Re: [PATCH] Don't use PLT nor GOT in libc.a [BZ #20750]

[Allan McRae <allan@archlinux.org>]

Ping.  My distribution wants to enable PIE and -z,now by default and
this is required for glibc to build.

Allan

On 08/11/16 03:13, H.J. Lu wrote:
> On Mon, Nov 7, 2016 at 8:03 AM, Florian Weimer <fweimer@redhat.com> wrote:
>> On 11/04/2016 08:25 PM, H.J. Lu wrote:
>>>
>>> On Fri, Nov 4, 2016 at 12:03 PM, Florian Weimer <fweimer@redhat.com>
>>> wrote:
>>>>
>>>> On 11/04/2016 06:47 PM, H.J. Lu wrote:
>>>>>
>>>>>
>>>>> There is no need to use PLT nor GOT in libc.a to branch to a function,
>>>>> regardless whether libc.a is compiled with PIC or not.
>>>>>
>>>>> Tested on x86-64.  OK for master?
>>>>
>>>>
>>>>
>>>> Isn't this header file used outside of libc as well?
>>>
>>>
>>> It is used for other .a files.  If they aren't used to create static
>>> binaries,
>>> PLT/GOT may be used.  The resulting executable will work correctly.
>>
>>
>> You mean because “name” is automatically mapped to “name@plt”?
> 
> No.  There is no "@plt".  Linker will create a PLT entry if the function
> is defined in a shared object.
> 
>> I find this comment not very illuminating:
>>
>> +/* For libc.a, we want to branch to target directly.  */
>>  # define JUMPTARGET(name)      name
>>
>> And cheating the static linker in this way seems like a future maintenance
>> hazard.
>>
> 
> It is ok as long as those static archives aren't used to create shared
> objects.
>