Re: [PATCH v3 4/5] mi/python: Allow redefinition of python MI commands

Pedro Alves
2019-06-18T20:03:04Z

On 5/30/19 2:48 PM, Jan Vrany wrote:
> Redefining python MI commands is especially useful when developing
> them.
>
> gdb/Changelog:
>
> * mi/mi-cmds.h (mi_command::can_be_redefined): New method.
> * mi/mi-cmds.c: (mi_command::can_be_redefined): New method.
> (insert_mi_cmd_entry): Allow redefinition of python-defined MI commands.
> * python/py-micmd.h (mi_command_py::can_be_redefined): New method.
> * python/py-micmd.c: (mi_command_py::can_be_redefined): New method.
> ---
> gdb/ChangeLog | 8 ++++++++
> gdb/mi/mi-cmds.c | 10 +++++++++-
> gdb/mi/mi-cmds.h | 3 +++
> gdb/python/py-micmd.c | 24 +++++++++++++++++-------
> gdb/python/py-micmd.h | 2 +-
> 5 files changed, 38 insertions(+), 9 deletions(-)
>
> diff --git a/gdb/ChangeLog b/gdb/ChangeLog
> index 241e5da68f..1d264c44f7 100644
> --- a/gdb/ChangeLog
> +++ b/gdb/ChangeLog
> @@ -1,3 +1,11 @@
> +2019-05-02 Jan Vrany <jan.vrany@fit.cvut.cz>
> +
> + * mi/mi-cmds.h (mi_command::can_be_redefined): New method.
> + * mi/mi-cmds.c: (mi_command::can_be_redefined): New method.

No ":" after the file name and before "(".

> + (insert_mi_cmd_entry): Allow redefinition of python-defined MI commands.
> + * python/py-micmd.h (mi_command_py::can_be_redefined): New method.
> + * python/py-micmd.c: (mi_command_py::can_be_redefined): New method.

Ditto.

Please double check the other ChangeLog entries in the other patches.

> +
> 2019-05-02 Didier Nadeau <didier.nadeau@gmail.com>
> Jan Vrany <jan.vrany@fit.cvut.cz>
>
> diff --git a/gdb/mi/mi-cmds.c b/gdb/mi/mi-cmds.c
> index 0aead954f9..e280e51daf 100644
> --- a/gdb/mi/mi-cmds.c
> +++ b/gdb/mi/mi-cmds.c
> @@ -41,7 +41,8 @@ insert_mi_cmd_entry (mi_cmd_up command)
> const std::string &name = command->name ();
>
> if (mi_cmd_table.find (name) != mi_cmd_table.end ())
> - return false;
> + if (! mi_cmd_table[name]->can_be_redefined ())
> + return false;

No space after !.

I'd combine the two ifs:

if (mi_cmd_table.find (name) != mi_cmd_table.end ()
&& !mi_cmd_table[name]->can_be_redefined ())
return false;

better even, avoid the second lookup:

auto foo = mi_cmd_table.find (name);
if (foo != mi_cmd_table.end () && !foo->can_be_redefined ())
return false;

>
> mi_cmd_table[name] = std::move (command);
>
> @@ -80,6 +81,13 @@ mi_command::mi_command (const char *name, int *suppress_notification)
> m_suppress_notification (suppress_notification)
> {}
>
> +bool
> +mi_command::can_be_redefined()

Space before parens.

> +{
> + return false;
> +}
> +
> +
>
> void
> mi_command::invoke (struct mi_parse *parse)
> diff --git a/gdb/mi/mi-cmds.h b/gdb/mi/mi-cmds.h
> index 5ca7232fca..331b1349df 100644
> --- a/gdb/mi/mi-cmds.h
> +++ b/gdb/mi/mi-cmds.h
> @@ -143,6 +143,9 @@ public:
> /* Execute the MI command. */
> void invoke (struct mi_parse *parse);
>
> + /* Return TRUE if command can be redefined, FALSE otherwise. */

"if THE command", or "if THIS command".

Double space after period.

> + virtual bool can_be_redefined();

Space before parens.

> +
> protected:
> gdb::optional<scoped_restore_tmpl<int>> do_suppress_notification ();
> virtual void do_invoke(struct mi_parse *parse) = 0;
> diff --git a/gdb/python/py-micmd.c b/gdb/python/py-micmd.c
> index e99632c97a..4f2b13f3c7 100644
> --- a/gdb/python/py-micmd.c
> +++ b/gdb/python/py-micmd.c
> @@ -171,6 +171,12 @@ mi_command_py::mi_command_py (const char *name, gdbpy_ref<> object)
> {
> }
>
> +bool
> +mi_command_py::can_be_redefined()

Space before parens.

> +{
> + return true;
> +}
> +
> void
> mi_command_py::do_invoke (struct mi_parse *parse)
> {
> @@ -179,6 +185,7 @@ mi_command_py::do_invoke (struct mi_parse *parse)
> if (parse->argv == NULL)
> error (_("Problem parsing arguments: %s %s"), parse->command, parse->args);
>
> + std::string name (this->name ());

As principle, prefer copy-initialization when possible:

std::string name = this->name ();

This style avoids unwanted explicit conversions, and
makes explicit conversions stand out, since they'll be
written with ()s.

I think this needs to be a copy because of what the
"THIS must not be used" comment below says.

A comment to the effect would help. Something like:

/* Must save a copy of the name because the Python code may
replace the very same command that is currently executing.
See further below. */
std::string name = this->name ();

> PyObject *obj = this->pyobj.get ();
>
> gdbpy_enter enter_py (get_current_arch (), current_language);
> @@ -187,15 +194,14 @@ mi_command_py::do_invoke (struct mi_parse *parse)
>
> if (!PyObject_HasAttr (obj, invoke_cst))
> error (_("-%s: Python command object missing 'invoke' method."),
> - name ().c_str ());
> -
> + name.c_str ());
>
> gdbpy_ref<> argobj (PyList_New (parse->argc));
> if (argobj == nullptr)
> {
> gdbpy_print_stack ();
> error (_("-%s: failed to create the Python arguments list."),
> - name ().c_str ());
> + name.c_str ());
> }
>
> for (int i = 0; i < parse->argc; ++i)
> @@ -205,11 +211,16 @@ mi_command_py::do_invoke (struct mi_parse *parse)
> if (PyList_SetItem (argobj.get (), i, str.release ()) != 0)
> {
> error (_("-%s: failed to create the Python arguments list."),
> - name ().c_str ());
> + name.c_str ());
> }
> }
>
> gdb_assert (PyErr_Occurred () == NULL);
> +
> + /* From this point on, THIS must not be used since Python code may replace
> + the the very same command that is currently executing. This in turn leads
> + to desctruction of THIS making it invalid. See insert_mi_cmd_entry. */

Double "the" in "the the".

Typo "desctruction".

Double space after period at the end.

> +
> gdbpy_ref<> result (
> PyObject_CallMethodObjArgs (obj, invoke_cst, argobj.get (), NULL));
> if (PyErr_Occurred () != NULL)
> @@ -218,9 +229,9 @@ mi_command_py::do_invoke (struct mi_parse *parse)
> gdb::unique_xmalloc_ptr<char> ex_msg (ex.to_string ());
>
> if (ex_msg == NULL || *ex_msg == '\0')
> - error (_("-%s: failed to execute command"), name ().c_str ());
> + error (_("-%s: failed to execute command"), name.c_str ());
> else
> - error (_("-%s: %s"), name ().c_str (), ex_msg.get ());
> + error (_("-%s: %s"), name.c_str (), ex_msg.get ());
> }
> else
> {
> @@ -233,7 +244,6 @@ void mi_command_py::finalize ()
> {
> this->pyobj.reset (nullptr);
> }
> -
> /* Initialize the MI command object. */

Spurious deletion of that line.

>
> int
> diff --git a/gdb/python/py-micmd.h b/gdb/python/py-micmd.h
> index deadc0116b..0d61069ca5 100644
> --- a/gdb/python/py-micmd.h
> +++ b/gdb/python/py-micmd.h
> @@ -44,7 +44,7 @@ class mi_command_py : public mi_command
>
> mi_command_py (const char *name, gdbpy_ref<> object);
>
> -
> + bool can_be_redefined() override;
> /* This is called just before shutting down a Python interpreter
> to release python object implementing the command. */

Space before parens.

Add empty line between the new declaration and the unrelated
comment below.

Double space after period.

Thanks,
Pedro Alves