[doc/tracepoint] Add a note for assigning values of inferior to trace state variables

[doc/tracepoint] Add a note for assigning values of inferior to trace state variables

[Hui Zhu]

Hi,

I talk about a bug about assigning values of inferior to trace state variables
http://sources.redhat.com/ml/gdb/2011-07/msg00009.html

this issue can be handle by convert value to (uint64_t), for example:
teval $tmp=(uint64_t)a

So I make a patch to update the doc.

Please help me review it.

Thanks,
Hui

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

	* gdb.texinfo (Tracepoint Action Lists): Add a note for assigning
	values of inferior to trace state variables.

---
 doc/gdb.texinfo |    6 ++++++
 1 file changed, 6 insertions(+)

--- a/doc/gdb.texinfo
+++ b/doc/gdb.texinfo
@@ -10321,6 +10321,12 @@ are discarded, so this is mainly useful
 state variables (@pxref{Trace State Variables}) without adding those
 values to the trace buffer, as would be the case if the @code{collect}
 action were used.
+Please note that if you want assigning values of inferior to trace state
+variables, please convert it to unsigned 64bit first.  For example:
+
+@smallexample
+>teval $c=(uint64_t)jiffies_64
+@end smallexample

 @kindex while-stepping @r{(tracepoints)}
 @item while-stepping @var{n}

Re: [doc/tracepoint] Add a note for assigning values of inferior to trace state variables

[Eli Zaretskii]

> From: Hui Zhu <teawater@gmail.com>
> Date: Fri, 16 Sep 2011 16:56:36 +0800
> Cc: Eli Zaretskii <eliz@gnu.org>
> 
> I talk about a bug about assigning values of inferior to trace state variables
> http://sources.redhat.com/ml/gdb/2011-07/msg00009.html

That thread died with Tom asking for details.  Was the issue resolved
off-list?

> this issue can be handle by convert value to (uint64_t), for example:
> teval $tmp=(uint64_t)a

Isn't this specific to the platform where this runs?  I don't think we
should have platform-specific information, and such minor details at
that, in general sections.

Re: [doc/tracepoint] Add a note for assigning values of inferior to trace state variables

[Joel Brobecker]

> > this issue can be handle by convert value to (uint64_t), for example:
> > teval $tmp=(uint64_t)a
> 
> Isn't this specific to the platform where this runs?  I don't think we
> should have platform-specific information, and such minor details at
> that, in general sections.

One of the things that struck me when I read the diff is that
I asked myself why this conversion is necessary. The patch is
only a small piece of the documentation, so perhaps the reasons
are clear already.  But otherwise, it might be worth explaining.

-- 
Joel

Re: [doc/tracepoint] Add a note for assigning values of inferior to trace state variables

[Hui Zhu]

The issue is:
2d000b    setv
260003    reg
1620        ext
27            end

Setv before put value to the stack.

After convert will OK.

Do you have idea on it?

Thanks,
Hui



On Sat, Sep 17, 2011 at 04:27, Joel Brobecker <brobecker@adacore.com> wrote:
>> > this issue can be handle by convert value to (uint64_t), for example:
>> > teval $tmp=(uint64_t)a
>>
>> Isn't this specific to the platform where this runs?  I don't think we
>> should have platform-specific information, and such minor details at
>> that, in general sections.
>
> One of the things that struck me when I read the diff is that
> I asked myself why this conversion is necessary. The patch is
> only a small piece of the documentation, so perhaps the reasons
> are clear already.  But otherwise, it might be worth explaining.
>
> --
> Joel
>

Re: [doc/tracepoint] Add a note for assigning values of inferior to trace state variables

[Pedro Alves]

On Saturday 17 September 2011 15:34:33, Hui Zhu wrote:
> The issue is:
> 2d000b    setv
> 260003    reg
> 1620        ext
> 27            end
> 
> Setv before put value to the stack.
> 
> After convert will OK.
> 
> Do you have idea on it?

I still don't understand the problem.  :-(  Please show with
e.g., `maint agent-eval' what you think is wrong, and what you
think should be happening.

-- 
Pedro Alves

Re: [doc/tracepoint] Add a note for assigning values of inferior to trace state variables

[Pedro Alves]

On Friday 16 September 2011 09:56:36, Hui Zhu wrote:

> I talk about a bug about assigning values of inferior to trace state variables
> http://sources.redhat.com/ml/gdb/2011-07/msg00009.html
> 
> this issue can be handle by convert value to (uint64_t), for example:
> teval $tmp=(uint64_t)a

Note trace state variables are signed, not unsigned.

-- 
Pedro Alves