[Bug fortran/88248] [F18] Bogus warning about obsolescent feature: Labeled DO statement

[kargl at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88248

kargl at gcc dot gnu.org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |janus at gcc dot gnu.org,
                   |                            |kargl at gcc dot gnu.org

--- Comment #4 from kargl at gcc dot gnu.org ---
(In reply to G. Steinmetz from comment #0)
> Branching out via END=, ERR= or EOR= specifier in combination with
> CONTINUE is interpreted as a labeled DO loop. Option -std=f2018 
> misleadingly flags this with a warning -- (low prio).
> 
> 
> $ cat z1.f90
> program p
>    do
>       rewind (1, err=99)
>    end do
> 99 continue
> end
> 
> 
> $ cat z2.f90
> program p
>    character(3) :: c = 'abc'
>    integer :: k
>    do k = 1, 10
>       open (k, err=99)
>       close (k, err=99)
>       backspace (k, err=99)
>       endfile (k, err=99)
>       rewind (k, err=99)
>       flush (k, err=99)
>       inquire (k, err=99)
>       read (k, '(a)', end=97) c
>       read (k, '(a)', eor=98, advance='no') c
>       read (k, '(a)', err=99) c
>       write (k, '(a)', err=99) c
>       wait (k, end=97)
>       wait (k, eor=98)
>       wait (k, err=99)
>    end do
> 97 continue
> 98 continue
> 99 continue
> end
> 
> 
> $ gfortran-9-20181125 -c z1.f90 -std=f2008
> $
> $ gfortran-9-20181125 -c z1.f90 -std=f2018
> z1.f90:5:2:
> 
>     5 | 99 continue
>       |  1
> Warning: Fortran 2018 obsolescent feature: Labeled DO statement at (1)

The warning was added by Janus in r260705.  I'll need to look
deeper, but I don't think there is an easy way to distinguish
between a labeled statement used as do-loop terminator and 
a ordinary labeled statement.