title: Does not display printf result in cgo
body: <p>When I ran this code, I expected to printing result like <code>A: 4, B: 89</code>.
  But actually, Does not display nothing.</p>
  
  <p>Why this program does not display result to stdout?</p>
  
  <p>main.go:</p>
  
  <pre><code>package main
  
  /*
  #include "c.h"
  
  */
  import "C"
  
  import (
      "unsafe"
  )
  
  type S struct {
      A int
      B int
  }
  
  func main() {
      s := &amp;S{A: 4, B: 89}
      pass_to_c := (*C.S)(unsafe.Pointer(s))
      C.gostruct(pass_to_c)
  }
  </code></pre>
  
  <hr>
  
  <p>c.h</p>
  
  <pre><code>#include &lt;stdio.h&gt;
  #include &lt;stdlib.h&gt;
  
  typedef struct {
      long int A;
      long int B;
  } S;
  
  extern void gostruct(S *struct_s) {
      printf("A: %ld, B: %ld\n", struct_s-&gt;A, struct_s-&gt;B);
  }
  </code></pre>