How come we have const_cast but no volatile_cast?

Oleg.
--
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Pete Becker <petebecker@acm.org> wrote:

: Oleg Zabluda wrote:
: >
: > How come we have const_cast but no volatile_cast?
: >

: const_cast adds and removes CV qualifiers. That is, you can change
: constness and volatileness with it. I suppose it could have been split
: into two different casts, but I don't see any significant benefits from
: doing this.

OK, let me show my ignorance.  Which of the following (which I think
are all valid) are invalid?

T* pt;
T const* pct;
T volatile* pvt;
T const volatile* pcvt;

pt = const_cast<T*>(pct);
pt = const_cast<T*>(pvt);
pt = const_cast<T*>(pcvt);
pct = static_cast<T const*>(pt);
pct = const_cast<T const*>(pvt);
pct = const_cast<T const*>(pcvt);
pvt = static_cast<T volatile*>(pt);
pvt = const_cast<T volatile*>(pct);
pvt = const_cast<T volatile*>(pcvt);
pcvt = static_cast<T const volatile*>(pt);
pcvt = static_cast<T const volatile*>(pct);
pcvt = static_cast<T const volatile*>(pcvt);

Could I have used static_cast anywhere else?

John
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Oleg Zabluda <zabluda@math.psu.edu> wrote:
>How come we have const_cast but no volatile_cast?

We do have it. It's spelled "const_cast". :-)


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Herb Sutter (mailto:herbs@cntc.com)

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Oleg Zabluda <zabluda@math.psu.edu> writes:

> How come we have const_cast but no volatile_cast?
>
> Oleg.

We do; it's just spelled "const_cast".

You use const_cast to remove cv-qualifications, that is, const,
volatile, and const volatile.


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Oleg Zabluda wrote:
>
> How come we have const_cast but no volatile_cast?
>

const_cast adds and removes CV qualifiers. That is, you can change
constness and volatileness with it. I suppose it could have been split
into two different casts, but I don't see any significant benefits from
doing this.
 -- Pete
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>>>>> "Oleg" == Oleg Zabluda <zabluda@math.psu.edu> writes:

    Oleg> How come we have const_cast but no volatile_cast?

const_cast cast can cast away volatility as well.  Perhaps naming it
cv_cast would have made things clearer.
--
Pete Forman
Western Geophysical
pete.forman@bedford.waii.com
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John Potter wrote:
>
> Pete Becker <petebecker@acm.org> wrote:
>
> : const_cast adds and removes CV qualifiers. That is, you can change
> : constness and volatileness with it. I suppose it could have been split
> : into two different casts, but I don't see any significant benefits from
> : doing this.
>
> OK, let me show my ignorance.  Which of the following (which I think
> are all valid) are invalid?
>
 > T* pt;
 > T const* pct;
 > T volatile* pvt;
 > T const volatile* pcvt;
 >
 > pt = const_cast<T*>(pct);
 > pt = const_cast<T*>(pvt);
 > pt = const_cast<T*>(pcvt);
 > pct = static_cast<T const*>(pt);
 > pct = const_cast<T const*>(pvt);
 > pct = const_cast<T const*>(pcvt);
 > pvt = static_cast<T volatile*>(pt);
 > pvt = const_cast<T volatile*>(pct);
 > pvt = const_cast<T volatile*>(pcvt);
 > pcvt = static_cast<T const volatile*>(pt);
 > pcvt = static_cast<T const volatile*>(pct);
 > pcvt = static_cast<T const volatile*>(pcvt);
>
> Could I have used static_cast anywhere else?

I don't think so, but it's late. The real point, though, is that you
could have used const_cast for all of these. The cases where you must
use const_cast to remove constness is when the constness occurs below
the top level:

T * const * p1;
T ** p2;

p2 = const_cast<T**>(p1);
p2 = static_cast<T**>(p1); // illegal

 -- Pete
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