Generalize varobj iterator

This patch generalizes varobj iterator, in a python-independent way.
Note varobj_item is still a typedef of PyObject, we can only focus on
API changes, and leave the data type changes to the next patch.  As a
result, we include "varobj-iter.h" after the typedef of PyObject in
varobj.c, but it is an intermediate state.  Finally, varobj-iter.h is
independent of PyObject.

This change is helpful to move some python-related code out of
varobj.c.

 V2:
  - Fix a missing cleanup.
  - Fix typos.
  - Use XNEW.
  - Check against NULL explicitly.
  - Update copyright year for new added files.

 V3:
  - Call PyGILState_Ensure before Py_XDECREF.
  - Use CPYCHECKER_STEALS_REFERENCE_TO_ARG.
  - Code indentation.

 V4:
  - use varobj_ensure_python_env instead of PyGILState_Ensure.

gdb:

2014-06-12  Pedro Alves  <pedro@codesourcery.com>
	    Yao Qi  <yao@codesourcery.com>

	* Makefile.in (SUBDIR_PYTHON_OBS): Add "py-varobj.o".
	(SUBDIR_PYTHON_SRCS): Add "python/py-varobj.c".
	(HFILES_NO_SRCDIR): Add "varobj-iter.h".
	(py-varobj.o): New rule.
	* python/py-varobj.c: New file.
	* python/python-internal.h (py_varobj_get_iterator): Declare.
	* varobj-iter.h: New file.
	* varobj.c: Include "varobj-iter.h"
	(struct varobj) <child_iter>: Change its type from "PyObject *"
	to "struct varobj_iter *".
	<saved_item>: Likewise.
	[HAVE_PYTHON] (varobj_ensure_python_env): Make it extern.
	[HAVE_PYTHON] (varobj_get_iterator): New function.
	(update_dynamic_varobj_children) [HAVE_PYTHON]: Move
	python-specific code to python/py-varobj.c.
	(install_visualizer): Call varobj_iter_delete instead of
	Py_XDECREF.
	* varobj.h (varobj_ensure_python_env): Declare.

1 files changed, 63 insertions, 0 deletions

diff --git a/gdb/varobj-iter.h b/gdb/varobj-iter.h
new file mode 100644
index 0000000..3a530bc
--- /dev/null
+++ b/gdb/varobj-iter.h
@@ -0,0 +1,63 @@
+/* Iterator of varobj.
+   Copyright (C) 2013-2014 Free Software Foundation, Inc.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+struct varobj_iter_ops;
+
+typedef PyObject varobj_item;
+
+/* A dynamic varobj iterator "class".  */
+
+struct varobj_iter
+{
+  /* The 'vtable'.  */
+  const struct varobj_iter_ops *ops;
+
+  /* The varobj this iterator is listing children for.  */
+  struct varobj *var;
+
+  /* The next raw index we will try to check is available.  If it is
+     equal to number_of_children, then we've already iterated the
+     whole set.  */
+  int next_raw_index;
+};
+
+/* The vtable of the varobj iterator class.  */
+
+struct varobj_iter_ops
+{
+  /* Destructor.  Releases everything from SELF (but not SELF
+     itself).  */
+  void (*dtor) (struct varobj_iter *self);
+
+  /* Returns the next object or NULL if it has reached the end.  */
+  varobj_item *(*next) (struct varobj_iter *self);
+};
+
+/* Returns the next varobj or NULL if it has reached the end.  */
+
+#define varobj_iter_next(ITER)	(ITER)->ops->next (ITER)
+
+/* Delete a varobj_iter object.  */
+
+#define varobj_iter_delete(ITER)	       \
+  do					       \
+    {					       \
+      if ((ITER) != NULL)		       \
+	{				       \
+	  (ITER)->ops->dtor (ITER);	       \
+	  xfree (ITER);		       \
+	}				       \
+    } while (0)