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From: Paul Brook <paul@codesourcery.com>
Subject: Re: [Qemu-devel] Re: [PATCH][RFC] Run time TCGv size check for
	debugging
Date: Thu, 30 Oct 2008 01:07:41 +0100
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	<4908D7A3.7030309@bellard.org>
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To: qemu-devel@nongnu.org
Cc: Blue Swirl <blauwirbel@gmail.com>

On Wednesday 29 October 2008, Fabrice Bellard wrote:
> Blue Swirl wrote:
> > Hi,
> >
> > When emulating a mixed 32/64 bit Qemu target CPUs it's easy to confuse
> > the TCGv size, passing 32 bit TCGv to a function expecting a 64 bit
> > one and vice versa. This patch adds a run time sanity check for TCGv
> > sizes.
> >
> > Because a 32 bit Qemu host does not really use 64 bit TCGvs, the patch
> > is only functional on a 64 bit host. Of course also a pure 32 bit Qemu
> > target is not likely to suffer from TCGv size confusion.
> >
> > Some use cases are not covered yet. Comments?
>
> Theses tests can be done at compile time by introducing the TCGv_i32 and
> TCGv_i64 types. The same can be done with the helpers by using a few
> macros to declare them.

That would also require updating all the target code in translate.c to use 
these types.  In principle there's no reason why this couldn't be done, but 
it'd be a much more invasive change.
AFAIK there's no way of doing compile time inheritance checking in C.  

Paul