From mboxrd@z Thu Jan  1 00:00:00 1970
From: Peter Zijlstra <peterz@infradead.org>
Subject: Re: [PATCH] pid: change task_struct::pid to read-only
Date: Fri, 20 Dec 2013 22:33:48 +0100
Message-ID: <20131220213348.GE7959@laptop.programming.kicks-ass.net>
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To: Oleg Nesterov <oleg@redhat.com>
Cc: Richard Guy Briggs <rgb@redhat.com>, linux-audit@redhat.com, linux-kernel@vger.kernel.org, Eric Paris <eparis@redhat.com>
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On Fri, Dec 20, 2013 at 08:01:57PM +0100, Oleg Nesterov wrote:
> The only problem is that
> 
> 	#define ASSIGN_CONST(l, r)      (*(typeof(r) *)&(l) = (r))
> 
> obviously can't work in this case ;) We need something more clever.

Hmm indeed, C++ has both the const_cast<>() thingy and the template
system is powerful enough to actually implement const_cast<>() inside
the language.

But I cannot find anything useful for C. Your attempt to use the rvalue
type to hopefully obtain a const-less lvalue type is clever, but does
indeed fail where the rvalue is const too.