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

Thu Sep 20 14:22:14 PDT 2018

Awesome, having reviewers puts us ahead of the curve! I'm quite excited for
this to make it in.

On Thu, Sep 20, 2018 at 1:59 PM Juergen Ributzka <juergen at ributzka.de>
wrote:

> 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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>>>>> cfe-dev at lists.llvm.org
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>>>>>
>>>>
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