On Tue, May 3, 2016 at 1:03 AM, 'Ilya' via address-sanitizer <
address-sanitizer@googlegroups.com> wrote:
> Hello everybody,
> first of all: thanks for reading. I have questions regarding the
> UndefinedBehaviourSanitizer and didn't know where else to post them.
>
Usually, ubsan-related questions get answered at llvm-...@lists.llvm.org,
we we can reply too :)
>
> I am currently working on an embedded system project, porting the UBSan
> RTL (GCC) to work with our stuff. After lots of ripping out this works,
> with a few side effects though (for example no support for flags in the RTL
> (yet)). To make this work in a long perspective I'd like to get rid of all
> current ubs. However, since low-level stuff is low-level, we have some
> occurrences of ub which are to be accepted and will last (a few null
> pointer dereferences, packed structures, etc..). I figured out how to get
> rid of some warnings (function-wise attributes),
>
You mean, __attribute__((no_sanitizer("your-but-type"))), right?
That's the best.
> but this won't help with for example the packed structures.
>
> So I want to suppress the warnings in a few occasions. I however can't
> figure out, how exactly issue suppression (other than function-wise via
> attributes) works in the UBSan. I do see the suppression context being
> created, with the file being parsed. However the only usage of that in the
> UBSan I can find is the "IsVptrCheckSuppressed" function.
>
> So, main questions:
> Which file described in the Clang documentation is being parsed into the
> suppression context? (fsanitize-blacklist, or UBSAN_OPTIONS=suppressions=
> MyUBSan.supp ?)
>
fsanitize-blacklist is a compile-time suppression mechanism -- the code in
the blacklist is not instrumented.
This would have been preferable, but AFIACT, gcc does not support this
flag. (correct me if I am wrong).
> Is the suppression context used in another way that I don't see?
>
> And how is the other file used then?
>
I am not sure I understand your question about
UBSAN_OPTIONS=suppressions=MyUBSan.supp
If you can provide a small example where something does not work as
expected (with the fresh clang) we can take a look.
Note that UBSAN_OPTIONS=suppressions=... is a run-time option and if you
hit the bug you are going to suppress very often
the suppression will slow down the run significantly.
--kcc
>
> Thank you, for taking the time and the great tools,
> Ilya
>
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