How to change the Makefile to create object file? - makefile

Question

I am following a code from GitHub (https://github.com/dmalhotra/pvfmm).
There is a Fortran file in ./examples/src/example-f.f90. I have created a subroutine from this example-f.f90 so that I can make an object file out of it and can call this subroutine in our in-house code. The installation guide is given here (https://github.com/dmalhotra/pvfmm/blob/develop/INSTALL).
The Makefile to compile the example-f.f90 is as (https://github.com/dmalhotra/pvfmm/blob/develop/examples/Makefile):
ifndef PVFMM_DIR
PVFMM_DIR=./..
endif
-include $(PVFMM_DIR)/MakeVariables
ifndef CXX_PVFMM
$(error Cannot find file: MakeVariables)
endif
# FC=$(FC_PVFMM) # TODO: for now, FC must be provided by user
# CC=$(CC_PVFMM) # TODO: for now, CC must be provided by user
CXX=$(CXX_PVFMM)
CXXFLAGS=$(CXXFLAGS_PVFMM)
LDLIBS=$(LDLIBS_PVFMM)
RM = rm -f
MKDIRS = mkdir -p
BINDIR = ./bin
SRCDIR = ./src
OBJDIR = ./obj
INCDIR = ./include
TARGET_BIN = \
$(BINDIR)/example1 \
$(BINDIR)/example2 \
$(BINDIR)/example-sctl \
$(BINDIR)/fmm_pts \
$(BINDIR)/fmm_cheb
all : $(TARGET_BIN)
$(BINDIR)/%: $(SRCDIR)/%.f90
-#$(MKDIRS) $(dir $#)
$(PVFMM_DIR)/libtool --mode=link --tag=FC $(FC) $(CXXFLAGS) -I$(INCDIR) $^ $(LDLIBS) -o $#
...
The MakeVariables can be found in the above link.
I changed this make file so that I can make an object file of example-f.f90 (subroutine, I converted as I told before to link it in our in-house code) and also other files in our in-house code and link at the end. The new makefile looks like:
ifndef PVFMM_DIR
PVFMM_DIR=./..
endif
-include $(PVFMM_DIR)/MakeVariables
ifndef CXX_PVFMM
$(error Cannot find file: MakeVariables)
endif
FC_PVMM = mpif90
FC = mpif90
FC=$(FC_PVFMM) # TODO: for now, FC must be provided by user
CC=$(CC_PVFMM) # TODO: for now, CC must be provided by user
CXX=$(CXX_PVFMM)
CXXFLAGS=$(CXXFLAGS_PVFMM)
LDLIBS=$(LDLIBS_PVFMM)
RM = rm -f
MKDIRS = mkdir -p
BINDIR = ./bin
SRCDIR = ./src
OBJDIR = ./obj
INCDIR = ./include
all : $(project_final)
project_final: $(project)
$(PVFMM_DIR)/libtool --mode=link --tag=FC mpif90 $(CXXFLAGS) -I$(INCDIR) $^ $(LDLIBS) -o $#
project: example-f.o
cd ./src && $(MAKE)
example-f.o: $(SRCDIR)/example-f.f90
$(PVFMM_DIR)/libtool --mode=link --tag=FC mpif90 $(CXXFLAGS) -I$(INCDIR) $^ $(LDLIBS) -c $#
...
Kindly note 'project: example-f.o
cd ./src && $(MAKE)' doing to make object files of our inhouse code. In src we have separate makefile to create object files for out in-house code.
But it gives me the following:
cd ./examples && make;
make[1]: Entering directory '/home/bidesh/Coding/FMM/pvfmm-1.3.0/examples'
make[1]: Nothing to be done for 'all'.
make[1]: Leaving directory '/home/bidesh/Coding/FMM/pvfmm-1.3.0/examples'
How can I modify the makefile so that I can compile the whole code that includes example-f.f90 (subroutine) along with other subroutines (in-house code)?
Thanks a lot.