From: Philippe Proulx <eeppeliteloop@gmail.com>
Date: Wed, 22 Jul 2015 21:05:36 +0000 (-0400)
Subject: ir: add BT_CTF_MOVE()
X-Git-Tag: v2.0.0-pre1~1207
X-Git-Url: http://drtracing.org/?a=commitdiff_plain;h=e693822d3c00dbca7336ee2f9ba8f756599c7a3b;p=babeltrace.git

ir: add BT_CTF_MOVE()

Adds semantics to ownership transfers of CTF IR objects.

This is something that is done often enough to justify the
existence of this macro:

    struct bt_ctf_field_type *type;
    struct bt_ctf_field_type *ret_type;

    /* ... */

    /* move ownership */
    ret_type = type;
    type = NULL;

    /* ... */

    /* put both (safe since type was set to NULL) */
    bt_ctf_put(ret_type);
    bt_ctf_put(type);

With BT_CTF_MOVE():

    struct bt_ctf_field_type *type;
    struct bt_ctf_field_type *ret_type;

    /* ... */

    /* move ownership */
    BT_CTF_MOVE(ret_type, type);

    /* ... */

    /* put both (safe since ownership was moved) */
    bt_ctf_put(ret_type);
    bt_ctf_put(type);

Signed-off-by: Philippe Proulx <eeppeliteloop@gmail.com>
Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>
---

diff --git a/include/babeltrace/ctf-ir/ref.h b/include/babeltrace/ctf-ir/ref.h
index fa612ca0..acc89d17 100644
--- a/include/babeltrace/ctf-ir/ref.h
+++ b/include/babeltrace/ctf-ir/ref.h
@@ -50,6 +50,22 @@
 		(_obj) = NULL;		\
 	} while (0)
 
+/*
+ * BT_CTF_MOVE: moves the ownership of a CTF object, setting the old
+ *	owner to NULL.
+ *
+ * This macro sets the variable _dst to the value of the variable _src,
+ * then sets _src to NULL, effectively moving the ownership of a CTF
+ * object from one variable to the other.
+ *
+ * @param obj CTF IR object.
+ */
+#define BT_CTF_MOVE(_dst, _src)		\
+	do {				\
+		(_dst) = (_src);	\
+		(_src) = NULL;		\
+	} while (0)
+
 /*
  * bt_ctf_get: increments the reference count of a CTF IR object.
  *