Run-time support routines for throwing bad_cast and bad_typeid

[Mark Mitchell]

Both EDG and G++ call run-time library routines to throw the bad_cast
and bad_typeid exceptions, rather than trying to expand the throws
inline.  This is much more convenient since those exceptions can be
thrown without the headers declaring bad_cast being included.  I think
we should follow this exisitng practice and provide appropriate entry
points.  How about:

  extern "C" void __cxa_bad_cast ();
  extern "C" void __cxa_bad_typeid ();

?

--
Mark Mitchell                   mark at codesourcery.com
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