Backslash character at the end of a comment

Backslash character at the end of a comment

[Vladimír Fuka]

Hello,

I noticed strange error after adding a comment. Unexpected elses and end if.

I realized the comment had \ at the end. I added a space after it and I got

strings.f90:102:76: warning: backslash and newline separated by space
[enabled by default]
         ! " finishes the string and is not counted to it if not escaped by \
 ^
strings.f90:119.10:

and again the same error, unexpected elses and end if.

Does this reject valid source files or not? What purpose does it
serve? Does it mean a comment is continued on the next line by using a
backslash?

Regards,

  Vladimir

RE: Backslash character at the end of a comment

[Klint Gore]

-----Original Message-----
>From: fortran-owner@gcc.gnu.org [mailto:fortran-owner@gcc.gnu.org] On Behalf Of Vladimír Fuka
>Sent: Tuesday, 26 September 2017 1:41 AM
>
>Does this reject valid source files or not? What purpose does it serve? Does it mean a comment is continued on the next line by using a backslash?

The comment is continued to the next line.  I posted back in March about it https://gcc.gnu.org/ml/fortran/2017-03/msg00020.html .  There were no replies as to what the expected behaviour should be.  In my case, the backslash was meaningless so I could just get rid of them.

Klint.

Re: Backslash character at the end of a comment

[Vladimír Fuka]

So it was the -cpp which was in effect, although there were no macros
in the source files. The code is

  !\
  if (i>1) then
  end if
end

The error

> gfortran -cpp   backslash.f90
backslash.f90:3.3:

end if
   1
Error: Expecting END PROGRAM statement at (1)


I knew the backslash is  used to continue a macro on the next line,
but I didn't know it has en effect also outside of macros.

Regards,

  Vlad

2017-09-25 18:49 GMT+02:00 Dominique d'Humières <dominiq@lps.ens.fr>:
>
>> Le 25 sept. 2017 à 18:40, Vladimír Fuka <vladimir.fuka@gmail.com> a écrit :
>>
>> I suppose the code can be just
>>
>> !\
>> end
>>
>>   Vlad
>
> % cat > backslash_1.f90
> !\
> end
> % gfc backslash_1.f90
> % ./a.out
> %
>
> for all the revisions I have tested with/without -fbackslash.
>
> Dominique
>

Re: Backslash character at the end of a comment

[Dominique d'Humières]

> Le 25 sept. 2017 à 18:40, Vladimír Fuka <vladimir.fuka@gmail.com> a écrit :
> 
> I suppose the code can be just
> 
> !\
> end
> 
>   Vlad

% cat > backslash_1.f90
!\
end
% gfc backslash_1.f90
% ./a.out 
%

for all the revisions I have tested with/without -fbackslash.

Dominique

Re: Backslash character at the end of a comment

[Vladimír Fuka]

I suppose the code can be just

!\
end

  Vlad

Dne 25. 9. 2017 6:38 odpoledne napsal uživatel "Dominique d'Humières" <
dominiq@lps.ens.fr>:

> Vladimir,
>
> > I noticed strange error after adding a comment. Unexpected elses and end
> if.
> >
> > I realized the comment had \ at the end. I added a space after it and I
> got
> > …
>
> Could you please post the code? AFAIR, backslash is not part of the
> Fortran character set and can only appear in strings (no patience to look
> at the standard). Gfortran has an option -fbackslash allowing backslash to
> be interpreted as an escape character (again AFAIU). You may want to have a
> look at gfortran.dg/backslash*.
>
> Cheers,
>
> Dominique
>
>

Re: Backslash character at the end of a comment

[Dominique d'Humières]

Vladimir,

> I noticed strange error after adding a comment. Unexpected elses and end if.
>
> I realized the comment had \ at the end. I added a space after it and I got
> …

Could you please post the code? AFAIR, backslash is not part of the Fortran character set and can only appear in strings (no patience to look at the standard). Gfortran has an option -fbackslash allowing backslash to be interpreted as an escape character (again AFAIU). You may want to have a look at gfortran.dg/backslash*.

Cheers,

Dominique