From: Mauricio Fernandez <mfp@...>
Date: 2007-01-04T02:06:29+09:00
Subject: Re: Suggestion: Post indentation style guideline to "Rules for Core Developers"

On Mon, Jan 01, 2007 at 11:58:18PM +0900, Rob Muhlestein wrote:
> On Sun, 2006-12-31 at 15:02 +0900, Eric Hodel wrote:
> > On Dec 30, 2006, at 20:02, Rob Muhlestein wrote:
> > > What *is* the preferred indentation style for ruby core C code?
> > 
> > It appears to by four spaces with hard tabs.  All the files I've  
> > encountered have this structure.
> > 
> Really, humm, in which files specifically are you seeing the mostly hard
> tabs? I'm seeing mostly soft tabs. In fact I see very few hard tabs in
> io.c, error.c, marshal.c, regcomp.c (which also has 2 space instead of
> 4) with vi ':set list' turned on (and thanks richard for the vi rc setup
> reminders, been using them for years). Here's io.c for example:
> 
>    1883 static VALUE$
>    1884 rb_io_readline(int argc, VALUE *argv, VALUE io)$
>    1885 {$
>    1886     VALUE line = rb_io_gets_m(argc, argv, io);$
>    1887 $
>    1888     if (NIL_P(line)) {$
>    1889 ^Irb_eof_error();$
>    1890     }$
>    1891     return line;$
>    1892 }$
> 
> Notice the ^I indicating a tab on 1889 where everything
> else is using spaces. 

IIRC a mixture of hard tabs (considered as 8-space ones) and spaces is used,
with 4-space indentation for most files (regcomp.c belongs to Oniguruma
which seems to use 2-space). For a given indentation level, as many tabs as
possible are used, and up to 7 spaces are added to reach the desired
indentation.

In the above snippet, only line 1889 is indented >= 8 characters, and it's
thus the only one where a hard tab was used.

This explains it better:

$ ruby -e 'ARGF.each_with_index{|x,i| puts "%06d %s" % [i, x.gsub(/\t/,"###TAB##")]}' eval.c
...
001988 void
001989 rb_frozen_class_p(klass)
001990     VALUE klass;
001991 {
001992     char *desc = "something(?!)";
001993 
001994     if (OBJ_FROZEN(klass)) {
001995 ###TAB##if (FL_TEST(klass, FL_SINGLETON))
001996 ###TAB##    desc = "object";
001997 ###TAB##else {
001998 ###TAB##    switch (TYPE(klass)) {
001999 ###TAB##      case T_MODULE:
002000 ###TAB##      case T_ICLASS:
002001 ###TAB#####TAB##desc = "module"; break;
002002 ###TAB##      case T_CLASS:
002003 ###TAB#####TAB##desc = "class"; break;
002004 ###TAB##    }
002005 ###TAB##}
002006 ###TAB##rb_error_frozen(desc);
002007     }
002008 }

-- 
Mauricio Fernandez  -   http://eigenclass.org   -  singular Ruby