> Unfortunately, std::optional implements operator* and operator-> which are UB if the optional is null -- that's even worse than the situation with pointers,
Dereferencing null optionals is UB for consistency with dereferencing pointers. All uses of operator* should have the same semantics and the C++ standards committee did the right thing by ensuring that with optionals. Checking for null in operator* would break consistency.
If you want to dereference an optional that may be null, use the .value_or() method. For the times when you absolutely know the optional has a value use operator*.
If you’re wondering why you would use an optional over a pointer. The idea is that optionals allow you to pass optional data by value. Previously if you wanted to pass optional data, you’d have to do it by reference with a pointer. This is part of c++’s push towards a value-based style, which is more amenable to optimization and more efficient in general for small structs (avoiding the heap, direct access of data). Move semantics are a part of that same push.
Dereferencing null optionals is UB for consistency with dereferencing pointers. All uses of operator* should have the same semantics and the C++ standards committee did the right thing by ensuring that with optionals. Checking for null in operator* would break consistency.
If you want to dereference an optional that may be null, use the .value_or() method. For the times when you absolutely know the optional has a value use operator*.
If you’re wondering why you would use an optional over a pointer. The idea is that optionals allow you to pass optional data by value. Previously if you wanted to pass optional data, you’d have to do it by reference with a pointer. This is part of c++’s push towards a value-based style, which is more amenable to optimization and more efficient in general for small structs (avoiding the heap, direct access of data). Move semantics are a part of that same push.