libcamera: camera_manager: Construct CameraManager instances manually

The CameraManager class is not supposed to be instantiated multiple
times, which led to a singleton implementation. This requires a global
instance of the CameraManager, which is destroyed when the global
destructors are executed.

Relying on global instances causes issues with cleanup, as the order in
which the global destructors are run can't be controlled. In particular,
the Android camera HAL implementation ends up destroying the
CameraHalManager after the CameraManager, which leads to use-after-free
problems.

To solve this, remove the CameraManager::instance() method and make the
CameraManager class instantiable directly. Multiple instances are still
not allowed, and this is enforced by storing the instance pointer
internally to be checked when an instance is created.

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

test/list-cameras.cpp

@@ -20,8 +20,8 @@ class ListTest : public Test
 protected:
 	int init()
 	{
-		cm = CameraManager::instance();
-		cm->start();
+		cm_ = new CameraManager();
+		cm_->start();
 
 		return 0;
 	}
@@ -30,7 +30,7 @@ protected:
 	{
 		unsigned int count = 0;
 
-		for (const std::shared_ptr<Camera> &camera : cm->cameras()) {
+		for (const std::shared_ptr<Camera> &camera : cm_->cameras()) {
 			cout << "- " << camera->name() << endl;
 			count++;
 		}
@@ -40,11 +40,12 @@ protected:
 
 	void cleanup()
 	{
-		cm->stop();
+		cm_->stop();
+		delete cm_;
 	}
 
 private:
-	CameraManager *cm;
+	CameraManager *cm_;
 };
 
 TEST_REGISTER(ListTest)