[PATCH, gfortran] Escalate failure when Hollerith constant to real conversion fails [PR103628]

[Steve Kargl]

On Thu, Mar 02, 2023 at 01:07:32AM +0100, Bernhard Reutner-Fischer wrote:
> On Wed, 1 Mar 2023 07:39:40 -0800
> Steve Kargl via Gcc-patches <gcc-patches@gcc.gnu.org> wrote:
> 
> > In fact, Hollerith should be hidden behind a -fallow-hollerith
> > option and added to -std=legacy.
> 
> While i'd be all for that, in my mind this will block off literally all
> consultants and quite some scientists unless we error out
> with a specific hint to an option that re-enable this.
> 
> So yea, but please forgivingly for the decades to come?
> 

It has already been decades.  It seems to me that only
way to motivate people to fix their code is to nag.

Hollerith is pre-F77 era code.  gfortran already provide a
warning.  The warning should be made into an error, and yes,
it can point to -fallow-hollerith.  The option would downgrade
the error to a warning.  The only way to suppress the warning
is to suppress all warnings with -w.   See -fallow-invalid-boz.

% cat > a.f90
program foo            ! free-form source code is post-f77.
   real :: b = 4H1234  ! No code, in particular, legacy has 
   print *, b          ! initialization expressions.
end program foo
% gfcx -o z a.f90
a.f90:2:14:

    2 |    real :: b = 4H1234
      |              1
Warning: Extension: Conversion from HOLLERITH to REAL(4) at (1)
a.f90:2:18:

    2 |    real :: b = 4H1234
      |                  1
Warning: Legacy Extension: Hollerith constant at (1)

-- 
Steve