Re: [PATCH 3/5] compiler_attributes: Add overflow_behavior macros __ob_trap and __ob_wrap

Kees Cook
2026-04-01T20:21:17Z

On Wed, Apr 01, 2026 at 11:08:15AM +0200, Peter Zijlstra wrote:
> On Tue, Mar 31, 2026 at 12:52:10PM -0700, Kees Cook wrote:
>
> > I think for this series, __ob_trap/__ob_wrap is what should be used.
> >
> > And for other folks, the background here is that we originally wanted
> > to use macros for "__trap" and "__wrap", but the powerpc C compiler
> > (both Clang and GCC) have a builtin macro named "__trap" already. So
> > I switched to just using the Clang-native type qualifier. We can use
> > the attribute style too, but there was a lot of confusion during the
> > Clang development phases where people kept forgetting this was a type
> > qualifier, not an attribute (i.e. the attribute is an internal alias
> > for the qualifier, and the qualifier is a new type).
>
> Since you mention qualifiers...
>
> What is the result of __typeof_unqual__(int __ob_trap) ?

Hmm, it seems like "const" doesn't get peeled off. That can be fixed, if
that's needed?

'typeof_unqual(int)' (aka 'int')
'typeof_unqual(__ob_trap int)' (aka '__ob_trap int')
'typeof_unqual(const int)' (aka 'int')
'typeof_unqual(__ob_trap const int)' (aka '__ob_trap const int')

-Kees

--
Kees Cook