What are the limitations of std::variant in C++17?

What are the limitations of std::variant in C++17?

Some limitations of std::variant in C++17 include its inability to hold types that are not copyable or movable, and the fact that it does not support type erasure.

Can you explain why it can't hold non-copyable types?

Certainly! std::variant requires its contained types to be copyable or movable because it needs to manage the memory and state of the active type. Non-copyable types cannot be duplicated, which complicates this management.

Are there any performance concerns with using std::variant?

Yes, there can be performance concerns, especially with large types. The overhead of managing the active state and potential type conversions can lead to increased compile times and runtime costs.

How does std::variant compare to union types?

std::variant is safer than unions because it keeps track of the active type, preventing undefined behavior when accessing inactive types, which is a common issue with unions.

What alternatives to std::variant exist in C++?

Alternatives include using boost::variant, or implementing your own type-safe union, but std::variant is generally preferred for its safety and ease of use.