[cfe-dev] [llvm-dev] [RFC] Open sourcing and contributing TAPI back to the LLVM community

Thu Sep 20 13:59:24 PDT 2018

This is great to hear. Please add Steven Wu and me as reviewers.
Unfortunately I won't be available for the next weeks, because I am on my
honeymoon, but I would like a chance to review the code once I am back.

Thanks

Cheers,
Juergen

On Thu, Sep 20, 2018 at 11:50 AM Nico Weber <thakis at chromium.org> wrote:

> Great to hear, thanks!
>
> On Thu, Sep 20, 2018 at 1:56 PM Jake Ehrlich <jakehehrlich at google.com>
> wrote:
>
>> A member of my team +Armando Montanez <amontanez at google.com> is going to
>> drop a proposal for the ELF part of this soon (like sometime next week) and
>> will be working on the implementation. I'll be one of the reviewers for
>> anything that comes out of that so we can be sure it will get reviewed as
>> well. The goal is to have a single tool/library that would include
>> Juergen's original code and the new ELF code.
>>
>> On Thu, Sep 20, 2018 at 10:45 AM Nico Weber <thakis at chromium.org> wrote:
>>
>>> Was there any progress in the upstreaming effort? I'd be interested in
>>> having lld be able to link against tbd files, and I think it'd be cool if
>>> libtool -static could write tbd files (similar to thin archives on linux)
>>> since that should make archiving much faster.
>>>
>>> Juergen, maybe uploading your initial patch to phabricator instead of
>>> attaching might get more traction?
>>>
>>> On Wed, Apr 25, 2018 at 8:53 AM Juergen Ributzka via cfe-dev <
>>> cfe-dev at lists.llvm.org> wrote:
>>>
>>>> The code on opensource.apple.com is the minimal code needed for
>>>> libtapi to read TBD files with ld64. The code I pushed to GitHub on the
>>>> other side includes the full TAPI tool source code. If you check the code
>>>> you will see that I already use the LLVM license for everything, because
>>>> the goal has always been to contribute this back to the community.
>>>>
>>>> I attached an initial patch for libtapi and nm support to my original
>>>> email. I also have some updated patches for that too, but somehow got
>>>> derailed into "lets rewrite libobject" discussions.
>>>>
>>>> On Tue, Apr 10, 2018 at 4:15 PM, John Ericson via llvm-dev <
>>>> llvm-dev at lists.llvm.org> wrote:
>>>>
>>>>> That sounds great to me, thanks Jake. I'm not Jurgen either, of
>>>>> course, but I'm happy to assist you if he is unavailable. I'm not also not
>>>>> qualified to audit the license, but do note Apple formally also released
>>>>> some code at https://opensource.apple.com/tarballs/tapi/. If there's
>>>>> anything else I can do to help, let me know.
>>>>>
>>>>> Cheers,
>>>>>
>>>>> John
>>>>>
>>>>> On 04/10/2018 06:13 PM, Jake Ehrlich wrote:
>>>>>
>>>>> Ideally Jurgen would cut up the code on github, put up an initial diff
>>>>> for a minimal viable tool, and then we would review it and then continue to
>>>>> copy code from the github repo into llvm and review it. I'm also willing to
>>>>> do that if Jurgen doesn't want to at this point though. I'd like the OK
>>>>> from Jurgen on that and I'd also like the OK from someone that the license
>>>>> stuff is all good to go (I'm not sure who should check licence stuff).
>>>>>
>>>>> Best,
>>>>> Jake
>>>>>
>>>>> On Tue, Apr 10, 2018 at 2:39 PM John Ericson
>>>>> <john.ericson at obsidian.systems> <john.ericson at obsidian.systems> wrote:
>>>>>
>>>>>> Seems like there are a few of us interested in this then. I new
>>>>>> around here and don't really know how decisions are made, so what's next?
>>>>>> Just open a diff with the entire library??
>>>>>>
>>>>>> John
>>>>>> On 04/10/2018 05:33 PM, Jake Ehrlich wrote:
>>>>>>
>>>>>> Benifits of TBD:
>>>>>> 1) It's human readable and diffs on TBDs correspond to changes in the
>>>>>> ABI. Diffs can be automatically added to review processes to ensure that
>>>>>> changes to the ABI are reviewed. The TBDs also document your precise ABI.
>>>>>> 2) The size is smaller which means they can be shipped in an SDK
>>>>>> instead of binaries to reduce the size of an SDK
>>>>>> 3) Stubs are producible from TBDs (or should be) which means stubs
>>>>>> for linking can be produced even if we don't directly support them in LLD.
>>>>>> This lets you ship the smaller TBD files in place of larger binaries and
>>>>>> still link things without direct linker support (assuming you already ship
>>>>>> a toolchain with your SDK or expect your users to have this tool)
>>>>>>
>>>>>> Since stubs are producible from TBDs I don't really see a downside. I
>>>>>> think we need both, I was going to propose a yaml based representation for
>>>>>> ELF for the above reasons anyhow.
>>>>>>
>>>>>> On Tue, Apr 10, 2018 at 1:14 PM Andrew Kelley via llvm-dev <
>>>>>> llvm-dev at lists.llvm.org> wrote:
>>>>>>
>>>>>>> On Mon, Apr 9, 2018 at 10:11 PM, John Ericson via llvm-dev <
>>>>>>> llvm-dev at lists.llvm.org> wrote:
>>>>>>>
>>>>>>>> > Regardless of any of that, given that TBD files _are_ an integral
>>>>>>>> part of the apple platform, supporting them is certainly a necessity in
>>>>>>>> order to have a working apple linker. So, if making LLD work for
>>>>>>>> Apple/MachO is the justification for adding TBD support to LLVM, that seems
>>>>>>>> self-evidently a reasonable thing to do. On the other hand, it looks like
>>>>>>>> the LLD mach-o code is unmaintained and nobody seems to be much interested
>>>>>>>> in it. And having code for reading TBD files in LLVM seems not terribly
>>>>>>>> interesting, unless it is as part of a project to make the LLD MachO linker
>>>>>>>> actually functional and supported.
>>>>>>>>
>>>>>>>> Yes. I hope this can be reason enough. Hobbyists could push for LLD
>>>>>>>> support for Mach-O besides Apple, and if LLD is to displace other linkers
>>>>>>>> this is a necessary component as you say. Better to upstream now before the
>>>>>>>> code diverges than more work later? Conversely if nothing happens, I doubt
>>>>>>>> libtapi would be a greater drag on the codebase than the MachO LLD code, so
>>>>>>>> whatever cost/benefit analysis exists for keeping that around could also
>>>>>>>> apply to this.
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> Speaking for the Zig project here, our goal is to support
>>>>>>> cross-compilation for any target, on any target, without requiring
>>>>>>> installation of any target-specific SDK. So, for example, these use cases:
>>>>>>>  * on linux, compile & link a binary targeting macos
>>>>>>>  * on windows, compile & link a binary targeting macos
>>>>>>>
>>>>>>> This works today, although it depends on a patch to LLD to fix the
>>>>>>> MACH-O linker that is not high enough quality to upstream.
>>>>>>>
>>>>>>> So we have a vested interest in improving the MACH-O linker, and in
>>>>>>> fact a Zig community member has fixed at least one bug in MACH-O LLD:
>>>>>>> reviews.llvm.org/D35387
>>>>>>>
>>>>>>> I don't fully understand how TBD or TAPI works, but I hope that it
>>>>>>> results in improvements to the MACH-O linker.
>>>>>>>
>>>>>>>
>>>>>>> _______________________________________________
>>>>>>> LLVM Developers mailing list
>>>>>>> llvm-dev at lists.llvm.org
>>>>>>> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>>>>>>>
>>>>>>
>>>>>>
>>>>>
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>>>>>
>>>>>
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