[llvm] r243934 - [UB] Fix yet another use of memcpy with a null pointer argument. I think

[Chandler Carruth]

Should probably pull this into the release as it fixes something that could
miscompile in the future with a new host compiler.

On Mon, Aug 3, 2015 at 6:05 PM Chandler Carruth <chandlerc at gmail.com> wrote:

> Author: chandlerc
> Date: Mon Aug  3 20:00:56 2015
> New Revision: 243934
>
> URL: http://llvm.org/viewvc/llvm-project?rev=243934&view=rev
> Log:
> [UB] Fix yet another use of memcpy with a null pointer argument. I think
> this is the last of them in my build of LLVM. Haven't tried Clang yet.
>
> Found via UBSan.
>
> Modified:
>     llvm/trunk/lib/Support/MemoryBuffer.cpp
>
> Modified: llvm/trunk/lib/Support/MemoryBuffer.cpp
> URL:
> http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Support/MemoryBuffer.cpp?rev=243934&r1=243933&r2=243934&view=diff
>
> ==============================================================================
> --- llvm/trunk/lib/Support/MemoryBuffer.cpp (original)
> +++ llvm/trunk/lib/Support/MemoryBuffer.cpp Mon Aug  3 20:00:56 2015
> @@ -57,7 +57,8 @@ void MemoryBuffer::init(const char *BufS
>  /// CopyStringRef - Copies contents of a StringRef into a block of memory
> and
>  /// null-terminates it.
>  static void CopyStringRef(char *Memory, StringRef Data) {
> -  memcpy(Memory, Data.data(), Data.size());
> +  if (!Data.empty())
> +    memcpy(Memory, Data.data(), Data.size());
>    Memory[Data.size()] = 0; // Null terminate string.
>  }
>
>
>
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