Re: [ft-devel] Curb the scaling

[Alexei Podtelezhnikov]

On Fri, Oct 13, 2017 at 2:00 PM, Kostya Serebryany <address@hidden> wrote:
>
>
> On Fri, Oct 13, 2017 at 7:43 AM, Alexei Podtelezhnikov <address@hidden>
> wrote:
>>
>> > [*] Actually, what's ugly is the macro syntax.  I would like to have
>> >     compiler support like
>> >
>> >       foo = bar + baz      __attribute__ ((allowed_overflow));
>> >
>> >     so that the mathematical operators are not hidden.
>>
>> I would like to address this to Kostya. Please do tell us how to
>> inform ftfuzzer that the overflow is acceptable here. Perhaps, we can
>> add a special comment /* ftfuzzer overflow */ or something. GCC has a
>> special flag -fwrapv or make sure that the overflow wraps around.

>
> You may shut it down with an attribute on a function:
> https://clang.llvm.org/docs/UndefinedBehaviorSanitizer.html#disabling-instrumentation-with-attribute-no-sanitize-undefined

This __attribute__((no_sanitize("signed-integer-overflow"))) is
actually pretty close to what ADD_ and SUB_ macros achieve. This is
not as fine grained but the effect is mostly the same. We just declare
that the we accept the overflows in this function.