Command File Scope Checking

Command File Scope Checking

[Rob Quill]

Hi,

Is it possible to check if a variable is in scope when using a command
file, because I don't want control to return to GDB when a variable
goes out of scope, so I would like to know if a variable is in scope
before I check the value of it.

Thanks.

Rob

Re: Command File Scope Checking

[Eli Zaretskii]

> Date: Mon, 23 Oct 2006 11:45:23 +0100
> From: "Rob Quill" <rob.quill@gmail.com>
> 
> Is it possible to check if a variable is in scope when using a command
> file, because I don't want control to return to GDB when a variable
> goes out of scope, so I would like to know if a variable is in scope
> before I check the value of it.

    (gdb) info address foobar
    No symbol "foobar" in current context.

If the variable _is_ in scope, you will see a different message, like
this:

    (gdb) info address arglen
    Symbol "arglen" is a variable in register eax.

or maybe this:

    Symbol "gdb_use_lsb" is static storage at address 0x815e720

Command File Scope Checking

[Rob Quill]

On 23/10/06, Eli Zaretskii <eliz@gnu.org> wrote:
> > Date: Mon, 23 Oct 2006 11:45:23 +0100
> > From: "Rob Quill" <rob.quill@gmail.com>
> >
> > Is it possible to check if a variable is in scope when using a command
> > file, because I don't want control to return to GDB when a variable
> > goes out of scope, so I would like to know if a variable is in scope
> > before I check the value of it.
>
>     (gdb) info address foobar
>     No symbol "foobar" in current context.

So is it possible to check the result of doing info address foobar,
whilst still in the command file? So that if it is out of scope the
script can do action B instead of action A?

Thanks,
Rob

>
> If the variable _is_ in scope, you will see a different message, like
> this:
>
>     (gdb) info address arglen
>     Symbol "arglen" is a variable in register eax.
>
> or maybe this:
>
>     Symbol "gdb_use_lsb" is static storage at address 0x815e720
>

Re: Command File Scope Checking

[Daniel Jacobowitz]

On Mon, Oct 23, 2006 at 09:15:31PM +0100, Rob Quill wrote:
> On 23/10/06, Eli Zaretskii <eliz@gnu.org> wrote:
> >> Date: Mon, 23 Oct 2006 11:45:23 +0100
> >> From: "Rob Quill" <rob.quill@gmail.com>
> >>
> >> Is it possible to check if a variable is in scope when using a command
> >> file, because I don't want control to return to GDB when a variable
> >> goes out of scope, so I would like to know if a variable is in scope
> >> before I check the value of it.
> >
> >    (gdb) info address foobar
> >    No symbol "foobar" in current context.
> 
> So is it possible to check the result of doing info address foobar,
> whilst still in the command file? So that if it is out of scope the
> script can do action B instead of action A?

No, this sort of thing is not possible in the current GDB scripting
interface.  Yet, anyway.

-- 
Daniel Jacobowitz
CodeSourcery

Re: Command File Scope Checking

[Rob Quill]

On 23/10/06, Daniel Jacobowitz <drow@false.org> wrote:
> On Mon, Oct 23, 2006 at 09:15:31PM +0100, Rob Quill wrote:
> > On 23/10/06, Eli Zaretskii <eliz@gnu.org> wrote:
> > >> Date: Mon, 23 Oct 2006 11:45:23 +0100
> > >> From: "Rob Quill" <rob.quill@gmail.com>
> > >>
> > >> Is it possible to check if a variable is in scope when using a command
> > >> file, because I don't want control to return to GDB when a variable
> > >> goes out of scope, so I would like to know if a variable is in scope
> > >> before I check the value of it.
> > >
> > >    (gdb) info address foobar
> > >    No symbol "foobar" in current context.
> >
> > So is it possible to check the result of doing info address foobar,
> > whilst still in the command file? So that if it is out of scope the
> > script can do action B instead of action A?
>
> No, this sort of thing is not possible in the current GDB scripting
> interface.  Yet, anyway.

In that case, I'm in need of some advice. I was thinking it would work
something like this:

Write program that given an LTL formula, writes a GDB command file
representing the automaton and stepping through the code, checking
values of variables and using these to make transitions. Pipe the
output to a file and then analyse the file is some way to decide if
the condition had been met.

But if I am stepping through the code, and a variable goes out of
scope, how do you suggest I go about dealing with this?

Rob

>
> --
> Daniel Jacobowitz
> CodeSourcery
>

Re: Command File Scope Checking

[Jim Blandy]

"Rob Quill" <rob.quill@gmail.com> writes:
> On 23/10/06, Daniel Jacobowitz <drow@false.org> wrote:
>> On Mon, Oct 23, 2006 at 09:15:31PM +0100, Rob Quill wrote:
>> > On 23/10/06, Eli Zaretskii <eliz@gnu.org> wrote:
>> > >> Date: Mon, 23 Oct 2006 11:45:23 +0100
>> > >> From: "Rob Quill" <rob.quill@gmail.com>
>> > >>
>> > >> Is it possible to check if a variable is in scope when using a command
>> > >> file, because I don't want control to return to GDB when a variable
>> > >> goes out of scope, so I would like to know if a variable is in scope
>> > >> before I check the value of it.
>> > >
>> > >    (gdb) info address foobar
>> > >    No symbol "foobar" in current context.
>> >
>> > So is it possible to check the result of doing info address foobar,
>> > whilst still in the command file? So that if it is out of scope the
>> > script can do action B instead of action A?
>>
>> No, this sort of thing is not possible in the current GDB scripting
>> interface.  Yet, anyway.
>
> In that case, I'm in need of some advice. I was thinking it would work
> something like this:
>
> Write program that given an LTL formula, writes a GDB command file
> representing the automaton and stepping through the code, checking
> values of variables and using these to make transitions. Pipe the
> output to a file and then analyse the file is some way to decide if
> the condition had been met.
>
> But if I am stepping through the code, and a variable goes out of
> scope, how do you suggest I go about dealing with this?

I'm surprised that your LTL automaton would need to check this.  If
your conditions are referring to variables that are out of scope, then
something strange is going on.

Re: Command File Scope Checking

[Eli Zaretskii]

> Date: Mon, 23 Oct 2006 22:08:19 +0100
> From: "Rob Quill" <rob.quill@gmail.com>
> 
> But if I am stepping through the code, and a variable goes out of
> scope, how do you suggest I go about dealing with this?

Why do you need to ``deal'' with that?  I guess I don't understand
your problem, because I don't see any reason to care about such a
situation: at most, GDB will print an error message.

Can you show a small GDB script similar to what you use, and tell what
happens when a variable goes out of scope and how does that interfere
with the script?

Re: Command File Scope Checking

[Rob Quill]

On 24/10/06, Eli Zaretskii <eliz@gnu.org> wrote:
> > Date: Mon, 23 Oct 2006 22:08:19 +0100
> > From: "Rob Quill" <rob.quill@gmail.com>
> >
> > But if I am stepping through the code, and a variable goes out of
> > scope, how do you suggest I go about dealing with this?
>
> Why do you need to ``deal'' with that?  I guess I don't understand
> your problem, because I don't see any reason to care about such a
> situation: at most, GDB will print an error message.
>
> Can you show a small GDB script similar to what you use, and tell what
> happens when a variable goes out of scope and how does that interfere
> with the script?

I suppose you're right actually. Really I need to gert an
implementation together and see how it goes before I worry about these
problems. Thanks for your help, I'll keep yolu updated on how it goes.

Thanks,
Rob