Define unique_ptr specialization for Py_buffer.

This patch causes PyBuffer_Release() to be called when the associated
buffer goes out of scope.  I've been using it as follows:

 ...
 Py_buffer_up buffer_up;
 Py_buffer py_buf;

 if (PyObject_CheckBuffer (obj)
     && PyObject_GetBuffer (obj, &py_buf, PyBUF_SIMPLE) == 0)
   {
      /* Got a buffer, py_buf, out of obj.  Cause it to released
         when it goes out of scope.  */
     buffer_up.reset (&py_buf);
   }
   ...

This snippet of code was taken directly from an upcoming patch to
python-value.c.

gdb/ChangeLog:

	* python/python-internal.h (Py_buffer_deleter): New struct.
	(Py_buffer_up): New typedef.

1 files changed, 13 insertions, 0 deletions

diff --git a/gdb/python/python-internal.h b/gdb/python/python-internal.h
index 3cb9ebc..d11af83 100644
--- a/gdb/python/python-internal.h
+++ b/gdb/python/python-internal.h
@@ -801,4 +801,17 @@ struct varobj;
 struct varobj_iter *py_varobj_get_iterator (struct varobj *var,
 					    PyObject *printer);
 
+/* Deleter for Py_buffer unique_ptr specialization.  */
+
+struct Py_buffer_deleter
+{
+  void operator() (Py_buffer *b) const
+  {
+    PyBuffer_Release (b);
+  }
+};
+
+/* A unique_ptr specialization for Py_buffer.  */
+typedef std::unique_ptr<Py_buffer, Py_buffer_deleter> Py_buffer_up;
+
 #endif /* PYTHON_PYTHON_INTERNAL_H */