ISO Aliasing rules question

[Mark Mitchell]

>  >Bottom line: the optimization in the code you showed is correct.
> Meaning that execute/20000603-1.c is a bogus test :-)

The key thing there is that b doesn't really point to an s2, so accesses 
through it are invalid.  Although I can't find the part of the standard 
that says that any more!

The C++ standard has this language:

  If  a program attempts to access the stored value of an object through
  an lvalue of other than one of the following  types  the  behavior  is
  undefined25):

  --the dynamic type of the object,

  ...

The problem here is that b doesn't have the dynamic type s2.

I think the C standard has similar language -- somewhere.

-- 
Mark Mitchell                mark@codesourcery.com
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