So you are asking for a way to know at runtime inside a constructor, whether the constructed object is const or non-const? Like an implicit parameter? Not ABI compatible, performance cost.   Or at compile-time? Then the constructor would have to be a template to generate two functions.   It is not supported by the current standard.     As alternative you could use two different factory functions instead.   -----Ursprüngliche Nachricht----- Von:Frederick Virchanza Gotham via Std-Proposals <std-proposals_at_[hidden]> Gesendet:Do 28.09.2023 12:50 Betreff:[std-proposals] Let constructor know if object is const or volatile An:std-proposals <std-proposals_at_[hidden]>; CC:Frederick Virchanza Gotham <cauldwell.thomas_at_[hidden]>; Consider the following code snippet: #include <iostream>                       // cout, endl #include <type_traits>                    // is_const, remove_pointer struct Monkey {    int i;    void NonConst(void) { i = 7; }    Monkey(void)    {        this->NonConst();    // 'this' must be a pointer to non-const here        if ( std::is_const_v< std::remove_pointer_t<decltype(this)> > )        {            std::cout << "This is a const object\n";        }    } }; int main(void) {    Monkey obj1;    Monkey const obj2; } This code snippet doesn't print "This is a const object" because 'this' is a pointer to non-const inside the constructor. Perhaps we could have an implicit type inside every constructor, something like "_This_t" to be used as followed:    Monkey::Monkey(void)    {        this->NonConst();    // 'this' must be a pointer to non-const here        if ( std::is_const_v< std::remove_pointer_t<_This_t> > )        {            std::cout << "This is a const object\n";        }    } -- Std-Proposals mailing list Std-Proposals_at_[hidden] https://lists.isocpp.org/mailman/listinfo.cgi/std-proposals