Re: [gfortran] Add new -std=legacy command line option

[Janne Blomqvist <jblomqvi at cc dot hut dot fi>]

On Sat, May 28, 2005 at 01:59:22PM -0600, Roger Sayle wrote:
> 
> The following patch refines the semantics of gfortran's extensions
> into two categories; GFC_STD_GNU for useful functionality not defined
> in any official fortran standard (i.e. stuff we're proud of) and
> GFC_STD_LEGACY for functionality we're forced to support for backward
> compatibility with other compilers and crusty dusty-deck fortran
> (i.e. the stuff we're embarassed by).
> 
> Making this distiction allows us to fine-tune the default behaviour
> of gfortran, to accept both kinds of extensions but to warn about
> the latter.  This is the behaviour of -std=gnu.  As an enhancement
> to shut up these warnings, I've also added -std=legacy which makes
> a best effort to compile whatever it can without warnings.  I've
> also allowed -pedantic to pretty much undo -std=legacy warning wise,
> and effectively "-std=legacy -pedantic" is equivalent to "-std=gnu".

I like the general idea. Perhaps I would personally have chosen
GFC_STD_DUSTY, but I guess _LEGACY is just as good and working code
beats talk any day. ;-)
 
> Although there are no users of this infrastructure yet, it should
> resolve the LOGICAL <-> INTEGER conversion issue to everyone's
> staisfaction and allow extensions such as using real numbers to
> index arrays, or omitting commas to reclassified as GFC_STD_LEGACY.
> These are really things that warning about, and writers of new code
> should be exposed to these warnings even without specifying
> -pedantic or -std=f95.

I think stuff like Hollerith would be well suited for GFC_STD_LEGACY
as well (wasn't there a patch to add Hollerith support a few days
ago?).

> Ok for mainline?

I'll see if I have time to regtest the patch tomorrow, but on the
surface it looks good, and as I said, I like the general idea.

> ===================================================================
> RCS file: /cvs/gcc/gcc/gcc/fortran/options.c,v
> retrieving revision 1.19
> diff -c -3 -p -r1.19 options.c
> *** options.c	10 May 2005 22:06:43 -0000	1.19
> --- options.c	28 May 2005 18:36:06 -0000

[snip]

> *************** gfc_post_options (const char **pfilename
> *** 113,118 ****
> --- 114,122 ----
>     /* If -pedantic, warn about the use of GNU extensions.  */
>     if (pedantic && (gfc_option.allow_std & GFC_STD_GNU) != 0)
>       gfc_option.warn_std |= GFC_STD_GNU;
> +   /* -std=legacy -pendantic is effectively -std=gnu.  */
                        1
Typo at (1).


-- 
Janne Blomqvist