[Bug fortran/65086] New: Segfault: Invalid copy-out of temporary as argument is in read-only memory

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65086

            Bug ID: 65086
           Summary: Segfault: Invalid copy-out of temporary as argument is
                    in read-only memory
           Product: gcc
           Version: 5.0
            Status: UNCONFIRMED
          Keywords: wrong-code
          Severity: normal
          Priority: P3
         Component: fortran
          Assignee: unassigned at gcc dot gnu.org
          Reporter: burnus at gcc dot gnu.org

>From James Van Buskirk's example in the comp.lang.fortran thread "Is INTENT
(IN) ever used to control code generation?" /
https://groups.google.com/d/msg/comp.lang.fortran/nzq3Sad_zQE/APiZzlGdNPQJ


The following program segfaults at run time, unless INTENT(IN) is specified for
sub4. The problem is the copy-out part as the original variable is in read-only
memory.


"Both gfortran and ifort throw an error at runtime for the above program with
the INTENT(IN) statements commented out, but ifort runs to completion if either
or both of them are in effect whereas gfortran only works if the INTENT(IN)
statement in subroutine sub4 is in effect."


And:
"But as the standard is written it seems the Fortran processor has to do this
comparison before it can copy out, which seems absolutely horrible to me,
[...]"

Bob replies: "Why does it seem horrible?  Oracle Solaris Studio Fortran uses
this implementation."


module mod1
   implicit none
   character(*), parameter :: x = 'This is a constant string.'
end module mod1

module mod2
   implicit none
   contains
      subroutine sub1(x)
         character(*) x
         call sub2(x,len(x))
      end subroutine sub1
      subroutine sub2(x,size)
         integer size
         character x(size)
         call sub3(x)
      end subroutine sub2
      subroutine sub3(x)
         character x(:)
!INTENT(IN) :: x
         call sub4(x(1::2))
      end subroutine sub3
      subroutine sub4(x)
!INTENT(IN) :: x  ! REQUIRED
         character x(*)
      end subroutine sub4
end module mod2

program main
   use mod1
   use mod2
   implicit none
   write(*,'(a)') x
   call sub1(x)
   write(*,'(a)') x
end program main