From mboxrd@z Thu Jan  1 00:00:00 1970
Date: Tue, 17 Mar 2009 02:31:42 +0100
From: Martin Neubauer <m.ne@gmx.net>
To: Fans of the OS Plan 9 from Bell Labs <9fans@9fans.net>
Message-ID: <20090317013142.GA990@shodan.homeunix.net>
References: <5d375e920903161626o78226952j8a6088c1373cfbe3@mail.gmail.com>
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In-Reply-To: <5d375e920903161626o78226952j8a6088c1373cfbe3@mail.gmail.com>
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Subject: Re: [9fans] Strange rc bug for the 9fans bug-squashing squad
Topicbox-Message-UUID: bca9231c-ead4-11e9-9d60-3106f5b1d025

Hi,

I think the following gives a clue:

	% cmp f f2
	f f2 differ: char 8193

The following snippet from the Xbackq code seems to be the culprit:

	char wd[8193];
	int c;
	char *s, *ewd=&wd[8192], *stop;

	...

		while((c = rchr(f))!=EOF){
			if(strchr(stop, c) || s==ewd){
				if(s!=wd){
					*s='\0';
					v = newword(wd, v);
					s = wd;
				}
			}
			else *s++=c;
		}

Keeping the loop from dropping characters is trivial.  Getting rid of
the inserted space probably requires a dynamic buffer.  I might give
it a shot.

Regards,
	Martin

* Uriel (uriel99@gmail.com) wrote:
> At first I thought very big rc variables seem to become strangely corrupted.
>
> % for(i in `{seq 1000}) { echo 0123456789 >> f }
> % ifs='' {x=`{cat f}}
> % echo -n $x > f2
> % diff f f2
> 745c745
> < 0123456789
> ---
> > 01234567 9
>
> But the bug seems to be in `{ } because replacing the use of the x var
> with simply:
>
> % ifs='' { echo -n `{cat f} > f2}
>
> Produces the same results.
>
> Longer strings get more random(?) characters 'blanked'.
>
> The results are identical in p9p and native plan9.
>
> I looked a bit around the rc source that seemed relevant, but didn't
> see any obvious errors, but I don't fully understand the code.
>
> Peace
>
> uriel