I had the same problem sometime ago.
I solved it like this:

Qt Code: 
  1. self.connect(self.http, SIGNAL("responseHeaderReceived(const QHttpResponseHeader &)"), self.handleHeaderResponse)
  2.  
  3. [...]
  4.  
  5.     def handleHeaderResponse(self, resp):
  6.         code = resp.statusCode()
  7.         if (code >= 300 and code < 400 and resp.hasKey("location")):
  8.             location = QUrl(resp.value("location"))
  9.             self.http.setHost(location.host())
  10.             self.http.get(location.toString())
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As you can see it's copied from my PyQt4 application... In C++ it should be something like this (not tested!)

Qt Code: 
  1. connect(http, SIGNAL(responseHeaderReceived(const QHttpResponseHeader &)), this, SLOT(handleHeaderResponse(const QHttpResponseHeader &)));
  2.  
  3. [...]
  4.  
  5.     void MyClass::handleHeaderResponse(const QHttpResponseHeader &resp):
  6.         int code = resp.statusCode();
  7.         if (code >= 300 and code < 400 and resp.hasKey("location")) {
  8.             QUrl location = QUrl(resp.value("location"));
  9.             http.setHost(location.host());
  10.             http.get(location.toString());
  11.         }
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Hope it helps you!