I'm not sure what exactly points of discussion are, but in HarfBuzz we do
purposefully ignore position overflows.  We use a macro like this for that:

#define HB_NO_SANITIZE_SIGNED_INTEGER_OVERFLOW
__attribute__((no_sanitize("signed-integer-overflow")))

If you want to copy the macro, please copy its surrounding conditions as
well.

b

On Tue, Aug 13, 2019 at 3:04 PM <ar...@hasitzka.com> wrote:

> >> Whether with -wrapv or with the unsigned macros, we simply disable
> >> some compiler optimizations, perhaps some good optimizations too.
> >
> > Most certainly, yes.  But there are a lot more things that slow down the
> > potential performance of FreeType -- C in itself is a trade-off between
> > maintainability and performance.
> >
> >> Why? Is it because we got scared? There is absolutely no evidence of
> >> real bugs in FreeType. It is reasonable to disable optimizations with
> >> -wrapv, if scared, but macros are too rigid. Some compilers recognize
> >> /* fall through */ comment to suppress particular warnings. I wish we
> >> could just add a comment to silence these warnings after adjudication.
> >
> > It's not about being scared but about making sure we understand _what_
> the
> > code within FT does.  If we proactively mark operations that have a
> certain
> > behaviour we make those operations explicit to whomever reads that thing
> in
> > the future.  `-wrapv' has two downsides IMO:  (1) we lose track of what
> it
> > does and _where_ ... maybe, really covering up bugs (2) we rely on 3rd
> parties
> > to compile FT in a very specific way to avoid certain types of reports.
>
> For reference, find the patch attached (most code in that area is already
> wrapped in `*_LONG' macros).
>
> @Werner: should I apply it?
>
> Armin
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> Freetype-devel@nongnu.org
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>


-- 
behdad
http://behdad.org/
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