2010/12/14 Dave Abrahams <dave@boostpro.com>

Unless oldstruct and newclass are both POD, the above has
implementation-defined behavior. The portable way to do it, if they
indeed have the same layout, is

newclass& s2= *static_cast<newclass*>(static_cast<void*>(&s1));

Using s2 causes undefined behavior (accessing an object through a pointer to unrelated type). reinterpret_cast has the same problem and compilers taking advantage of anti-aliasing rules can produce "unexpected" results for this code.

Roman Perepelitsa.