C结构中的内存错误

Question

The following code snippet causes a memory error for big MAXV values. How can I define this struct that I can use it for many values in edges and degree?

#define MAXV  1441295   
typedef struct {
    edgenode *edges[MAXV+1];           
    int degree[MAXV+1];     
    int nvertices;      
    int nedges;         
    int directed;       
} graph;


initialize_graph(graph *g, bool directed)
{
    int i;              

    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;
}

Answer 1

Reading from my crystal ball, I see that you are creating local variables of type graph . Each of these local variables are in excess of 10,000,000 bytes large, which overflows the available stack space in your system.

Try creating the objects either as static objects or heap-allocated objects.

That is, don't do this:

int f(graph g) {
   graph newg = g;
}

Rather, do this:

graph g;
int f() {
  g.ediges[g.nedges++] = 0;
}

or this:

int f(graph *pg) {
  pg->edges[17] = 0;
}

Answer 2

Either use dynamic allocation or increase stack size (asserting linux-like OS) by executing:

ulimit -s 1000000

size would be in kB thus max allowed stack size would be ~100MB.