Re: [RFC][PATCH] A generic boolean (version 6)

From: Nicholas Miell
Date: Thu Jul 27 2006 - 01:31:35 EST

On Thu, 2006-07-27 at 04:48 +0200, Arnd Bergmann wrote:
> On Wednesday 26 July 2006 22:28, ricknu-0@xxxxxxxxxxxxxx wrote:
> > Have not found any (real) reason letting the cpp know about false/true. As I
> > said in the last version, the only reason seem to be for the userspace. Well, as
> > there is no program of my knowlage that needs it, they were removed.
> >
> If we don't expect this to show up in the ABI (which I hope is true), then
> the definition should probably be inside of #ifdef __KERNEL__. Right
> now, it's inside of (!__KERNEL_STRICT_NAMES), which is not exactly the
> same.

If _Bool does end up in the user-kernel ABI, be advised that validating
them will be tricky ("b == true || b == false" or "!!b" won't work), and
the compiler could in theory generate code which tests truthfulness by
comparing to 1 in one place and non-zero in another.

My brief IRC conversation with gcc people regarding validating untrusted
_Bool resulted in the instruction to never store a value in a _Bool
until after it has been validated.

Nicholas Miell <nmiell@xxxxxxxxxxx>

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