Why can I assign struct with a pointer?
c++, implicit-conversion
Solution
You're hitting the fact that you didn't mark your constructor as `explicit`, and thus it can be used for implicit conversions.
`new UE(true)` returns a pointer. All pointers can be implicitly converted to `bool`, resulting in `true` if they are non-null. `UE` can be implicitly constructed from a `bool`. So in effect, the pointer returned by `new` is converted to `bool`, which is converted to `UE` using your constructor, and then the copy assignment operator of `UE` is called. Of course, the memory allocated by `new` is leaked.
The take-home message is: always mark your single-argument constructors as `explicit` unless you actually want them to be usable for implicit conversions. By "single-argument constructor," I mean one which can be called with a single argument. Either because it has one parameter, or it has more and all parameters after the first have default arguments.
Problem
Why does it even compile? ``` struct UE{ UE(bool a = true) { }; // UE(){}; // if UE took no initial args and called below, gcc will complain. }; class VA { protected: UE ue; public: VA(); }; VA::VA() { ue = new UE(true); // ???why??? // ue = new UE(); // will complain } ``` I tried with gcc (GCC) 4.6.2. How can I assign a struct with a pointer?