[llvm-commits] ELFReader.cpp update - Add support for References.

[Clow, Marshall]

On Sep 12, 2012, at 11:32 AM, Bill Wendling <wendling at apple.com> wrote:

> On Sep 11, 2012, at 1:24 PM, "Clow, Marshall" <mclow at qualcomm.com> wrote:
> 
>> On Sep 11, 2012, at 12:50 PM, Bill Wendling <wendling at apple.com> wrote:
>>> On Sep 11, 2012, at 11:49 AM, "Clow, Marshall" <mclow at qualcomm.com> wrote:
>>>> On Sep 11, 2012, at 11:21 AM, Sid Manning <sidneym at codeaurora.org> wrote:
>>>> 
>>>>> On 09/07/12 16:45, Michael Spencer wrote:
>>>>>> On Fri, Sep 7, 2012 at 8:41 AM, Sid Manning<sidneym at codeaurora.org>  wrote:
>>>>>>> 
>>>>> ....
>>>>>> 
>>>>>>> +                    (reinterpret_cast<const Elf_Rela *>(contents.data()));
>>>>>>> +
>>>>>>> +        // Get rid of the leading .rela so Atoms can use their own section
>>>>>>> +        // name to find the relocs.
>>>>>>> +        sectionName = sectionName.drop_front(5);
>>>>>>> +
>>>>>>> +        auto&ref = RelocationAddendReferences[sectionName];
>>>>>> 
>>>>>> Ref.
>>>>>> 
>>>>>>> +        for (unsigned int i=0; i<section->getEntityCount(); i++) {
>>>>>>> +          ref.push_back(relocs+i);
>>>>>> 
>>>>>> This is still wrong. The offset to use for each relocation entry is based on
>>>>>> sh_entsize. See the getRel and getEntry templates in Object/ELF.h. We can expose
>>>>>> these, or better yet, proper iterators to them. I dislike duplicating the work
>>>>>> of file format parsing.
>>>>>> 
>>>>> 
>>>>> OK I can push this up to ELF.h by adding a new interface, getELFRelaVector(Elf_Shdr *) that returns relocations in a vector.  
>>>> 
>>>> While I like the 
>>>> I don't like embedding the return type in the name of the function.
>>>> How about (something like):
>>>> 	std::vector <const Elf_Rel *> getSectionRelocations ( section );
>>>> 
>>> Instead of returning a std::vector, please pass in a reference and fill that.
>> 
>> Why?
>> 
> If it has move semantics, then it's fine. Otherwise, it will cause a copy of the vector from a temporary to the final one, which is expensive.

std::vector has move semantics in c++11.
For c++03, we have RVO.

-- Marshall