[PATCH 2/5] Add Python Inferior object debug traces

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

I added those printfs while trying to debug the refcount issue fixed by
a following patch.  I thought it could be useful to have debug traces
for anything Python-related.  I have only added prints to track Inferior
the lifetime of Inferior objects because that's all I needed, but we
might want to add the same for other types in the future.

While debugging, I also made some kind of "maint python refcounts" that
would print the refcounts of each known Inferior object.  If you think
it could be useful I could dig it up.

gdb/ChangeLog:

	* python/python-internal.h (debug_python): New variable
	declaration.
	* python/python.c (debug_python): New variable.
	(_initialize_python): Add "set debug python" command.
	* python/py-inferior.c (inferior_to_inferior_object): Add debug
	print.
	(infpy_dealloc): Likewise.
	(py_free_inferior): Likewise.
---
 gdb/python/py-inferior.c     | 15 +++++++++++++++
 gdb/python/python-internal.h |  4 ++++
 gdb/python/python.c          | 12 ++++++++++++
 3 files changed, 31 insertions(+)

diff --git a/gdb/python/py-inferior.c b/gdb/python/py-inferior.c
index b2aaf25e8a..5c215fef44 100644
--- a/gdb/python/py-inferior.c
+++ b/gdb/python/py-inferior.c
@@ -215,6 +215,10 @@ inferior_to_inferior_object (struct inferior *inferior)
   inf_obj = (inferior_object *) inferior_data (inferior, infpy_inf_data_key);
   if (!inf_obj)
     {
+      if (debug_python)
+	printf_filtered ("Creating Python Inferior object inf = %d\n",
+			 inferior->num);
+
       inf_obj = PyObject_New (inferior_object, &inferior_object_type);
       if (!inf_obj)
 	  return NULL;
@@ -758,6 +762,14 @@ infpy_dealloc (PyObject *obj)
   inferior_object *inf_obj = (inferior_object *) obj;
   struct inferior *inf = inf_obj->inferior;
 
+  if (debug_python)
+    {
+      if (inf != NULL)
+	printf_filtered ("infpy_dealloc inf = %d\n", inf->num);
+      else
+	printf_filtered ("infpy_dealloc inf = <unknown>\n");
+    }
+
   if (! inf)
     return;
 
@@ -777,6 +789,9 @@ py_free_inferior (struct inferior *inf, void *datum)
 
   gdbpy_enter enter_py (python_gdbarch, python_language);
 
+  if (debug_python)
+    printf_filtered ("py_free_inferior inf = %d\n", inf->num);
+
   inf_obj->inferior = NULL;
 
   /* Deallocate threads list.  */
diff --git a/gdb/python/python-internal.h b/gdb/python/python-internal.h
index e2ebc1b8a2..ac98f12ab3 100644
--- a/gdb/python/python-internal.h
+++ b/gdb/python/python-internal.h
@@ -240,6 +240,10 @@ struct inferior;
 
 extern int gdb_python_initialized;
 
+/* True if debug output about Python features is enabled.  */
+
+extern int debug_python;
+
 extern PyObject *gdb_module;
 extern PyObject *gdb_python_module;
 extern PyTypeObject value_object_type
diff --git a/gdb/python/python.c b/gdb/python/python.c
index ab5a6a416d..dc0fa25054 100644
--- a/gdb/python/python.c
+++ b/gdb/python/python.c
@@ -106,6 +106,10 @@ const struct extension_language_defn extension_language_python =
 
 int gdb_python_initialized;
 
+/* See python-internal.h  */
+
+int debug_python = 0;
+
 extern PyMethodDef python_GdbMethods[];
 
 #ifdef IS_PY3K
@@ -1605,6 +1609,14 @@ message == an error message without a stack will be printed."),
 			&user_set_python_list,
 			&user_show_python_list);
 
+  add_setshow_boolean_cmd ("python", class_maintenance,
+			   &debug_python, _("\
+Set Python debug output."), _("\
+Show Python debug output."), _("\
+When on, debugging output for Python-related features is displayed."),
+			    NULL, NULL,
+			    &setdebuglist, &showdebuglist);
+
 #ifdef HAVE_PYTHON
 #ifdef WITH_PYTHON_PATH
   /* Work around problem where python gets confused about where it is,
-- 
2.11.0