c++ - Is the copy constructor called when an object is passed by reference? -

when class object passed value function, copy constructor called create local object , destructor called when object returned. but, copy constructor called if object reference passed?

nope, won't called.

a reference alias, is, name an existing variable , not copy.

take @ example:

class line { public:    int getlength( void ){}    // simple constructor    line(  ){       cout<<"constructor"<<endl;    }       // copy constructor              line( const line &obj){       cout<<"copy cts\n";    }   };  void callr(line& l){    cout<<"call ref\n"; } void callc(line l){    cout<<"call copy\n"; }   int main() {     line line;    cout<<"before call reference\n";    callr(line);    cout<<"before call copy\n";    callc(line); } 

which produces following output:

constructor ->  line line; before call reference call ref  before call copy copy cts call copy 

as can see copy constructor not called when object passed reference. think of reference pointer.