https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87142
Bug ID: 87142
Summary: Aliasing issue with overloaded assignment and
allocatable components
Product: gcc
Version: 7.3.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: fortran
Assignee: unassigned at gcc dot gnu.org
Reporter: mscfd at gmx dot net
Target Milestone: ---
The following code does not work, as the left hand side in "str = str%cs(1:10)"
is deallocated, before the right hand side, where str also appears, is
evaluated. With gfortran-7.3.0, the output looks right, but I see invalid
memory accesses in valgrind. In other circumstances, depending on the length of
the string and with 8.1.0, I have also seen wrong results, but then depending
on the optimisation level. As far as I know, this is a violation of the
standard, which requires that the right hand side is evaluated before the left
hand side is modified (i.e. in this case deallocated).
module mod
implicit none
private
type, public :: string
character(len=:), allocatable :: cs
contains
procedure, public :: assign
generic, public :: assignment(=) => assign
end type string
contains
elemental subroutine assign(self, cs)
class(string), intent(inout) :: self
character(len=*), intent(in) :: cs
! this is not working if cs and self%cs are aliasing
self%cs = cs
end subroutine assign
end module mod
program assign_alias
use mod
implicit none
type(string) :: str
str%cs = repeat('0123456789', 100)
str = str%cs(1:10)
end program assign_alias
