[Bug fortran/56596] New: Invalid read of size 4 gfortran.dg/class_array_7.f03

[dominiq at lps dot ens.fr]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56596

             Bug #: 56596
           Summary: Invalid read of size 4 gfortran.dg/class_array_7.f03
    Classification: Unclassified
           Product: gcc
           Version: 4.8.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: fortran
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: dominiq@lps.ens.fr


Running gfortran.dg/class_array_7.f03 under valgrind gives

==54979== Invalid read of size 4
==54979==    at 0x100001731: __realloc_MOD_assign (class_array_7.f03:25)
==54979==    by 0x100001629: __realloc_MOD_reallocate (class_array_7.f03:33)
==54979==    by 0x1000019D8: MAIN__ (class_array_7.f03:55)
==54979==    by 0x100001B7D: main (class_array_7.f03:49)
==54979==  Address 0x10044a408 is 0 bytes after a block of size 40 alloc'd
==54979==    at 0x100013679: malloc (vg_replace_malloc.c:266)
==54979==    by 0x1000017E0: MAIN__ (class_array_7.f03:53)
==54979==    by 0x100001B7D: main (class_array_7.f03:49)
==54979== 
==54979== 
==54979== HEAP SUMMARY:
==54979==     in use at exit: 88 bytes in 1 blocks
==54979==   total heap usage: 25 allocs, 24 frees, 7,061 bytes allocated
==54979== 
==54979== LEAK SUMMARY:
==54979==    definitely lost: 0 bytes in 0 blocks
==54979==    indirectly lost: 0 bytes in 0 blocks
==54979==      possibly lost: 0 bytes in 0 blocks
==54979==    still reachable: 0 bytes in 0 blocks
==54979==         suppressed: 88 bytes in 1 blocks
==54979== 
==54979== For counts of detected and suppressed errors, rerun with: -v
==54979== ERROR SUMMARY: 5 errors from 1 contexts (suppressed: 0 from 0)

The test also aborts if it is compiled with -fsanitize=address.

Reduced test

module realloc
  implicit none

  type :: base_type
     integer :: i
  contains
    procedure :: assign
    generic :: assignment(=) => assign   ! define generic assignment
  end type base_type

  type, extends(base_type) :: extended_type
     integer :: j
  end type extended_type

contains

  elemental subroutine assign (a, b)
    class(base_type), intent(out) :: a
    class(base_type), intent(in) :: b
    a%i = b%i
  end subroutine assign

  subroutine reallocate (a)
    class(extended_type), dimension(:), allocatable :: tmp
    class(base_type), dimension(:), allocatable, intent(inout) :: a
    allocate (extended_type :: tmp (size (a))) ! how to alloc b with same type
as a ?
    tmp = a             ! polymorphic l.h.s.
    call move_alloc (from=tmp, to=a)
  end subroutine reallocate

end module realloc

program main
  use realloc
  implicit none
  class(base_type), dimension(:), allocatable :: a

  allocate (extended_type :: a(10))
  call reallocate (a)
end program main