諸事情でC++のreferenceを見ていて発見した。 If expression evaluates to a null pointer value, no destructors are called, and the deallocation function may or may not be called (it's implementation-defined), but the default deallocation functions are guaranteed to do nothing when handed a null pointer. (until C++14) If expression evaluates to a null pointer value, no destructors are called, and the deallocation fun