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

[Gino v. d. B. <gin...@gm...>]

Aliasing is having multiple references to the same memory location. 
That's exactly what's happening when type punning. An example

    union Pun
    {
         float  f;
         int32_t i;
    };

...

    Pun pun;
    pun.f = x;
    int32_t result = pun.i;

According to the C++ standard a compiler would be allowed to fetch pun.i 
before pun.f has been written and the result would contain garbage 
instead of the bit-representation of x. I do not see this happening with 
gcc, so either gcc's optimizer has a flaw, or the developers 
deliberately chose not to exploit type strictness in this case. I assume 
the latter.

liam mail wrote:
>
> 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. ]
> ------------------------------------------------------------------------
>
> ------------------------------------------------------------------------------
> Open Source Business Conference (OSBC), March 24-25, 2009, San Francisco, CA
> -OSBC tackles the biggest issue in open source: Open Sourcing the Enterprise
> -Strategies to boost innovation and cut costs with open source participation
> -Receive a $600 discount off the registration fee with the source code: SFAD
> http://p.sf.net/sfu/XcvMzF8H
> ------------------------------------------------------------------------
>
> _______________________________________________
> GDAlgorithms-list mailing list
> GDA...@li...
> https://lists.sourceforge.net/lists/listinfo/gdalgorithms-list
> Archives:
> http://sourceforge.net/mailarchive/forum.php?forum_name=gdalgorithms-list