Note: This answer applies to C++03, and it seems like the behavior was changed in C++11 and higher so that this is now undefined behavior. It turns out that in this particular case the code is legal, but you’re ε-away from undefined behavior. The C++03 standard defines the notion of the “lifetime” of an object … Read more
Another way of looking at this – rather than just quoting the spec which says that structs can’t/don’t have destructors – consider what would happen if the spec was changed so that they did – or rather, let’s ask the question: can we guess why did the language designers decide to not allow structs to … Read more
Rarely do you ever need to call the destructor explicitly. Instead, the destructor is called when an object is destroyed. For an object like ob2 that is a local variable, it is destroyed when it goes out of scope: int main() { date ob2(12); } // ob2.~date() is called here, automatically! If you dynamically allocate … Read more
What makes you think the object n points to should be deleted by default? The default destructor destroys the pointer, not what it’s pointing to. Edit: I’ll see if I can make this a little more clear. If you had a local pointer, and it went out of scope, would you expect the object it … Read more
The requirements of the call to the function object Deleter are specific on this as listed in the requirements of the std::unique_ptr<T>::reset() member. From [unique.ptr.single.modifiers]/3, circa N4660 §23.11.1.2.5/3; unique_ptr modifiers void reset(pointer p = pointer()) noexcept; Requires: The expression get_deleter()(get()) shall be well formed, shall have well-defined behavior, and shall not throw exceptions. In general … Read more
This is not supported. There is nothing like a destructor in Dart. JS garbage collector doesn’t provide a way to implement this. See also https://stackoverflow.com/a/20490161/217408 and https://github.com/dart-lang/sdk/issues/3691
Temporary objects are destroyed at the end of the full expression they’re part of. A full expression is an expression that isn’t a sub-expression of some other expression. Usually this means it ends at the ; (or ) for if, while, switch etc.) denoting the end of the statement. In your example, it’s the end … Read more
Warning: This answer pertains to C++ only; the rules are quite different in C. Won’t x be leaked? No, absolutely not. It is a myth that goto is some low-level construct that allows you to override C++’s built-in scoping mechanisms. (If anything, it’s longjmp that may be prone to this.) Consider the following mechanics that … Read more
To add the element a copy constructor is invoked on a temporary object. After the push_back() the temporary object is destroyed – that’t the first destructor call. Then vector instance goes out of scope and destroys all the elements stored – that’s the second destructor call.
A virtual destructor is only useful for inheritance scenarios. STL containers are not designed to be inherited from (nor is it a supported scenario). Hence they don’t have virtual destructors.