[RFC][PATCH] -d_lines

[Tobias Schlüter]

Bernhard Fischer wrote:
> Several "ancient" fortran programs do exercise -- as well as most
> commercial compilers do support -- a variant of fixed-mode where 'D'
> resp. 'd' in the first column of source is either treated as comment --
> per default -- or as code -- if the compiler sees an argument akin to
> -d_lines.
> 
> gfortran is, ATM, not able to deal with those, however.

Attached patch adds this support to gfortran.  I thought the easiest way of
getting this simple thing in without having to wait for Bernhard's copyright
assigment, would be to take the 5 minutes and reimplement it myself.

Unfortunately, I was wrong: in order to detect the use of the -f{no-}d-line
options in free form at option parse time, I had to move the determination of
the source form into the option handling.  I think this is a worthwhile
cleanup in itself, it actually removes a bit of unnecessary code which I found
when reviewing a patch by Steve a few days ago.  Nevertheless, the patch
became much larger than what I originally thought.

There are two questions:
1. we had two places where we store the source file: gfc_options.source and
gfc_source_file.  I decided to keep the latter and remove the former, but I
can also understand if we would rather want to keep the former (this would
follow the spirit of keeping everything given on the command line into
gfc_option)?  In the same spirit, should we also move gfc_current_form into
gfc_option?
2. I've decided to create three possibilities:
   - -fd-lines given: treat 'd' in column 1 as equivalent to a single blank
   - -fno-d-lines given: treat 'D' in column 1 as equivalent to a 'C'
     (=comment)
   - neither option given: syntax error (behavior following the standard)
Does everybody agree that this is the right way to deal with this?

Bootstrapped and regtested on i686-pc-linux, patch and testcases attached.  Ok?

- Tobi

2005-08-17  Tobias Schl"uter  <tobias.schlueter@physik.uni-muenchen.de>
fortran/
	* gfortran.h (gfc_option_t): Remove source field.  Add
	flag_d_lines field.
	(gfc_new_file): Remove arguments in prototype.
	* f95-lang.c (gfc_init): Use gfc_source_file instead of
	gfc_option.source.  Call gfc_new_file without arguments.
	* invoke.texi: Document new option '-fd-lines'.
	* lang.opt: Add new option '-fd-lines'.  Alphabetize.
	* options.c (gfc_init_options): Initialize gfc_source_file instead
	of gfc_option.source.  Initialize gfc_option.flag_d_lines.
	(form_from_filename): Move here from scanner.c
	(gfc_post_options): Set gfc_source_file.  Determine source form.
	* scanner.c (skip_fixed_comments): Deal with d-lines.
	(form_from_filename): Moved to options.c.
	(gfc_new_file): Remove arguments.  Don't initialize
	gfc_source_file, don't determine source form.
	* trans-const.c (gfc_init_constants): Use gfc_source_file instead
	of gfc_option.source.
	
testsuite/
	* d_lines_1.f, d_lines_2.f, d_lines_3.f, d_lines_4.f: New.
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