Memory Error in C struct - c

Question

The following code causes a memory error in the insert_edge function (in the line p->next = g->edges[x] I guess) for large MAXV values. For smaller ones it works great. Where is the problem? How can I define the struct that it works?
#include <stdlib.h>
#include <stdio.h>
#define MAX_LINE_SIZE (1024*128)
#define MAXV 23947347 /* maximum number of vertices */
#define NULLO 0 /* null pointer */
#define TRUE 1
#define FALSE 0
typedef int bool;
typedef struct edgenode {
int y; /* adjancency info */
int weight; /* edge weight, if any */
struct edgenode *next; /* next edge in list */
} edgenode;
typedef struct {
edgenode *edges[MAXV+1]; /* adjacency info */
int degree[MAXV+1]; /* outdegree of each vertex */
int nvertices; /* number of vertices in the graph */
int nedges; /* number of edges in the graph */
int directed; /* is the graph directed? */
} graph;
initialize_graph(graph *g, bool directed)
{
int i; /* counter */
g -> nvertices = 0;
g -> nedges = 0;
g -> directed = directed;
for (i=1; i<=MAXV; i++)
g->degree[i] = 0;
for (i=1; i<=MAXV; i++)
g->edges[i] = NULL;
}
read_graph(graph *g, bool directed, const char *filename)
{
FILE *f;
char line[MAX_LINE_SIZE], buf[10];
int format, rc;
int edge;
int vertex_n;
int vertex_m;
char *token,*token2, *s;
int v;
int i; /* counter */
/* open file */
f = fopen (filename, "r");
if (f == NULL)
return NULL;
rc = sscanf (line, "%d %d %d", &(vertex_n), &(vertex_m), &(edge));
initialize_graph(g, directed);
for (i=1; i<=edge; i++) {
s = fgets (line, MAX_LINE_SIZE, f);
token = strtok (line, " ");
token2 = strtok (NULL, " ");
int s = atoi(token);
int t = atoi(token2);
printf("%d, %d\n", start, ziel);
insert_edge(g,s,t,directed);
}
}
insert_edge(graph *g, int x, int y, bool directed)
{
edgenode *p; /* temporary pointer */
p = malloc(sizeof(edgenode)); /* allocate storage for edgenode */
p->weight = NULL;
p->y = y;
p->next = g->edges[x];
g->edges[x];
g->edges[x] = p; /* insert at head of list */
g->degree[x] ++;
if (directed == FALSE)
insert_edge(g,y,x,TRUE);
else
g->nedges ++;
}
main()
{
graph g;
read_graph(&g,FALSE, "/path/graph_with_23947347_nodes.mtx");//
}

Answer 1

graph g;
graph is definitively too big to fit on the stack. Put it in the heap instead:
graph* g=malloc(sizeof(graph));
And follow Graham's advice too. It may be too big even for the heap.

Answer 2

It looks like it may be a stack overflow. graph is a large data structure and you are allocating it locally (i.e. on the stack) in main. Try changing main to:
int main(void)
{
graph *g = malloc(sizeof(graph));
if (g != NULL)
{
read_graph(g, FALSE, "/path/graph_with_23947347_nodes.mtx");
free(g);
}
return 0;
}

Answer 3

Are you checking the return value from this malloc?
p = malloc(sizeof(edgenode)); /* allocate storage for edgenode */
It could be that you are simply running out of memory. Check that p is not NULL before proceeding.

Answer 4

p->next = g->edges[x];
g->edges[x];
g->edges[x] = p; /* insert at head of list */
This code doesn't make any sense.
In a single-linked list, you cannot insert a new node before an existing node, without having a pointer to the previous node before it. Otherwise, how can the previous node have its next pointer updated?
This inserts your node after an existing node:
p->next = g->edges[x]->next;
g->edges[x]->next = p;