value_ptr_ issue when copying/moving hardware_interface::Handle

[kimsh5904]

Describe the bug

• It seems value_ptr_ points the same value_ after calling the below operators

ros2_control/hardware_interface/include/hardware_interface/handle.hpp

Lines 75 to 125 in d4139b7

	Handle(const Handle & other) noexcept
	{
	std::unique_lock<std::shared_mutex> lock(other.handle_mutex_);
	std::unique_lock<std::shared_mutex> lock_this(handle_mutex_);
	prefix_name_ = other.prefix_name_;
	interface_name_ = other.interface_name_;
	handle_name_ = other.handle_name_;
	value_ = other.value_;
	value_ptr_ = other.value_ptr_;
	}
	Handle(Handle && other) noexcept
	{
	std::unique_lock<std::shared_mutex> lock(other.handle_mutex_);
	std::unique_lock<std::shared_mutex> lock_this(handle_mutex_);
	prefix_name_ = std::move(other.prefix_name_);
	interface_name_ = std::move(other.interface_name_);
	handle_name_ = std::move(other.handle_name_);
	value_ = std::move(other.value_);
	value_ptr_ = std::move(other.value_ptr_);
	}
	Handle & operator=(const Handle & other)
	{
	if (this != &other)
	{
	std::unique_lock<std::shared_mutex> lock(other.handle_mutex_);
	std::unique_lock<std::shared_mutex> lock_this(handle_mutex_);
	prefix_name_ = other.prefix_name_;
	interface_name_ = other.interface_name_;
	handle_name_ = other.handle_name_;
	value_ = other.value_;
	value_ptr_ = other.value_ptr_;
	}
	return *this;
	}
	Handle & operator=(Handle && other)
	{
	if (this != &other)
	{
	std::unique_lock<std::shared_mutex> lock(other.handle_mutex_);
	std::unique_lock<std::shared_mutex> lock_this(handle_mutex_);
	prefix_name_ = std::move(other.prefix_name_);
	interface_name_ = std::move(other.interface_name_);
	handle_name_ = std::move(other.handle_name_);
	value_ = std::move(other.value_);
	value_ptr_ = std::move(other.value_ptr_);
	}
	return *this;
	}

[saikishor]

Hello @kimsh5904,

Thank you for reporting the issue. Let me check and get back to you. If you already have a minimal example, it already helps to reproduce it.

Thank you!

[Wiktor-99]

I think what we can see here is wrong ptr copy, I'm not sure but maybe we wold like to do something like this:

Handle(const Handle & other) noexcept 
 { 
   std::unique_lock<std::shared_mutex> lock(other.handle_mutex_); 
   std::unique_lock<std::shared_mutex> lock_this(handle_mutex_); 
   prefix_name_ = other.prefix_name_; 
   interface_name_ = other.interface_name_; 
   handle_name_ = other.handle_name_; 
   value_ = other.value_; 
   value_ptr_ = std::get_if<double>(&value_);
 } 

We would like copy only the value but the pointer should still point to our member value_ not to member of the other class

[saikishor]

I've added some tests here: #2011

The changes look good to me. See if you can find some issues in the tests. I'm happy to check back and fix them.

Thank you for your time guys! :)