manager: preserve constness in NM_MANAGER_GET_PRIVATE() and add compile-time type check

1 files changed, 13 insertions, 2 deletions

diff --git a/src/nm-manager.c b/src/nm-manager.c
index ab1a5744b7..b3576b02fd 100644
--- a/src/nm-manager.c
+++ b/src/nm-manager.c
@@ -147,14 +147,25 @@ typedef struct {
 
 struct _NMManager {
 	NMExportedObject parent;
-	NMManagerPrivate priv;
+	NMManagerPrivate _priv;
 };
 
 typedef struct {
 	NMExportedObjectClass parent;
 } NMManagerClass;
 
-#define NM_MANAGER_GET_PRIVATE(o) ({ nm_assert (NM_IS_MANAGER (o)); &((o)->priv); })
+#define NM_MANAGER_GET_PRIVATE(self) \
+	({ \
+		/* preserve the const-ness of self. Unfortunately, that
+		 * way, @self cannot be a void pointer */ \
+		typeof (self) _self = (self); \
+		\
+		/* Get compiler error if variable is of wrong type */ \
+		_nm_unused const NMManager *_self2 = (_self); \
+		\
+		nm_assert (NM_IS_MANAGER (_self)); \
+		&_self->_priv; \
+	})
 
 G_DEFINE_TYPE (NMManager, nm_manager, NM_TYPE_EXPORTED_OBJECT)