title: dynamic_cast with RTTI disabled
body: <p>I'm curious to know what happens when compiling code with a dynamic cast whith RTTI disabled 
  (either with <code>-fno-rtti</code>on GCC or with <code>/GR-</code> on visual studio). Does the compiler "falls back" to <code>static_cast</code> ? Since (at least on VS) it does only issue a warning, what will the compiled code do ?</p>
  
  <p>More specifically, what bad things could happen if I compile without RTTI a code where I'm sure that there are no error possible with dynamic_cast (i.e. where <code>dynamic_cast</code> could be safely replaced by a <code>static_cast</code>) like this one :</p>
  
  <pre><code>class A{ /*...*/ } ;
  class B : public A {
      int foo() { return 42 ;}
  } ;
  //...
  A * myA = new B() ;
  int bar = (dynamic_cast&lt;B*&gt;(myA))-&gt;foo() ;
  </code></pre>