Access violation in c++

Question

Beginner programmer here. I'm getting an access violation error in my directed graph program, and I'm wondering if anyone can tell me why.

Here's the trouble code (don't worry, it's not much). This code is from my main function. I've just read some info in from a file, parsed it, and am trying to insert it into a bucket using a function called InitialInsert.

//Store parsed file values
sourceCity = line[0]; 
destinationCity = line[1]; 
miles = stoi(line[2]); 
cost = stoi(line[3]); 

//Insert parsed values into Info bucket
graph.InitialInsert(sourceCity, destinationCity, miles, cost, size++); //Size is initialized to 0

This is the initial insert function.

//InitialInsert function
void Graph::InitialInsert(string source, string destination, int distance, int price, int index)
{
    InfoBuckets[index]->sourceCity = source; 
    InfoBuckets[index]->destinationCity = destination; 
    InfoBuckets[index]->miles = distance; 
    InfoBuckets[index]->cost = price; 
}

And this is from my header file.

static int const ARRAY_SIZE = 1000; 
struct InitialInfo
{
    string sourceCity; 
    string destinationCity;
    int miles; 
    int cost; 
};
InitialInfo* InfoBuckets[ARRAY_SIZE];

I'm getting the error "Access violation reading location 0xCCCCCCE4" when I hit the first line of my InitialInsert function. This is probably a silly problem, but can anyone help me out?

I'm guessing you don't make the pointers in `InfoBuckets` point anywhere good before using them. — juanchopanza, Dec 15 '14 at 22:35
Where is `size` initialized? What value should it be when you first call the function? — wolfPack88, Dec 15 '14 at 22:35
it looks like you're not allocating any space for your individual `InitialInfo` objects — Sam I am says Reinstate Monica, Dec 15 '14 at 22:37
Why are you using an array of pointers? Why not just an array of `InitialInfo`? — Barmar, Dec 15 '14 at 22:39
For that matter, why are you using a C-style array, instead of `std::vector`? — Barmar, Dec 15 '14 at 22:39
I think that you have to allocate each individual `InitialInfo` object with the [new](http://www.cplusplus.com/reference/new/operator%20new/). I believe that [malloc](http://www.cplusplus.com/reference/cstdlib/malloc/?kw=malloc) will probably also work, but people are going to get on my case if I don't mention that `malloc` is a `c` thing, and it's probably not a good idea to use it in `c++` — Sam I am says Reinstate Monica, Dec 15 '14 at 22:44
@SamIam _"I believe that malloc will probably also work"_ o-O ... — πάντα ῥεῖ, Dec 15 '14 at 22:50
@SamIam "it's absolutely a terrible idea to use it in c++". Fixed that for you... — Roddy, Dec 15 '14 at 22:53

score 1 · Answer 1 · edited May 23 '17 at 11:57

1

You are defined an ARRAY of 1000 pointers of InifitalInfo, but InitialInfo[0] never has been initialized.

Try this:

Array of Objects

InitialInfo InfoBuckets[ARRAY_SIZE];

...

void Graph::InitialInsert(string source, string destination, int distance, int price, int index)
{
   InfoBuckets[index].sourceCity = source; 
   InfoBuckets[index].destinationCity = destination; 
   InfoBuckets[index].miles = distance; 
   InfoBuckets[index].cost = price; 
}

or

Array of pointers

InitialInfo *InfoBuckets[ARRAY_SIZE];

...

InfoBuckets[0] = new InitialInfo(); // You need create the object first before using

...

void Graph::InitialInsert(string source, string destination, int distance, int price, int index)
{
   InfoBuckets[index]->sourceCity = source; 
   InfoBuckets[index]->destinationCity = destination; 
   InfoBuckets[index]->miles = distance; 
   InfoBuckets[index]->cost = price; 
}

As @Roddy recomends, you must use smart pointers instead of new operators. You can read about in this link .

edited May 23 '17 at 11:57

Community

1
1

answered Dec 15 '14 at 22:50

David Isla

619
7
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what if you did `InfoBuckets[index] = new InitialInfo();` in the `InitialInsert` method? – Sam I am says Reinstate Monica Dec 15 '14 at 22:54
Remove the array of pointers, and you have a chance of a +1. Otherwise, at least make is smart pointers :-( – Roddy Dec 15 '14 at 22:55
Took David Isla's advice and got it working. (I knew it was a stupid problem, but thanks for indulging me. :) ) – Kalie Walker Dec 15 '14 at 23:09
@SamIam you can do it, but I think that this program is only a sketch. Would you use an index variable in an Initializer function? Only Kalie knows it ;) – David Isla Dec 15 '14 at 23:21

Access violation in c++

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