realloc and Segmentation Fault

[Jonathan Shan <jonshan@xxxxxxxxxxxxxxxxxxx>]

Hello all,

The goal of my program is to create a dynamic array of a struct type. The 
struct type has two strings inside it. From time to time I want to copy 
strings into the strings in the dynamic array. Then increase the size of 
the dynamic array. I have narrowed the problem down to the realloc 
function but I still don't know why it says segmentation fault or hangs 
(sometimes).

Here is the simplified code which exhibits the problem:

/*libraries here */

#define SIZEOF_BUCKETSTRUCT 70
#define SIZEOF_HOSTNAME 20
#define SIZEOF_DESCRIPTION 50

int bucketsize = 1;
struct bucket
{
	char *hostname;
	char *description;
};
void function1(struct bucket *valid)
{
	valid[bucketsize - 1].hostname = malloc (sizeof(char) * 20);
	strncpy(valid[bucketsize - 1].hostname, "test hostname", 20);
	valid[bucketsize - 1].hostname[19] = '\0';
	printf("hostname is %s \n", valid[bucketsize - 1].hostname);

	valid[bucketsize - 1].description = malloc (sizeof(char) * 50);
	strncpy(valid[bucketsize - 1].description, "test buf", 50);
	valid[bucketsize - 1].description[49] = '\0';
	printf("description is %s \n", valid[bucketsize - 1].description);
/* problem is here */
	valid = (struct bucket *) realloc (valid, 70 * ((bucketsize) + 
1));
	bucketsize++;
}
int main()
{
  struct bucket *valid;
  valid = (struct bucket *) malloc (SIZEOF_BUCKETSTRUCT);
  if (valid == NULL)
  {
	printf("error in allocating memory \n");
	exit(1);
  }

  function1(valid);
  function1(valid);

  return 0;
}

Thank you,

Jonathan Shan