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Re: Specify how undefined weak symbol should be resolved in executable
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?
--
H.J.