[lld] r259455 - Replace auto with the real type.

[David Blaikie via llvm-commits]

On Mon, Feb 1, 2016 at 6:29 PM, Rui Ueyama via llvm-commits <
llvm-commits at lists.llvm.org> wrote:

> Author: ruiu
> Date: Mon Feb  1 20:29:03 2016
> New Revision: 259455
>
> URL: http://llvm.org/viewvc/llvm-project?rev=259455&view=rev
> Log:
> Replace auto with the real type.
>
> Modified:
>     lld/trunk/ELF/OutputSections.cpp
>
> Modified: lld/trunk/ELF/OutputSections.cpp
> URL:
> http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/OutputSections.cpp?rev=259455&r1=259454&r2=259455&view=diff
>
> ==============================================================================
> --- lld/trunk/ELF/OutputSections.cpp (original)
> +++ lld/trunk/ELF/OutputSections.cpp Mon Feb  1 20:29:03 2016
> @@ -144,7 +144,7 @@ template <class ELFT> void GotSection<EL
>
>  template <class ELFT> void GotSection<ELFT>::writeTo(uint8_t *Buf) {
>    Target->writeGotHeader(Buf);
> -  for (const auto &L : MipsLocalGotPos) {
> +  for (std::pair<uintX_t, size_t> &L : MipsLocalGotPos) {
>

This is probably accidentally causing a copy, because the value type of a
map is usually std::pair<const K, V> - so this sort of for loop introduces
an implicit conversion and then causes local reference extension to occur
(Clang has a warning for this - so I hope this is triggering a warning)

This is one of the reasons auto is particularly encouraged in places like
this - to avoid the possibility of mismatching with the type (though
Clang's warning makes this a less risky proposition)


>      uint8_t *Entry = Buf + L.second * sizeof(uintX_t);
>      write<uintX_t, ELFT::TargetEndianness, sizeof(uintX_t)>(Entry,
> L.first);
>    }
>
>
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