Implement dbus_clear_connection(), etc.

These are inspired by GLib's g_clear_pointer() and g_clear_object(),
which in turn is descended from CPython's Py_CLEAR_OBJECT. They should
make our code a lot less repetitive.

Signed-off-by: Simon McVittie <smcv@collabora.com>
Reviewed-by: Philip Withnall <withnall@endlessm.com>
Bug: https://bugs.freedesktop.org/show_bug.cgi?id=101895

1 files changed, 20 insertions, 0 deletions

diff --git a/dbus/dbus-macros.h b/dbus/dbus-macros.h
index 0e784fe1..2c8956e3 100644
--- a/dbus/dbus-macros.h
+++ b/dbus/dbus-macros.h
@@ -215,6 +215,26 @@
 #  define DBUS_PRIVATE_EXPORT /* no decoration */
 #endif
 
+/* Implementation for dbus_clear_message() etc. This is not API,
+ * do not use it directly.
+ *
+ * We're using a specific type (T ** and T *) instead of void ** and
+ * void * partly for type-safety, partly to be strict-aliasing-compliant,
+ * and partly to keep C++ compilers happy. This code is inlined into
+ * users of libdbus, so we can't rely on it having dbus' own compiler
+ * settings. */
+#define _dbus_clear_pointer_impl(T, pointer_to_pointer, destroy) \
+  do { \
+    T **_pp = (pointer_to_pointer); \
+    T *_value = *_pp; \
+    \
+    *_pp = NULL; \
+    \
+    if (_value != NULL) \
+      destroy (_value); \
+  } while (0)
+/* Not (destroy) (_value) in case destroy() is a function-like macro */
+
 /** @} */
 
 #endif /* DBUS_MACROS_H */