Wire rust_objcopy into the generated sysroot action inputs#3972
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UebelAndre merged 1 commit intobazelbuild:mainfrom Apr 16, 2026
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bazelbuild#3727 added a `rust_objcopy` attribute to `rust_toolchain`, a separate `rust-objcopy` filegroup in the compiler repo BUILD, and automatic opt-in for Rust 1.84+/recent nightlies. But the glue to turn that attribute into a real action input is missing: `ctx.file.rust_objcopy` is stashed on ToolchainInfo and never used again. It never flows through `_generate_sysroot` into `direct_files`, so it doesn't land in `toolchain.all_files` and isn't declared as an input to the Rustc action. On Linux/macOS with symlink-based sandboxing this is masked — rustc happens to see the neighboring file in the unsandboxed rules_rust external repo. Under remote execution, Windows (file-copy sandbox), or stricter local sandboxes, rustc invokes `rust-objcopy` and fails with: error: unable to run `rust-objcopy`: No such file or directory Thread: bazelbuild#3307 Fix: mirror the `linker` handling — symlink `rust_objcopy` into the generated sysroot at its sibling-of-rustc path (`lib/rustlib/<triple>/bin/rust-objcopy`, which is where rustc looks) and add the symlink to `direct_files` so it joins `all_files` and becomes a declared Rustc action input. Verified by: - Patched rules_rust via `local_path_override` in a minimal smoke workspace using rustc 1.93.0, aarch64-apple-darwin. - `bazel build -c opt //:hello` succeeds (regression: opt-mode process_wrapper uses `-Cstrip=debuginfo`, which invokes rust-objcopy). - `bazel aquery 'mnemonic("Rustc", //:hello)'` now lists the sysroot rust-objcopy symlink as a declared input (was absent before).
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Summary
#3727 added a
rust_objcopyattribute torust_toolchain, a separaterust-objcopyfilegroup, and automatic opt-in for Rust 1.84+/recent nightlies. But the glue to turn that attribute into a real action input is missing:ctx.file.rust_objcopyis stashed onToolchainInfoand never used again. It never flows through_generate_sysrootintodirect_files, so it doesn't jointoolchain.all_filesand isn't declared as an input to the Rustc action.On Linux/macOS with symlink-based sandboxing this is masked — rustc happens to see the neighboring file in the unsandboxed
rules_rustexternal repo. Under remote execution, Windows (file-copy sandbox), or stricter local sandboxes, rustc invokesrust-objcopyand fails:Tracking: #3307.
Fix
Mirror the
linkerhandling in_generate_sysroot: symlinkrust_objcopyinto the sysroot atlib/rustlib/<triple>/bin/rust-objcopy(where rustc looks) and append it todirect_filesso it becomes a declared Rustc action input.Verification
Patched
rules_rustvialocal_path_overridein a minimal smoke workspace using rustc 1.93.0 on aarch64-apple-darwin:bazel build -c opt //:hellosucceeds (opt-modeprocess_wrapperuses-Cstrip=debuginfo, which invokes rust-objcopy).bazel aquery 'mnemonic("Rustc", //:hello)'now lists the sysrootrust-objcopysymlink as a declared input — it was absent before.Before: no
rust-objcopyentry in the Rustc action inputs.After:
bazel-out/.../rust_toolchain/lib/rustlib/aarch64-apple-darwin/bin/rust-objcopy.