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linker: Remove special case for rust-lld in detect_self_contained_mingw #149590

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Dec 3, 2025
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linker: Remove special case for rust-lld in detect_self_contained_mingw #149590

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4 changes: 0 additions & 4 deletions compiler/rustc_codegen_ssa/src/back/link.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1763,10 +1763,6 @@ fn link_output_kind(sess: &Session, crate_type: CrateType) -> LinkOutputKind {

// Returns true if linker is located within sysroot
fn detect_self_contained_mingw(sess: &Session, linker: &Path) -> bool {
// Assume `-C linker=rust-lld` as self-contained mode
if linker == Path::new("rust-lld") {
return true;
}
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@bjorn3 bjorn3 Dec 3, 2025

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Below only the sysroot from which we get the standard library is checked, not the fallback sysroot that rustc itself is contained in. rust-lld is likely to be contained only in the latter if the former is overriden.

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@mati865 mati865 Dec 3, 2025

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I'm fairly sure from my tests the sysroot would point at ~/.rustup/toolchains/<toolchain>.

If I read

rust/compiler/rustc_session/src/filesearch.rs

Line 190 in 8202d11

fn default_from_rustc_driver_dll() -> Result<PathBuf, String> {
right, it would indeed stirp all the subdirectories.

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@bjorn3 bjorn3 Dec 3, 2025 •
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The code below only strips sess.opts.sysroot.path(), which only returns the value explicitly passed to --sysroot if passed, only returning the fallback sysroot when it isn't passed.

rust/compiler/rustc_session/src/config.rs

Lines 1345 to 1348 in 8202d11

/// Return explicit sysroot if it was passed with `--sysroot`, or default sysroot otherwise.
pub fn path(&self) -> &Path {
self.explicit.as_deref().unwrap_or(&self.default)
}
You need sess.opts.sysroot.all_paths() to check both.

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@mati865 mati865 Dec 3, 2025

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Good point, but is --sysroot ever passed to rustc when building natively (host == target)?

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@bjorn3 bjorn3 Dec 3, 2025

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There are legitimate reasons to pass it when building natively. For example miri does for it's copy of the standard library that contains MIR for all functions (though it doesn't need a linker). cargo build -Zbuild-std doesn't use --sysroot currently, but I think it should pass --sysroot /dev/null or something like that to prevent accidentally picking up libraries from the sysroot. The only thing that leads to is lang item conflicts. --sysroot /dev/null would give nicer error messages.

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@mati865 mati865 Dec 3, 2025

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--sysroot /dev/null would break all cases of implicit self-contained detection, not just rust-lld. I mean, there is no obvious issue caused by this PR, not that there is no general issue with implicit self-contained detection.

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@bjorn3 bjorn3 Dec 3, 2025

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Right. The self-contained components are themself only looked up in --sysroot. Didn't think of that.

let linker_with_extension = if cfg!(windows) && linker.extension().is_none() {
linker.with_extension("exe")
} else {
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