Simple merge sort

merge.c

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

#define sz 100

void msort(int *out, int *begin, int *end);
static void merge(int *out, int *lbeg, int *lend, int *rend);
void printr(int *arr, int *end);
void rfillr(int *arr, int *end);

int cmp(const void *a, const void *b);

int main(int argc, char *argv[])
{
	int sorted_r[sz];
	int r[sz];

	rfillr(r, r+sz);
	printf("Array (unsorted): \n\t");
	printr(r, r+sz);
	printf("\n");
	msort(sorted_r, r, r+sz);
	printf("Array (sorted): \n\t");
	printr(sorted_r, sorted_r+sz);
	printf("\n");
	printf("qsort: \n\t");
	qsort(r, sz, sizeof(int), cmp);
	printr(r, r+sz);
	printf("\n");
	if (memcmp(sorted_r, r, sz*sizeof(int)) == 0)
		printf("array is sorted\n");
	else
		printf("array is not sorted\n");
	return 0;
}

int cmp(const void *a, const void *b)
{
	return *(const int *)a > *(const int *)b;
}

void printr(int *arr, int *end)
{
	for (; arr < end; ++arr)
		printf("%d ", *arr);
}

void rfillr(int *arr, int *end)
{
	int len;

	srand(time(NULL));
	for (len=(end-arr)*3; arr < end; )
		*arr++ = rand() % len;
}

void msort(int *out, int *begin, int *end)
{
	int *c = begin + (end-begin)/2;
	if (end - begin > 2) {
		msort(out, begin, c);
		msort(out+(c-begin), c, end);
	}
	merge(out, begin, c, end);	
}

static void merge(int *out, int *lbeg, int *lend, int *rend)
{
	int *rbeg, *begin, *end, *bout;
	begin=lbeg;
	end=rend;
	bout=out;
	for (rbeg = lend; lbeg < lend || rbeg < rend;)
		if (lbeg < lend && (rbeg == rend || *lbeg < *rbeg))
			*out++ = *lbeg++;
		else
			*out++ = *rbeg++;
	memcpy(begin, bout, (end-begin)*sizeof(int));
}