Convert a nullptr to std::span

Question

I have a const z* zs = nullptr;

I want to convert zs to std::span

When I try to do std::span<const z>(zs) I get an error saying

error: no matching function for call to ‘std::span::span(const z* const&)’

How do I convert to zs to std::span

I tried std::span<const z>(zs[0]) it seems to compile. Is that way correct?

Answer 1

You need to provide a length to go along with your pointer. A null pointer points to 0 elements. Are you reassigning sz somewhere?

An empty span is constructed from no arguments.

std::span<const z>{}

Answer 2

std::span has a constructor which takes a pointer and a size, use that:

std::span<const z>(zs, 0)