[PATCH 6/6] Some frame-related Python safety fixes

[Tom Tromey <tom@tromey.com>]

This makes some frame-related Python safety fixes, with a goal of
simplifying some code and removing some FIXMEs.

A method can now return a frame_info_ptr; this will be handled by a
new to_python overload.

A safe wrapper is now provided for frame_info_to_frame_object.
---
 gdb/python/py-frame.c        | 49 ++++++++++++++++----------------------------
 gdb/python/py-inferior.c     |  2 +-
 gdb/python/py-safety.h       | 11 ++++++++++
 gdb/python/python-internal.h |  5 +++--
 4 files changed, 33 insertions(+), 34 deletions(-)

diff --git a/gdb/python/py-frame.c b/gdb/python/py-frame.c
index e34d4b5d2e9..f9e95f3aec3 100644
--- a/gdb/python/py-frame.c
+++ b/gdb/python/py-frame.c
@@ -108,12 +108,12 @@ struct frame_object : public PyObject
   /* Implementation of gdb.Frame.older (self) -> gdb.Frame.
      Returns the frame immediately older (outer) to this frame, or None if
      there isn't one.  */
-  gdbpy_ref<> older ();
+  frame_info_ptr older ();
 
   /* Implementation of gdb.Frame.newer (self) -> gdb.Frame.
      Returns the frame immediately newer (inner) to this frame, or None if
      there isn't one.  */
-  gdbpy_ref<> newer ();
+  frame_info_ptr newer ();
 
   /* Implementation of gdb.Frame.find_sal (self) -> gdb.Symtab_and_line.
      Returns the frame's symtab and line.  */
@@ -282,8 +282,6 @@ frame_object::function ()
 
 /* Convert a frame_info struct to a Python Frame object.
    Sets a Python exception and returns NULL on error.  */
-/* FIXME: Python safety.  This function should be converted, but the
-   callers aren't ready yet.  */
 
 gdbpy_ref<>
 frame_info_to_frame_object (const frame_info_ptr &frame)
@@ -307,27 +305,26 @@ frame_info_to_frame_object (const frame_info_ptr &frame)
 }
 
 gdbpy_ref<>
+safe_frame_info_to_frame_object (const frame_info_ptr &frame)
+{
+  gdbpy_ref<> result = frame_info_to_frame_object (frame);
+  if (result == nullptr)
+    throw gdb_python_exception ();
+  return result;
+}
+
+frame_info_ptr
 frame_object::older ()
 {
   frame_info_ptr frame = require_frame ();
-  frame_info_ptr prev = get_prev_frame (frame);
-
-  if (prev)
-    return frame_info_to_frame_object (prev);
-
-  return py_none ();
+  return get_prev_frame (frame);
 }
 
-gdbpy_ref<>
+frame_info_ptr
 frame_object::newer ()
 {
   frame_info_ptr frame = require_frame ();
-  frame_info_ptr next = get_next_frame (frame);
-
-  if (next)
-    return frame_info_to_frame_object (next);
-
-  return py_none ();
+  return get_next_frame (frame);
 }
 
 gdbpy_ref<>
@@ -431,29 +428,19 @@ frame_object::static_link ()
 /* Implementation of gdb.newest_frame () -> gdb.Frame.
    Returns the newest frame object.  */
 
-gdbpy_ref<>
+frame_info_ptr
 gdbpy_newest_frame ()
 {
-  /* FIXME: Python safety.  Convert frame_info_to_frame_object.  */
-  gdbpy_ref<> result = frame_info_to_frame_object (get_current_frame ());
-  if (result == nullptr)
-    throw gdb_python_exception ();
-  return result;
+  return get_current_frame ();
 }
 
 /* Implementation of gdb.selected_frame () -> gdb.Frame.
    Returns the selected frame object.  */
 
-gdbpy_ref<>
+frame_info_ptr
 gdbpy_selected_frame ()
 {
-  frame_info_ptr frame
-    = get_selected_frame ("No frame is currently selected.");
-  /* FIXME: Python safety.  Convert frame_info_to_frame_object.  */
-  gdbpy_ref<> result = frame_info_to_frame_object (frame);
-  if (result == nullptr)
-    throw gdb_python_exception ();
-  return result;
+  return get_selected_frame ("No frame is currently selected.");
 }
 
 /* Implementation of gdb.stop_reason_string (Integer) -> String.
diff --git a/gdb/python/py-inferior.c b/gdb/python/py-inferior.c
index 5e77f9f37bd..84a4b1ae6ee 100644
--- a/gdb/python/py-inferior.c
+++ b/gdb/python/py-inferior.c
@@ -1023,7 +1023,7 @@ python_context_changed (user_selected_what selection)
   try
     {
       if (has_stack_frames ())
-	frame_obj = gdbpy_selected_frame ();
+	frame_obj = safe_frame_info_to_frame_object (gdbpy_selected_frame ());
       else
 	frame_obj = py_none ();
     }
diff --git a/gdb/python/py-safety.h b/gdb/python/py-safety.h
index 0d5a45e72fd..b8e6434d168 100644
--- a/gdb/python/py-safety.h
+++ b/gdb/python/py-safety.h
@@ -120,6 +120,17 @@ to_python (gdbpy_ref<> &&value)
   return value.release ();
 }
 
+static inline PyObject *
+to_python (const frame_info_ptr &frame)
+{
+  if (frame.is_null ())
+    return py_none ().release ();
+
+  /* Note that currently this might return NULL on error; but that is
+     fine in this context.  */
+  return frame_info_to_frame_object (frame).release ();
+}
+
 static inline PyObject *
 to_python (symbol *sym)
 {
diff --git a/gdb/python/python-internal.h b/gdb/python/python-internal.h
index ee1a19131bd..8aaf96021f7 100644
--- a/gdb/python/python-internal.h
+++ b/gdb/python/python-internal.h
@@ -543,8 +543,8 @@ gdbpy_ref<> gdbpy_lookup_static_symbols (gdbpy_borrowed_ref<> args,
 PyObject *gdbpy_start_recording (PyObject *self, PyObject *args);
 PyObject *gdbpy_current_recording (PyObject *self, PyObject *args);
 PyObject *gdbpy_stop_recording (PyObject *self, PyObject *args);
-gdbpy_ref<> gdbpy_newest_frame ();
-gdbpy_ref<> gdbpy_selected_frame ();
+frame_info_ptr gdbpy_newest_frame ();
+frame_info_ptr gdbpy_selected_frame ();
 PyObject *gdbpy_lookup_type (PyObject *self, PyObject *args, PyObject *kw);
 int gdbpy_is_field (PyObject *obj);
 PyObject *gdbpy_create_lazy_string_object (CORE_ADDR address, long length,
@@ -578,6 +578,7 @@ gdbpy_ref<> block_to_block_object (const struct block *block,
 gdbpy_ref<> value_to_value_object (struct value *v);
 gdbpy_ref<> type_to_type_object (struct type *);
 gdbpy_ref<> frame_info_to_frame_object (const frame_info_ptr &frame);
+gdbpy_ref<> safe_frame_info_to_frame_object (const frame_info_ptr &frame);
 gdbpy_ref<> symtab_to_linetable_object (PyObject *symtab);
 gdbpy_ref<> pspace_to_pspace_object (struct program_space *);
 PyObject *pspy_get_printers (PyObject *, void *);

-- 
2.49.0