How to find LLD with old versions of gcc? · Issue #97402 · rust-lang/rust (original) (raw)

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This issue is related to stabilizing use of LLD from rustc and/or making it default - rust-lang/compiler-team#510, #39915.

GCC and Clang have several ways to specify linker.

-B directory, you specify a search directory, then the compiler finds a file named ld in it an uses it as a linker.
This is the old way working on all versions of GCC and Clang that we want to support (?).
-fuse-ld=bfd|gold|lld|mold limited to 4 well-known linker names, you specify the name, then the compiler finds a file named ld.name in its search directories.
This is a somewhat new way, the well-known name -fuse-ld=lld works in Clang, and in GCC since 2018 (which GCC version?).
-fuse-ld=/absolute/path/to/lld, where you specify the full linker path.
This doesn't work with GCC, and worked with Clang since 2016, but is now deprecated in favor of --ld-path.
--ld-path=/absolute/path/to/lld, where you specify the full linker path.
This doesn't work with GCC, and works with Clang since 2021.

rustc needs to tell C compiler to use LLD in two modes

"Self-contained" mode when we need to find the LLD shipped with rustc.
This mode always uses -B directory right now (after Simplify implementation of -Z gcc-ld #97375) just because it's simple to do, but it also means that old compilers are supported.
Mode in which we should find system-provided LLD.
QUESTIONS:
- How should we do it?
- Do we care about older GCC versions that don't support -fuse-ld=lld?