mirror of
https://sourceware.org/git/binutils-gdb.git
synced 2026-08-27 00:26:02 -04:00
60cd57ff6e
All of our custom Python types are created as structs, like this:
struct some_new_type : public PyObject
{
... various fields ...
};
Then instances of this struct are created by calling PyObject_New,
either directly within GDB's C++ code, or within Python when a user's
Python script creates an instance of that class.
The problem is that Python is written in C, and PyObject_New doesn't
call any constructors for `some_new_type`, nor for any of the fields
within `some_new_type`.
If `some_new_type` is Plain Old Data (POD), then this is fine. Or, to
be more C++ specific, if `some_new_type` is trivially default
constructable, then we're fine.
But if a field within `some_new_type` has a non-trivial constructor,
then we're in trouble as that constructor will never be run.
An example of a problematic field type is frame_info_ptr. The
constructor for this type registers the new object with a central
management object, recording the `this` pointer, using this type within
`some_new_type` will not work as expected; frame invalidation will not
show up within the frame_info_ptr as you might expect.
And so, this type trait exists. Whenever a struct is created to define
a new Python type we should add a line like:
static_assert (gdb::is_python_allocatable_v<some_new_type>);
This will fail if any field of `some_new_type` are unsuitable for this
use.
We don't actually check is_trivially_default_constructible here. Some
types, e.g. ui_file_style::color, have non-trivial (or no default)
constructors, but are still safe to use within `some_new_type` because
their constructors just initialise data fields; there's nothing
"special" that the constructor does that cannot be achieved by
assigning the fields after creation with PyObject_New.
What actually matters is that the type is trivially destructible
(Python won't call C++ destructors, so destructors with side effects,
like deregistering from a list, would be skipped) and trivially
copyable (Python may copy objects with memcpy). Types like
frame_info_ptr, whose constructors and destructors have side effects
such as registering with a central management object, will be caught
because they are neither trivially destructible nor trivially copyable.
Simple POD types like ui_file_style are trivially destructible and
copyable, so pass this trait.
This commit adds the new type trait, and makes use of it in all cases
but one, pending_frame_object in python/py-unwind.c, has a field of
type frame_info_ptr, which is currently broken. This will be fixed,
and the static_assert added, in the next commit.
Approved-By: Tom Tromey <tom@tromey.com>
57 lines
1.6 KiB
C
57 lines
1.6 KiB
C
/* Python interface to inferior events.
|
|
|
|
Copyright (C) 2009-2026 Free Software Foundation, Inc.
|
|
|
|
This file is part of GDB.
|
|
|
|
This program is free software; you can redistribute it and/or modify
|
|
it under the terms of the GNU General Public License as published by
|
|
the Free Software Foundation; either version 3 of the License, or
|
|
(at your option) any later version.
|
|
|
|
This program is distributed in the hope that it will be useful,
|
|
but WITHOUT ANY WARRANTY; without even the implied warranty of
|
|
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
|
|
GNU General Public License for more details.
|
|
|
|
You should have received a copy of the GNU General Public License
|
|
along with this program. If not, see <http://www.gnu.org/licenses/>. */
|
|
|
|
#ifndef GDB_PYTHON_PY_EVENTS_H
|
|
#define GDB_PYTHON_PY_EVENTS_H
|
|
|
|
#include "command.h"
|
|
#include "python-internal.h"
|
|
#include "inferior.h"
|
|
|
|
/* Stores a list of objects to be notified when the event for which this
|
|
registry tracks occurs. */
|
|
|
|
struct eventregistry_object : public PyObject
|
|
{
|
|
PyObject *callbacks;
|
|
};
|
|
|
|
static_assert (gdb::is_python_allocatable_v<eventregistry_object>);
|
|
|
|
/* Struct holding references to event registries both in python and c.
|
|
This is meant to be a singleton. */
|
|
|
|
struct events_object
|
|
{
|
|
#define GDB_PY_DEFINE_EVENT(name) \
|
|
eventregistry_object *name;
|
|
#include "py-all-events.def"
|
|
#undef GDB_PY_DEFINE_EVENT
|
|
|
|
PyObject *mod;
|
|
|
|
};
|
|
|
|
/* Python events singleton. */
|
|
extern events_object gdb_py_events;
|
|
|
|
extern eventregistry_object *create_eventregistry_object (void);
|
|
extern bool evregpy_no_listeners_p (eventregistry_object *registry);
|
|
|
|
#endif /* GDB_PYTHON_PY_EVENTS_H */
|