Hands-On High Performance Programming with Qt 5

Conversions

Another context where temporaries could arise was in the case of constant reference parameters in function calls. As such, references would be allowed to bind to a temporary object and implicit conversion could be triggered, creating a temporary only used inside of the function:

struct T {  T(int i) { ... }};void func(const T& o);main(){ func(1); // creates temporary object T! }

For that reason, the explicit annotation for constructors was introduced, which blocks such unwanted implicit conversions.