[PATCH] D67122: [UBSan][clang][compiler-rt] Applying non-zero offset to nullptr is undefined behaviour

Dávid Bolvanský via Phabricator via cfe-commits cfe-commits at lists.llvm.org
Tue Sep 3 15:20:29 PDT 2019


xbolva00 added inline comments.


================
Comment at: llvm/docs/ReleaseNotes.rst:59
+  ``getelementptr inbounds`` can not change the null status of a pointer,
+  meaning it can not produce non-null pointer given null base pointer, and
+  likewise given non-null base pointer it can not produce null pointer; if it
----------------
lebedev.ri wrote:
> xbolva00 wrote:
> > lebedev.ri wrote:
> > > xbolva00 wrote:
> > > > Please add a reference to C/C++ standard that this is a UB.
> > > It is irrelevant what semantics C/C++ standard has/doesn't have for whatever C/C++ construct,
> > > this is talking about LLVM IR.
> > Ok, so Clang docs?
> > 
> > “The compiler now optimizes ... since ... is a UB according to ... Use UBSan to catch these cases.”
> ... see `clang/docs/ReleaseNotes.rst` then?
> Those words were present in the first revision of the differential already,
> https://reviews.llvm.org/D67122?id=218504#change-RNUd6wICb9iD
Oh, sorry. 


Repository:
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CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D67122/new/

https://reviews.llvm.org/D67122





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