[Bug fortran/48700] memory leak with MOVE_ALLOC

["janus at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48700

janus at gcc dot gnu.org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|[OOP] memory leak with      |memory leak with MOVE_ALLOC
                   |MOVE_ALLOC  of polymorphic  |
                   |variables                   |

--- Comment #2 from janus at gcc dot gnu.org 2011-05-15 11:05:24 UTC ---
(In reply to comment #0)
> ==25909== 176 (96 direct, 80 indirect) bytes in 1 blocks are definitely lost in
> loss record 4 of 4
> ==25909==    at 0x4A05E46: malloc (vg_replace_malloc.c:195)
> ==25909==    by 0x400DCF: MAIN__ (testmv3.f90:30)
> ==25909==    by 0x401729: main (testmv3.f90:22)

This one indeed seems to be a problem with MOVE_ALLOC, but apparently unrelated
to OOP/polymorphism. Reduced test case:


program testmv3
  type bar
    integer, allocatable  :: ia(:), ja(:)
  end type

  type(bar), allocatable :: sm,sm2

  allocate(sm)
  allocate(sm%ia(10),sm%ja(10))

  call move_alloc(sm2,sm)

end program testmv3 


I think the 80 indirectly lost bytes should be the allocatable components
(40+40), while the 96 are probably their array descriptors (48+48).

The MOVE_ALLOC statement is simply translated to:

        sm = sm2;
        sm2 = 0B;

We miss to deallocate "sm", before it gets overridden.

The standard definitely requires this, because
1) it says that the second argument ('TO') of MOVE_ALLOC is INTENT(OUT), cf.
F08:13.7.118,
2) allocatable INTENT(OUT) arguments must be deallocated upon procedure call,
cf. F08:6.7.3.2.