From: "H.J. Lu" <hjl.tools@gmail.com>
To: Michael Matz <matz@suse.de>
Cc: gnu-gabi@sourceware.org
Subject: Re: Specify how undefined weak symbol should be resolved in executable
Date: Fri, 01 Jan 2016 00:00:00 -0000 [thread overview]
Message-ID: <CAMe9rOq=VrVO4b9fJFMB0ZfzAWPMDbCC+FEW0geCzd_Ju0aqoA@mail.gmail.com> (raw)
In-Reply-To: <CAMe9rOq=aMiTZ_nwS9aO9ba5bj_ak4gpk9D+JSfwged70VM3mg@mail.gmail.com>
On Mon, Feb 22, 2016 at 2:43 PM, H.J. Lu <hjl.tools@gmail.com> wrote:
> On Mon, Feb 22, 2016 at 10:28 AM, H.J. Lu <hjl.tools@gmail.com> wrote:
>> On Mon, Feb 22, 2016 at 10:17 AM, Michael Matz <matz@suse.de> wrote:
>>> Hi,
>>>
>>> On Mon, 22 Feb 2016, H.J. Lu wrote:
>>>
>>>> > Typo? What is the meaning of "dynamic relocation available at
>>>> > runtime". Are you talking about a relocation entry or the relocation
>>>> > process?
>>>>
>>>> Dynamic relocation isn't available with static linking.
>>>
>>> So you _are_ talking about the process. I think it's customary to call
>>> such executables "dynamic", or perhaps non-static, isn't it? (Why I'm
>>> confused with your wording: a dynamic executable which happens to have no
>>> dynamic reloc entries, has "no dynamic relocation available at runtime",
>>> and so we couldn't add one :))
>>>
>>>> > How about "When creating a dynamic executable the link editor should
>>>> > ..."?
>>>
>>> So, I still can understand my version better (possibly with
>>> s/dynamic/non-static/) :)
>>>
>>
>> Let's go with:
>>
>> When creating dynamic executable, the link editor should generate dynamic
>> relocations against unresolved weak symbols so that their values will be
>> resolved at run-time.
>>
>
> Second thought. To generate dynamic relocation for R_X86_64_32
> against fun in:
>
> [hjl@gnu-6 pr19704]$ objdump -dwr foo.o
>
> foo.o: file format elf64-x86-64
>
>
> Disassembly of section .text.startup:
>
> 0000000000000000 <main>:
> 0: b8 00 00 00 00 mov $0x0,%eax 1: R_X86_64_32 fun
> 5: 48 85 c0 test %rax,%rax
> 8: 74 10 je 1a <main+0x1a>
> a: 48 83 ec 08 sub $0x8,%rsp
> e: e8 00 00 00 00 callq 13 <main+0x13> f: R_X86_64_PC32 fun-0x4
> 13: 31 c0 xor %eax,%eax
> 15: 48 83 c4 08 add $0x8,%rsp
> 19: c3 retq
> 1a: 31 c0 xor %eax,%eax
> 1c: c3 retq
> [hjl@gnu-6 pr19704]$
>
> we create executable with dynamic R_X86_64_32 relocation against
> fun .text section, which leads to DT_TEXTREL. Is this what we want?
>
I believe the intention of undefined weak symbol is it should be resolved
at link-time when creating executable, dynamic or static.
--
H.J.
next prev parent reply other threads:[~2016-02-22 22:47 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-01-01 0:00 H.J. Lu
2016-01-01 0:00 ` H.J. Lu
2016-01-01 0:00 ` Michael Matz
2016-01-01 0:00 ` H.J. Lu
2016-01-01 0:00 ` Michael Matz
2016-01-01 0:00 ` H.J. Lu
2016-01-01 0:00 ` H.J. Lu
2016-01-01 0:00 ` H.J. Lu [this message]
2016-01-01 0:00 ` H.J. Lu
2016-01-01 0:00 ` Alan Modra
2016-01-01 0:00 ` H.J. Lu
2016-01-01 0:00 ` Michael Matz
2016-01-01 0:00 ` H.J. Lu
2016-01-01 0:00 ` Michael Matz
2016-01-01 0:00 ` Szabolcs Nagy
2016-01-01 0:00 ` Michael Matz
2016-01-01 0:00 ` H.J. Lu
2016-01-01 0:00 ` Michael Matz
2016-01-01 0:00 ` H.J. Lu
2016-01-01 0:00 ` Michael Matz
2016-01-01 0:00 ` H.J. Lu
2016-01-01 0:00 ` Alan Modra
2016-01-01 0:00 ` H.J. Lu
2016-01-01 0:00 ` Alan Modra
2016-01-01 0:00 ` Carlos O'Donell
2016-01-01 0:00 ` H.J. Lu
2016-01-01 0:00 ` Michael Matz
2016-01-01 0:00 ` H.J. Lu
2016-01-01 0:00 ` Michael Matz
2016-01-01 0:00 ` H.J. Lu
2016-01-01 0:00 ` Michael Matz
2016-01-01 0:00 ` H.J. Lu
2016-01-01 0:00 ` H.J. Lu
2016-01-01 0:00 ` H.J. Lu
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