Re: [boost] [config] RFC PR 82

Subject: Re: [boost] [config] RFC PR 82
From: Agustín K-ballo Bergé (kaballo86_at_[hidden])
Date: 2015-11-26 07:44:45

On 11/26/2015 8:51 AM, Andrey Semashev wrote:
> On 2015-11-26 05:13, Agustín K-ballo Bergé wrote:
>> On 11/25/2015 10:52 PM, Andrey Semashev wrote:
>>>
>>> IMHO, the standard should just
>>> follow C11 semantics and say it more clearly.
>>
>> That's unlikely to happen, C has *vastly* weaker aliasing rules than
>> C++, to the point that several C implementations choose to follow the
>> C++ rules instead. You'd be asking for the opposite to happen.
>
> I can see the benefits of strict aliasing rules in other contexts, but
> unions specifically exist to provide the common storage for objects of
> different types in a relatively less messy way compared to, e.g. a raw
> byte buffer. I'm not seeing people using unions and somehow expecting
> type aliasing to not happen, quite the contrary. I think the language
> here is being too limiting for no practical reason.

How would that work? If one could read a `float` as if it were an `int`, 
then ints and floats may alias. If they may alias, then whenever you get 
a pointer to an `int` you'll have to ask could it be this other `float` 
instead?

Until the whole program is compiled and all `union`s are seen, 
everything may alias with anything else. We'd be back in a land of bits 
and bytes...

Regards,
-- 
Agustín K-ballo Bergé.-
http://talesofcpp.fusionfenix.com