> 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
> @Werner: should I apply it?
Yes, please.
Werner
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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
>> 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
>
> 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
On Sat, Aug 10, 2019 at 7:32 PM Nikolaus Waxweiler
wrote:
>
> > Undefined does not mean scary.
>
> Actually yes. Have you read e.g.
> http://blog.llvm.org/2011/05/what-every-c-programmer-should-know_14.html?
>
Whether with -wrapv or with the unsigned macros, we simply disable some
compiler
Undefined does not mean scary.
Actually yes. Have you read e.g.
http://blog.llvm.org/2011/05/what-every-c-programmer-should-know_14.html?
Why do we even care?
The burden is actually on the compiler to not do anything crazy or
face consequences from users and public. For some reason the
> This, sadly, brings us back to the current way of dealing with these things;
> adding ugly macros that transfer these operations from UB space into defined
> C space ... Not saying I'm happy with that but I believe this is the
> cleanest solution in the big picture right now.
Undefined
>> .. and undo those macros?
>
> Well, if you then can? Signed integer overflow being undefined strikes me as a
> severe deficiency in the C language. This of course makes -wrapv a compiler
> level workaround, which may not be available to every compiler FreeType wants
> to support. Hm.
It's one
>
> .. and undo those macros?
>
Well, if you then can? Signed integer overflow being undefined strikes me
as a severe deficiency in the C language. This of course makes -wrapv a
compiler level workaround, which may not be available to every compiler
FreeType wants to support. Hm.
>
On Fri, Aug 9, 2019 at 2:38 PM Nikolaus Waxweiler wrote:
>
> This makes me wonder if maybe FreeType should be compiled with -wrapv
> by default?
.. and undo those macros? These warnings are OCD in its ugliest. It is
fleetingly rare when they reveal real bugs. We silence them but pay
dearly with
This makes me wonder if maybe FreeType should be compiled with -wrapv
by default?
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> Thanks for looking into it. FWIW, my commit merely re-enabled an older
code
> path.
NW we've already fixed a lot of those that came up in our own fuzzers :) ...
it's actually harmless but a side product of fuzzers throwing super random
input at apps. Some overflow when facing gigantic glyphs
Thanks for looking into it. FWIW, my commit merely re-enabled an older
code path.
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Sent: 06 August 2019 20:08
To: freetype-devel
Subject: [ft-devel] Fwd: Issue 977845 in chromium: pdf_font_fuzzer:
Integer-overflow in compute_glyph_metrics
Forwarding the following message I received regarding a fuzzer find.
I'm not sure what to do about it.
-- Weitergeleitete Nachricht
Forwarding the following message I received regarding a fuzzer find.
I'm not sure what to do about it.
-- Weitergeleitete Nachricht --
Von: kkal… via monorail
Betreff: Issue 977845 in chromium: pdf_font_fuzzer: Integer-overflow in
compute_glyph_metrics
Datum: Wed, 10 Jul 2019
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