Code change:
When I install the latest master toolchains via and try to build with them, linking fails: I did some bisection, and it looks like the problem started happening with Cc
The error is actually already mentioned in However, I am building Miri with cargo, so I don't know how I'd "use LLD instead".
Hm, we probably need to revert that PR. I did not realize we'd need lld downstream too, I thought that was only on our builder. cc
Yes, a revert seems appropriate. We're going to have to figure out where that's actually coming from. The only change I saw between 10 and 11 by grepping was the removal of llgo, but maybe there's some bad remnant.
Yeah, I thought this issue would be limited to the rustc build, but it makes sense that it can also affect project linking against rustc shared objects. I've looked a bit into what the root cause is, and what I have so far as that the symbol comes from and is present as a weak symbol both when compiling with clang-10 and clang-11. The only difference I see from is this: So apparently was treated as a symbol of the library, while now it's treated as a symbol of -- I'm not sure what that actually means, but presumably that refers to the compiler runtime libraries. My guess is that previously it just ended up being nulled out as a missing weak symbol, but now it's actually being found and linking fails because ... reasons. I'm not good at linkers :) Edit: shows these as:
can you prepare a revert PR?
Done in . If nobody has an idea on how to avoid the linker error, two more options would be to comment out the symbol in our llvm-project fork, or to avoid upgrading clang altogether and just build both Python 2 and Python 3 for that image.
The issue is probably going to be in how exactly the objects that comprise are compiled, not linked. I suspect just ends up ignoring the malformed object or otherwise not reporting the issue, but the object and the relevant symbols ultimately end up in the anyway. Alas, reasons these obscure failures can occur are many – I've seen them occur from things as trivial as forgetting to . The question is: is there perhaps a way to disable ExecutionEngine entirely? Intuitively nothing we do should depend on that code. And if not, I'm comfortable patching out in our fork as we get closer to Feb 11 and continue having trouble pinpointing exact cause of this problem.
We normally don't link ExecutionEngine, but dist-x8664-linux in particular builds LLVM with ThinLTO, in which case we link as shared, instead of statically linking individual components into rustcllvm.
It seems to be possible to configure the components in using , but I'm not sure to what degree we can restrict those (not sure if this job also ships LLVM tools).
So, I think we could have used to exclude unnecessary parts from , as LLVM tools can still statically link the parts not in the dylib. But in the end, we can't use the option anyway due to
Looks like I'm getting this locally when trying to bootstrap rustc (while building ), might happen since the llvm upgrade but I'm not 100% sure. Are there some workarounds I can put into my for this? I'm using lld to link. <details<summaryBacktrace</summary<p</p</details
which commit are you trying to build?
latest git master
Probably best to open a new issue then; this one has been closed and the steps to reproduce it still work without error -- you might be having a different problem.
Opened
Did anyone file an upstream bug report about this? I'm observing it outside of Rust, but with a similar setup ( with lld+ThinLTO, then linking it into a binary with ). If not, I'd try to build a reproducer.
I've opened for this.
The bug has been fixed, the fix will be in LLVM 12.0.1.
Thanks! We can try updating clang again once the 12.0.1 tag is there.

Related discussion:
text: rm -rf /tmp/rustc-pgo <del> python3 ../x.py build --target=$PGO_HOST --host=$PGO_HOST  </del> <ins> python2.7 ../x.py build --target=$PGO_HOST --host=$PGO_HOST  </ins> --stage 2 library/std --rust-profile-generate=/tmp/rustc-pgo ./build/$PGO_HOST/stage2/bin/rustc --edition=2018