Question

This is a simple code that i’ve written because i need a confirmation about a thing.

#include <stdio.h>
#include <string.h>

void pr(int a);

int main(void)
{
  int a;

  printf("starting...\n");
  h1:
  scanf("%d", &a);
  if (a == 20)
    return 0;
  pr(a);
  goto h1;
  printf("ending...\n");
  return 0;
}

void pr(int a)
{
  char buf[256];
  if (a == 1)
    strcpy(buf, "number 1 has been choosed");
  else
    strcpy(buf, "other number");
  printf("BUF: %s\n", buf);
}

My question is:
Every time the function pr is called, the array buf is automatically cleared or it is more secure to do a memset before the function end?

Answer 1

every time the function pr is called, the array buf is automatically cleared

No, it will contain undefined data since it has automatic storage. The simplest would be to:

char buf[256] = {0}; /* Zeroes entire array. */

Or, since you’re using buf as a string, you could go with the cheaper:

char buf[256];
buf[0] = 0;

---

Side note: the way your code looks you don’t need this initialization since strcpy doesn’t depend on it and you have a strcpy on each branch.