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Re: bison bug when standard input is closed

From: Hans Aberg
Subject: Re: bison bug when standard input is closed
Date: Sat, 01 Jan 2005 19:48:10 +0100
User-agent: Microsoft-Outlook-Express-Macintosh-Edition/5.0.6

On 2005/01/01 10:26, Paul Eggert at address@hidden wrote:

>> There is a bug in the scan-skel.l dating back to at least Bison 1.75: The
>> rule that opens the file streams, at the first run, it tries to close the
>> standard output stream.
> Thanks for reporting this.  I installed the following patch. ...
> +  if (outname)
> +    {
> +      free (outname);
> +      xfclose (yyout);
> +    }
> outname = xstrdup (filename);
> -  xfclose (yyout);
> yyout = xfopen (outname, "w");
> lineno = 1;
> }

It seems to work with me. Strictly speaking, I think the operation of
closing an already closed file under C is undefined. So it is probably good
to fix this type of problem, because it is a kind of bug very hard to
detect, when it causes a problem.

There is the same rror in the last rule:
  <<EOF>>       xfclose (yyout); free (outname); return EOF;
This is an error of skeleton files that do not contain an @output.

So change to say
  <<EOF>>       if (outname)  xfclose (yyout); free (outname); return EOF;
  <<EOF>>     if (outname) { xfclose (yyout); free (outname); } return EOF;

I am not sure why skeleton files without @output causes nontermination.
There must be an input pattern not matched by any of the rules.

  Hans Aberg

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