title: enable_shared_from_this - empty internal weak pointer?
body: <p>I'm using <code>enable_shared_from_this&lt;Base&gt;</code> and then inherit from <code>Base</code>. When trying to use <code>shared_from_this()</code> in <code>Derived</code>'s constructor (not initializer list), I get an exception. Turns out that the internal weak pointer is null and doesn't point to <code>this</code> at all. How can this happen? My other use case of exactly this works perfectly fine. I don't even know where to start. I looked down at the source code of <code>enable_shared_from_this</code>, and it looks to me like that pointer would always be nullptr.</p>