Fix move assignments

- Add self-assignment checks
- Free resources of object which is going to be replaced to avoid
  resource leaks

SDL2pp/AudioDevice.cc

@@ -51,6 +51,9 @@ AudioDevice::AudioDevice(AudioDevice&& other) noexcept : device_id_(other.device
 }
 
 AudioDevice& AudioDevice::operator=(AudioDevice&& other) noexcept {
+	if (&other == this)
+		return *this;
+
 	if (device_id_)
 		SDL_CloseAudioDevice(device_id_);
 

SDL2pp/AudioLock.cc

@@ -37,6 +37,12 @@ AudioDevice::LockHandle::LockHandle(AudioDevice::LockHandle&& other) noexcept :
 }
 
 AudioDevice::LockHandle& AudioDevice::LockHandle::operator=(AudioDevice::LockHandle&& other) noexcept {
+	if (&other == this)
+		return *this;
+
+	if (device_ != nullptr)
+		SDL_UnlockAudioDevice(device_->device_id_);
+
 	device_ = other.device_;
 
 	other.device_ = nullptr;

SDL2pp/RWops.cc

@@ -149,6 +149,10 @@ RWops::RWops(RWops&& other) noexcept : rwops_(other.rwops_) {
 }
 
 RWops& RWops::operator=(RWops&& other) noexcept {
+	if (&other == this)
+		return *this;
+	if (rwops_ != nullptr)
+		Close();
 	rwops_ = other.rwops_;
 	rwops_->hidden.unknown.data2 = static_cast<void*>(this);
 	other.rwops_ = nullptr;

SDL2pp/Renderer.cc

@@ -47,6 +47,10 @@ Renderer::Renderer(Renderer&& other) noexcept : renderer_(other.renderer_) {
 }
 
 Renderer& Renderer::operator=(Renderer&& other) noexcept {
+	if (&other == this)
+		return *this;
+	if (renderer_ != nullptr)
+		SDL_DestroyRenderer(renderer_);
 	renderer_ = other.renderer_;
 	other.renderer_ = nullptr;
 	return *this;

SDL2pp/Texture.cc

@@ -65,6 +65,10 @@ Texture::Texture(Texture&& other) noexcept : texture_(other.texture_) {
 }
 
 Texture& Texture::operator=(Texture&& other) noexcept {
+	if (&other == this)
+		return *this;
+	if (texture_ != nullptr)
+		SDL_DestroyTexture(texture_);
 	texture_ = other.texture_;
 	other.texture_ = nullptr;
 	return *this;

SDL2pp/TextureLock.cc

@@ -38,6 +38,12 @@ Texture::LockHandle::LockHandle(Texture::LockHandle&& other) noexcept : texture_
 }
 
 Texture::LockHandle& Texture::LockHandle::operator=(Texture::LockHandle&& other) noexcept {
+	if (&other == this)
+		return *this;
+
+	if (texture_ != nullptr)
+		SDL_UnlockTexture(texture_->Get());
+
 	texture_ = other.texture_;
 	pixels_ = other.pixels_;
 	pitch_ = other.pitch_;

SDL2pp/Wav.cc

@@ -47,6 +47,12 @@ Wav::Wav(Wav&& other) : audio_buffer_(other.audio_buffer_), audio_length_(other.
 }
 
 Wav& Wav::operator=(Wav&& other) {
+	if (&other == this)
+		return *this;
+
+	if (audio_buffer_ != nullptr)
+		SDL_FreeWAV(audio_buffer_);
+
 	spec_ = std::move(other.spec_);
 	audio_buffer_ = other.audio_buffer_;
 	audio_length_ = other.audio_length_;

SDL2pp/Window.cc

@@ -41,6 +41,10 @@ Window::Window(Window&& other) noexcept : window_(other.window_) {
 }
 
 Window& Window::operator=(Window&& other) noexcept {
+	if (&other == this)
+		return *this;
+	if (window_ != nullptr)
+		SDL_DestroyWindow(window_);
 	window_ = other.window_;
 	other.window_ = nullptr;
 	return *this;