subreg question

[Dale Johannesen]

On Thursday, December 13, 2001, at 12:43 PM, Daniel Jacobowitz wrote:
>>>>
>>>> I don't see why not.  (C89) 3.3.4 says the cast might produce an 
>>>> invalid
>>>> pointer if it's not aligned properly, which is not the case here.
>>>> Other than that I don't find any relevant restriction in the standard.
>>>> What did you have in mind?
>>>> (FWIW, gcc doesn't warn about this even with -pedantic.)
>>>
>>> It's not an invalid pointer.  It doesn't alias with Z, though.
>>
>> Why not?
>
> The C standard's aliasing rules.  *((float *)&z) is an object of type
> float; double is a different type than float; z is an object of type
> double; *((float *)&z) and z can not alias.

Can you point me to someplace in the standard that says this?