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

Thu Sep 20 11:49:48 PDT 2018

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.
>>>>>>
>>>>>>
>>>>>> _______________________________________________
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>>>>>> llvm-dev at lists.llvm.org
>>>>>> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>>>>>>
>>>>>
>>>>>
>>>>
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>>>>
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