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Re: [PATCH] Use comdat instead of .gnu.linkonce for i386 setup pic register
On 17/01/2017 08:24, Adhemerval Zanella wrote:
>
>
> On 10/01/2017 12:02, Adhemerval Zanella wrote:
>>
>>
>> On 09/01/2017 18:26, Zack Weinberg wrote:
>>> On Mon, Jan 9, 2017 at 2:48 PM, Adhemerval Zanella
>>> <adhemerval.zanella@linaro.org> wrote:
>>>> GCC has moved from using .gnu.linkonce for i386 setup pic register with
>>>> minimum current version (as for binutils minimum binutils that support
>>>> comdat). This patch replace linkonce usage by comdat.
>>>
>>> Is this change compatible with older GCC/binutils versions as well as
>>> the new ones?
>>>
>>> zw
>>>
>>
>> I am trying to pinpoint when binutils added comdat support for i686 and
>> this [1] is the oldest thread I found.
>>
>> I also checked with some ancient binutils version and version older than
>> 2.16 I see:
>>
>> test.o: In function `__x86.get_pc_thunk.bx':
>> test.o(.text.__x86.get_pc_thunk.bx+0x0): multiple definition of `__x86.get_pc_thunk.bx'
>> /usr/lib/gcc/x86_64-linux-gnu/5/../../../i386-linux-gnu/crti.o(.gnu.linkonce.t.__x86.get_pc_thunk.bx+0x0): first defined here
>>
>> Which seems that the can not handle either comdat at all or the mix of
>> linkonce and comdat. For binutils 2.16.1 and forward I am getting a
>> different issue trying to link a binary with and more recent ctri.o
>> (unrecognized relocation (0x2b) in section `.init', which is R_386_GOT32X
>> and old binutils won't generate it anyway).
>>
>> So I think that either unlikely someone will use an older binutils than
>> the one used to glibc and even this scenario may fail with some issue
>> as the R_386_GOT32X. Also, 2.16.1 is quite old and not really supported
>> (glibc itself required 2.22).
>>
>> [1] https://gcc.gnu.org/ml/gcc/2004-05/msg00030.html
>>
>
> Ping.
>
Ping.