Question

Consider function f

void f(const std::string& s) {
    ...
}

Is it safe to call f with a fixed string like the following:

f("abc");

Answer 1

The lifetime of the std::string implicitly constructed from "abc" is until the call to f() ends. So long as you aren’t keeping that reference around somewhere else after f() ends, it is perfectly safe.

std::string const *pstr;

void f(std::string const &s)
{
    s.length(); // safe. s has an instance backing
                // it for the lifetime of this function.

    pstr = &s; // still technically safe, but only if you don't
               // dereference pstr after this function completes.
}

f("abc");

pstr->length(); // undefined behavior, the instance
                // pstr pointed to no longer exists.