Can I call a public function in a destructor to free memory?

I am implementing a LinkedList. Instead of redoing the work, can I reuse a public function that I wrote to delete and free the nodes(memory too) in the destructor. Output turn out to be fine/correct, but I'm wondering if I'm missing anything behind the scene. I've seen this but my main concern is about whether am I doing it correctly in terms of freeing up the memory in my C++ code.

My destructor:

~LinkedList(){

    Node *next = head;

    while(head != NULL){

        DeleteEndVal();

    }

}

My public function DeleteEndVal();:

// delete value from the end of the list

int DeleteEndVal(){

    if(CheckListEmpty() == true){

        cout << "Empty list. Nothing to delete." << endl;

        return -1;

    }

    else{

        int val;

        Node *prev;

        Node *cur;

        if(head->next == NULL){

            val = tail->data;

            head = NULL;

            tail = NULL; 



        }

        else{

            prev = head;

            cur = head->next;

            while (cur->next != NULL){

                prev = prev->next;

                cur = cur->next;

                val = cur->data;

            }

            prev->next = NULL;

            free(cur);

        }

        return val;

    }

}

asked Nov 25 '18 at 22:35

ccsalison

2417

can I reuse a public function that I wrote to delete and free the nodes(memory too) in the destructor -- If the function works, yes you can. But if you're going to do things this way, why not delete the first value repeatedly instead of deleting the last value? Deleting the last value incurs a performance penalty due to you having to traverse all the way to the end.

– PaulMcKenzie
Nov 25 '18 at 22:40

@PaulMcKenzie Ah! You are right. Thanks for bringing that up!

– ccsalison
Nov 25 '18 at 23:31

The other thing to watch out for is that the function you're calling, it shouldn't throw an exception if you're going to utilize it in the destructor, or at the very least, make sure no exception escapes from the destructor. Thus your destructor needs to make sure the exception doesn't escape from it, else std::terminate will be called. You can ensure this in many ways, but just to round out the things you have to watch out for when calling other functions in a destructor.

– PaulMcKenzie
Nov 26 '18 at 1:10

add a comment |

My destructor:

~LinkedList(){

    Node *next = head;

    while(head != NULL){

        DeleteEndVal();

    }

}

My public function DeleteEndVal();:

// delete value from the end of the list

int DeleteEndVal(){

    if(CheckListEmpty() == true){

        cout << "Empty list. Nothing to delete." << endl;

        return -1;

    }

    else{

        int val;

        Node *prev;

        Node *cur;

        if(head->next == NULL){

            val = tail->data;

            head = NULL;

            tail = NULL; 



        }

        else{

            prev = head;

            cur = head->next;

            while (cur->next != NULL){

                prev = prev->next;

                cur = cur->next;

                val = cur->data;

            }

            prev->next = NULL;

            free(cur);

        }

        return val;

    }

}

asked Nov 25 '18 at 22:35

ccsalison

2417

can I reuse a public function that I wrote to delete and free the nodes(memory too) in the destructor -- If the function works, yes you can. But if you're going to do things this way, why not delete the first value repeatedly instead of deleting the last value? Deleting the last value incurs a performance penalty due to you having to traverse all the way to the end.

– PaulMcKenzie
Nov 25 '18 at 22:40

@PaulMcKenzie Ah! You are right. Thanks for bringing that up!

– ccsalison
Nov 25 '18 at 23:31

The other thing to watch out for is that the function you're calling, it shouldn't throw an exception if you're going to utilize it in the destructor, or at the very least, make sure no exception escapes from the destructor. Thus your destructor needs to make sure the exception doesn't escape from it, else std::terminate will be called. You can ensure this in many ways, but just to round out the things you have to watch out for when calling other functions in a destructor.

– PaulMcKenzie
Nov 26 '18 at 1:10

add a comment |

My destructor:

~LinkedList(){

    Node *next = head;

    while(head != NULL){

        DeleteEndVal();

    }

}

My public function DeleteEndVal();:

// delete value from the end of the list

int DeleteEndVal(){

    if(CheckListEmpty() == true){

        cout << "Empty list. Nothing to delete." << endl;

        return -1;

    }

    else{

        int val;

        Node *prev;

        Node *cur;

        if(head->next == NULL){

            val = tail->data;

            head = NULL;

            tail = NULL; 



        }

        else{

            prev = head;

            cur = head->next;

            while (cur->next != NULL){

                prev = prev->next;

                cur = cur->next;

                val = cur->data;

            }

            prev->next = NULL;

            free(cur);

        }

        return val;

    }

}

asked Nov 25 '18 at 22:35

ccsalison

2417

My destructor:

~LinkedList(){

    Node *next = head;

    while(head != NULL){

        DeleteEndVal();

    }

}

My public function DeleteEndVal();:

// delete value from the end of the list

int DeleteEndVal(){

    if(CheckListEmpty() == true){

        cout << "Empty list. Nothing to delete." << endl;

        return -1;

    }

    else{

        int val;

        Node *prev;

        Node *cur;

        if(head->next == NULL){

            val = tail->data;

            head = NULL;

            tail = NULL; 



        }

        else{

            prev = head;

            cur = head->next;

            while (cur->next != NULL){

                prev = prev->next;

                cur = cur->next;

                val = cur->data;

            }

            prev->next = NULL;

            free(cur);

        }

        return val;

    }

}

c++ memory linked-list destructor singly-linked-list

asked Nov 25 '18 at 22:35

ccsalison

2417

asked Nov 25 '18 at 22:35

ccsalison

2417

asked Nov 25 '18 at 22:35

ccsalison

2417

asked Nov 25 '18 at 22:35

ccsalison

2417

asked Nov 25 '18 at 22:35

ccsalison

2417

can I reuse a public function that I wrote to delete and free the nodes(memory too) in the destructor -- If the function works, yes you can. But if you're going to do things this way, why not delete the first value repeatedly instead of deleting the last value? Deleting the last value incurs a performance penalty due to you having to traverse all the way to the end.

– PaulMcKenzie
Nov 25 '18 at 22:40

@PaulMcKenzie Ah! You are right. Thanks for bringing that up!

– ccsalison
Nov 25 '18 at 23:31

The other thing to watch out for is that the function you're calling, it shouldn't throw an exception if you're going to utilize it in the destructor, or at the very least, make sure no exception escapes from the destructor. Thus your destructor needs to make sure the exception doesn't escape from it, else std::terminate will be called. You can ensure this in many ways, but just to round out the things you have to watch out for when calling other functions in a destructor.

– PaulMcKenzie
Nov 26 '18 at 1:10

add a comment |

can I reuse a public function that I wrote to delete and free the nodes(memory too) in the destructor -- If the function works, yes you can. But if you're going to do things this way, why not delete the first value repeatedly instead of deleting the last value? Deleting the last value incurs a performance penalty due to you having to traverse all the way to the end.

– PaulMcKenzie
Nov 25 '18 at 22:40

@PaulMcKenzie Ah! You are right. Thanks for bringing that up!

– ccsalison
Nov 25 '18 at 23:31

The other thing to watch out for is that the function you're calling, it shouldn't throw an exception if you're going to utilize it in the destructor, or at the very least, make sure no exception escapes from the destructor. Thus your destructor needs to make sure the exception doesn't escape from it, else std::terminate will be called. You can ensure this in many ways, but just to round out the things you have to watch out for when calling other functions in a destructor.

– PaulMcKenzie
Nov 26 '18 at 1:10

can I reuse a public function that I wrote to delete and free the nodes(memory too) in the destructor -- If the function works, yes you can. But if you're going to do things this way, why not delete the first value repeatedly instead of deleting the last value? Deleting the last value incurs a performance penalty due to you having to traverse all the way to the end.

– PaulMcKenzie
Nov 25 '18 at 22:40

@PaulMcKenzie Ah! You are right. Thanks for bringing that up!

– ccsalison
Nov 25 '18 at 23:31

The other thing to watch out for is that the function you're calling, it shouldn't throw an exception if you're going to utilize it in the destructor, or at the very least, make sure no exception escapes from the destructor. Thus your destructor needs to make sure the exception doesn't escape from it, else std::terminate will be called. You can ensure this in many ways, but just to round out the things you have to watch out for when calling other functions in a destructor.

– PaulMcKenzie
Nov 26 '18 at 1:10

add a comment |

1 Answer
1

active

oldest

votes

You can call a function inside your destructor, so first-off answering your original question: Yes, that's ok.

There are several other aspects though:

First, you should not recode a basic concept like a linked list by hand. This is error-prone and/or may be an inefficient implementation. Use foundation classes or standard C++ libraries instead.

When sticking to your code, I wonder why:

there is a Node *next = head; in the destructor. IMHO, it does nothing.

you seem to have a tail attribute. If the method is removing the tail element (maybe rename it DeleteTail), then you shouldn't walk through the entire linked list. Instead, take the tail, get its previous element (I assume your linked list is bi-directional), and update that link instead.

as a consequence, your current implementation has a nested while loop to destroy the list, taking an order of n*n in time. For the destruction use-case, you don't even need to update the elements, use a simple while loop and destroy them without relinking.

answered Nov 25 '18 at 22:46

Thomas Jacob

31118

1) I deleted the Node *next = head; and it seems to not have any affect on the output. 2) My linked list is singly. I think I would remove it with head as per suggestion by Paul above. 3) You are right. Let me see how I can rewrite and optimize it. Thanks Thomas!

– ccsalison
Nov 25 '18 at 23:32

add a comment |

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1 Answer
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votes

You can call a function inside your destructor, so first-off answering your original question: Yes, that's ok.

There are several other aspects though:

First, you should not recode a basic concept like a linked list by hand. This is error-prone and/or may be an inefficient implementation. Use foundation classes or standard C++ libraries instead.

When sticking to your code, I wonder why:

there is a Node *next = head; in the destructor. IMHO, it does nothing.

you seem to have a tail attribute. If the method is removing the tail element (maybe rename it DeleteTail), then you shouldn't walk through the entire linked list. Instead, take the tail, get its previous element (I assume your linked list is bi-directional), and update that link instead.

as a consequence, your current implementation has a nested while loop to destroy the list, taking an order of n*n in time. For the destruction use-case, you don't even need to update the elements, use a simple while loop and destroy them without relinking.

answered Nov 25 '18 at 22:46

Thomas Jacob

31118

1) I deleted the Node *next = head; and it seems to not have any affect on the output. 2) My linked list is singly. I think I would remove it with head as per suggestion by Paul above. 3) You are right. Let me see how I can rewrite and optimize it. Thanks Thomas!

– ccsalison
Nov 25 '18 at 23:32

add a comment |

You can call a function inside your destructor, so first-off answering your original question: Yes, that's ok.

There are several other aspects though:

First, you should not recode a basic concept like a linked list by hand. This is error-prone and/or may be an inefficient implementation. Use foundation classes or standard C++ libraries instead.

When sticking to your code, I wonder why:

there is a Node *next = head; in the destructor. IMHO, it does nothing.

you seem to have a tail attribute. If the method is removing the tail element (maybe rename it DeleteTail), then you shouldn't walk through the entire linked list. Instead, take the tail, get its previous element (I assume your linked list is bi-directional), and update that link instead.

as a consequence, your current implementation has a nested while loop to destroy the list, taking an order of n*n in time. For the destruction use-case, you don't even need to update the elements, use a simple while loop and destroy them without relinking.

answered Nov 25 '18 at 22:46

Thomas Jacob

31118

1) I deleted the Node *next = head; and it seems to not have any affect on the output. 2) My linked list is singly. I think I would remove it with head as per suggestion by Paul above. 3) You are right. Let me see how I can rewrite and optimize it. Thanks Thomas!

– ccsalison
Nov 25 '18 at 23:32

add a comment |

You can call a function inside your destructor, so first-off answering your original question: Yes, that's ok.

There are several other aspects though:

First, you should not recode a basic concept like a linked list by hand. This is error-prone and/or may be an inefficient implementation. Use foundation classes or standard C++ libraries instead.

When sticking to your code, I wonder why:

there is a Node *next = head; in the destructor. IMHO, it does nothing.

you seem to have a tail attribute. If the method is removing the tail element (maybe rename it DeleteTail), then you shouldn't walk through the entire linked list. Instead, take the tail, get its previous element (I assume your linked list is bi-directional), and update that link instead.

as a consequence, your current implementation has a nested while loop to destroy the list, taking an order of n*n in time. For the destruction use-case, you don't even need to update the elements, use a simple while loop and destroy them without relinking.

answered Nov 25 '18 at 22:46

Thomas Jacob

31118

You can call a function inside your destructor, so first-off answering your original question: Yes, that's ok.

There are several other aspects though:

First, you should not recode a basic concept like a linked list by hand. This is error-prone and/or may be an inefficient implementation. Use foundation classes or standard C++ libraries instead.

When sticking to your code, I wonder why:

there is a Node *next = head; in the destructor. IMHO, it does nothing.

you seem to have a tail attribute. If the method is removing the tail element (maybe rename it DeleteTail), then you shouldn't walk through the entire linked list. Instead, take the tail, get its previous element (I assume your linked list is bi-directional), and update that link instead.

as a consequence, your current implementation has a nested while loop to destroy the list, taking an order of n*n in time. For the destruction use-case, you don't even need to update the elements, use a simple while loop and destroy them without relinking.

answered Nov 25 '18 at 22:46

Thomas Jacob

31118

answered Nov 25 '18 at 22:46

Thomas Jacob

31118

answered Nov 25 '18 at 22:46

Thomas Jacob

31118

answered Nov 25 '18 at 22:46

Thomas Jacob

31118

1) I deleted the Node *next = head; and it seems to not have any affect on the output. 2) My linked list is singly. I think I would remove it with head as per suggestion by Paul above. 3) You are right. Let me see how I can rewrite and optimize it. Thanks Thomas!

– ccsalison
Nov 25 '18 at 23:32

add a comment |

1) I deleted the Node *next = head; and it seems to not have any affect on the output. 2) My linked list is singly. I think I would remove it with head as per suggestion by Paul above. 3) You are right. Let me see how I can rewrite and optimize it. Thanks Thomas!

– ccsalison
Nov 25 '18 at 23:32

1) I deleted the Node *next = head; and it seems to not have any affect on the output. 2) My linked list is singly. I think I would remove it with head as per suggestion by Paul above. 3) You are right. Let me see how I can rewrite and optimize it. Thanks Thomas!

– ccsalison
Nov 25 '18 at 23:32

add a comment |

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