On Sat, Dec 26, 2020, 3:03 PM Thiago Macieira via Std-Proposals <std-proposals@lists.isocpp.org> wrote:
On Saturday, 26 December 2020 03:38:20 -03 Tony V E via Std-Proposals wrote:
> An implementation can probably hide the ‎bool inside an unused bit of the
> pointer (or length),

A third option is to use one of the unused bits in the pointer on CPUs that
support address masking / colouring.

Storing in the integer length: almost certainly okay.
Storing in the pointer: almost certainly not okay, unless I have failed to keep up with C++20 constexpr rules. string_view is specified to be constexpr-friendly in C++17 and later. That means no type-punning.