llvm dev - Sep 2015 - Dynamic detection of signed integer overflow

Thanks John, seems like a dynamic runtime instrumentation is then not a good
idea. I had a look at the UBSan features in Clang and I might be able to use
them instead. But it seems like that vector operations are not instrumented with
overflow checks if I specify the option -fsanitize=signed-integer-overflow. Am I
missing some other option or is there a special reason why vector operations are
not checked?

Regards,

Moritz

> On 14 Sep 2015, at 08:25, John Regehr <regehr at cs.utah.edu> wrote:
> 
> Moritz,
> 
> While implementing the dynamic integer overflow checks that eventually lead
to UBSan, we did two implementations: one based on generated IR and the other
inside Clang.  The latter approach was better and is the one that stuck.
> 
> John

> Thanks John, seems like a dynamic runtime instrumentation is then not a 
> good idea. I had a look at the UBSan features in Clang and I might be 
> able to use them instead. But it seems like that vector operations are 
> not instrumented with overflow checks if I specify the option 
> -fsanitize=signed-integer-overflow. Am I missing some other option or is 
> there a special reason why vector operations are not checked?
I might be misunderstanding you, and I haven't looked at this code lately, 
but the goal of UBSan is to check C's rules for integer UBs.  Since C does 
not have vectors, I'm not sure exactly what you are expecting here.  Could 
you give a bit more detail?

John

On 15 September 2015 at 09:48, John Regehr via llvm-dev <
llvm-dev at lists.llvm.org> wrote:
> Thanks John, seems like a dynamic runtime instrumentation is then not a
>> good idea. I had a look at the UBSan features in Clang and I might be
able
>> to use them instead. But it seems like that vector operations are not
>> instrumented with overflow checks if I specify the option
>> -fsanitize=signed-integer-overflow. Am I missing some other option or
is
>> there a special reason why vector operations are not checked?
>>
>
> I might be misunderstanding you, and I haven't looked at this code
lately,
> but the goal of UBSan is to check C's rules for integer UBs.  Since C
does
> not have vectors, I'm not sure exactly what you are expecting here. 
Could
> you give a bit more detail?

OpenCL as a language is a modified C99, which does have, amongst a few
other things, support for vector types for basic types (char, short, int,
long and their unsigned variants as well as floating point types half,
float and double).

So, there is probably some work required to implement this for OpenCL's
native vector support. I haven't looked at the code, so can't say if
there's any particular difficulty in this particular case.

--
Mats
>
>
> John
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