https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92703
Bug ID: 92703
Summary: VALUE attribute: CLASS and derived-type with
allocatable components mishandled
Product: gcc
Version: 10.0
Status: UNCONFIRMED
Keywords: wrong-code
Severity: normal
Priority: P3
Component: fortran
Assignee: unassigned at gcc dot gnu.org
Reporter: burnus at gcc dot gnu.org
Blocks: 92702
Target Milestone: ---
The test case shows that allocatable components of derived types are not copied
– just the derived type is (automatically) passed by value (according to the
platform ABI).
Hence, it works fine for data which is directly in the derived type – but not
for allocatable components.
With CLASS, I am not quite sure what goes wrong. I initially thought it is just
a missing copy – as the dump shows:
class.20._data = &var;
classy (&class.20);
But if I print x%A(:), it looks complete random and uninitialized.
Xref: PR 92702 – As it is also about copy-in of data (and later
finalizing/deallocation, if needed), I cross reference PR fortran/92702 which
is about VALUE + DIMENSION (permitted since F2008).
Testcase:
! { dg-do run }
!
! VALUE mishandled for CLASS and with ALLOCATABLE components
!
program main
implicit none (type, external)
type t
integer :: A(100)
complex :: B(1000,1000)
end type t
type t2
integer, allocatable :: C(:)
end type t2
type(t) :: var
type(t2) :: var2
integer :: i
allocate(var2%C(5))
var2%C = [1,2,3,4,5]
call foo(var2) ! var passed by value but var2%C not copied, hence:
if (any(var2%C /= [1,2,3,4,5])) stop 2 ! FAILS HERE
var%A = [((21*i), i = 1,100)]
call classy(var)
if (any(var%A /= [((21*i), i = 1, 100)])) stop 1
contains
subroutine foo(y)
type(t2), value :: y
if (any(y%C /= [1,2,3,4,5])) stop 11
y%C = [99,98,97,96,95]
if (any(y%C /= [99,98,97,96,95])) stop 13
end subroutine foo
subroutine classy(y)
class(t), value :: y
if (any(y%A /= [((21*i), i = 1, 100)])) stop 1 ! FAILS HERE
y%A(1) = 4
if (y%A(1) /= 4) stop 22
end subroutine classy
end program main
Referenced Bugs:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92702
[Bug 92702] [F2008] (and hence [F2018]) Implement VALUE support for arrays
