[RFC 4/8] mi/python: C++ify python MI command handling code

[Jan Vrany <jan.vrany@fit.cvut.cz>]

Use gdbpy_ref<> instead of manually calling Py_DECREF().
Use gdb::unique_xmalloc_ptr<> instead of manually calling xfree().

gdb/Changelog:

	* python/py-micmd.c (parse_mi_result): Use gdb::unique_xmalloc_ptr<>
	instead of manually calling xfree().
	(py_mi_invoke): Use gdbpy_ref<> instead of PyObject * with Py_DECREF().
	Do not call Py_DECREF() on individual strings in python argument list
	object as PyList_SetItem() steals reference.
	(micmdpy_parse_command_name): Fix formatting.
	(micmdpy_init): Use gdb::unique_xmalloc_ptr<> instead of manually
	calling xfree().
---
 gdb/ChangeLog         | 11 ++++++++++
 gdb/python/py-micmd.c | 50 ++++++++++++++++---------------------------
 2 files changed, 29 insertions(+), 32 deletions(-)

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index ef77fdbb5c..692b937fee 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,14 @@
+2018-12-11  Jan Vrany  <jan.vrany@fit.cvut.cz>
+
+	* python/py-micmd.c (parse_mi_result): Use gdb::unique_xmalloc_ptr<>
+	instead of manually calling xfree().
+	(py_mi_invoke): Use gdbpy_ref<> instead of PyObject * with Py_DECREF().
+	Do not call Py_DECREF() on individual strings in python argument list
+	object as PyList_SetItem() steals reference.
+	(micmdpy_parse_command_name): Fix formatting.
+	(micmdpy_init): Use gdb::unique_xmalloc_ptr<> instead of manually
+	calling xfree().
+
 2019-04-17  Tom Tromey  <tromey@adacore.com>
 
 	* dwarf2read.c (dwarf2_init_complex_target_type): Check "tt"
diff --git a/gdb/python/py-micmd.c b/gdb/python/py-micmd.c
index ee612e2bc5..0683a02017 100644
--- a/gdb/python/py-micmd.c
+++ b/gdb/python/py-micmd.c
@@ -53,11 +53,9 @@ parse_mi_result (PyObject *result, const char *field_name)
       ui_out_emit_list list_emitter (uiout, field_name);
       for(i = 0; i < PyList_GET_SIZE (result); ++i)
 	{
-	  //struct cleanup *cleanup_item = make_cleanup_ui_out_tuple_begin_end (uiout, NULL);
           ui_out_emit_tuple tuple_emitter (uiout, NULL);
 	  item = PyList_GetItem (result, i);
 	  parse_mi_result (item, NULL);
-	  //do_cleanups (cleanup_item);
 	}      
     }
   else if ( PyDict_Check (result))
@@ -66,9 +64,8 @@ parse_mi_result (PyObject *result, const char *field_name)
       Py_ssize_t pos = 0;
       while ( PyDict_Next (result, &pos, &key, &value) )
 	{
-	  char *key_string = gdbpy_obj_to_string (key).release ();
-	  parse_mi_result (value, key_string);
-	  xfree ( (void *) key_string);
+	  gdb::unique_xmalloc_ptr<char> key_string (gdbpy_obj_to_string (key));
+	  parse_mi_result (value, key_string.get ());
 	}
     }
 }
@@ -79,7 +76,6 @@ void
 py_mi_invoke (void *py_obj, char **argv, int argc)
 {
   micmdpy_object *obj = (micmdpy_object *) py_obj;
-  PyObject *argobj, *result,  **strings;
   int i;
 
   gdbpy_enter enter_py (get_current_arch (), current_language);
@@ -92,9 +88,8 @@ py_mi_invoke (void *py_obj, char **argv, int argc)
       error (_("Python command object missing 'invoke' method."));
     }
 
-  strings = (PyObject **) malloc (sizeof(PyObject *) * argc);
-  argobj = PyList_New (argc);
-  if ( !argobj)
+  gdbpy_ref<> argobj (PyList_New (argc));
+  if (argobj == nullptr)
     {
       gdbpy_print_stack ();
       error (_("Failed to create the python arguments list."));
@@ -102,28 +97,22 @@ py_mi_invoke (void *py_obj, char **argv, int argc)
 
   for (i = 0; i < argc; ++i)
     {
-      strings[i] = PyUnicode_Decode (argv[i], strlen(argv[i]), host_charset (), NULL);
-      if (PyList_SetItem (argobj, i, strings[i]) != 0)
+      /* Since PyList_SetItem steals the reference, we don't use
+       * gdbpy_ref<> to hold on arg string. */
+      PyObject* str  = PyUnicode_Decode (argv[i], strlen (argv[i]), host_charset (), NULL);
+      if (PyList_SetItem (argobj.get (), i, str) != 0)
 	{
 	  error (_("Failed to create the python arguments list."));
 	}
     }
 
-  result = PyObject_CallMethodObjArgs ((PyObject *) obj, invoke_cst, argobj,
-				       NULL);
+  gdbpy_ref<> result (PyObject_CallMethodObjArgs ((PyObject *) obj, invoke_cst, argobj.get (),
+				       NULL));
 
-  if (result)
+  if (result != nullptr)
     {
-      parse_mi_result (result, NULL);
-      Py_DECREF (result);
+      parse_mi_result (result.get (), NULL);
     }
-
-  Py_DECREF (argobj);
-  for (i = 0; i < argc; ++i)
-    {
-      Py_DECREF (strings[i]);
-    }
-  free (strings);
 }
 
 /* Parse the name of the MI command to register.
@@ -150,7 +139,7 @@ micmdpy_parse_command_name (const char *name)
 
   /* Skip preceding whitespaces. */
   /* Find first character of the final word.  */
-   for (; i > 0 && (isalnum (name[i - 1])
+  for (; i > 0 && (isalnum (name[i - 1])
  		   || name[i - 1] == '-'
  		   || name[i - 1] == '_');
         --i)
@@ -158,10 +147,10 @@ micmdpy_parse_command_name (const char *name)
    /* Skip the first dash to have to command name only.
     * i.e. -thread-info -> thread-info
     */
-   if(name[i] == '-' && i < len - 2)
+  if(name[i] == '-' && i < len - 2)
      i++;
 
-   if( i == lastchar)
+  if( i == lastchar)
     {
       PyErr_SetString (PyExc_RuntimeError, _("No command name found."));
       return NULL;
@@ -185,20 +174,19 @@ static int
 micmdpy_init (PyObject *self, PyObject *args, PyObject *kw)
 {
   const char *name;
-  char *cmd_name;
 
   if(! PyArg_ParseTuple (args, "s", &name))
     return -1;
 
-  cmd_name = micmdpy_parse_command_name (name);
-  if (! cmd_name)
+  gdb::unique_xmalloc_ptr<char> cmd_name (micmdpy_parse_command_name (name));
+  if (cmd_name == nullptr)
     return -1;
 
   Py_INCREF (self);
 
   try
   {
-    mi_command *micommand = new mi_command_py (cmd_name, NULL, (void *) self);
+    mi_command *micommand = new mi_command_py (cmd_name.get (), NULL, (void *) self);
 
     bool result = insert_mi_cmd_entry (mi_cmd_up (micommand));
 
@@ -211,7 +199,6 @@ micmdpy_init (PyObject *self, PyObject *args, PyObject *kw)
   }
   catch (const gdb_exception &except)
   {
-    xfree (cmd_name);
     Py_DECREF (self);
     PyErr_Format (except.reason == RETURN_QUIT
 		    ? PyExc_KeyboardInterrupt : PyExc_RuntimeError,
@@ -219,7 +206,6 @@ micmdpy_init (PyObject *self, PyObject *args, PyObject *kw)
     return -1;
   }
 
-  xfree (cmd_name);
   return 0;
 }
 
-- 
2.20.1