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Re: Re: g77 legacy features in gfortran
- From: "Timothy C Prince" <tprince at myrealbox dot com>
- To: burnus at net-b dot de
- Cc: howarth at bromo dot msbb dot uc dot edu, fortran at gcc dot gnu dot org
- Date: Mon, 08 Oct 2007 15:43:22 +0000
- Subject: Re: Re: g77 legacy features in gfortran
- Reply-to: tprince at computer dot org
-----Original Message-----
From: Tobias Burnus <burnus@net-b.de>
To: Jack Howarth <howarth@bromo.msbb.uc.edu>
Date: Mon, 08 Oct 2007 16:58:02 +0200
Subject: Re: g77 legacy features in gfortran
Hi Jack,
Regarding g77 and gfortran:
gfortran supports Fortran 95, which includes all of Fortran 77 (modulo
some deleted features, which all Fortran 95 compilers support
nonetheless); it also supports a large subset of vendor extensions
[including some unsupported by g77] and strives to be g77 compatible. In
some, very limited cases it was decided not to be fully compatible with
g77; additionally, some extensions might be missing because they were
overlooked so far - or PRs exist.
Jack Howarth wrote:
> 1) support for multiple entry points in subprocedures (sad but necessary
> for legacy code);
>
ENTRY is (still) part of the Fortran standard and thus supported.
> 3) stabs or dwarf debugging information for COMMON and EQUIVALENCE
> symbols;
>
I think this is supported, but I did not check. Debugging information is
a weak point in gfortran - last but not least because none of the main
gfortran developers is a dwarf expert.
> 4) source input compatibility (tab handling and free-form continuation).
>
Tab is supported. Regarding free-form continuation: The free format is
supported (as required by the Fortran standard, but by default less
strict); I don't know, however, what exactly is meant by "free-form
continuation".
Regarding Tim's remarks: In fixed format, everything after column 78
(free format: 132) is ignored by default. This can be tuned via
-ffixed-line-length-n (or -ffree-line-length-n); some programs make use
of this by putting comments, a "&" or similar in columns > 78.
_______________________________---
Choice of column 78 is unusual. Fortran standard would ignore everything after column 72, in fixed format. I agree that I don't expect g77 to be standard conforming there, which could make it difficult to achieve g77 compatibility.
Tim Prince