C + + primer on exercise 13.13 write their own program to understand constructors, copy structure, destructor, copy assignment, but finish found that there are problems,
1. Why test1 (b) and test1 (* c) without any output?
2. Why only copy in pushing b into the container without destruction? Then why include * c in container copy destructor and copy?

 
# include & lt; iostream> 
# include & lt; Vector> 
Using STD: : cin; Using STD: : cout; Using STD: : string; Using STD: : endl; Using STD: : vector; 
Struct X 
{
X () {cout & lt; <"Structure" & lt; X (const X&) {cout & lt; <"Copy" & lt; X& Operator=(const X& X) 
{
Cout & lt; <"Assignment" & lt; Return * this; 
} 
~ X () {cout & lt; <"Destruction" & lt; }; 
Void test1 (X& X) {return; } 
Void test2 (X) X {return; } 
Int main () 
{
A=new X X * (); 
X b; 
Delete a; 
X * c=new X (); 
Cout & lt; <"Test1 (b) : \ n"; 
Test1 (b); 
Cout & lt; <"\ ntest1 (*) c: \ n"; 
Test1 (* c); 
Cout & lt; <"\ ntest2 (b) : \ n"; 
Test2 (b); 
Cout & lt; <"\ ntest2 (*) c: \ n"; 
Test2 (* c); 
Cout & lt; <"\ nvec push_back (b) : \ n"; 
Vector Vec. 
Vec. Push_back (b); 
Cout & lt; <"\ nvec push_back () * c: \ n"; 
Vec. Push_back (* c); 
system("pause"); 
return 0; 
} 

CodePudding user response:

Because test1 transfer reference, don't copy

CodePudding user response:

2, and the destructor to happen before the vec destructor, and vec destructor is the end of the main function will call