[LLVMdev] How to prevent LLVM from emitting R_X86_64_32 ELF relocations?

Jiong Wang
Sat, 27 Apr 2013 03:36:59 -0000

On 04/27/2013 11:02 AM, Yuri wrote:
> On 04/26/2013 19:50, Jiong Wang wrote:
>>
>>
>>   why do you want to prevent R_X86_64_32 generation? for 32bit dwarf,
>> I think generation of R_X86_64_32 is reasonable.
>>
>>   you can check http://dwarfstd.org/doc/DWARF4.pdf.
>
> Because R_X86_64_32 elements are 4-byte addresses and can't be
> relocated for the 64-bit address space over 32-bit limit.
>
> Dwarf2 actually allows for both 32bit and 64-bit relocations. The
> document, mentioned by you, explains this in section 7.5.1.1 on page
> 143. If the first DWORD of .debug_info section is 0xffffffff, then
> this is 64-bit format.
>
> But LLVM for some reason always chooses DWARF 32-bit format. This is
> why I asked the question. Resulting relocable 64-bit objects can't be
> loaded into addresses that are over 32-bit limit.

there is no support for Dwarf 64 yet. From what I known, there is no way
you can get rid of that.

looks like there are some discussions on this already, you can search
bugzilla.

http://llvm.org/bugs/show_bug.cgi?id=14969
http://llvm.org/bugs/show_bug.cgi?id=15173



>
> Yuri


--
Regards,
Jiong. Wang
Tilera Corporation.