[Doc]tracepoint: change *$esp@300 to *(unsigned char *)$esp@300

[Eli Zaretskii]

> Date: Tue, 24 Aug 2010 10:32:58 -0700
> From: Michael Snyder <msnyder@vmware.com>
> CC: Eli Zaretskii <eliz@gnu.org>, 
>  "gdb-patches@sourceware.org" <gdb-patches@sourceware.org>
> 
> Hui Zhu wrote:
> > On Tue, Aug 24, 2010 at 11:07, Eli Zaretskii <eliz@gnu.org> wrote:
> >>> From: Hui Zhu <teawater@gmail.com>
> >>> Date: Tue, 24 Aug 2010 10:10:19 +0800
> >>> Cc: Eli Zaretskii <eliz@gnu.org>
> >>>
> >>> But *(unsigned char *)$esp@300 can work:
> >> What about *(int *)$esp@300 ?
> >>
> > 
> > It will make trace collect 1200.
> > If "unsigned char" is too big, what about *(char *)$esp@300?
> 
> But 300 words might be good too.  What about:
> 
> +bytes from the stack pointer with something like @code{*
> (char *)$esp@@300}, or 300 words with @code{*(int *)$esp@@300}.

Fine with me.