[llvm] r255258 - Avoid undefined behavior when vector is empty.

[David Blaikie via llvm-commits]

On Thu, Dec 10, 2015 at 8:35 AM, Rafael Espindola via llvm-commits <
llvm-commits at lists.llvm.org> wrote:

> Author: rafael
> Date: Thu Dec 10 10:35:06 2015
> New Revision: 255258
>
> URL: http://llvm.org/viewvc/llvm-project?rev=255258&view=rev
> Log:
> Avoid undefined behavior when vector is empty.
>
> Found by ubsan.
>
> Modified:
>     llvm/trunk/include/llvm/ADT/SetVector.h
>     llvm/trunk/lib/Linker/LinkModules.cpp
>
> Modified: llvm/trunk/include/llvm/ADT/SetVector.h
> URL:
> http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/ADT/SetVector.h?rev=255258&r1=255257&r2=255258&view=diff
>
> ==============================================================================
> --- llvm/trunk/include/llvm/ADT/SetVector.h (original)
> +++ llvm/trunk/include/llvm/ADT/SetVector.h Thu Dec 10 10:35:06 2015
> @@ -58,6 +58,8 @@ public:
>      insert(Start, End);
>    }
>
> +  ArrayRef<T> getArrayRef() const { return vector_; }
> +
>    /// \brief Determine if the SetVector is empty or not.
>    bool empty() const {
>      return vector_.empty();
>
> Modified: llvm/trunk/lib/Linker/LinkModules.cpp
> URL:
> http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Linker/LinkModules.cpp?rev=255258&r1=255257&r2=255258&view=diff
>
> ==============================================================================
> --- llvm/trunk/lib/Linker/LinkModules.cpp (original)
> +++ llvm/trunk/lib/Linker/LinkModules.cpp Thu Dec 10 10:35:06 2015
> @@ -772,8 +772,7 @@ bool ModuleLinker::run() {
>        Internalize.insert(GV->getName());
>    }
>
> -  if (Mover.move(SrcM,
> -                 makeArrayRef(&*ValuesToLink.begin(),
> ValuesToLink.size()),
>

Isn't vector already implicitly convertible to ArrayRef? (I guess there's
something else at work heer - 'move' is a function template & has weird arg
deduction issues? something else?)


> +  if (Mover.move(SrcM, ValuesToLink.getArrayRef(),
>                   [this](GlobalValue &GV, IRMover::ValueAdder Add) {
>                     addLazyFor(GV, Add);
>                   }))
>
>
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