Subject: Re: __UNCONST(a)
To: None <tech-userlevel@NetBSD.org>
From: der Mouse <mouse@Rodents.Montreal.QC.CA>
Date: 07/02/2004 01:36:47
>>>>> #define __DECONST(type, var) ((type)(uintptr_t)(const void *)(var))
>>>> Why cast to a specific type?
>>> because it's only sane way without typeof().
>> What's insane about just making it produce a void *?
> - in most cases, what you want is a specific type, isn't it?
Yes, but it's usually "the type of this thingy", and having to go look
up what type the thingy actually is is a pain - especially if there's
any significant chance that type's textual name will change.
If I had to use a __DECONST like that, I would almost certainly wrap a
DECONST() around it that simply provided void * as the type.
> - it strips out other qualifiers like volatile.
> (typeof() isn't enough for this either.)
It also has nothing to do with using - or not using - void *.
Actually, I usually want to strip all qualifiers. const simply happens
to be the most relevant one because it's the one for which poisoning is
most important. In a few programs I've used a deconst-alike that takes
const volatile void * and returns void *.
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