Description
Building the Rust compiler for Fuchsia fails with an error when building libunwind since . I don't have a fully minimal set of build steps (actual steps are documented in https://fuchsia.dev/fuchsia-src/development/build/rust_toolchain?hl=en), but one relevant piece of the config.toml is that we set llvm-libunwind = "in-tree"
When running x.py the build fails with
Building stage2 std artifacts (x86_64-unknown-linux-gnu -> aarch64-fuchsia)
Compiling cc v1.0.69
Compiling core v0.0.0 (/b/s/w/ir/x/w/fuchsia-third_party-rust/library/core)
Compiling libc v0.2.116
Compiling memchr v2.4.1
Compiling std v0.0.0 (/b/s/w/ir/x/w/fuchsia-third_party-rust/library/std)
Compiling compiler_builtins v0.1.70
Compiling unwind v0.0.0 (/b/s/w/ir/x/w/fuchsia-third_party-rust/library/unwind)
Compiling profiler_builtins v0.0.0 (/b/s/w/ir/x/w/fuchsia-third_party-rust/library/profiler_builtins)
Compiling rustc-std-workspace-core v1.99.0 (/b/s/w/ir/x/w/fuchsia-third_party-rust/library/rustc-std-workspace-core)
Compiling alloc v0.0.0 (/b/s/w/ir/x/w/fuchsia-third_party-rust/library/alloc)
Compiling cfg-if v0.1.10
Compiling adler v0.2.3
Compiling rustc-demangle v0.1.21
error: overriding linking modifiers from command line is not supported
--> library/unwind/src/libunwind.rs:96:1
|
96 | / extern "C-unwind" {
97 | | pub fn _Unwind_Resume(exception: *mut _Unwind_Exception) -> !;
98 | | }
| |_^
This happens building the Rust compiler since b75f384 was merged, and does not happen on any commit prior to that. Any newer commit can also be made to work by just reverting 1004783 so this seems to be caused by #93901
Running x.py -v shows
"/home/adanis/test_rust_build/fuchsia-build/x86_64-unknown-linux-gnu/stage2/bin/rustc" "--crate-name" "unwind" "--edition=2021" "library/unwind/src/lib.rs" "--error-format=json" "--json=diagnostic-rendered-ansi,artifacts,future-incompat" "--crate-type" "lib" "--emit=dep-info,metadata,link" "-C" "opt-level=3" "-C" "embed-bitcode=no" "-C" "codegen-units=1" "-C" "debuginfo=2" "--cfg" "feature=\"llvm-libunwind\"" "-C" "metadata=7bb16b80dd794b17" "-C" "extra-filename=-7bb16b80dd794b17" "--out-dir" "/home/adanis/test_rust_build/fuchsia-build/x86_64-unknown-linux-gnu/stage2-std/aarch64-fuchsia/release/deps" "--target" "aarch64-fuchsia" "-L" "dependency=/home/adanis/test_rust_build/fuchsia-build/x86_64-unknown-linux-gnu/stage2-std/aarch64-fuchsia/release/deps" "-L" "dependency=/home/adanis/test_rust_build/fuchsia-build/x86_64-unknown-linux-gnu/stage2-std/release/deps" "--extern" "cfg_if=/home/adanis/test_rust_build/fuchsia-build/x86_64-unknown-linux-gnu/stage2-std/aarch64-fuchsia/release/deps/libcfg_if-9d1324248f6fe0fb.rmeta" "--extern" "compiler_builtins=/home/adanis/test_rust_build/fuchsia-build/x86_64-unknown-linux-gnu/stage2-std/aarch64-fuchsia/release/deps/libcompiler_builtins-f51c9f6078312b82.rmeta" "--extern" "core=/home/adanis/test_rust_build/fuchsia-build/x86_64-unknown-linux-gnu/stage2-std/aarch64-fuchsia/release/deps/libcore-2599389f0623040c.rmeta" "--extern" "libc=/home/adanis/test_rust_build/fuchsia-build/x86_64-unknown-linux-gnu/stage2-std/aarch64-fuchsia/release/deps/liblibc-91b3aeedfc9688eb.rmeta" "--remap-path-prefix" "/home/adanis/test_rust_build=rustlib/src/rust" "-C" "link-arg=--sysroot=/home/adanis/test_rust_build/cipd/sdk/arch/arm64/sysroot" "-Lnative=/home/adanis/test_rust_build/cipd/sdk/arch/arm64/sysroot/lib" "-Lnative=/home/adanis/test_rust_build/cipd/sdk/arch/arm64/lib" "-C" "panic=abort" "-C" "force-unwind-tables=yes" "-Csymbol-mangling-version=legacy" "-Zunstable-options" "-Zunstable-options" "--check-cfg=names()" "--check-cfg=values()" "--check-cfg=values(bootstrap)" "--check-cfg=values(stdarch_intel_sde)" "--check-cfg=values(no_fp_fmt_parse)" "--check-cfg=values(no_global_oom_handling)" "--check-cfg=values(freebsd12)" "--check-cfg=values(backtrace_in_libstd)" "--check-cfg=values(target_env,\"libnx\")" "--check-cfg=values(target_os,\"watchos\")" "--check-cfg=values(target_arch,\"asmjs\",\"spirv\",\"nvptx\",\"nvptx64\",\"le32\",\"xtensa\")" "--check-cfg=values(dont_compile_me)" "-Zmacro-backtrace" "-Zsave-analysis" "-Cprefer-dynamic" "-Cembed-bitcode=yes" "-Zcrate-attr=doc(html_root_url=\"https://doc.rust-lang.org/nightly/\")" "-Z" "binary-dep-depinfo" "-l" "unwind" "-L" "native=/home/adanis/test_rust_build/fuchsia-build/x86_64-unknown-linux-gnu/stage2-std/aarch64-fuchsia/release/build/compiler_builtins-73408b68b88664ba/out" "-Wrust_2018_idioms" "-Wunused_lifetimes" "-Wsemicolon_in_expressions_from_macros" "-Dwarnings" "--sysroot" "/home/adanis/test_rust_build/fuchsia-build/x86_64-unknown-linux-gnu/stage2" "-Z" "force-unstable-if-unmarked"
And the main thing of interest there is the -l unwind that for a Fuchsia build with in-tree libunwind does not match the modifiers in libunwind and so the error therefore occurs.
I can manually make that invocation work by either dropping the -l unwind or adding the modifier via -l unwind,-bundle, but I don't know how to do that as part of the actual build so I'm not sure if that is the last issue.
From my inexperienced perspective linking against libunwind when building libunwind seems incorrect, but perhaps that's correct and there's something else going wrong?