Use a `zstring` or a `not_null<zstring>` to designate a C-style string

Reason

C-style strings are ubiquitous. They are defined by convention: zero-terminated arrays of characters. We must distinguish C-style strings from a pointer to a single character or an old-fashioned pointer to an array of characters.

If you don't need null termination, use string_view.

Example

Consider:

int length(const char* p);

When I call length(s) should I check if s is nullptr first? Should the implementation of length() check if p is nullptr?

// the implementor of length() must assume that p == nullptr is possible
int length(zstring p);

// it is the caller's job to make sure p != nullptr
int length(not_null<zstring> p);

Note

zstring does not represent ownership.

See also: Support library