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From: George Neville-Neil <gnn@neville-neil.com>
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Cc: FreeBSD Arch <freebsd-arch@freebsd.org>
Subject: Re: SYSCTL type safety
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On Jan 7, 2011, at 18:13 , mdf@FreeBSD.org wrote:

> Long ago at Isilon we ran into a problem with some sysctls in the
> stock FreeBSD tree using the wrong type, like SYSCTL_ULONG on an int,
> or just mixing unsigned/signed.  We have a patch that uses transparent
> unions to cause a compile-time error with a type mismatch.  For a
> while I was hesitant to push this since I wasn't sure about the use of
> a gcc extension, but the SYSCTL fixes and the way to keep them sane
> came up again when we started building a new driver locally, and the
> build failed until we fixed some SYSCTL stuff.
> 
> Anyways, the patch to sys/sysctl.h is at
> 
> http://people.freebsd.org/~mdf/bsd-sysctl-type-safety.diff
> 
> Please chime in if you think this is a bad thing to add to the tree.
> I will of course ensure a make universe passes locally before
> committing this part.  The plan is to change the SYSCTL use, not the
> base type of the variable, for any conflicts found.
> 

I have read, but not tried the patch.  I definitely like the idea.

Best,
George