Access violation reading location 0xCDCDCDCD - c

Question

As the title states, I'm getting an error
Access violation reading location 0xCDCDCDCD.
Now I'm dealing with an array of linked lists, and I believe the trouble to be something around adding to the linked list. I'm fine with this usually, but I feel I'm doing something wrong with memory allocation.
Here are my structs:
Graph:
typedef struct graph
{
int V;
int *state;
EdgeList *edges;
} Graph;
Edge:
typedef struct edge
{
int toVertex;
int weight;
} Edge;
EdgeList:
typedef struct edgeNode
{
Edge edge;
struct edgeNode *next;
} *EdgeList;
Here is the main function that runs it all:
main()
{
Graph myGraph;
scanf("%d", &(myGraph.V));
myGraph.state = (int)malloc(myGraph.V*sizeof(int));
myGraph.edges = (EdgeList*)malloc(myGraph.V*sizeof(EdgeList));
int *inDegrees;
inDegrees = (int)malloc(sizeof(int)*myGraph.V);
/* Sets all array values to 0 */
for (int counter = 0; counter < myGraph.V; counter++)
{
inDegrees[counter] = 0;
}
for (int i = 0; i < myGraph.V; i++)
{
int number_of_edges;
int input = 0; /*For that little experimental bit*/
scanf("%d", &(myGraph.state[i]));
scanf("%d", &number_of_edges);
if (number_of_edges > 0)
{
for (int j = 0; j < number_of_edges; j++)
{
Edge newEdge;
scanf("%d,%d", &(newEdge.toVertex), &(newEdge.weight));
inDegrees[newEdge.toVertex]++;
printf("%s%d\n", "\nOoh, new input for ", newEdge.toVertex);
/*insert at front*/
EdgeList newNode = (EdgeList)malloc(sizeof (struct edgeNode));
newNode->edge = newEdge;
newNode->next = myGraph.edges[i];
myGraph.edges[i] = newNode;
/* Bit to calculate state.*/
EdgeList current = myGraph.edges[i];
while (current != NULL)
{
if (current->edge.toVertex == i)
{
input += (current->edge.weight)*(myGraph.state[i]);
}
current = current->next;
}
}
if (input > 0)
{
myGraph.state[i] = 1;
}
else
{
myGraph.state[i] = 0;
}
}
}
//print
for (int k = 0; k < myGraph.V; k++)
{
printf("\n%s%d%s", "In degrees for ", k, ": ");
printf("%d", inDegrees[k]);
}
}
In particular, the error comes during the traversal of the linked list. It's in the above code, but I'll highlight it here:
EdgeList current = myGraph.edges[i];
while (current != NULL)
{
if (current->edge.toVertex == i)
{
input += (current->edge.weight)*(myGraph.state[i]);
}
current = current->next;
}
If anyone can help, it'd be greatly appreciated because I'm rather stuck.

Answer 1

An value in uninitialized buffer allocated via malloc() is assigned to newNode->edge in newNode->next = myGraph.edges[i];.
The newNode is set to current via myGraph.edges[i] = newNode; and EdgeList current = myGraph.edges[i];.
Assuming that malloc() succeeded, current isn't NULL here, so it is entering the loop.
The uninitialized value assinged in 1 is assigned to current in current = current->next;.
An undefined behavior is invoked by using value in buffer allocated via malloc() and uninitialized at current != NULL.
To fix this error, initialize myGraph.edges in, for example, this way:
myGraph.edges = (EdgeList*)malloc(myGraph.V*sizeof(EdgeList));
for (int i = 0; i < myGraph.V; i++)
{
myGraph.edges[i] = NULL;
}
Also, remove the harmful casts to int of the pointer returned from malloc(). Casting the return values to pointers explicitly is also not considered as good.