[Bug fortran/98433] double free detected in tcache 2, after merge of structures

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98433

anlauf at gcc dot gnu.org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
                 CC|                            |anlauf at gcc dot gnu.org
   Last reconfirmed|                            |2020-12-24
     Ever confirmed|0                           |1

--- Comment #5 from anlauf at gcc dot gnu.org ---
The user code is alright, it is the implementation of the intrinsic MERGE which
prevents doing the right thing when assigning to the l.h.s.

Extending the subroutine of the test program to

module bug_merge_m
  implicit none
contains
  subroutine bug_merge
    type t
       real, allocatable :: v(:)
    end type t

    type(t) :: x1, x2, x3, x4, x5
    logical :: f = .false.

    allocate(x1%v(1))
    x1%v = 1.
    allocate(x2%v(1))
    x2%v = 2.
    x3 = merge(x1, x2, .false.)
    print *, "x3%v = ", x3%v
    x4 = merge(x1, x2, f)
    print *, "x4%v = ", x4%v
    if (f) then; x5 = x1; else; x5 = x2; endif
    print *, "x5%v = ", x5%v
  end subroutine bug_merge
end module bug_merge_m

and looking a the generated dump-tree, one sees that the assignments to x3 and
x4 are generating wrong code, only the assignment to x5 is fine.

@Steve: that's pretty basic F2003 stuff, almost TR15581...