How to Swap stdout and stderr

$ cat >c.c
#include <stdio.h>

int main()
{
        fprintf(stdout, "stdout\n");
        fprintf(stderr, "stderr\n");
        return 0;
}
$ cc c.c
$ 3>&2 2>&1 1>&3 ./a.out | tee log
stdout
stderr
$ cat log
stderr
$