[swift-dev] Build failure? "LLVM ERROR: Cannot represent a subtraction with a weak symbol"

Jordan Rose jordan_rose at apple.com
Thu Jan 28 12:09:12 CST 2016

Hi, Brian. This required an update to LLVM as well, which Lang Hames should have cherry-picked to the stable branch. Are your LLVM and Clang fully up to date?


> On Jan 28, 2016, at 9:44 , Brian Gesiak via swift-dev <swift-dev at swift.org> wrote:
> Hello all!
> I'm encountering a build failure when compiling the stdlib, using the tip of master as of this morning (d44d6e). I'm running Ubuntu 15.10 on a x86_64 machine.
> Here are my build logs: https://gist.github.com/modocache/a85851a53b570d5fca47 <https://gist.github.com/modocache/a85851a53b570d5fca47>. The logs show that I remove my build directory completely, before starting a clean build with `utils/build-script -R`.
> I was surprised to see a build failure, so I tried a bisect to narrow down what may have caused it. Here's the log from the bisect, which I made between master (d44d6e) and a known good commit (061c77): https://gist.github.com/modocache/89c347a3c50767eee7eb <https://gist.github.com/modocache/89c347a3c50767eee7eb>
> The bisect points to commit 638e4b, "IRGen/Runtime: Use relative addresses in nominal type descriptors". But I'm skeptical: that commit is weeks old, and was even included in swift-DEVELOPMENT-SNAPSHOT-2016-01-25-a. I very much doubt it introduced a build failure.
> I tried building swift-DEVELOPMENT-SNAPSHOT-2016-01-25-a, and even *that* doesn't build on my system!! I assume this snapshot has passed CI, so I thought there must be something wrong with my system. But William Dillion tells me he's experiencing the same error (https://twitter.com/hpux735/status/692758868670058496 <https://twitter.com/hpux735/status/692758868670058496>).
> William and I are both working on armv7 ports, so perhaps both of our build machines are similarly broken. But I'm curious if anyone has any ideas on what the problem might be, or if this build error reproduces for anyone else building on Linux. Thoughts?
> - Brian Gesiak
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