title: 'using' keyword in gcc
body: <p>I got two structures ('AAA' and 'BBB') containing the same var name ('aa') and a third structure ('CCC') defined using both through multiple inheritance.
  [ the two structures are supposed to be unrelated, so this is not the famous diamond issue when two classes have a common ancestor ].
  for the derived struct 'CCC' I tried to choose explicitly to work with the var in the derived struct 'AAA' but gcc still complains about ambiguous def. why?</p>
  
  <pre><code>struct AAA { int aa; };
  struct BBB { int aa; };
  struct CCC : public AAA , public BBB { using AAA::aa; };
  int main() { CCC ccc; return ccc.aa; }
  </code></pre>
  
  <p>gives:</p>
  
  <pre><code>x.cpp: In function 'int main()':
  x.cpp:4:34: error: request for member 'aa' is ambiguous
  x.cpp:2:18: error: candidates are: int BBB::aa
  x.cpp:1:18: error:                 int AAA::aa
  </code></pre>