[lld] r264234 - Avoid UB when creating empty atoms. NFC.

[David Blaikie via llvm-commits]

On Wed, Mar 23, 2016 at 6:16 PM, Pete Cooper via llvm-commits <
llvm-commits at lists.llvm.org> wrote:

> Author: pete
> Date: Wed Mar 23 20:16:06 2016
> New Revision: 264234
>
> URL: http://llvm.org/viewvc/llvm-project?rev=264234&view=rev
> Log:
> Avoid UB when creating empty atoms.  NFC.
>
> The stack-size.yaml test had an empty atom content array.  This is
> legal, but asking a BumpPtrAllocator for 0 sized data may not be
> legal.  Instead just avoid requesting any data when we can just return
> an empty ArrayRef instead.
>
> Modified:
>     lld/trunk/lib/ReaderWriter/MachO/MachONormalizedFileYAML.cpp
>
> Modified: lld/trunk/lib/ReaderWriter/MachO/MachONormalizedFileYAML.cpp
> URL:
> http://llvm.org/viewvc/llvm-project/lld/trunk/lib/ReaderWriter/MachO/MachONormalizedFileYAML.cpp?rev=264234&r1=264233&r2=264234&view=diff
>
> ==============================================================================
> --- lld/trunk/lib/ReaderWriter/MachO/MachONormalizedFileYAML.cpp (original)
> +++ lld/trunk/lib/ReaderWriter/MachO/MachONormalizedFileYAML.cpp Wed Mar
> 23 20:16:06 2016
> @@ -334,6 +334,8 @@ struct MappingTraits<Section> {
>        NormalizedFile *file = info->_normalizeMachOFile;
>        assert(file != nullptr);
>        size_t size = _normalizedContent.size();
> +      if (!size)
> +        return ArrayRef<uint8_t>();
>

You can write this as "return None;" or "return {};" if you like.


>        uint8_t *bytes = file->ownedAllocations.Allocate<uint8_t>(size);
>        std::copy(_normalizedContent.begin(), _normalizedContent.end(),
> bytes);
>        return makeArrayRef(bytes, size);
>
>
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