fortran - Can An Allocatable Intent(inout) Argument Be Optional? -


i have problem trying define subroutine, argument contains allocatable, optional, intent(inout) variable shown below. code compiles fine, runtime error of "segmentation fault - invalid memory reference".

subroutine test_routine.f90

subroutine test_routine(a,b)  implicit none      real,allocatable,intent(in)               :: a(:,:)     real,allocatable,optional,intent(inout)   :: b(:,:)      b =     b(:,:) = 1  end subroutine

this subroutine packed in module, , called in main.

module test_module.f90

module test_module  implicit none      interface test_routine         module procedure test_routine     end interface  end module test_module

main test_main.f90

program main      use test_module  implicit none      real,allocatable    :: a(:,:),b(:,:)      allocate(a(6,6))     allocate(b(6,6))     a(:,:) = 0     call test_routine(a,b)    ! works fine     call test_routine(a)      ! doesn't work!  end program main

then tried assign variable op_b, make b, doesn't exist if main routine doesn't pass in. following code still doesn't work.

subroutine test_routine(a,b)  implicit none      real,allocatable,intent(in)    :: a(:,:)     real,allocatable,optional,intent(inout)   :: b(:,:)     real,allocatable               :: op_b(:,:)      if(.not. present(b))         allocate(op_b(size(a,1),size(a,2)))         b = op_b     end if     b =     b(:,:) = 1  end subroutine

by way, tried using fixed size array, still doesn't help. wonder if it's impossible such things?

dummy arguments can optional, allocatable , intent(inout).

but not permitted define or reference optional dummy argument, bar passing present or associating optional argument. if 'b' not present, cannot execute 'b = a'.


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