The following segfaults on the second call to mah because the allocatable components are automatically deallocated.  I have yet to check the F2003 standard but this logically makes no sense.  It comes about because t.data is NULLED on entry to mah

program boh
  !
  call mah (0)
  call mah (1)
  call mah (2)
  !
end program boh
!
subroutine mah (i)
  !
  integer, intent(in) :: i
  !
  type mix_type
     real(8), allocatable :: a(:)
     complex(8), allocatable :: b(:)
  end type mix_type
  type(mix_type), allocatable, save :: t(:)
  integer :: j, n=1024
  !
  if (i==0) then
     allocate (t(1))
     allocate (t(1)%a(n))
     allocate (t(1)%b(n))
     do j=1,n
        t(1)%a(j) = j
        t(1)%b(j) = n-j
     end do
  end if
  c = sum( t(1)%a(:) ) + sum( t(1)%b(:) )
  print *, 'c=',c
  if ( i==2) then
     deallocate (t(1)%b)
     deallocate (t(1)%a)
     deallocate (t)
  end if
end subroutine mah

Posted to the list by F-X COudert

http://gcc.gnu.org/ml/fortran/2008-01/msg00044.html