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

[Rui Ueyama via llvm-commits]

On Mon, Feb 1, 2016 at 6:36 PM, David Blaikie <dblaikie at gmail.com> wrote:

>
>
> 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)
>

Thank you for pointing that out. What's the best practice here? Just use
auto and immediately assign both values in a pair to some variables (to
give them names)?


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