CODEWITHSUNDEEP
c++pointers
user3190009
user3190009

Reputation: 43

Pointer causes access violation

I've got a console application reading some char-data from the console and then puts in into a structure. This structure is used as linked list, when it's constructed, I keep one pointer pointing to the first list element and one pointer for running through the list. What happens to me is, when I first run through my list and write its contents into the console, everything works perferctly. When I later want to set my running pointer to the lists last element, it keeps crashing with an c000005 access violation error. I will give you the interesting parts of my code:

definition of my structure:

struct musikdaten {
    char interpret[150];
    char titel[150];
    struct musikdaten* next;
};

printing the lists content:

while (it != NULL) {
    cout << it->interpret << ": " << it->titel << "\n";
    cout << "next: " << it->next << "\n";
    it = it->next;
}

setting "it" to the lists last element:

while (true) {
    if (it->next == NULL) {
        cout << "Assigning some memory...\n";
        it->next = new musikdaten;
        break;
    }
    else it = it->next;
}

However, this last part keeps crashing when the list contains more than two elements. Note: When a new list element is added while reading it's content from console, the next pointer is always initialized as NULL.

Upvotes: 0

Views: 122

Answers (1)

Henrik
Henrik

Reputation: 23324

You should initialize the next member with NULL to indicate the end of the list:

it->next = new musikdaten;
it->next->next = NULL;

Or add a default constructor:

struct musikdaten {
musikdaten() { next = NULL; /*TODO: init other members*/}     
char interpret[150];
char titel[150];
struct musikdaten* next;
};

Upvotes: 2

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