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<p class="MsoNormal">Hah, that’s what I get for not reading. Will respond there.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal" style="margin-left:.5in"><b><span style="font-size:12.0pt;color:black">From:
</span></b><span style="font-size:12.0pt;color:black">Nico Weber <thakis@chromium.org><br>
<b>Date: </b>Thursday, April 2, 2020 at 11:36 AM<br>
<b>To: </b>Shoaib Meenai <smeenai@fb.com><br>
<b>Cc: </b>Hans Wennborg <hans@chromium.org>, Louis Dionne <ldionne@apple.com>, "libcxx-commits@lists.llvm.org" <libcxx-commits@lists.llvm.org><br>
<b>Subject: </b>Re: [libcxx-commits] [libcxx] 61e8973 - [libc++] Simplify the configuration of the C++ ABI library<o:p></o:p></span></p>
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<p class="MsoNormal" style="margin-left:.5in"><o:p> </o:p></p>
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<p class="MsoNormal" style="margin-left:.5in">…see discussion on the bug that Louis linked to :)<o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:.5in"><o:p> </o:p></p>
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<p class="MsoNormal" style="margin-left:.5in">On Thu, Apr 2, 2020 at 2:34 PM Shoaib Meenai via libcxx-commits <<a href="mailto:libcxx-commits@lists.llvm.org">libcxx-commits@lists.llvm.org</a>> wrote:<o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:.5in">Can you just build the cxx-headers target instead of doing a full libc++ build? That's what we do for some of our builds which have a similar issue with requiring the headers.<br>
<br>
On 4/2/20, 9:54 AM, "libcxx-commits on behalf of Hans Wennborg via libcxx-commits" <<a href="mailto:libcxx-commits-bounces@lists.llvm.org" target="_blank">libcxx-commits-bounces@lists.llvm.org</a> on behalf of
<a href="mailto:libcxx-commits@lists.llvm.org" target="_blank">libcxx-commits@lists.llvm.org</a>> wrote:<br>
<br>
On Thu, Apr 2, 2020 at 8:21 AM Louis Dionne via libcxx-commits<br>
<<a href="mailto:libcxx-commits@lists.llvm.org" target="_blank">libcxx-commits@lists.llvm.org</a>> wrote:<br>
><br>
><br>
> Author: Louis Dionne<br>
> Date: 2020-04-02T02:21:15-04:00<br>
> New Revision: 61e89737c5daf7b65341936f88f68efb680cdcd4<br>
><br>
> URL: <a href="https://github.com/llvm/llvm-project/commit/61e89737c5daf7b65341936f88f68efb680cdcd4" target="_blank">
https://github.com/llvm/llvm-project/commit/61e89737c5daf7b65341936f88f68efb680cdcd4</a><br>
> DIFF: <a href="https://github.com/llvm/llvm-project/commit/61e89737c5daf7b65341936f88f68efb680cdcd4.diff" target="_blank">
https://github.com/llvm/llvm-project/commit/61e89737c5daf7b65341936f88f68efb680cdcd4.diff</a><br>
><br>
> LOG: [libc++] Simplify the configuration of the C++ ABI library<br>
><br>
> This commit removes support for building against the system libc++abi,<br>
> which was supported on Apple platforms. This is basically never what we<br>
> want to do, since libc++ and libc++abi are coupled and building a trunk<br>
> libc++ against an older libc++abi can lead to incompatibilities (and<br>
> good luck debugging them!). It might have made some sense to support<br>
> that when the monorepo did not exist, however I don't think this is<br>
> anything but a footgun nowadays.<br>
><br>
> Furthermore, based on the newly-made assumption that we're building<br>
> against the monorepo libc++abi, we can simplify the search path logic<br>
> for finding libc++abi.<br>
><br>
> This area of our build system has a lot of technical debt accumulated,<br>
> and it's surprisingly difficult to change. We've tried different things<br>
> and failed several times in the past. I did test this change on our<br>
> Docker image for the build bots and on Apple platforms, however it is<br>
> possible that this breaks some unknown configuration, in which case it<br>
> should be fine to revert this (so we can try again!).<br>
<br>
Well hello :-)<br>
<br>
This broke Chromium's packaging of Clang on Mac (see <a href="https://urldefense.proofpoint.com/v2/url?u=https-3A__crbug.com_1067216&d=DwIGaQ&c=5VD0RTtNlTh3ycd41b3MUw&r=o3kDXzdBUE3ljQXKeTWOMw&m=SWiE-LfJQGnDioVJ_1oMe3PytSX5eiUvQpefAQsuazY&s=lE5OJxnVAVB3rbcM6cb6l_98rAS88IWoGG10qGpGhdA&e=" target="_blank">
https://urldefense.proofpoint.com/v2/url?u=https-3A__crbug.com_1067216&d=DwIGaQ&c=5VD0RTtNlTh3ycd41b3MUw&r=o3kDXzdBUE3ljQXKeTWOMw&m=SWiE-LfJQGnDioVJ_1oMe3PytSX5eiUvQpefAQsuazY&s=lE5OJxnVAVB3rbcM6cb6l_98rAS88IWoGG10qGpGhdA&e=</a> ).<br>
<br>
We build libc++ as part of that process, not because we ship it with<br>
the compiler, but as part of the bootstrapping process: otherwise the<br>
just-built Clang doesn't find the c++ headers. Until now we've been<br>
building with -DLIBCXX_CXX_ABI=libcxxabi -DLIBCXX_CXX_ABI_SYSTEM=1<br>
however with your patch that stopped working.<br>
<br>
I tried adding libcxxabi to -DLLVM_ENABLE_PROJECTS and dropping those<br>
two flags, but now building libcxxabi failed for unclear reasons<br>
([1]).<br>
<br>
Would it be okay to revert your patch until we've figured this out?<br>
<br>
Thanks,<br>
Hans<br>
<br>
1. <a href="https://urldefense.proofpoint.com/v2/url?u=https-3A__logs.chromium.org_logs_chromium_buildbucket_cr-2Dbuildbucket.appspot.com_8884121514869999920_-2B_steps_package-5Fclang_0_stdout&d=DwIGaQ&c=5VD0RTtNlTh3ycd41b3MUw&r=o3kDXzdBUE3ljQXKeTWOMw&m=SWiE-LfJQGnDioVJ_1oMe3PytSX5eiUvQpefAQsuazY&s=sjaVvsQRbGGGSN4z6WyYuXoG8V1t706w716SXjj6TKw&e=" target="_blank">
https://urldefense.proofpoint.com/v2/url?u=https-3A__logs.chromium.org_logs_chromium_buildbucket_cr-2Dbuildbucket.appspot.com_8884121514869999920_-2B_steps_package-5Fclang_0_stdout&d=DwIGaQ&c=5VD0RTtNlTh3ycd41b3MUw&r=o3kDXzdBUE3ljQXKeTWOMw&m=SWiE-LfJQGnDioVJ_1oMe3PytSX5eiUvQpefAQsuazY&s=sjaVvsQRbGGGSN4z6WyYuXoG8V1t706w716SXjj6TKw&e=</a>
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