[Bug fortran/49324] Deep copy missing for array constructors of DT w/ allocatable components

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

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49324

--- Comment #9 from Tobias Burnus <burnus at gcc dot gnu.org> 2011-06-14 13:07:07 UTC ---
(Comment fixed 8 fixed the missing deep copy.)

Regarding the reallocate (cf. comment 6, but using scalars to reduce the dump
size): For
  type t
    integer, allocatable :: A
  end type t
  type(t), allocatable :: z
...
  z = [ x ]

One gets the following dump:

/* If not initialized. For arrays: Also realloc, if the size is wrong.  */
        if (z != 0B) goto L.1;
        z = (struct t *) __builtin_malloc (8);

So far so good, but one then has

        D.1552 = *z;
            if (D.1552.a != 0B)
                __builtin_free ((void *) D.1552.a);

which is only OK if "z.data" has neither been just allocated nor reallocated.
If it has, there are two problems: (a) The old memory is not freed. (b) if
malloc/realloc does not return nullified memory, free() operates on some random
pointer.

The question is how to handle it best? The assignment is handled in
gfc_trans_assignment_1, which calls gfc_alloc_allocatable_for_assignment for
the realloc and gfc_trans_scalar_assign for the assignment.