From: Paul Smith <paul@mad-scientist.net>
To: Jonathan Wakely <jwakely.gcc@gmail.com>
Cc: gcc-help <gcc-help@gcc.gnu.org>
Subject: Re: Help using the GDB C++ STL pretty-printers / xmethods
Date: Sun, 08 May 2022 16:26:20 -0400 [thread overview]
Message-ID: <0cb93fd8169d89f2263204de88ca45f68d39677e.camel@mad-scientist.net> (raw)
In-Reply-To: <7c6d308fdbbcabf83dd5423c33ca851666beaae7.camel@mad-scientist.net>
On Sun, 2022-05-08 at 15:44 -0400, Paul Smith wrote:
> On Sun, 2022-05-08 at 09:16 +0100, Jonathan Wakely wrote:
> > > gdb.set_convenience_variable('mgr', val['mgr'])
> > > init = gdb.parse_and_eval('$mgr->initialized')
> > >
> > > This will use the xmethod to evaluate the expression.
> >
> > And then:
> >
> > if init:
> > return gdb.parse_and_eval('*$mgr')
>
> Unfortunately, this doesn't work :(. I can't do it from the GDB
> command line or python (I have tried both with the same results).
> Something about convenience variables doesn't play well with xmethods
> (or maybe this xmethod implementation specifically?)
Hm. I have done a fair amount of work writing GDB Python convenience
functions and commands, but I've only done a small amount of pretty-
printer work and no xmethod implementations.
But I don't understand this from the C++ STL xmethods.py:
class UniquePtrGetWorker(gdb.xmethod.XMethodWorker):
...
def __call__(self, obj):
impl_type = obj.dereference().type.fields()[0].type.tag
Why are we using dereference() here? Aren't we expecting to receive a
gdb.Value of type std::unique_ptr here, not _pointer to_
std::unique_ptr?
But, it definitely doesn't work to remove the dereference(), and also
the value we get normally IS a pointer; adding debugging above I see:
type: 'std::unique_ptr<Foo, std::default_delete<Foo> > *'
I don't really grok xmethods so I'm not sure how calling "foo->val"
when "foo" is std::unique_ptr<> results in the __call__ method being
invoked with a gdb.Value of type std::unique_ptr<>*.
My suspicion (not based on anything) is that whatever the reason is, is
why I can't use these xmethods with a convenience variable.
next prev parent reply other threads:[~2022-05-08 20:26 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-05-07 1:23 Paul Smith
2022-05-07 11:19 ` Hannes Domani
2022-05-07 15:07 ` Paul Smith
2022-05-07 15:35 ` Jonathan Wakely
2022-05-07 19:07 ` Paul Smith
2022-05-07 19:51 ` Jonathan Wakely
2022-05-07 23:08 ` Paul Smith
2022-05-08 8:13 ` Jonathan Wakely
2022-05-08 8:16 ` Jonathan Wakely
2022-05-08 14:09 ` Paul Smith
2022-05-08 14:36 ` Jonathan Wakely
2022-05-08 19:44 ` Paul Smith
2022-05-08 20:26 ` Paul Smith [this message]
2022-05-09 10:47 ` Hannes Domani
2022-05-09 10:52 ` Hannes Domani
2022-05-09 9:32 ` Jonathan Wakely
2022-05-09 11:23 ` Jonathan Wakely
2022-05-09 14:05 ` Paul Smith
2022-05-09 14:40 ` Paul Smith
2022-05-07 15:44 ` Hannes Domani
2022-05-07 15:25 ` Jonathan Wakely
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