title: Provide `char **` argument to C function from Rust?
body: <p>I've got a C function that (simplified) looks like this:</p>
  
  <pre><code>static char buffer[13];
  
  void get_string(const char **s) {
      sprintf(buffer, "Hello World!");
      *s = buffer;
  }
  </code></pre>
  
  <p>I've declared it in Rust:</p>
  
  <pre><code>extern pub fn get_string(s: *mut *const c_char);
  </code></pre>
  
  <p>But I can't figure out the required incantation to call it, and convert the result to a Rust string. Everything I've tried either fails to compile, or causes a SEGV.</p>
  
  <p>Any pointers?</p>