emerge doesn't rebuild rust (1.48.0) when/after llvm (and clang) is rebuilt with a different USE=debug flag (ie. from "-debug" to "debug") therefore running "rustc" binary yields error: rustc: symbol lookup error: /usr/lib/rust/lib/librustc_driver-74fb860692868825.so: undefined symbol: _ZN4llvm24DisableABIBreakingChecksE, version LLVM_11 Reproducible: Always Steps to Reproduce: I recommend using FEATURES=binpkg-multi-instance so that you can quickly emerge --usepkg=y between the different USE versions for llvm(and clang) 1. emerge llvm and clang with USE=-debug (ie. DISabled "debug" use flag) (clang needs to be emerged too otherwise emerging llvm won't be allowed if the "debug" use flag differs between llvm and clang, apparently) sys-devel/llvm-11.0.0 USE="libffi ncurses -debug -doc -exegesis -gold -libedit -test -xar -xml -z3" sys-devel/clang-11.0.0 USE="static-analyzer -debug -default-compiler-rt -default-libcxx -default-lld -doc -test -xml" 2. emerge rust dev-lang/rust-1.48.0 USE="clippy nightly parallel-compiler rls rustfmt system-bootstrap system-llvm -debug (-doc) -libressl (-miri) -test -wasm" 3. run "rustc -Vv" to see that it does work: # rustc -vV rustc 1.48.0-nightly binary: rustc commit-hash: unknown commit-date: unknown host: x86_64-unknown-linux-gnu release: 1.48.0-nightly LLVM version: 11.0 4. now re-emerge llvm and clang with "USE=debug" (ie. enabled "debug" use flag) but don't also (manually) re-emerge rust! 5. now you can run "rustc -vV" to see it's broken: # rustc -vV rustc: symbol lookup error: /usr/lib/rust/lib/librustc_driver-74fb860692868825.so: undefined symbol: _ZN4llvm24DisableABIBreakingChecksE, version LLVM_11 6. you can try to see if emerge wants to re-emerge rust, by running: emerge --verbose --tree --deep --with-bdeps=y --changed-use --newuse --ask --complete-graph=y --changed-deps=y --update --usepkg=y --binpkg-respect-use=y --binpkg-changed-deps=y --nospinner --backtrack=300 @world nothing happens. 7. now you can try to recompile rust (somehow) to make it work with the new llvm. or, you can re-emerge llvm and clang with the USE=-debug from step 1 and then step5 will work like step3 again :) Maybe rust-bin needs to be emerged? don't know... Exception: no cargo executable found at `/bin/cargo` * ERROR: dev-lang/rust-1.48.0::localrepo failed (compile phase): * (no error message) Actual Results: oh.. uhm.. Expected Results: maybe: emerge will want to somehow also re-emerge rust when llvm gets emerged with different USE=debug setting
If required sounds like would need bug #680496, but rust's system-bootstrap situation may complicate things even if that was implemented.
I seem to have forgotten to emphasize the obvious, rust is built with USE=system-llvm seems important. I haven't tried with USE=-system-llvm But if you want me to try, let me know.
