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Re: Timer
- From: Pedro Alves <palves at redhat dot com>
- To: Marc Brünink <marc at nus dot edu dot sg>
- Cc: Doug Evans <dje at google dot com>, gdb <gdb at sourceware dot org>
- Date: Tue, 07 May 2013 09:48:01 +0100
- Subject: Re: Timer
- References: <A941B6D9-B0CA-4EC2-AEFE-476014555337 at nus dot edu dot sg> <CADPb22Q0rQCQMee992CZBPHkjJOvBkCZMhqHx0V_y7v=VWDORA at mail dot gmail dot com> <52771B43-9617-412D-B9F8-5730757D6BAF at nus dot edu dot sg>
On 05/07/2013 07:42 AM, Marc Brünink wrote:
>
> On May 7, 2013, at 12:43 PM, Doug Evans wrote:
>
>> On Mon, May 6, 2013 at 2:52 AM, Marc Brünink <marc@nus.edu.sg> wrote:
>>> I want to execute a piece of code at regular intervals. Actually I'm sampling $pc.
>>> (let's not go into detail why I use gdb)
>>>
>>> My current solution just starts another process that sends a SIGTRAP to the debugged application. Using a simple script I can print the $pc.
>>>
>>> However, I just realised that this approach does not work too well. If gdb is stopped due to a breakpoint it will interpret the received SIGTRAP as another hit of the very same breakpoint.
>>>
>>> Reproduce:
>>> 1. Attach to any program
>>> 2. Create any breakpoint
>>> 3. Wait until breakpoint is hit
>>> 4. Send SIGTRAP to debugged application
>>> 5. continue
>>>
>>> Actually, now that I think about it, I should have anticipated this behaviour.
>>> Is there a better way to execute a piece of code at regular intervals?
You could also use another signal instead of SIGTRAP.
>> bash$ man setitimer
>
> I suppose you are suggesting to modify either GDB or the application. This is exactly what I don't want. Any other way to accomplish this (using gdb)?
You could use LD_PRELOAD to inject a library that uses setitimer into your program.
I guess you could do it with gdb python scripting too.
--
Pedro Alves