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(g77-295.info)Better Source Model

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Better Source Model
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   `g77' needs to provide, as the default source-line model, a "pure
visual" mode, where the interpretation of a source program in this mode
can be accurately determined by a user looking at a traditionally
displayed rendition of the program (assuming the user knows whether the
program is fixed or free form).

   The design should assume the user cannot tell tabs from spaces and
cannot see trailing spaces on lines, but has canonical tab stops and,
for fixed-form source, has the ability to always know exactly where
column 72 is (since the Fortran standard itself requires this for
fixed-form source).

   This would change the default treatment of fixed-form source to not
treat lines with tabs as if they were infinitely long--instead, they
would end at column 72 just as if the tabs were replaced by spaces in
the canonical way.

   As part of this, provide common alternate models (Digital, `f2c',
and so on) via command-line options.  This includes allowing
arbitrarily long lines for free-form source as well as fixed-form
source and providing various limits and diagnostics as appropriate.

   Also, `g77' should offer, perhaps even default to, warnings when
characters beyond the last valid column are anything other than spaces.
This would mean code with "sequence numbers" in columns 73 through 80
would be rejected, and there's a lot of that kind of code around, but
one of the most frequent bugs encountered by new users is accidentally
writing fixed-form source code into and beyond column 73.  So, maybe
the users of old code would be able to more easily handle having to
specify, say, a `-Wno-col73to80' option.