C++ Conversion by explicit constructor or explicit conversion function


A conversion that involves calling an explicit constructor or conversion function can't be done implicitly. We can request that the conversion be done explicitly using static_cast. The meaning is the same as that of a direct initialization, except that the result is a temporary.

class C {
    std::unique_ptr<int> p;
    explicit C(int* p) : p(p) {}
void f(C c);
void g(int* p) {
    f(p);                 // error: C::C(int*) is explicit
    f(static_cast<C>(p)); // ok
    f(C(p));              // equivalent to previous line
    C c(p); f(c);         // error: C is not copyable