[Bug fortran/100860] New: class(*) type is (character(*)) produces a segmentation fault when run

["thomas.robinson at noaa dot gov" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100860

            Bug ID: 100860
           Summary: class(*) type is (character(*)) produces a
                    segmentation fault when run
           Product: gcc
           Version: 11.1.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: fortran
          Assignee: unassigned at gcc dot gnu.org
          Reporter: thomas.robinson at noaa dot gov
  Target Milestone: ---

When a string is passed as an argument to a subroutine where the argument is
`class(*)`, there is a seg fault when the type is selected.  Other types seem
to be working.
Previous versions of gfortran have no problem compiling and running this simple
program.  I think the code is correct.  It seems to be gcc 11 that has an
issue.

Here is some test code:

module ctest
contains

subroutine sub (carg, slen)

 class(*), intent (in) :: carg
 integer, optional, intent (in)  :: slen

 select type (carg)
 type is (character(*))
   if (.not.present(slen)) then
     write (6,*) "This is an error dealing with a string"
   else
     write (6,*) "string length is ",slen
     write (6,*) "String is ",carg(1:slen)
   endif

 type is (integer)
   write (6,*) "Integer type is ", carg
 type is (real)
   write (6,*) "Real type is ", carg
 class default
   write (6,*) "Not the right type"
 end select


end subroutine sub


end module ctest

program test

use ctest

character (len=10) :: c10
character (len=:), allocatable :: sall
integer :: i=100
real :: r = 999.9
logical :: l = .true.
 call sub (r)
 call sub (i)
 call sub (l)
 c10="12345"
 allocate(character (len=i) :: sall)
 sall = "87654321"
! write (6,*) "c10=",trim(c10),"::LEN=",len_trim(c10)
! call sub(trim(c10), len_trim(c10))
 write (6,*) "sall=",trim(sall),"::LEN=",len_trim(sall)
 call sub(trim(sall),len_trim(sall))



end program test

Here is the output
 Real type is    999.900024    
 Integer type is          100
 Not the right type
 sall=87654321::LEN=           8

Program received signal SIGSEGV: Segmentation fault - invalid memory reference.


I tried with heap and stack strings, and both fail (you can see I have the
first one commented out).  Please let me know if there's any more information
you need.