C++: Use shared_from_this() exclusively on this

Never call shared_from_this() on any object other than "this".
Adapt the API so that it can be made protected.

bindings/cxx/classes.cpp

@@ -159,7 +159,7 @@ map<string, shared_ptr<Driver>> Context::drivers()
 	{
 		auto name = entry.first;
 		auto driver = entry.second;
-		result[name] = driver->get_shared_pointer(this);
+		result[name] = driver->get_shared_pointer(shared_from_this());
 	}
 	return result;
 }
@@ -171,7 +171,7 @@ map<string, shared_ptr<InputFormat>> Context::input_formats()
 	{
 		auto name = entry.first;
 		auto input_format = entry.second;
-		result[name] = input_format->get_shared_pointer(this);
+		result[name] = input_format->get_shared_pointer(shared_from_this());
 	}
 	return result;
 }
@@ -183,7 +183,7 @@ map<string, shared_ptr<OutputFormat>> Context::output_formats()
 	{
 		auto name = entry.first;
 		auto output_format = entry.second;
-		result[name] = output_format->get_shared_pointer(this);
+		result[name] = output_format->get_shared_pointer(shared_from_this());
 	}
 	return result;
 }
@@ -779,7 +779,7 @@ vector<shared_ptr<TriggerStage>> Trigger::stages()
 {
 	vector<shared_ptr<TriggerStage>> result;
 	for (auto stage : _stages)
-		result.push_back(stage->get_shared_pointer(this));
+		result.push_back(stage->get_shared_pointer(shared_from_this()));
 	return result;
 }
 
@@ -787,7 +787,7 @@ shared_ptr<TriggerStage> Trigger::add_stage()
 {
 	auto stage = new TriggerStage(sr_trigger_stage_add(_structure));
 	_stages.push_back(stage);
-	return stage->get_shared_pointer(this);
+	return stage->get_shared_pointer(shared_from_this());
 }
 
 TriggerStage::TriggerStage(struct sr_trigger_stage *structure) : 
@@ -810,7 +810,7 @@ vector<shared_ptr<TriggerMatch>> TriggerStage::matches()
 {
 	vector<shared_ptr<TriggerMatch>> result;
 	for (auto match : _matches)
-		result.push_back(match->get_shared_pointer(this));
+		result.push_back(match->get_shared_pointer(shared_from_this()));
 	return result;
 }
 
@@ -925,7 +925,7 @@ shared_ptr<Device> Session::get_device(const struct sr_dev_inst *sdi)
 {
 	if (_owned_devices.count(sdi))
 		return static_pointer_cast<Device>(
-			_owned_devices[sdi]->get_shared_pointer(this));
+			_owned_devices[sdi]->get_shared_pointer(shared_from_this()));
 	else if (_other_devices.count(sdi))
 		return _other_devices[sdi];
 	else
@@ -1092,7 +1092,7 @@ const PacketType *Packet::type() const
 shared_ptr<PacketPayload> Packet::payload()
 {
 	if (_payload)
-		return _payload->get_shared_pointer(this);
+		return _payload->get_shared_pointer(shared_from_this());
 	else
 		throw Error(SR_ERR_NA);
 }
@@ -1115,7 +1115,7 @@ Header::~Header()
 {
 }
 
-shared_ptr<PacketPayload> Header::get_shared_pointer(Packet *_parent)
+shared_ptr<PacketPayload> Header::get_shared_pointer(shared_ptr<Packet> _parent)
 {
 	return static_pointer_cast<PacketPayload>(
 		ParentOwned::get_shared_pointer(_parent));
@@ -1143,7 +1143,7 @@ Meta::~Meta()
 {
 }
 
-shared_ptr<PacketPayload> Meta::get_shared_pointer(Packet *_parent)
+shared_ptr<PacketPayload> Meta::get_shared_pointer(shared_ptr<Packet> _parent)
 {
 	return static_pointer_cast<PacketPayload>(
 		ParentOwned::get_shared_pointer(_parent));
@@ -1169,7 +1169,7 @@ Logic::~Logic()
 {
 }
 
-shared_ptr<PacketPayload> Logic::get_shared_pointer(Packet *_parent)
+shared_ptr<PacketPayload> Logic::get_shared_pointer(shared_ptr<Packet> _parent)
 {
 	return static_pointer_cast<PacketPayload>(
 		ParentOwned::get_shared_pointer(_parent));
@@ -1200,7 +1200,7 @@ Analog::~Analog()
 {
 }
 
-shared_ptr<PacketPayload> Analog::get_shared_pointer(Packet *_parent)
+shared_ptr<PacketPayload> Analog::get_shared_pointer(shared_ptr<Packet> _parent)
 {
 	return static_pointer_cast<PacketPayload>(
 		ParentOwned::get_shared_pointer(_parent));
@@ -1290,8 +1290,7 @@ shared_ptr<Input> InputFormat::create_input(
 	auto input = sr_input_new(_structure, map_to_hash_variant(options));
 	if (!input)
 		throw Error(SR_ERR_ARG);
-	return shared_ptr<Input>(
+	return shared_ptr<Input>(new Input(_parent, input), Input::Deleter());
-		new Input(_parent->shared_from_this(), input), Input::Deleter());
 }
 
 Input::Input(shared_ptr<Context> context, const struct sr_input *structure) :

bindings/cxx/include/libsigrokcxx/libsigrokcxx.hpp

@@ -164,21 +164,14 @@ protected:
 	{
 	}
 
-public:
-	/* Get parent object that owns this object. */
-	shared_ptr<Parent> parent()
-	{
-		return _parent;
-	}
-
 	/* Note, this implementation will create a new smart_ptr if none exists. */
 	shared_ptr<Class> shared_from_this()
 	{
-		shared_ptr<Class> shared;
+		shared_ptr<Class> shared = _weak_this.lock();
 
-		if (!(shared = _weak_this.lock()))
+		if (!shared)
 		{
-			shared = shared_ptr<Class>(static_cast<Class *>(this), reset_parent);
+			shared.reset(static_cast<Class *>(this), &reset_parent);
 			_weak_this = shared;
 		}
 
@@ -193,11 +186,11 @@ public:
 		return shared_from_this();
 	}
 
-	shared_ptr<Class> get_shared_pointer(Parent *parent)
+public:
+	/* Get parent object that owns this object. */
+	shared_ptr<Parent> parent()
 	{
-		if (!parent)
+		return _parent;
-			throw Error(SR_ERR_BUG);
-		return get_shared_pointer(parent->shared_from_this());
 	}
 };
 
@@ -205,14 +198,6 @@ public:
 template <class Class, typename Struct>
 class SR_API UserOwned : public enable_shared_from_this<Class>
 {
-public:
-	shared_ptr<Class> shared_from_this()
-	{
-		auto shared = enable_shared_from_this<Class>::shared_from_this();
-		if (!shared)
-			throw Error(SR_ERR_BUG);
-		return shared;
-	}
 protected:
 	Struct *_structure;
 
@@ -221,6 +206,14 @@ protected:
 	{
 	}
 
+	shared_ptr<Class> shared_from_this()
+	{
+		auto shared = enable_shared_from_this<Class>::shared_from_this();
+		if (!shared)
+			throw Error(SR_ERR_BUG);
+		return shared;
+	}
+
 	/* Deleter needed to allow shared_ptr use with protected destructor. */
 	class Deleter
 	{
@@ -714,8 +707,15 @@ class SR_API PacketPayload
 protected:
 	PacketPayload();
 	virtual ~PacketPayload() = 0;
-	virtual shared_ptr<PacketPayload> get_shared_pointer(Packet *parent) = 0;
+private:
+	virtual shared_ptr<PacketPayload> get_shared_pointer(shared_ptr<Packet> parent) = 0;
 
+	/** Deleter needed to allow shared_ptr use with protected destructor. */
+	class Deleter
+	{
+	public:
+		void operator()(PacketPayload *payload) { delete payload; }
+	};
 	friend class Deleter;
 	friend class Packet;
 	friend class Output;
@@ -734,7 +734,7 @@ public:
 private:
 	explicit Header(const struct sr_datafeed_header *structure);
 	~Header();
-	shared_ptr<PacketPayload> get_shared_pointer(Packet *parent);
+	shared_ptr<PacketPayload> get_shared_pointer(shared_ptr<Packet> parent);
 	friend class Packet;
 };
 
@@ -749,7 +749,7 @@ public:
 private:
 	explicit Meta(const struct sr_datafeed_meta *structure);
 	~Meta();
-	shared_ptr<PacketPayload> get_shared_pointer(Packet *parent);
+	shared_ptr<PacketPayload> get_shared_pointer(shared_ptr<Packet> parent);
 	map<const ConfigKey *, Glib::VariantBase> _config;
 	friend class Packet;
 };
@@ -769,7 +769,7 @@ public:
 private:
 	explicit Logic(const struct sr_datafeed_logic *structure);
 	~Logic();
-	shared_ptr<PacketPayload> get_shared_pointer(Packet *parent);
+	shared_ptr<PacketPayload> get_shared_pointer(shared_ptr<Packet> parent);
 	friend class Packet;
 };
 
@@ -794,7 +794,7 @@ public:
 private:
 	explicit Analog(const struct sr_datafeed_analog *structure);
 	~Analog();
-	shared_ptr<PacketPayload> get_shared_pointer(Packet *parent);
+	shared_ptr<PacketPayload> get_shared_pointer(shared_ptr<Packet> parent);
 	friend class Packet;
 };