GDB: Setting the prompt from python

GDB: Setting the prompt from python

[Paul Smith]

Is it possible to change the GDB prompt from within Python, such that
the prompt contains a trailing space (like the default prompt)?

I cannot figure it out.

If I run set prompt from the normal command interpreter I can easily
just put a space at the end and it works:

  (gdb) set prompt XXX\n
  XXXprint 1
  1

  (gdb) set prompt XXX \n
  XXX print 1
  1

showing \n to indicate where I type ENTER

Fine.  But this doesn't work from Python:

  (gdb) python
  > gdb.execute('set prompt XXX ', True)
  > ^D
  XXXprint 1
  1

It seems that no matter what I do, the trailing space is stripped off.
Is there some other way to set the prompt from Python?

Help!!

Re: GDB: Setting the prompt from python

[Matt Rice]

On Sun, Oct 18, 2020 at 3:27 AM Paul Smith via Gdb <gdb@sourceware.org> wrote:
>
> Is it possible to change the GDB prompt from within Python, such that
> the prompt contains a trailing space (like the default prompt)?
>
> I cannot figure it out.
>
> If I run set prompt from the normal command interpreter I can easily
> just put a space at the end and it works:
>
>   (gdb) set prompt XXX\n
>   XXXprint 1
>   1
>
>   (gdb) set prompt XXX \n
>   XXX print 1
>   1
>
> showing \n to indicate where I type ENTER
>
> Fine.  But this doesn't work from Python:
>
>   (gdb) python
>   > gdb.execute('set prompt XXX ', True)
>   > ^D
>   XXXprint 1
>   1
>
> It seems that no matter what I do, the trailing space is stripped off.
> Is there some other way to set the prompt from Python?

Weird, using the python prompt hook does work.

(gdb) python
>gdb.prompt_hook = lambda old_prompt: "XXX "
>end
XXX quit

Re: GDB: Setting the prompt from python

[Paul Smith]

On Sun, 2020-10-18 at 09:24 +0000, Matt Rice wrote:
> > It seems that no matter what I do, the trailing space is stripped
> > off. Is there some other way to set the prompt from Python?
> 
> Weird, using the python prompt hook does work.
> 
> (gdb) python
> > gdb.prompt_hook = lambda old_prompt: "XXX "
> > end
> XXX quit

Aha!  Thanks.

Well, it kind of makes sense to me but is unfortunate.  The problem is
probably that GDB is stripping the command that is passed to it via
gdb.execute() before running it so the whitespace goes away before GDB
tries to run the command.

In the prompt_hook version the static string containing the space is
returned and so is preserved.

Re: GDB: Setting the prompt from python

[Matt Rice]

On Sun, Oct 18, 2020 at 2:08 PM Paul Smith <psmith@gnu.org> wrote:
>
> On Sun, 2020-10-18 at 09:24 +0000, Matt Rice wrote:
> > > It seems that no matter what I do, the trailing space is stripped
> > > off. Is there some other way to set the prompt from Python?
> >
> > Weird, using the python prompt hook does work.
> >
> > (gdb) python
> > > gdb.prompt_hook = lambda old_prompt: "XXX "
> > > end
> > XXX quit
>
> Aha!  Thanks.
>
> Well, it kind of makes sense to me but is unfortunate.  The problem is
> probably that GDB is stripping the command that is passed to it via
> gdb.execute() before running it so the whitespace goes away before GDB
> tries to run the command.
>
> In the prompt_hook version the static string containing the space is
> returned and so is preserved.
>

I forgot to mention, I believe when doing this via the prompt hook,
neither set prompt, or set extended-prompt are going to work again
unless the user also sets the prompt hook to None,
which may or may not be an issue for you, but something to be aware of.