From 7770b06b06efc4abda75e608e67044a0a344771e Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?R=C3=A9my=20Rakic?= Date: Tue, 13 Sep 2022 11:17:13 +0200 Subject: [PATCH] only specify --target by default for -Zgcc-ld=lld on wasm On macOS, it's not yet clear which cases of clang/OS/target/SDK version impact how to find ld/lld/rust-lld. The --target is not needed on our current targets with a vanilla config, but may be in some cases. Specifying it all the time breaks the 10.7+ targets on x64 macOS. We try to only specify it on macOS if the linker flavors are different, for possible cases of cross-compilation with `-Zgcc-ld=lld` but the expectation is that it should be passed manually when needed in these situations. --- compiler/rustc_codegen_ssa/src/back/link.rs | 21 ++++++++++++++++++++- 1 file changed, 20 insertions(+), 1 deletion(-) diff --git a/compiler/rustc_codegen_ssa/src/back/link.rs b/compiler/rustc_codegen_ssa/src/back/link.rs index edde1537b81e1..36f7e5954bf2a 100644 --- a/compiler/rustc_codegen_ssa/src/back/link.rs +++ b/compiler/rustc_codegen_ssa/src/back/link.rs @@ -2822,11 +2822,30 @@ fn add_gcc_ld_path(cmd: &mut dyn Linker, sess: &Session, flavor: LinkerFlavor) { // Implement the "linker flavor" part of -Zgcc-ld // by asking cc to use some kind of lld. cmd.arg("-fuse-ld=lld"); + if !flavor.is_gnu() { // Tell clang to use a non-default LLD flavor. // Gcc doesn't understand the target option, but we currently assume // that gcc is not used for Apple and Wasm targets (#97402). - cmd.arg(format!("--target={}", sess.target.llvm_target)); + // + // Note that we don't want to do that by default on macOS: e.g. passing a + // 10.7 target to LLVM works, but not to recent versions of clang/macOS, as + // shown in issue #101653 and the discussion in PR #101792. + // + // It could be required in some cases of cross-compiling with + // `-Zgcc-ld=lld`, but this is generally unspecified, and we don't know + // which specific versions of clang, macOS SDK, host and target OS + // combinations impact us here. + // + // So we do a simple first-approximation until we know more of what the + // Apple targets require (and which would be handled prior to hitting this + // `-Zgcc-ld=lld` codepath anyway), but the expectation is that until then + // this should be manually passed if needed. We specify the target when + // targeting a different linker flavor on macOS, and that's also always + // the case when targeting WASM. + if sess.target.linker_flavor != sess.host.linker_flavor { + cmd.arg(format!("--target={}", sess.target.llvm_target)); + } } } }