[doc/tracepoint] Change *$esp@300 to *(unsigned char *)$esp@300.

[Hui Zhu <teawater@gmail.com>]

Hi,

I found that if want collect stack in tracepoint action like doc said
will got error.

collect $rsp@512
Left operand of `@' must be an object in memory.

But change to:
collect *(unsigned char *)$rsp@512

Will fix it.

So I make a patch for doc.

Please help me review it.

Thanks,
Hui

2011-09-16  Hui Zhu  <teawater@gmail.com>

	* gdb.texinfo (Tracepoint Restrictions): Change *$esp@300
	to *(unsigned char *)$esp@300.
---
 doc/gdb.texinfo |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/doc/gdb.texinfo
+++ b/doc/gdb.texinfo
@@ -10627,7 +10627,7 @@ by @code{ptr}.
 @item
 It is not possible to collect a complete stack backtrace at a
 tracepoint.  Instead, you may collect the registers and a few hundred
-bytes from the stack pointer with something like @code{*$esp@@300}
+bytes from the stack pointer with something like @code{*(unsigned
char *)$esp@@300}
 (adjust to use the name of the actual stack pointer register on your
 target architecture, and the amount of stack you wish to capture).
 Then the @code{backtrace} command will show a partial backtrace when