[llvm-dev] Embedding LLD version to executables

[Sean Silva via llvm-dev]

On Wed, Oct 19, 2016 at 3:39 AM, Dave Bozier via llvm-dev <
llvm-dev at lists.llvm.org> wrote:

> Hi,
>
> > Scenario 1: you added -fuse-ld=lld to your command line, but you are
> suspecting that the option is ignored. Currently, it's actually
> surprisingly hard to tell if an output was created by LLD.
>
> Can't you use -v to see what linker the compiler driver invoked?
>

Sometimes, things are buried very deep in a build system, such that
extracting the clang invocation is difficult.

-- Sean Silva


>
>
> On Wed, Oct 19, 2016 at 4:41 AM, Rui Ueyama via llvm-dev <
> llvm-dev at lists.llvm.org> wrote:
>
>> On Tue, Oct 18, 2016 at 8:22 PM, Mehdi Amini <mehdi.amini at apple.com>
>> wrote:
>>
>>>
>>> > On Oct 18, 2016, at 6:44 PM, Rui Ueyama via llvm-dev <
>>> llvm-dev at lists.llvm.org> wrote:
>>> >
>>> > I'd like to make LLD embed version information so that we can
>>> determine if an executable was created by LLD and if that's the case which
>>> version of LLD.
>>>
>>> Pardon my ignorance, but what’s the motivation?
>>>
>>
>> It should make trouble shooting linker issues easier. Here are a few
>> scenarios.
>>
>> Scenario 1: you added -fuse-ld=lld to your command line, but you are
>> suspecting that the option is ignored. Currently, it's actually
>> surprisingly hard to tell if an output was created by LLD.
>>
>> Scenario 2: someone reported an issue about an executable linked by LLD,
>> and we know that version X has a similar bug, then the first thing we want
>> to do is to check if the executable was created with version X.
>>
>>
>>>
>>> We don’t embed the clang version in every binary clang generates for
>>> instance.
>>>
>>> >
>>> > ld.bfd doesn't seem to embed any information, so we cannot tell
>>> whether an executable was linked by ld.bfd or not easily.
>>> >
>>> > ld.gold embeds a string "GNU gold <version>" as
>>> ".note.gnu.gold-version" section contents.
>>> >
>>> > I'm wondering what we should do for LLD. The gold's way seems almost
>>> right, but I think we don't want to use the same section name because it
>>> contains "gold" as part of the section name. However, at the same time, I
>>> don't believe we want to create ".note.gnu.lld-version", because if we do,
>>> all programs that determine linker version need to look at
>>> ".note.gnu.<linker-name>-version" for all known linkers. That's absurd.
>>> (Also, our product is not GNU, so ".gnu" part is probably irrelevant.)
>>> >
>>> > I'm leaning towards ".note.linker-version" in hope that other linkers
>>> follow it.
>>>
>>> At least that would look much better than a .gnu.xxxx
>>>
>>> —
>>> Mehdi
>>>
>>>
>>>
>>
>> _______________________________________________
>> LLVM Developers mailing list
>> llvm-dev at lists.llvm.org
>> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>>
>>
>
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20161029/a59f5a06/attachment.html>