-Z gcc-ld=lld fails again

[tschuett]

I tried this code:

RUSTFLAGS='-Z gcc-ld=lld' cargo +nightly build --release

I expected to see this happen: it builds my crate.

Instead, this happened:

 = note: rust-lld: error: library not found for -lcrt1.10.6.o
          clang: error: linker command failed with exit code 1 (use -v to see invocation)

Meta

rustc --version --verbose:

rustc +nightly --version --verbose
rustc 1.65.0-nightly (1120c5e01 2022-09-08)
binary: rustc
commit-hash: 1120c5e01df508de64fe6642f22fadeb574afd6d
commit-date: 2022-09-08
host: x86_64-apple-darwin
release: 1.65.0-nightly
LLVM version: 15.0.0

I found in the invocation of cc

nightly-x86_64-apple-darwin/lib/rustlib/x86_64-apple-darwin/bin/gcc-ld" "-fuse-ld=lld" "--target=x86_64-apple-macosx10.7.0"

> clang --version
Apple clang version 13.1.6 (clang-1316.0.21.2.5)
Target: x86_64-apple-darwin21.6.0
Thread model: posix
InstalledDir: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin
> xcrun --sdk macosx --show-sdk-path
/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX12.3.sdk
> cc --print-target-triple
x86_64-apple-darwin21.6.0

Backtrace

<backtrace>

See #101504 (comment).

[tschuett]

#100200 introduced the target parameter

[lqd]

I managed to find an old x64 mac, Xcode 13 on OS 11.6.1, and can reproduce the issue there, so I'll try to look into it.

[tschuett]

>  find /Applications/Xcode.app/Contents/Developer/Platforms -name crt1.10.6.o
/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk/usr/lib/crt1.10.6.o

There is a crt1.10.6.o file on my system, but it is not a library.

[lqd]

nightly-2022-09-02 does not reproduce the issue, so it may be a different change from #100200 which landed in the following nightly (in particular the check about the ld flavor; which may need to also check for the ld64 one).

On aarch64-apple-darwin, the LLVM target is arm64-apple-macosx11.0.0, a lot more recent than the one on x64, so maybe that's why it currently works there.

[lqd]

So removing the --target argument fixes it for me on the x64 machine: it manages to use rust-lld 15.0.0.

On this osx/sdk/etc, clang does find gcc-ld/ld64.lld without the --target mentioned in #97402 (comment).

(Similarly, on the aarch64, it still works and finds ld64.lld without that argument)

I'll make a PR soon.

[Wyvern]

Any progress on it? Nightly build 2022-09-13 still reproduce the problem.