How to run Fortran file with too many subroutine and function? - fortran

Question

The main program with too many subroutines and functions is existed. Some of the subroutines and functions also use subroutines, functions, and modules. I decided to write them in independent files due to clarity in the main program. Then I created an independent file as a module to collect them with the include command.
Now I have one main program and one independent file for the module. I compile the program but it shows an error. The error is about missing mentioned subroutine in the above independent file.
My question in general is: If you have a program with one main program and a number of sub-programs (subroutines, functions, and modules), which also they have sub-programs, what method do you use to assemble and run it?
I write my code in PLATO as a fortran95.
I will appreciate any comments that give me a little help and forgive me for writing shortcomings
What is the problem?
Consider the following structure.
On the independent file as the main program:
MAIN PROGRAM
CALL A
CALL B
CALL C
END PROGRAM
On the independent file as the subroutine A:
SUBROUTINE A
...
END SUBROUTINE
On the independent file as the subroutine B:
SUBROUTINE B
CALL B1
CALL B2
END SUBROUTINE
---------------
SUBROUTINE B1
...
END SUBROUTINE
--------------
FUNCTION B2
...
END FUNCTION
On the independent file as the subroutine C:
SUBROUTINE C
USE C1
CALL C2
END SUBROUTINE
---------------
SUBROUTINE C1
...
END SUBROUTINE
On the independent file as the module C1:
MODULE C1
CONTAINS
SUBROUTINE C1-1
SUBROUTINE C1-2
SUBROUTINE C1-3
...
END MODULE
What I did:
I created an independent file as Module:
MODUL D
INCLUDE A.F95
INCLUDE B.F95
INCLUDE C.F95
END MODULE
Consequently, for the main program:
MAIN PROGRAM
USE D
CALL A
CALL B
CALL C
END PROGRAM
What is the Error:
Warning: Missing A (File address), Missing B (File address), Missing C
(File address)

Answer 1

The following makefile should work for your setup.
FC := gfortran
main: c1.o d.o main.o
#$(FC) $^ -o main
main.o: main.f90 d.f90
#$(FC) -c $<
d.o: d.f90 a.f90 b.f90 c.f90 c1.o
#$(FC) -c $<
c1.o: c1.f90
#$(FC) -c $<
clean:
#rm -rf *.{o,mod} main
I used the following files (note the filenames and .f90 extensions)
! main.f90
program main
use d
print *, 'main'
call a()
call b()
call c()
end program
! b.f90
subroutine b()
logical :: tmp
print *, 'b'
call b1()
tmp = b2()
end subroutine
subroutine b1()
print *, 'b1'
end subroutine
logical function b2() ! added: function needs return type.
print *, 'b2'
b2 = .true.
end function
! c.f90
subroutine c()
use c1
print *, 'c'
call c1_1() ! added this line. otherwise module c1 would not be used at all.
call c2()
end subroutine
subroutine c2()
print *, 'c2'
end subroutine
! c1.f90
module c1
contains
subroutine c1_1()
print *, 'c1_1'
end subroutine
subroutine c1_2()
print *, 'c1_2'
end subroutine
subroutine c1_3()
print *, 'c1_3'
end subroutine
end module
! d.90
module d
contains ! added: files a.f90,b.d90,c.f90 define procedures and must be included after `contains`.
include 'a.f90'
include 'b.f90'
include 'c.f90'
end module