Re: [committed, PATCH] Always create dynsym section with dynamic sections

[Faraz Shahbazker <faraz dot shahbazker at imgtec dot com>]

On 04/23/16 05:27, H.J. Lu wrote:
> On Fri, Apr 22, 2016 at 7:31 PM, Faraz Shahbazker
> <faraz.shahbazker@imgtec.com> wrote:
>> On 04/22/16 19:05, H.J. Lu wrote:
>>> On Fri, Apr 22, 2016 at 6:37 PM, Faraz Shahbazker
>>> <faraz.shahbazker@imgtec.com> wrote:
>>>> On 04/22/16 16:24, H.J. Lu wrote:
>>>>> On Fri, Apr 22, 2016 at 2:49 PM, Faraz Shahbazker
>>>>> <Faraz.Shahbazker@imgtec.com> wrote:
>>>>>> On 04/22/2016 12:28 PM, H.J. Lu wrote:
>>>>>>> On Fri, Apr 22, 2016 at 11:55 AM, Faraz Shahbazker
>>>>>>>> + if (dynsymcount != 0 || elf_hash_table (info)->dynamic_sections_created)
>>>>>>>> +     ++dynsymcount;
>>>>>>>
>>>>>>> Are you saying dynamic_sections_created is 0 for MIPS here
>>>>>>> and will become 1 later?
>>>>>>
>>>>>> No, it will remain 0. The link is static, but the hash_table is still used to
>>>>>> record global symbols that have GOT relocations against them. Ofc, this
>>>>>> hash_table does not result in creation of a dynsym section, because well,
>>>>>> dynamic_sections_created is 0.
>>>>>>
>>>>>> Check the list of callers to bfd_elf_link_record_dynamic_symbol(), a number of
>>>>>> architectures use the link_hash_table in situations where it is not clear whether it is
>>>>>> being used to track dynamic symbols for a dynamic executable, as it is for x86.
>>>>>>
>>>>>
>>>>> So MIPS doesn't have dynamic symbols in this case.  It just borrows
>>>>> dynsymcount for different purpose.  Is this correct?
>>>>
>>>> Not quite! MIPS is expecting dynsymcount to count the number of symbols
>>>> that would have gone in to the .dynsym, even for a static executable. That way
>>>> parts of the arch-specific code can remain agnostic to the static/dynamic nature
>>>> of the link. It may not be used exactly as documented, but its not being used
>>>> for what one would call a different purpose.
>>>>
>>>> All we need is for handling of dynsymcount when renumbering to be consistent with
>>>> its initialization. If the initial increment for a NULL symbol was not gated by
>>>> dynamic_sections_created, then the increment when renumbering should also not.
>>>> If the increment when renumbering has to be gated by dynamic_sections_created,
>>>> then the initial increment must also be so.
>>>
>>> From what you are saying, shouldn't dynsymcount be incremented
>>> unconditionally?
>> No. Always, when the table is non-empty + whatever else you need.
>>
> 
> You said dynsym should be treated treated the same for static and
> dynamic executables.   dynsymcount is number of dynsym + 1 in
> dynamic executable.  Why isn't it true for static executable?

It is, or at least used to be, before this patch. It still is for both,
before renumbering. But now the +1 only happens for dynamic executables
when renumbering.