Support distributed ThinLTO for Linux cdylibs - #55
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Preserve rustc export metadata and bundled native archives while letting the C++ toolchain own ThinLTO backends and the shared-library link. Forward PyO3 CcInfo and keep opaque Cargo native objects outside distributed LTO. Assisted-by: OpenAI Codex
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Linux cdylibs currently use rustc-owned linking even when the C++
thin_ltofeature is enabled. Route them throughcc_common.linkwhilepreserving rustc's ELF export script, symbol roots, and bundled native
archives. Keep the existing paths for other operating systems.
Forward
CcInfothrough the PyO3 toolchain adapters so the separate linkreceives their inputs. Keep Cargo build-script C/C++ compilation outside
ThinLTO because opaque archive members have no Bazel backend actions.
The existing one-codegen-unit-per-crate distributed model is unchanged.
This is a draft: native bitcode passed through build scripts without
CcInforemains unsupported. Custom native linker arguments and dynamicnative dependencies need further coverage before general enablement.
All 21 focused LTO and process-wrapper tests pass on the rebased source,
as does the new runtime fixture with normal linking. The LLVM runtime
fixture is blocked while building process_wrapper because
the toolchain cannot find
-lgcc_s. Earlier Linux integration probescovered dependency C exports, native archives, allocation, and Python
extension loading. Buildifier formatting passes; its lint diagnostics are
unchanged from main.