fortran - Proper way to pass pointers into many subroutines -

i'm not programmer , i'm trying interface model provides data pointers. these pointers passed down through several subroutines before data written them. i'm not sure how avoid memory leaks.

let's have array pointer a passed several subroutines before being written to, how handle declarations, allocations, , deallocations?

module data  implicit none contains   subroutine s1(a) real, pointer, intent(out) :: a(5,5)  call s2(a) end subroutine s1  subroutine s2(a) real, pointer, intent(out) :: a(5,5) integer ::   = 1,5    a(:,i) = 5.0 end end subroutine s2 end module data  program test use data, : s1, s2 real, pointer, dimension(:,:) :: => null() allocate(a(5,5)) call s1(a) write(*,*) deallocate(a) end program test 

please note code not fortran 90. intent attribute dummy (formal) arguments pointers introduced in fortran 2003.

the intent refers association status of pointer, not target. also, if argument derived type pointer components, intent applies type object itself, not targets of pointers. is, if, example, intent(in) used, data area pointer targeted @ can modified:

module mytype_mod    implicit none   private    type, public :: mytype      integer, pointer :: ptr(:)    contains      procedure :: sub => my_type_sub   end type mytype  contains    subroutine my_type_sub(self)     ! dummy argument     class(mytype), intent(in) :: self      ! following legal,     ! though intent(in) specified     self%ptr = 42    end subroutine my_type_sub  end module mytype_mod  program main    use mytype_mod, only: &        mytype    implicit none    type(mytype) :: foo   integer      :: alloc_stat    allocate( integer :: foo%ptr(100), stat=alloc_stat )   call foo%sub()  end program main 

even though not required, in case such previous example, better state intent(inout) indicate reader modification of data taking place.

on note, may find answer useful fortran subroutine returning wrong values