bootstrap: use target's LLVM libdir when cross-compiling - #162170
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`Cargo::cargo` adds LLVM's library search path to `rustflags` for `ToolRustcPrivate`/`Codegen` so that tools linking against compiler libraries can find `libLLVM`. However, it always queried `host_llvm_config()`, which resolves to the *host*'s `llvm-config` regardless of the requested `target`. When cross-compiling, this appends the host's LLVM libdir to the target's link flags, which can cause linking to fail. Only use `llvm-config --libdir` when `target` is the host. Otherwise, ensure the `Llvm` step for `target` and derive the libdir from its `root_dir()` instead of invoking `llvm-config`, since the resulting binary may not be executable on the host if it was built for a different target.
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| .to_owned() | ||
| } else { | ||
| let llvm_output = self.ensure(Llvm { target }); | ||
| llvm_output.root_dir().join("lib").to_string_lossy().into_owned() |
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Does this work also on macOS/Windows? That being said, it is surely better than passing the host LLVM libdir :)
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It seems to work on macOS/Windows, but I don't have an environment to verify it. Could we test it on CI?
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Cargo::cargoadds LLVM's library search path torustflagsforToolRustcPrivate/Codegenso that tools linking against compiler libraries can findlibLLVM. However, it always queriedhost_llvm_config(), which resolves to the host'sllvm-configregardless of the requestedtarget. When cross-compiling, this appends the host's LLVM libdir to the target's link flags, which can cause linking to fail.Only use
llvm-config --libdirwhentargetis the host. Otherwise, ensure theLlvmstep fortargetand derive the libdir from itsroot_dir()instead of invokingllvm-config, since the resulting binary may not be executable on the host if it was built for a different target.