Unstable sorting (selection, fast)

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

#define TEST(arr, n, func, ...) {
      \ int *num = (int *) malloc (sizeof(int) * n);\ memcpy(num, arr, sizeof(int) * n);\ output(num,n);\ printf("%s = ", #func);\ func(__VA_ARGS__);\ output(num,n);\ free(num);\ printf("\n");\ }

#define swap(a,b){
      \ int temp = a;\ a = b;\ b = temp;\ }

void output(int* arr, int n) {
    
	printf("[");
	for (int i = 0; i < n; i++) {
    
		i&& printf(", ");
		printf("%d",arr[i]);
	}
	printf("]\n");
	return;
}

void select_sort(int* num, int n) {
    
	for (int i = 0; i < n - 1; i++) {
    
		int ind = i;
		for (int j = i + 1; j < n; j++) {
    
			if (num[j] < num[ind]) ind = j;
		}
		swap(num[i], num[ind]);
	}
	return;
}

void quick_sort(int* num, int l, int r) {
    
	if (l > r) return;
	int x = l, y = r, z = num[x];
	while (x < y) {
    
		while ( x < y && num[y] > z) y--;
		if (x < y) num[x++] = num[y];
		while (x < y && num[x] < z) x++;
		if (x < y) num[y--] = num[x];
	}
	num[x] = z;
	quick_sort(num, l, x - 1);
	quick_sort(num, x + 1, r);
	return;
}

void randint(int* arr, int n) {
    
	while (n--)
		arr[n] = rand() % 100;
	return;
}

int main() {
    
	srand(time(0));
	#define MAX_N 20
	int arr[MAX_N];
	randint(arr, MAX_N);
	TEST(arr, MAX_N, select_sort, num, MAX_N);
	TEST(arr, MAX_N, quick_sort, num, 0, MAX_N - 1);
	return 0;
}