<div dir="ltr"><div class="gmail_default" style="font-family:monospace,monospace">I've bisected down the previously mentioned commit deltas to the following commit. This is the first instance of the warning message.</div><div class="gmail_default" style="font-family:monospace,monospace"><br></div><div class="gmail_default" style="font-family:monospace,monospace"><a href="https://github.com/llvm/llvm-project/commit/21450545d14">https://github.com/llvm/llvm-project/commit/21450545d14</a> </div><div class="gmail_default" style="font-family:monospace,monospace"><br></div><p class="gmail-commit-title" style="box-sizing:border-box;margin:0px 0px 8px;color:rgb(5,38,76);font-size:18px;font-weight:600;font-family:-apple-system,BlinkMacSystemFont,"Segoe UI",Helvetica,Arial,sans-serif,"Apple Color Emoji","Segoe UI Emoji","Segoe UI Symbol"">[libc++] decoupling Freestanding atomic<T> from libatomic.a</p><div class="gmail-commit-desc" style="box-sizing:border-box;color:rgb(36,41,46);font-family:-apple-system,BlinkMacSystemFont,"Segoe UI",Helvetica,Arial,sans-serif,"Apple Color Emoji","Segoe UI Emoji","Segoe UI Symbol";font-size:14px"><pre style="box-sizing:border-box;font-family:SFMono-Regular,Consolas,"Liberation Mono",Menlo,Courier,monospace;font-size:13px;margin-bottom:0px;margin-top:10px;color:rgb(68,77,86);line-height:1.45;max-width:100%;white-space:pre-wrap;overflow:visible">This patch introduces non-lockfree atomics that do not require using
an external libatomic. This work is done with the long-term goal of
allowing the use of <atomic> in freestanding environments.
Thanks to Olivier Giroux for the patch.
Differential Revision: <a href="https://reviews.llvm.org/D56913" rel="nofollow" style="box-sizing:border-box;background-color:transparent;color:rgb(3,102,214);text-decoration-line:none">https://reviews.llvm.org/D56913</a>
</pre></div><div class="gmail_default" style="font-family:monospace,monospace"><span style="color:rgb(68,77,86);font-family:SFMono-Regular,Consolas,"Liberation Mono",Menlo,Courier,monospace;font-size:13px;white-space:pre-wrap">llvm-svn: 355318</span></div><div class="gmail_default" style="font-family:monospace,monospace"> <br></div></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Wed, Mar 27, 2019 at 3:43 PM Brian M. Rzycki <<a href="mailto:brzycki@gmail.com">brzycki@gmail.com</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div dir="ltr"><div class="gmail_default" style="font-family:monospace,monospace">Sorry, I wasn't clear. I meant the change is somewhere between those two commits: those are two nightly builds 24 hours apart.</div></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Wed, Mar 27, 2019 at 3:08 PM JF Bastien <<a href="mailto:jfbastien@apple.com" target="_blank">jfbastien@apple.com</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div><br><div><br><blockquote type="cite"><div>On Mar 27, 2019, at 12:59 PM, Brian M. Rzycki via cfe-dev <<a href="mailto:cfe-dev@lists.llvm.org" target="_blank">cfe-dev@lists.llvm.org</a>> wrote:</div><br class="gmail-m_-2714281943330344387gmail-m_-905194210222011549Apple-interchange-newline"><div><div dir="ltr"><div dir="ltr"><div class="gmail_default"><font face="monospace, monospace">Hello Krzysztof,</font></div><div class="gmail_default"><font face="monospace, monospace"><br></font></div><div class="gmail_default"><font face="monospace, monospace">I've seen these errors in our nightly builds as well and noticed them when tracking down a different set of build breaks last month. I don't honestly know if they can be safely ignored. Our nightly compilers work for our testing even with the errors. I would be interested in knowing what this means and if it impacts us though.</font></div><div class="gmail_default"><font face="monospace, monospace"><br></font></div><div class="gmail_default"><font face="monospace, monospace">I did a little digging and found when we started seeing the messages. These SHAs are from the LLVM monorepo (<a href="https://github.com/llvm/llvm-project.git" rel="noreferrer" target="_blank">https://github.com/llvm/llvm-project.git</a>). We started seeing them in our builds 2019-March-05. I don't have the exact commit but may have time tomorrow to dig in a bit more.</font></div><font face="monospace, monospace"><br>b306ef12f04635-master (llvm-svn: 355299) <span class="gmail_default" style="font-family:monospace,monospace"> </span># <span class="gmail_default" style="font-family:monospace,monospace">clean</span><br>81dbc02671b223-master (llvm-svn: 355375) <span class="gmail_default" style="font-family:monospace,monospace"> </span># <span class="gmail_default" style="font-family:monospace,monospace">emits</span><span class="gmail_default" style="font-family:monospace,monospace"></span><span class="gmail_default" style="font-family:monospace,monospace"></span> "Host compiler must support std::atomic!”</font></div></div></div></blockquote><div><br></div><div>This change?</div></div><blockquote style="margin:0px 0px 0px 40px;border:none;padding:0px"><div><div><a href="https://github.com/llvm/llvm-project/commit/81dbc02671b223" target="_blank">https://github.com/llvm/llvm-project/commit/81dbc02671b223</a></div></div></blockquote><div><div>It’s an LLDB commit, doesn’t seem related. Maybe an adjacent change was the root cause?</div><div><br></div><br><blockquote type="cite"><div><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Wed, Mar 27, 2019 at 1:20 PM Krzysztof Parzyszek via cfe-dev <<a href="mailto:cfe-dev@lists.llvm.org" target="_blank">cfe-dev@lists.llvm.org</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">I'm seeing the following warning during cmake. I'm not sure when it started. Is this a known issue? Can it be safely ignored?<br>
<br>
CMake Warning at projects/libcxx/cmake/Modules/CheckLibcxxAtomic.cmake:49 (message):<br>
Host compiler must support std::atomic!<br>
Call Stack (most recent call first):<br>
projects/libcxx/cmake/config-ix.cmake:63 (include)<br>
projects/libcxx/CMakeLists.txt:476 (include)<br>
<br>
It's also showing up in the upstream bots:<br>
<a href="http://lab.llvm.org:8011/builders/libcxx-libcxxabi-x86_64-linux-debian/builds/1189/steps/cmake/logs/stdio" rel="noreferrer" target="_blank">http://lab.llvm.org:8011/builders/libcxx-libcxxabi-x86_64-linux-debian/builds/1189/steps/cmake/logs/stdio</a><br>
<br>
The linker errors (in my cmake) are actually:<br>
CMakeFiles/cmTC_354e0.dir/src.cxx.o: In function `__clang_call_terminate':<br>
src.cxx:(.text.__clang_call_terminate[__clang_call_terminate]+0x2): undefined reference to `__cxa_begin_catch'<br>
src.cxx:(.text.__clang_call_terminate[__clang_call_terminate]+0xb): undefined reference to `std::terminate()'<br>
CMakeFiles/cmTC_354e0.dir/src.cxx.o:(.data.DW.ref.__gxx_personality_v0[DW.ref.__gxx_personality_v0]+0x0): undefined reference to `__gxx_personality_v0'<br>
clang-8: error: linker command failed with exit code 1 (use -v to see invocation)<br>
CMakeFiles/cmTC_354e0.dir/build.make:97: recipe for target 'cmTC_354e0' failed<br>
<br>
-- <br>
Krzysztof Parzyszek <a href="mailto:kparzysz@quicinc.com" target="_blank">kparzysz@quicinc.com</a> LLVM compiler development<br>
<br>
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