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Re: [Qemu-devel] [PATCH, RFC] More than 2G of memory on 64-bit hosts

From: Julian Seward
Subject: Re: [Qemu-devel] [PATCH, RFC] More than 2G of memory on 64-bit hosts
Date: Wed, 27 Jun 2007 12:20:36 +0100
User-agent: KMail/1.9.5

> > > > This means you have a choice: Write standard conforming code (long)
> > > > that works on all known systems except win64, or use features that
> > > > do't exist on many systems. IIRC C99 types like intptr_t are not
> > > > supported on several fairly common unix systems.
> > >
> > > In that case I'll vote for unsigned long. I'd pass the issue to those
> > > doing a win64 port, if ever that happens.
> >
> > In Valgrind-world we use an alternative approach, which is to typedef
> > a set of new integral types and use those exclusively, and not use the
> > native 'int', 'long' etc.  The new types have a single fixed meaning
> > regardless of the host or guest and it is up to the configure script
> > to set up suitable typedefs.  At startup Valgrind checks the size and
> > signedness of these types is as expected, so any configuration errors
> > are caught.  This has proved very helpful in porting to a number of
> > platforms.

So in this particular case we have the types UWord and Word 
(unsigned and signed machine words) which it is guaranteed are
the same size as void*, on all platforms.

We also capitalise the first letter of all type names as that
makes the code easier to read and makes it obvious when you are
inadvertantly using the native 'int', 'long' etc.


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