit recipes in both building and linking rules. This make it a bit complicated.

2. if I put # comment at the end of the line of export OBJDIR, it causes mysterious error message in rules involve the variable.


```
## src/Makefile

# Makefile for top dir

export OBJDIR = $(dir $(realpath $(lastword $(MAKEFILE_LIST))))/objdir_tmp

# $(call version_number,1.2.3)
# major.minor.patch
# libtool manual 4.2: -version-number
define version_number
	$(MAKE) -C $@ [email protected].$(word 1,$(subst ., ,$(1)))
	cp $(OBJDIR)/$@/$@ $(OBJDIR)/$@/[email protected].$(1)
	cd $(OBJDIR)/$@; ln -f -s $(OBJDIR)/$@/[email protected].$(1) $(OBJDIR)/$@/[email protected].$(word 1,$(subst ., ,$(1))); cd ..
	cd $(OBJDIR)/$@; ln -f -s $(OBJDIR)/$@/[email protected].$(1) $(OBJDIR)/$@/[email protected]; cd ..
endef

SUBDIRS = main foo

all : $(SUBDIRS)
install : $(SUBDIRS)

main : foo
main : ; $(MAKE) -C $@
foo : ; $(call version_number,6.2.3)

# make DESTDIR=~/foo install
install :
	install -d "$(DESTDIR)/usr/local/bin"
	install -d "$(DESTDIR)/usr/local/lib"
	install -m 0755 $(OBJDIR)/main/main "$(DESTDIR)/usr/local/bin"
	install -m 0755 $(OBJDIR)/foo/*.so* "$(DESTDIR)/usr/local/lib"

clean : ; -rm -fr $(OBJDIR)

.PHONY : $(SUBDIRS) all install clean
```


---


```
## src/main/Makefile

# Makefile for subdir

# build shared library with -fPIC, -shared
CFLAGS    = # -g -O3 -fPIC # CXXFLAGS for .cpp
CPPFLAGS  = -MMD -MP -I../foo
LDFLAGS   = -L$(OBJDIR)/foo # -shared
LDLIBS    = -lfoo
#CC       = $(CXX) # link with CXX for .cpp

LDFLAGS  += -Wl,-rpath,$(OBJDIR)/foo
LDFLAGS  += -Wl,-rpath,'$$ORIGIN/../lib'
#LDFLAGS += -Wl,-soname,$(soname)

# make # NDEBUG=1
ifdef NDEBUG
CPPFLAGS += -DNDEBUG
CFLAGS   += -O3 # .cpp
else
CFLAGS   += -g # .cpp
LDFLAGS  += -fsanitize=address
endif

all : $(OBJDIR)/main/main # foo

$(OBJDIR)/main/main : $(OBJDIR)/main/$(patsubst %.c,%.o,$(wildcard *.c))
	$(CC) $(LDFLAGS) $^ $(LDLIBS) -o $@  # CXX for .cpp

$(OBJDIR)/main/%.o : %.c | $(OBJDIR)/main
	$(CC) $(CFLAGS) $(CPPFLAGS) -c -o $@ $<  # CXX CXXFLAGS for .cpp

$(OBJDIR)/main: ; mkdir -p $(OBJDIR)/main

-include $(OBJDIR)/main/*.d
clean : ; -rm -fr $(OBJDIR)

.PHONY : all clean
```


---


```
## src/foo/Makefile

# Makefile for subdir

# build shared library with -fPIC, -shared
CFLAGS    = -fPIC # -g -O3 # CXXFLAGS for .cpp
CPPFLAGS  = -MMD -MP # -I../bar
LDFLAGS   = -shared # -L../bar
LDLIBS    = # -lbar
#CC       = $(CXX) # link with CXX for .cpp

LDFLAGS  += -Wl,-rpath,'$$ORIGIN/../bar'
LDFLAGS  += -Wl,-rpath,'$$ORIGIN/../lib'
LDFLAGS  += -Wl,-soname,$(soname)

# make # NDEBUG=1
ifdef NDEBUG
CPPFLAGS += -DNDEBUG
CFLAGS   += -O3 # .cpp
else
CFLAGS   += -g # .cpp
LDFLAGS  += -fsanitize=address
endif

all : $(OBJDIR)/foo/foo # foo

$(OBJDIR)/foo/foo : $(OBJDIR)/foo/$(patsubst %.c,%.o,$(wildcard *.c))
	$(CC) $(LDFLAGS) $^ $(LDLIBS) -o $@  # CXX for .cpp

$(OBJDIR)/foo/%.o : %.c | $(OBJDIR)/foo
	$(CC) $(CFLAGS) $(CPPFLAGS) -c -o $@ $<  # CXX CXXFLAGS for .cpp

$(OBJDIR)/foo: ; mkdir -p $(OBJDIR)/foo

-include $(OBJDIR)/foo/*.d
clean : ; -rm -fr $(OBJDIR)

.PHONY : all clean
```

---