Re: [Boost-users] Access violation in Boost.Format usingabsolutetabulations

From: Edson Tadeu (e.tadeu_at_[hidden])
Date: 2006-05-24 17:25:51

Joaquín,

Actually I tried to simplify into a test case a code in a real application I
was debugging, but I forgot to put a line in it:

using boost::format;
format f("%0s%-32.32s:%|40t|%|.6|%|55t|%25s\n");
f.bind_arg(1,"");
f % "test1" % 2.0 % "test3";
f % "test4" % 5.0 % "test6"; // calls clear() and breaks

It didn't call clear() explicitly, but operator%() automatically calls it to
refresh to a new string. Your test does the same thing and is much clearer
and simpler. I got a crash on your code too, when debugging on msvc 7.

I changed the offending line to:

            if( bound_.size()==0 || (items_[i].argN_ >= 0) && !bound_[
items_[i].argN_ ] )

And now it is ok here!
  Regards,

Edson Tadeu M. Manoel

On 5/24/06, Joaquín Mª López Muñoz <joaquin_at_[hidden]> wrote:
>
> Edson Tadeu ha escrito:
>
> > If the format string have an absolute tabulation (%t), the
> > basic_format::clear()
> > method throws an access violation because of this piece code in
> > format_implementation.hpp(138):
> >
> >             if( bound_.size()==0 || !bound_[ items_[i].argN_ ] )
> >
> > Here items_[i].argN_ can be negative (defined in internals.hpp(70)),
> > which
> > is an invalid index to bound_[].
> > I think a simple check of greather than zero would suffice to fix it.
> > Here is a code that catches it:
> >
> > using boost::format;
> > format f("%0s%-32.32s:%|40t|%|.6|%|55t|%25s\n");
> > f % "test1" % 2.0 % "test3";
> > f % "test4" % 5.0 % "test6"; // calls clear() and breaks
>
> Hello Edson,
>
> The test case you propose doesn't call clear() nor shows the error
> you refer to: instead, a boost::io::too_many_args is thrown. Am I
> missing something?
>
> Anyway, seems like you spotted a real problem, and the following
> does actually call bound_[ items_[i].argN_ ] with items_[i].argN_
> negative inside basic_format::clear(), at least for the Boost.Format
> code in the CVS trunk:
>
>     format f("%40t%1%");
>     int x=0;
>     f.bind_arg(1,x);
>     f.clear();
>
> Can you also observe a crash with this snippet? If so, I can try to
> propose and commit a fix following your suggestion of adding
> a positiveness check in the offending if.
>
> Joaquín M López Muñoz
> Telefónica, Investigación y Desarrollo
>
>
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