why the destructor is called only one time when the constructor is called 5 times?

Question

I'm trying to learn more about C++ ,int this code I'm allocating an array of A's (5 in this case), what I understand that 5 A's will be allocated ...so the compiler will call 5 times the constructer , but in case of deleting that array it calls the destructor one time only ,so my question is why does it call the destructor one time only when it has 5 A's , shouldn't he call the destructor 5 times??

I have this code :

#include <iostream>
using namespace std;

class A {
public:
    A() { std::cout << "IM in C'tor" << std::endl; };
    ~A() { std::cout << "IM in De'tor" << std::endl; }
};


int main()

{
    A* a = new A[5];
    delete a;  // ingone the errors,the important thing is calling the 
                 C'tor and D'tor` 
    return 0;
}

`new[]` and `delete[]` should be used in pair. So `delete[] a;`. — songyuanyao, Jul 05 '22 at 13:36
Your `cout` statements in the destructor and constructor should print `this`, not just a simple message. If you did that, you will see what the issue is. — PaulMcKenzie, Jul 05 '22 at 13:44

paxdiablo · Accepted Answer · 2022-07-05T13:42:38.053

1

You need to use delete[] a to delete an array of things allocated with new[]. If you do that, you'll see the correct output:

IM in C'tor
IM in C'tor
IM in C'tor
IM in C'tor
IM in C'tor
IM in De'tor
IM in De'tor
IM in De'tor
IM in De'tor
IM in De'tor

edited Jul 05 '22 at 13:42

answered Jul 05 '22 at 13:40

paxdiablo

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Could've just closed this as dupe. Moreover this was a typo. – Jason Jul 05 '22 at 13:41
1

@Anoop, I don't consider this a typographical error, this is more a misunderstanding of the language features. – paxdiablo Jul 05 '22 at 13:44
I see. I found the dupe. – Jason Jul 05 '22 at 13:45
ok. lets say I didn't change my code , what does "delete a" deletes exactly, does is delete the first element in the array ? ? – sallyaaa Jul 05 '22 at 13:57
@paxdiablo , I didn't write the code , it was a question in my exam – sallyaaa Jul 05 '22 at 13:59
1

@sallyaaa It's UB (undefined behaviour), so all bets are off. I'm surprised it didn't crash outright, actually. – Paul Sanders Jul 05 '22 at 14:00
yeah it didn't crash ,it throws an exception . – sallyaaa Jul 05 '22 at 14:06

why the destructor is called only one time when the constructor is called 5 times?

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