rust-lang · lqd · Mar 17, 2025 · Mar 18, 2025 · Mar 19, 2025 · Mar 19, 2025
diff --git a/compiler/rustc_codegen_ssa/src/back/link.rs b/compiler/rustc_codegen_ssa/src/back/link.rs
@@ -1395,7 +1395,7 @@ pub fn linker_and_flavor(sess: &Session) -> (PathBuf, LinkerFlavor) {
        }
    }

-    let features = sess.opts.unstable_opts.linker_features;
+    let features = sess.opts.cg.linker_features;

    // linker and linker flavor specified via command line have precedence over what the target
    // specification specifies

diff --git a/compiler/rustc_session/src/config.rs b/compiler/rustc_session/src/config.rs
@@ -368,12 +368,40 @@ impl LinkSelfContained {
    }

    /// To help checking CLI usage while some of the values are unstable: returns whether one of the
-    /// components was set individually. This would also require the `-Zunstable-options` flag, to
-    /// be allowed.
-    fn are_unstable_variants_set(&self) -> bool {
-        let any_component_set =
-            !self.enabled_components.is_empty() || !self.disabled_components.is_empty();
-        self.explicitly_set.is_none() && any_component_set
+    /// unstable components was set individually, for the given `TargetTuple`. This would also
+    /// require the `-Zunstable-options` flag, to be allowed.
+    fn check_unstable_variants(&self, target_tuple: &TargetTuple) -> Result<(), String> {
+        if self.explicitly_set.is_some() {
+            return Ok(());
+        }
+
+        // `-C link-self-contained=[-+]linker` is only stable on x64 linux.
+        let check_linker = |components: LinkSelfContainedComponents, polarity: &str| {
+            let has_linker = components.is_linker_enabled();
+            if has_linker && target_tuple.tuple() != "x86_64-unknown-linux-gnu" {
+                return Err(format!(
+                    "`-C link-self-contained={polarity}linker` is unstable on the `{target_tuple}` \
+                    target. The `-Z unstable-options` flag must also be passed to use it on this target",
+                ));
+            }
+            Ok(())
+        };
+        check_linker(self.enabled_components, "+")?;
+        check_linker(self.disabled_components, "-")?;
+
+        // Since only the linker component is stable, any other component used is unstable, and
+        // that's an error.
+        let unstable_enabled = self.enabled_components - LinkSelfContainedComponents::LINKER;
+        let unstable_disabled = self.disabled_components - LinkSelfContainedComponents::LINKER;
+        if !unstable_enabled.union(unstable_disabled).is_empty() {
+            return Err(String::from(
+                "only `-C link-self-contained` values `y`/`yes`/`on`/`n`/`no`/`off`/`-linker`\
+                /`+linker` are stable, the `-Z unstable-options` flag must also be passed to use \
+                the unstable values",
+            ));
+        }
+
+        Ok(())
    }

    /// Returns whether the self-contained linker component was enabled on the CLI, using the
@@ -400,7 +428,7 @@ impl LinkSelfContained {
    }
 }

-/// The different values that `-Z linker-features` can take on the CLI: a list of individually
+/// The different values that `-C linker-features` can take on the CLI: a list of individually
 /// enabled or disabled features used during linking.
 ///
 /// There is no need to enable or disable them in bulk. Each feature is fine-grained, and can be
@@ -440,6 +468,44 @@ impl LinkerFeaturesCli {
            _ => None,
        }
    }
+
+    /// When *not* using `-Z unstable-options` on the CLI, ensure only stable linker features are
+    /// used, for the given `TargetTuple`. Returns `Ok` if no unstable variants are used.
+    /// The caller should ensure that e.g. `nightly_options::is_unstable_enabled()`
+    /// returns false.
+    pub(crate) fn check_unstable_variants(&self, target_tuple: &TargetTuple) -> Result<(), String> {
+        // `-C linker-features=[-+]lld` is only stable on x64 linux.
+        let check_lld = |features: LinkerFeatures, polarity: &str| {
+            let has_lld = features.is_lld_enabled();
+            if has_lld && target_tuple.tuple() != "x86_64-unknown-linux-gnu" {
+                return Err(format!(
+                    "`-C linker-features={polarity}lld` is unstable on the `{target_tuple}` \
+                    target. The `-Z unstable-options` flag must also be passed to use it on this target",
+                ));
+            }
+            Ok(())
+        };
+        check_lld(self.enabled, "+")?;
+        check_lld(self.disabled, "-")?;
+
+        // Since only lld is stable, any non-lld feature used is unstable, and that's an error.
+        let unstable_enabled = self.enabled - LinkerFeatures::LLD;
+        let unstable_disabled = self.disabled - LinkerFeatures::LLD;
+        if !unstable_enabled.union(unstable_disabled).is_empty() {
+            let unstable_features: Vec<_> = unstable_enabled
+                .iter()
+                .map(|f| format!("+{}", f.as_str().unwrap()))
+                .chain(unstable_disabled.iter().map(|f| format!("-{}", f.as_str().unwrap())))
+                .collect();
+            return Err(format!(
+                "the requested `-C linker-features={}` are unstable, and also require the \
+                `-Z unstable-options` flag to be usable",
+                unstable_features.join(","),
+            ));
+        }
+
+        Ok(())
+    }
 }

 /// Used with `-Z assert-incr-state`.
@@ -2601,26 +2667,21 @@ pub fn build_session_options(early_dcx: &mut EarlyDiagCtxt, matches: &getopts::M
        }
    }

-    if !nightly_options::is_unstable_enabled(matches)
-        && cg.force_frame_pointers == FramePointer::NonLeaf
-    {
+    let unstable_options_enabled = nightly_options::is_unstable_enabled(matches);
+    if !unstable_options_enabled && cg.force_frame_pointers == FramePointer::NonLeaf {
        early_dcx.early_fatal(
            "`-Cforce-frame-pointers=non-leaf` or `always` also requires `-Zunstable-options` \
                and a nightly compiler",
        )
    }

-    // For testing purposes, until we have more feedback about these options: ensure `-Z
-    // unstable-options` is required when using the unstable `-C link-self-contained` and `-C
-    // linker-flavor` options.
-    if !nightly_options::is_unstable_enabled(matches) {
-        let uses_unstable_self_contained_option =
-            cg.link_self_contained.are_unstable_variants_set();
-        if uses_unstable_self_contained_option {
-            early_dcx.early_fatal(
-                "only `-C link-self-contained` values `y`/`yes`/`on`/`n`/`no`/`off` are stable, \
-                the `-Z unstable-options` flag must also be passed to use the unstable values",
-            );
+    let target_triple = parse_target_triple(early_dcx, matches);
+
+    // Ensure `-Z unstable-options` is required when using the unstable `-C link-self-contained` and
+    // `-C linker-flavor` options.
+    if !unstable_options_enabled {
+        if let Err(error) = cg.link_self_contained.check_unstable_variants(&target_triple) {
+            early_dcx.early_fatal(error);
        }

        if let Some(flavor) = cg.linker_flavor {
@@ -2652,7 +2713,6 @@ pub fn build_session_options(early_dcx: &mut EarlyDiagCtxt, matches: &getopts::M
    let cg = cg;

    let sysroot_opt = matches.opt_str("sysroot").map(|m| PathBuf::from(&m));
-    let target_triple = parse_target_triple(early_dcx, matches);
    let opt_level = parse_opt_level(early_dcx, matches, &cg);
    // The `-g` and `-C debuginfo` flags specify the same setting, so we want to be able
    // to use them interchangeably. See the note above (regarding `-O` and `-C opt-level`)
@@ -2661,6 +2721,12 @@ pub fn build_session_options(early_dcx: &mut EarlyDiagCtxt, matches: &getopts::M
    let debuginfo = select_debuginfo(matches, &cg);
    let debuginfo_compression = unstable_opts.debuginfo_compression;

+    if !unstable_options_enabled {
+        if let Err(error) = cg.linker_features.check_unstable_variants(&target_triple) {
+            early_dcx.early_fatal(error);
+        }
+    }
+
    let crate_name = matches.opt_str("crate-name");
    let unstable_features = UnstableFeatures::from_environment(crate_name.as_deref());
    // Parse any `-l` flags, which link to native libraries.

diff --git a/compiler/rustc_session/src/options.rs b/compiler/rustc_session/src/options.rs
@@ -1994,6 +1994,8 @@ options! {
        on a C toolchain or linker installed in the system"),
    linker: Option<PathBuf> = (None, parse_opt_pathbuf, [UNTRACKED],
        "system linker to link outputs with"),
+    linker_features: LinkerFeaturesCli = (LinkerFeaturesCli::default(), parse_linker_features, [UNTRACKED],
+        "a comma-separated list of linker features to enable (+) or disable (-): `lld`"),
    linker_flavor: Option<LinkerFlavorCli> = (None, parse_linker_flavor, [UNTRACKED],
        "linker flavor"),
    linker_plugin_lto: LinkerPluginLto = (LinkerPluginLto::Disabled,
@@ -2284,8 +2286,6 @@ options! {
        "link native libraries in the linker invocation (default: yes)"),
    link_only: bool = (false, parse_bool, [TRACKED],
        "link the `.rlink` file generated by `-Z no-link` (default: no)"),
-    linker_features: LinkerFeaturesCli = (LinkerFeaturesCli::default(), parse_linker_features, [UNTRACKED],
-        "a comma-separated list of linker features to enable (+) or disable (-): `lld`"),
    lint_llvm_ir: bool = (false, parse_bool, [TRACKED],
        "lint LLVM IR (default: no)"),
    lint_mir: bool = (false, parse_bool, [UNTRACKED],

diff --git a/compiler/rustc_target/src/spec/mod.rs b/compiler/rustc_target/src/spec/mod.rs
@@ -722,7 +722,7 @@ impl ToJson for LinkSelfContainedComponents {
 }

 bitflags::bitflags! {
-    /// The `-Z linker-features` components that can individually be enabled or disabled.
+    /// The `-C linker-features` components that can individually be enabled or disabled.
    ///
    /// They are feature flags intended to be a more flexible mechanism than linker flavors, and
    /// also to prevent a combinatorial explosion of flavors whenever a new linker feature is
@@ -753,7 +753,7 @@ bitflags::bitflags! {
 rustc_data_structures::external_bitflags_debug! { LinkerFeatures }

 impl LinkerFeatures {
-    /// Parses a single `-Z linker-features` well-known feature, not a set of flags.
+    /// Parses a single `-C linker-features` well-known feature, not a set of flags.
    pub fn from_str(s: &str) -> Option<LinkerFeatures> {
        Some(match s {
            "cc" => LinkerFeatures::CC,
@@ -762,6 +762,17 @@ impl LinkerFeatures {
        })
    }

+    /// Return the linker feature name, as would be passed on the CLI.
+    ///
+    /// Returns `None` if the bitflags aren't a singular component (but a mix of multiple flags).
+    pub fn as_str(self) -> Option<&'static str> {
+        Some(match self {
+            LinkerFeatures::CC => "cc",
+            LinkerFeatures::LLD => "lld",
+            _ => return None,
+        })
+    }
+
    /// Returns whether the `lld` linker feature is enabled.
    pub fn is_lld_enabled(self) -> bool {
        self.contains(LinkerFeatures::LLD)

diff --git a/src/bootstrap/src/core/build_steps/compile.rs b/src/bootstrap/src/core/build_steps/compile.rs
@@ -1340,9 +1340,7 @@ pub fn rustc_cargo_env(
    }

    // Enable rustc's env var for `rust-lld` when requested.
-    if builder.config.lld_enabled
-        && (builder.config.channel == "dev" || builder.config.channel == "nightly")
-    {
+    if builder.config.lld_enabled {
        cargo.env("CFG_USE_SELF_CONTAINED_LINKER", "1");
    }


diff --git a/src/bootstrap/src/core/build_steps/test.rs b/src/bootstrap/src/core/build_steps/test.rs
@@ -262,7 +262,13 @@ impl Step for Cargotest {
            .args(builder.config.test_args())
            .env("RUSTC", builder.rustc(compiler))
            .env("RUSTDOC", builder.rustdoc(compiler));
-        add_rustdoc_cargo_linker_args(&mut cmd, builder, compiler.host, LldThreads::No);
+        add_rustdoc_cargo_linker_args(
+            &mut cmd,
+            builder,
+            compiler.host,
+            LldThreads::No,
+            compiler.stage,
+        );
        cmd.delay_failure().run(builder);
    }
 }
@@ -857,7 +863,7 @@ impl Step for RustdocTheme {
            .env("CFG_RELEASE_CHANNEL", &builder.config.channel)
            .env("RUSTDOC_REAL", builder.rustdoc(self.compiler))
            .env("RUSTC_BOOTSTRAP", "1");
-        cmd.args(linker_args(builder, self.compiler.host, LldThreads::No));
+        cmd.args(linker_args(builder, self.compiler.host, LldThreads::No, self.compiler.stage));

        cmd.delay_failure().run(builder);
    }
@@ -1033,7 +1039,13 @@ impl Step for RustdocGUI {
        cmd.env("RUSTDOC", builder.rustdoc(self.compiler))
            .env("RUSTC", builder.rustc(self.compiler));

-        add_rustdoc_cargo_linker_args(&mut cmd, builder, self.compiler.host, LldThreads::No);
+        add_rustdoc_cargo_linker_args(
+            &mut cmd,
+            builder,
+            self.compiler.host,
+            LldThreads::No,
+            self.compiler.stage,
+        );

        for path in &builder.paths {
            if let Some(p) = helpers::is_valid_test_suite_arg(path, "tests/rustdoc-gui", builder) {
@@ -1802,7 +1814,7 @@ NOTE: if you're sure you want to do this, please open an issue as to why. In the
        }

        let mut hostflags = flags.clone();
-        hostflags.extend(linker_flags(builder, compiler.host, LldThreads::No));
+        hostflags.extend(linker_flags(builder, compiler.host, LldThreads::No, compiler.stage));

        let mut targetflags = flags;


diff --git a/src/bootstrap/src/core/builder/cargo.rs b/src/bootstrap/src/core/builder/cargo.rs
@@ -115,7 +115,7 @@ impl Cargo {
            // No need to configure the target linker for these command types.
            Kind::Clean | Kind::Check | Kind::Suggest | Kind::Format | Kind::Setup => {}
            _ => {
-                cargo.configure_linker(builder);
+                cargo.configure_linker(builder, mode);
            }
        }

@@ -206,7 +206,7 @@ impl Cargo {

    // FIXME(onur-ozkan): Add coverage to make sure modifications to this function
    // doesn't cause cache invalidations (e.g., #130108).
-    fn configure_linker(&mut self, builder: &Builder<'_>) -> &mut Cargo {
+    fn configure_linker(&mut self, builder: &Builder<'_>, mode: Mode) -> &mut Cargo {
        let target = self.target;
        let compiler = self.compiler;

@@ -261,7 +261,15 @@ impl Cargo {
            }
        }

-        for arg in linker_args(builder, compiler.host, LldThreads::Yes) {
+        // When determining flags for the host (build scripts/proc macros),
+        // we use the snapshot compiler when building `Mode::Std` tools, and
+        // the current compiler when building anything else.
+        // We need to determine the current stage here to pass proper linker args (e.g. -C vs -Z)
+        // to the compiler used to compile build scripts.
+        // This should stay synchronized with the [cargo] function.
+        let host_stage = if mode == Mode::Std { 0 } else { compiler.stage };
+
+        for arg in linker_args(builder, compiler.host, LldThreads::Yes, host_stage) {
            self.hostflags.arg(&arg);
        }

@@ -271,10 +279,10 @@ impl Cargo {
        }
        // We want to set -Clinker using Cargo, therefore we only call `linker_flags` and not
        // `linker_args` here.
-        for flag in linker_flags(builder, target, LldThreads::Yes) {
+        for flag in linker_flags(builder, target, LldThreads::Yes, compiler.stage) {
            self.rustflags.arg(&flag);
        }
-        for arg in linker_args(builder, target, LldThreads::Yes) {
+        for arg in linker_args(builder, target, LldThreads::Yes, compiler.stage) {
            self.rustdocflags.arg(&arg);
        }


diff --git a/src/bootstrap/src/core/builder/mod.rs b/src/bootstrap/src/core/builder/mod.rs
@@ -1481,7 +1481,7 @@ impl<'a> Builder<'a> {
            cmd.arg("-Dwarnings");
        }
        cmd.arg("-Znormalize-docs");
-        cmd.args(linker_args(self, compiler.host, LldThreads::Yes));
+        cmd.args(linker_args(self, compiler.host, LldThreads::Yes, compiler.stage));
        cmd
    }


diff --git a/src/bootstrap/src/core/config/config.rs b/src/bootstrap/src/core/config/config.rs
@@ -2451,7 +2451,6 @@ impl Config {
        // build our internal lld and use it as the default linker, by setting the `rust.lld` config
        // to true by default:
        // - on the `x86_64-unknown-linux-gnu` target
-        // - on the `dev` and `nightly` channels
        // - when building our in-tree llvm (i.e. the target has not set an `llvm-config`), so that
        //   we're also able to build the corresponding lld
        // - or when using an external llvm that's downloaded from CI, which also contains our prebuilt
@@ -2460,10 +2459,7 @@ impl Config {
        //   thus, disabled
        // - similarly, lld will not be built nor used by default when explicitly asked not to, e.g.
        //   when the config sets `rust.lld = false`
-        if config.build.triple == "x86_64-unknown-linux-gnu"
-            && config.hosts == [config.build]
-            && (config.channel == "dev" || config.channel == "nightly")
-        {
+        if config.build.triple == "x86_64-unknown-linux-gnu" && config.hosts == [config.build] {
            let no_llvm_config = config
                .target_config
                .get(&config.build)