Hi , I wrote sample (below) program to check when copy constructor and assignment operator called. my doubt was if object a, b defined previous to statement a(b), then will a(b) call copy c_tor or assignment operator and why below program giving compilation error(mentioned inline) . Can anybody tell me how to fix the issue. I have tried using test(test& y) , still compiler gives " no matching function for call to ‘test::test(test)’" Code: #include<iostream> using namespace std; class test { int i; public: test(int x=0):i(x){} ~test(){} test(const test& y) { cout<<"cp_ctor"<<endl; } test& operator=(test& m) { cout<<"assingment"<<endl; return *this; } }; test sentobject(void) { test temp(88); cout<<"sending.."; return temp; } int main() { test a(3),b(6); cout<<"a(b)calls"; a(b);//error: no match for call to ‘(test) (test&)’ cout<<"sendobject calls"<<endl; test k = sentobject(); return 0; }
I am using g++ compiler g++ (Ubuntu/Linaro 4.5.2-8ubuntu4) 4.5.2 Copyright (C) 2010 Free Software Foundation, Inc. This is free software; see the source for copying conditions. There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
Hi trying the following: Code: int main() { //test a(3),b(6); test b(6); cout<<"a(b)calls"; test a(b); cout<<"sendobject calls"<<endl; test k = sentobject(); return 0; } [/quote]
Thank you Chong, In code suggested, test a(b) will call copy c_tor. But I wanted to know particular case of a(b) where both a and b pre-defined . According to my knowledge it will call assignment operator so I wrote this(posted) program.
Hi pushpat I have limited experience of C++ but I think that you should have "a=b;" instead of "a(b);" to use the assignment operator in your posted program!!? With a(b), my MS VC++ wont compile it!! Best regards Chong
Hi pushpat By the way, what made you think that a(b) will call call a copy constructor or assigment operator. As far as I know, once the object is made, it can not be remade once agian as a(b). best regards Chong
Hi Chong, According to my knowledge assignment operator called when we are assigning object to existing objects and copy c_tor called copying object to non-existing object(while creating object) . so I wrote sample program which is posted here to understand. Thanks Pushpa.T
Constructor for an object called, to initialize the object. It is a two step process in C++ 1) Allocates the Space 2) Initializes the allocated space by providing initial values to its data members Copy constructor is called when you Construct an Object from the already initialized one. In your case a(b), both are initialized object, and there is no need for construction at all. So why do you think it should call copy constructor. A(b) does't use any =, so assignment operator also not called. Finally the compiler decides a() as member function. But, you don't provide one and that's why you see a error message.
