That was legal C++, it was retroactively made UB on purpose a year ago (as far as I understand): https://www.open-std.org/jtc1/sc22/wg21/docs/cwg_closed.html#315 https://www.open-std.org/jtc1/sc22/wg21/docs/cwg_defects.html#2823   -----Ursprüngliche Nachricht----- Von:Frederick Virchanza Gotham via Std-Proposals <std-proposals_at_[hidden]> Gesendet:So 27.10.2024 21:16 Betreff:[std-proposals] Calling methods on a nullptr An:std-proposals <std-proposals_at_[hidden]>; CC:Frederick Virchanza Gotham <cauldwell.thomas_at_[hidden]>; This is a totally half-baked idea, but I just want to float it here sort of like a thought experiment to see if anyone is intrigued by the possibilities it could open up. C++ could potentially allow the invocation of a method on a nullptr. For example:    class MyClass {        string name;    public:        string GetName(void)        {            if ( nullptr == this ) return {};            return this->name;        }    }; It gets a little more complicated if the method is virtual, for example:    class MyClass {        string name;    public:        virtual string GetName(void)        {            if ( nullptr == this ) return {};            return this->name;        }    }; Because if we supply the following standalone function to an x86_64 compiler on Linux:    string Monkey(MyClass *const p)    {        return p->GetName();    } It will give us back something like:    mov r11, rdi    # Put the object pointer in R11    mov r11, [r11]  # Put the address of the VTable in R11    mov r11, [r11]  # Put the address of the first method in R11    jmp r11 This of course will segfault the first time it dereferences R11 because it's a nullptr. But if we were to mark the class as nullptr-friendly:    class MyClass friend nullptr {        string name;    public:        virtual string GetName(void)        {            if ( nullptr == this ) return {};            return this->name;        }    }; Then our 'Monkey' function would then know to check first whether 'p' is a nullptr, and if it is a nullptr, then instead of dereferencing 'p' to find a VTable pointer, it instead just uses the VTable of MyClass. So it could be possible in the future in C++ to accommodate the invocation of a method on a nullptr. -- Std-Proposals mailing list Std-Proposals_at_[hidden] https://lists.isocpp.org/mailman/listinfo.cgi/std-proposals