4.8 Passing the Address of an Anonymous Class Instance

You are not allowed to take the address of a temporary variable. For example, the following code is invalid because it takes the address of a variable created by a constructor call. However, the compiler accepts this invalid code when you use the -features=extensions option.

class C {
  public:
    C(int);
    ...
};
void f1(C*);
int main()
{
  f1(&C(2)); // invalid
}

Note that you can make this code valid by using an explicit variable.

C c(2);
f1(&c);

The temporary object is destroyed when the function returns. Ensuring that the address of the temporary variable is not retained is the programmer’s responsibility. In addition, the data that is stored in the temporary variable (for example, by f1) is lost when the temporary variable is destroyed.