Re: [PATCH 3/4] Change thread_to_thread_object to return a new reference

Simon Marchi
2018-09-16T02:11:12Z

I have some comments about style, correctness-wise is looks good to me.

On 2018-09-13 1:30 a.m., Tom Tromey wrote:
> diff --git a/gdb/python/py-inferior.c b/gdb/python/py-inferior.c
> index 1cf37296973..bf8ac75a316 100644
> --- a/gdb/python/py-inferior.c
> +++ b/gdb/python/py-inferior.c
> @@ -306,7 +306,7 @@ find_inferior_object (int pid)
> return NULL;
> }
>
> -thread_object *
> +gdbpy_ref<>
> thread_to_thread_object (thread_info *thr)
> {
> gdbpy_ref<inferior_object> inf_obj (inferior_to_inferior_object (thr->inf));
> @@ -317,7 +317,7 @@ thread_to_thread_object (thread_info *thr)
> thread != NULL;
> thread = thread->next)
> if (thread->thread_obj->thread == thr)
> - return thread->thread_obj;
> + return gdbpy_ref<>::new_reference ((PyObject *) thread->thread_obj);
>
> return NULL;
> }
> @@ -817,7 +817,7 @@ infpy_is_valid (PyObject *self, PyObject *args)
> PyObject *
> infpy_thread_from_thread_handle (PyObject *self, PyObject *args, PyObject *kw)
> {
> - PyObject *handle_obj, *result;
> + PyObject *handle_obj;
> inferior_object *inf_obj = (inferior_object *) self;
> static const char *keywords[] = { "thread_handle", NULL };
>
> @@ -826,8 +826,6 @@ infpy_thread_from_thread_handle (PyObject *self, PyObject *args, PyObject *kw)
> if (! gdb_PyArg_ParseTupleAndKeywords (args, kw, "O", keywords, &handle_obj))
> return NULL;
>
> - result = Py_None;
> -
> if (!gdbpy_is_value_object (handle_obj))
> {
> PyErr_SetString (PyExc_TypeError,
> @@ -835,29 +833,27 @@ infpy_thread_from_thread_handle (PyObject *self, PyObject *args, PyObject *kw)
>
> return NULL;
> }
> - else
> +
> + gdbpy_ref<> result;
> + TRY
> + {
> + struct thread_info *thread_info;
> + struct value *val = value_object_to_value (handle_obj);
> +
> + thread_info = find_thread_by_handle (val, inf_obj->inferior);
> + if (thread_info != NULL)
> + result = thread_to_thread_object (thread_info);
> + }
> + CATCH (except, RETURN_MASK_ALL)
> {
> - TRY
> - {
> - struct thread_info *thread_info;
> - struct value *val = value_object_to_value (handle_obj);
> -
> - thread_info = find_thread_by_handle (val, inf_obj->inferior);
> - if (thread_info != NULL)
> - {
> - result = (PyObject *) thread_to_thread_object (thread_info);
> - if (result != NULL)
> - Py_INCREF (result);
> - }
> - }
> - CATCH (except, RETURN_MASK_ALL)
> - {
> - GDB_PY_HANDLE_EXCEPTION (except);
> - }
> - END_CATCH
> + GDB_PY_HANDLE_EXCEPTION (except);
> }
> + END_CATCH
>
> - return result;
> + if (result == NULL)
> + result = gdbpy_ref<>::new_reference (Py_None);

I would suggest using Py_RETURN_NONE, which we already use at many places.

Instead of setting that result variable, is there something preventing you
from returning directly above, like this?

if (thread_info != NULL)
return thread_to_thread_object (thread_info).release ();

The bottom line could just be unconditionally Py_RETURN_NONE.

> +
> + return result.release ();
> }
>
>
> diff --git a/gdb/python/py-infthread.c b/gdb/python/py-infthread.c
> index 36ae71b6358..4b2705a0af6 100644
> --- a/gdb/python/py-infthread.c
> +++ b/gdb/python/py-infthread.c
> @@ -284,15 +284,7 @@ PyObject *
> gdbpy_selected_thread (PyObject *self, PyObject *args)
> {
> if (inferior_ptid != null_ptid)
> - {
> - PyObject *thread_obj
> - = (PyObject *) thread_to_thread_object (inferior_thread ());
> - if (thread_obj != NULL)
> - {
> - Py_INCREF (thread_obj);
> - return thread_obj;
> - }
> - }
> + return thread_to_thread_object (inferior_thread ()).release ();

I know it's logically not supposed to happen, but here it's possible for
thread_to_thread_object to return NULL. Returning NULL to Python is the
way to have it throw an exception, I believe, is that what you want to do
here? The previous code would return None in that case.

>
> Py_RETURN_NONE;
> }
> diff --git a/gdb/python/py-stopevent.c b/gdb/python/py-stopevent.c
> index f6bd207f3b8..cbdf7b7e7e0 100644
> --- a/gdb/python/py-stopevent.c
> +++ b/gdb/python/py-stopevent.c
> @@ -23,8 +23,8 @@
> gdbpy_ref<>
> create_stop_event_object (PyTypeObject *py_type)
> {
> - return create_thread_event_object (py_type,
> - py_get_event_thread (inferior_ptid));
> + gdbpy_ref<> thread = py_get_event_thread (inferior_ptid);
> + return create_thread_event_object (py_type, thread.get ());
> }
>
> /* Callback observers when a stop event occurs. This function will create a
> diff --git a/gdb/python/py-threadevent.c b/gdb/python/py-threadevent.c
> index 4f822b4ae09..13af1c840ba 100644
> --- a/gdb/python/py-threadevent.c
> +++ b/gdb/python/py-threadevent.c
> @@ -22,19 +22,19 @@
>
> /* See py-event.h. */
>
> -PyObject *
> +gdbpy_ref<>
> py_get_event_thread (ptid_t ptid)
> {
> - PyObject *pythread = nullptr;
> + gdbpy_ref<> pythread;
>
> if (non_stop)
> {
> thread_info *thread = find_thread_ptid (ptid);
> if (thread != nullptr)
> - pythread = (PyObject *) thread_to_thread_object (thread);
> + pythread = thread_to_thread_object (thread);
> }
> else
> - pythread = Py_None;
> + pythread = gdbpy_ref<>::new_reference (Py_None);

Again, I would suggest Py_RETURN_NONE.

I would also propose moving the code below in the if, to show that it only
really applies to the non-stop case (if I understand the code correctly).

>
> if (pythread == nullptr)
> {

Simon