On Thu, Apr 23, 2020 at 11:34:26AM +0000, Pascal Cuoq wrote:
> Hello again,
> 
> Rich Felker <dalias@libc.org> wrote:
> > I think this patch may result in wrong error behavior on a trivial
> > scanf that doesn't try to read anything. Instead it should be:
> >
> >        if (!f->rpos) __toread(f);
> >        if (!f->rpos) goto input_fail;
> >
> > so that the error path is taken only on failure to enter read mode,
> > not on EOF.
> 
> This has indeed fixed the invalid comparisons that were observed
> from the tests I mentioned earlier, but a different test still has
> the same problem.
> 
> As of commit 33338eb, the function wcstox does:
>         f.rpos = f.rend = 0;
>         f.buf = buf + 4;
> 
> (https://git.musl-libc.org/cgit/musl/tree/src/stdlib/wcstol.c?id=33338ebc853d37c80f0f236cc7a92cb0acc6aace#n38 )
> 
> It then passes the address of this f to shlim (line 45), causing the
> same invalid pointer subtraction f->buf - f->rpos that has already
> been discussed in this thread.

Thanks. The attached should fix it, I think.

Rich