libcamera: base: extensible: Pass private pointer as unique_ptr<>

The Extensible constructor takes a pointer to a Private instance, whose
lifetime it then manages. Make this explicit in the API by passing the
pointer as a std::unique_ptr<Private>.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Reviewed-by: Jacopo Mondi <jacopo@jmondi.org>

src/libcamera/base/class.cpp

@@ -147,9 +147,12 @@ namespace libcamera {
 /**
  * \brief Construct an instance of an Extensible class
  * \param[in] d Pointer to the private data instance
+ *
+ * The private data lifetime is managed by the Extensible class, which destroys
+ * it when the Extensible instance is destroyed.
  */
-Extensible::Extensible(Extensible::Private *d)
-	: d_(d)
+Extensible::Extensible(std::unique_ptr<Extensible::Private> d)
+	: d_(std::move(d))
 {
 	*const_cast<Extensible **>(&d_->o_) = this;
 }
@@ -163,6 +166,10 @@ Extensible::Extensible(Extensible::Private *d)
  * overriden _d() functions that return the correct pointer type to the
  * corresponding derived Private class.
  *
+ * The lifetime of the private data is tied to the Extensible class. The caller
+ * shall not retain any reference to the returned pointer for longer than it
+ * holds a reference to the Extensible instance.
+ *
  * \return A pointer to the private data instance
  */