inserting strings into linked list nodes

This is a discussion on inserting strings into linked list nodes within the C Programming forums, part of the General Programming Boards category; I've got a function which should malloc for a new node and then for space for a string in the ...

  1. #1
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    inserting strings into linked list nodes

    I've got a function which should malloc for a new node and then for space for a string in the data_item part of the node... but for the life of me I can't figure out why I get two errors... here is the function...


    Code:
    void insert_at_front(char *n, node_ptr list)
    {
            node_ptr new_node = (node_ptr) malloc(sizeof(struct node));
            new_node->data_item = (char *) malloc(sizeof(char) * strlen(n) + 1);
            strcpy(new_node->data_item, n); 
            new_node->next = list->next;
            list->next = new_node;
    }

    The two errors:

    -second malloc line error is: assignment makes integer from pointer without a cast

    -strcpy line error is: passing arg 1 of 'strcpy' makes pointer from integer without a cast

    If anyone can give me any clues this would be greatly appreciated as I've spent a lot of the day trying to nut it out with no real insight beyond knowing it is a casting issue...

  2. #2
    ATH0 quzah's Avatar
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    You need to include the right header if you expect to use the functions described by said header.


    Quzah.
    Hope is the first step on the road to disappointment.

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    Hi, yes I think the header is alright but just to check...

    Code:
    #include "list.h"   /* is on the same page as the function */
    list.h contains:

    Code:
    typedef struct node *node_ptr;
    struct node
    {
        char data_item;
        node_ptr next;
    };
    
    /* Function to insert n at front of list */
    void insert_at_front(char *n, node_ptr list);
    This seems correct to me but obviously somewhere its going belly up... thanks for replying so fast btw...

  4. #4
    ATH0 quzah's Avatar
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    No, I mean to use malloc you have to include stdlib.h, and to use strcpy you have to include string.h.


    Quzah.
    Hope is the first step on the road to disappointment.

  5. #5
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    oh sorry... yes I have it in the top of the file with the function as the first malloc doesnt' throw an error...

    Code:
    #include <stdlib.h>

  6. #6
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    Code:
    #include <stdio.h>
    #include <stdlib.h>
    #include <string.h>
    #include "list.h"

  7. #7
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    so basically at this point I can't really see why I'm getting those two cast errors on the second malloc and the strcpy functions...

    any suggestions?

  8. #8
    and the hat of int overfl Salem's Avatar
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    1. See the FAQ about casting malloc.

    2. Your data_item is a char (in other words, a small int - hence all the warnings) where it should be a char*
    If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
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  9. #9
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    thanks Salem, I'll read the FAQ and scratch my head and wonder why I never even thought of that one... I am pretty new at C though for sure.

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