Question

I keep getting a segmentation with the following code. Changing the 4000 to 1000 makes the code run fine. I would think that I have enough memory here… How can I fix this?

#include <stdio.h>
#include <math.h>
#include <stdlib.h>
#include <string.h>
#define MAXLEN 4000

void initialize_mx(float mx[][MAXLEN])
{
  int i, j;
  float c=0;
  for(i=0;i<MAXLEN;i++){
  for(j=0;j<MAXLEN;j++) mx[i][j]=c;
  }
}
int main(int ac, char *av[])
{
  int i, j;
  float confmx[MAXLEN][MAXLEN];
  initialize_mx(confmx);
  return 0;
}

Answer 1

The problem is you’re overflowing the stack.

When you call initialize_mx() it allocates stack space for it’s local variables (confmx in your case). This space, which is limited by your OS (check ulimit if you’re on linux), can get overflowed if local variables are too big.

Basically you can:

1. Declare confmx as a global variable as cnicutar suggests.
2. Allocate memory space for your array dynamically. and pass a pointer to initialize_mx()

EDIT: Just realized you must still allocate memory space if you pass a pointer so you have those two options 🙂