bjselnx2>cat test_Variable_length_array.c
#include <stdio.h>

void reverse(const char *str, int n);

int main(int argc, char * argv[]){
char *buf = "hello";
reverse(buf,5);
return 0;
}

void reverse(const char *str, int n){
int i;
char new[n];
for (i = 0; i < n; i++)
new[i] = str[n-i-1];
printf("%.*s\n", n, new);
}
bjselnx2>cc -o test test_Variable_length_array.c
bjselnx2>./test hello
olleh