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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>
81 lines
2.5 KiB
C
81 lines
2.5 KiB
C
/* Python interface to record targets.
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Copyright 2017-2026 Free Software Foundation, Inc.
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This file is part of GDB.
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 3 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <http://www.gnu.org/licenses/>. */
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#ifndef GDB_PYTHON_PY_RECORD_H
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#define GDB_PYTHON_PY_RECORD_H
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#include "inferior.h"
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#include "python-internal.h"
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#include "record.h"
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/* Python Record object. */
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struct recpy_record_object : public PyObject
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{
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/* The thread this object refers to. */
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thread_info *thread;
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/* The current recording method. */
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enum record_method method;
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};
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static_assert (gdb::is_python_allocatable_v<recpy_record_object>);
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/* Python recorded element object. This is generic enough to represent
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recorded instructions as well as recorded function call segments, hence the
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generic name. */
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struct recpy_element_object : public PyObject
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{
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/* The thread this object refers to. */
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thread_info *thread;
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/* The current recording method. */
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enum record_method method;
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/* Element number. */
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Py_ssize_t number;
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};
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static_assert (gdb::is_python_allocatable_v<recpy_element_object>);
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/* Python RecordInstruction type. */
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extern PyTypeObject recpy_insn_type;
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/* Python RecordFunctionSegment type. */
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extern PyTypeObject recpy_func_type;
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/* Python RecordAuxiliary type. */
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extern PyTypeObject recpy_aux_type;
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/* Create a new gdb.RecordInstruction object. */
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extern PyObject *recpy_insn_new (thread_info *thread, enum record_method method,
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Py_ssize_t number);
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/* Create a new gdb.RecordFunctionSegment object. */
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extern PyObject *recpy_func_new (thread_info *thread, enum record_method method,
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Py_ssize_t number);
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/* Create a new gdb.RecordGap object. */
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extern PyObject *recpy_gap_new (int reason_code, const char *reason_string,
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Py_ssize_t number);
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/* Create a new gdb.RecordGap object. */
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extern PyObject *recpy_aux_new (thread_info *thread, enum record_method method,
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Py_ssize_t number);
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#endif /* GDB_PYTHON_PY_RECORD_H */
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