Re: [Algorithms] How to get 3dvector largest coordinate index?

[liam m. <lia...@go...>]

2009/3/6 Gino van den Bergen <gin...@gm...>

> Yes, I know. Call me reckless but I just do not believe that
> strict-aliasing on union fields will be exploited by a C++ compiler any
> time soon. It will break too much existing code (not only mine).
>
> liam mail wrote:
> >
> >
> > 2009/3/6 Gino van den Bergen <gin...@gm...
> > <mailto:gin...@gm...>>
> >
> >     The whole "union is
> >     considered harmful" debate seems to be a mostly religious one.
> >
> > It is really quite simple in that it is undefined behaviour to type
> > cast using a union. Now if you want to heed this information it is up
> > to you, just because something works on day X on compiler Y does not
> > mean it will work on a different version of the compiler or on a
> > different compiler altogether.
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I am sorry I do not understand why you think this is to do with aliasing?
The standard guarantees that union fields occupy the same space yet that
only one maybe active.

9.5 Unions [class.union]
1 In a union, at most one of the data members can be active at any time,
that is, the value of at most one of
the data members can be stored in a union at any time. [Note: one special
guarantee is made in order to
simplify the use of unions: If a POD-union contains several POD-structs that
share a common initial
sequence (9.2), and if an object of this POD-union type contains one of the
POD-structs, it is permitted to
inspect the common initial sequence of any of POD-struct members; see 9.2. ]