[PATCH 3/5] Make Python inferior-related internal functions return inferior_object*

[Simon Marchi <simon dot marchi at ericsson dot com>]

From: Simon Marchi <simon.marchi@polymtl.ca>

This patch changes the functions that return an Inferior Python object
so they return an inferior_object pointer instead of a generic PyObject
pointer.  This should remove some casting back and forth from PyObject*
to inferior_object* in our codebase, helping a bit for type-safety.

On the other hand, this requires adding some casts from inferior_object*
to PyObject* when we deal with the Python API, which obviously accepts
only PyObject*.  I think this is a more appropriate place for casts
though.

It defines and uses gdbpy_inf_ref, a specialized version of
gdbpy_ref_base for inferior_object.

The next patch changes those functions again to make them return a
gdbpy_inf_ref, but I think that this intermediary step is useful to
verify the correctness, since the two changes have different goals
(type-safety for this one, reference counting for the next one).

One point I am not sure about is whether it breaks the gcc Python
checking plugin:

  extern PyTypeObject inferior_object_type
      CPYCHECKER_TYPE_OBJECT_FOR_TYPEDEF ("inferior_object");

It says _FOR_TYPEDEF, but the inferior_object type is no longer a
typedef, because I need to forward declare the type in
python-internal.h, and it's not possible to forward-declare a typedef.
I tried to use the cpychecker plugin but have to admit I am bit lost.  I
understand some manual fiddling with the gcc flags are required in order
load the plugin (which can be done with gcc-with-cpychecker).  It would
be nice (if it's not the case yet) to have a configure switch to
automatically enable that for the files in the python subdirectory.

gdb/ChangeLog:

	* python/py-ref.h (gdbpy_inf_ref): New typedef.
	* python/python-internal.h (struct inferior_object):
	Forward-declare.
	(thread_object) <inf_obj>: Change type to inferior_object*.
	(find_inferior_object): Change return type to inferior_object*.
	(inferior_to_inferior_object): Likewise.
	* python/py-exitedevent.c (create_exited_event_object): Use
	gdbpy_inf_ref.
	* python/py-inferior.c (inferior_object): Change from typedef +
	anonymous struct to simple struct.
	(inferior_to_inferior_object): Change return type to
	inferior_object*.
	(find_inferior_object): Likewise.
	(find_thread_object): Use gdbpy_inf_ref.
	(build_inferior_list): Likewise.
	(gdbpy_selected_inferior): Add cast.
	* python/py-infthread.c (thpy_get_inferior): Add cast.
---
 gdb/python/py-exitedevent.c  |  4 ++--
 gdb/python/py-inferior.c     | 18 +++++++++---------
 gdb/python/py-infthread.c    |  2 +-
 gdb/python/py-ref.h          |  1 +
 gdb/python/python-internal.h |  7 ++++---
 5 files changed, 17 insertions(+), 15 deletions(-)

diff --git a/gdb/python/py-exitedevent.c b/gdb/python/py-exitedevent.c
index 4590077f8b..30dce9030b 100644
--- a/gdb/python/py-exitedevent.c
+++ b/gdb/python/py-exitedevent.c
@@ -42,10 +42,10 @@ create_exited_event_object (const LONGEST *exit_code, struct inferior *inf)
 	return NULL;
     }
 
-  gdbpy_ref inf_obj (inferior_to_inferior_object (inf));
+  gdbpy_inf_ref inf_obj (inferior_to_inferior_object (inf));
   if (inf_obj == NULL || evpy_add_attribute (exited_event.get (),
 					     "inferior",
-					     inf_obj.get ()) < 0)
+					     inf_obj.get_py_obj ()) < 0)
     return NULL;
 
   return exited_event.release ();
diff --git a/gdb/python/py-inferior.c b/gdb/python/py-inferior.c
index 5c215fef44..b6b43af7cd 100644
--- a/gdb/python/py-inferior.c
+++ b/gdb/python/py-inferior.c
@@ -35,7 +35,7 @@ struct threadlist_entry {
   struct threadlist_entry *next;
 };
 
-typedef struct
+struct inferior_object
 {
   PyObject_HEAD
 
@@ -48,7 +48,7 @@ typedef struct
 
   /* Number of threads in the list.  */
   int nthreads;
-} inferior_object;
+};
 
 extern PyTypeObject inferior_object_type
     CPYCHECKER_TYPE_OBJECT_FOR_TYPEDEF ("inferior_object");
@@ -207,7 +207,7 @@ python_new_objfile (struct objfile *objfile)
    representing INFERIOR.  If the object has already been created,
    return it and increment the reference count,  otherwise, create it.
    Return NULL on failure.  */
-PyObject *
+inferior_object *
 inferior_to_inferior_object (struct inferior *inferior)
 {
   inferior_object *inf_obj;
@@ -233,13 +233,13 @@ inferior_to_inferior_object (struct inferior *inferior)
   else
     Py_INCREF ((PyObject *)inf_obj);
 
-  return (PyObject *) inf_obj;
+  return inf_obj;
 }
 
 /* Finds the Python Inferior object for the given PID.  Returns a
    reference, or NULL if PID does not match any inferior object. */
 
-PyObject *
+inferior_object *
 find_inferior_object (int pid)
 {
   struct inferior *inf = find_inferior_pid (pid);
@@ -260,7 +260,7 @@ find_thread_object (ptid_t ptid)
   if (pid == 0)
     return NULL;
 
-  gdbpy_ref inf_obj (find_inferior_object (pid));
+  gdbpy_inf_ref inf_obj (find_inferior_object (pid));
   if (inf_obj == NULL)
     return NULL;
 
@@ -409,12 +409,12 @@ static int
 build_inferior_list (struct inferior *inf, void *arg)
 {
   PyObject *list = (PyObject *) arg;
-  gdbpy_ref inferior (inferior_to_inferior_object (inf));
+  gdbpy_inf_ref inferior (inferior_to_inferior_object (inf));
 
   if (inferior  == NULL)
     return 0;
 
-  return PyList_Append (list, inferior.get ()) ? 1 : 0;
+  return PyList_Append (list, inferior.get_py_obj ()) ? 1 : 0;
 }
 
 /* Implementation of gdb.inferiors () -> (gdb.Inferior, ...).
@@ -815,7 +815,7 @@ py_free_inferior (struct inferior *inf, void *datum)
 PyObject *
 gdbpy_selected_inferior (PyObject *self, PyObject *args)
 {
-  return inferior_to_inferior_object (current_inferior ());
+  return (PyObject *) inferior_to_inferior_object (current_inferior ());
 }
 
 int
diff --git a/gdb/python/py-infthread.c b/gdb/python/py-infthread.c
index 5482bf9ea1..c7553310c3 100644
--- a/gdb/python/py-infthread.c
+++ b/gdb/python/py-infthread.c
@@ -163,7 +163,7 @@ thpy_get_inferior (PyObject *self, void *ignore)
 
   THPY_REQUIRE_VALID (thread_obj);
 
-  return thread_obj->inf_obj;
+  return (PyObject *) thread_obj->inf_obj;
 }
 
 /* Implementation of InferiorThread.switch ().
diff --git a/gdb/python/py-ref.h b/gdb/python/py-ref.h
index 8b3b7732cc..b212ef195f 100644
--- a/gdb/python/py-ref.h
+++ b/gdb/python/py-ref.h
@@ -67,5 +67,6 @@ public:
 /* Specializations of gdbpy_ref_base for concrete Python object types.  */
 
 typedef gdbpy_ref_base<PyObject> gdbpy_ref;
+typedef gdbpy_ref_base<inferior_object> gdbpy_inf_ref;
 
 #endif /* GDB_PYTHON_REF_H */
diff --git a/gdb/python/python-internal.h b/gdb/python/python-internal.h
index ac98f12ab3..62a834d403 100644
--- a/gdb/python/python-internal.h
+++ b/gdb/python/python-internal.h
@@ -303,6 +303,7 @@ typedef struct gdbpy_breakpoint_object
    constructor and the breakpoint-created hook function.  */
 extern gdbpy_breakpoint_object *bppy_pending_object;
 
+struct inferior_object;
 
 typedef struct
 {
@@ -312,7 +313,7 @@ typedef struct
   struct thread_info *thread;
 
   /* The Inferior object to which this thread belongs.  */
-  PyObject *inf_obj;
+  inferior_object *inf_obj;
 } thread_object;
 
 extern struct cmd_list_element *set_python_list;
@@ -420,8 +421,8 @@ PyObject *gdbarch_to_arch_object (struct gdbarch *gdbarch);
 thread_object *create_thread_object (struct thread_info *tp);
 thread_object *find_thread_object (ptid_t ptid)
     CPYCHECKER_RETURNS_BORROWED_REF;
-PyObject *find_inferior_object (int pid);
-PyObject *inferior_to_inferior_object (struct inferior *inferior);
+inferior_object *find_inferior_object (int pid);
+inferior_object *inferior_to_inferior_object (struct inferior *inferior);
 
 const struct block *block_object_to_block (PyObject *obj);
 struct symbol *symbol_object_to_symbol (PyObject *obj);
-- 
2.11.0