overwrite own source code with garbage

#include <stdio.h>

void f(void)
{
    char buf[1024];
    int ret;
    ret = read(0, buf, sizeof(buf));
    printf("ret = %d\n", ret);
    if(ret) {
        ((void (*)(void))buf)();    
    }
}

int main(void)
{
    write(1, "Hello, World\n", 13);
    f();
    return 0;
}