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only specify --target by default for -Zgcc-ld=lld on wasm

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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.
This commit is contained in:
Rémy Rakic 2022-09-13 11:17:13 +02:00
parent d6f99e535a
commit 7770b06b06
1 changed files with 20 additions and 1 deletions
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21
compiler/rustc_codegen_ssa/src/back/link.rs
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@ -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));
}
}
}
}