Build problem Arch Linux

[neundorf]

Hi,

carbon sounds exciting, maybe I can even contribute....
I have no experience with bazel, so some pointers would be appreciated.

I'm trying to run the very first step: ld.lld: error: unable to find library -l:libunwind.a
I don't have a libunwind.a on my system. Is this really what ld.lld is looking for ?
In the meantime I have built in the meantime libunwind with --enable-static, so there is now a /usr/local/lib/libunwind.a, but the error message still appears.

clang is version 20.1.8.

Any pointers how to fix this issue ?

Here is the full output:

$ ./scripts/run_bazelisk.py run //toolchain -- help
INFO: Invocation ID: 78f4b26d-3ae7-42a2-8dd8-2a7eea79ec81
INFO: Analyzed target //toolchain:toolchain (0 packages loaded, 0 targets configured).
ERROR: /home/alex/.cache/bazel/_bazel_alex/8e029023b5566a89b4eb15c88ac2cf0b/external/+llvm_project+llvm-project/llvm/BUILD.bazel:683:10: Linking external/+llvm_project+llvm-project/llvm/llvm-min-tblgen [for tool] failed: (Exit 1): clang++ failed: error executing CppLink command (from target @@+llvm_project+llvm-project//llvm:llvm-min-tblgen) /usr/bin/clang++ @bazel-out/k8-opt-exec-ST-d57f47055a04/bin/external/+llvm_project+llvm-project/llvm/llvm-min-tblgen-0.params

Use --sandbox_debug to see verbose messages from the sandbox and retain the sandbox build root for debugging
ld.lld: error: unable to find library -l:libunwind.a
ld.lld: error: unable to find library -l:libunwind.a
clang++: error: linker command failed with exit code 1 (use -v to see invocation)
Target //toolchain:carbon failed to build
Use --verbose_failures to see the command lines of failed build steps.
INFO: Elapsed time: 0.710s, Critical Path: 0.34s
INFO: 17 processes: 4 action cache hit, 17 internal.
ERROR: Build did NOT complete successfully
ERROR: Build failed. Not running target
$ 

Thanks
Alex

[neundorf]

Ok, I found out a bit more. So this is inside some sandbox.
It fails when trying to link llvm-min-tblgen.

Below are the options in the llvm-min-tblgen-0.params file.
How does this sandboxing work ?
Does it search (bazel ?) for libunwind on my "normal" system, or somewhere in those sandbox directories ? If so, in which ?

-no-canonical-prefixes
-fcolor-diagnostics
-std=c++20
-stdlib=libc++
-Wl,-S
-fuse-ld=lld
-stdlib=libc++
-unwindlib=libunwind
-static-libstdc++
-static-libgcc
-rtlib=compiler-rt
-L/usr/bin/../lib
-lpthread
-l:libc++abi.a

[neundorf]

It looks like I got that part working.
I downloaded llvm 20.1.8 sources from github, and built libunwind.a from there (using clang 20.1.8) , and put it into /usr/lib/, and this is now somehow picked up by bazel.