Use lld by default on x86_64-unknown-linux-gnu stable

compiler/rustc_codegen_ssa/src/back/link.rs

@@ -1379,7 +1379,7 @@ 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
@@ -3327,35 +3327,6 @@ fn add_lld_args(
     // this, `wasm-component-ld`, which is overridden if this option is passed.
     if !sess.target.is_like_wasm {
         cmd.cc_arg("-fuse-ld=lld");
-
-        // On ELF platforms like at least x64 linux, GNU ld and LLD have opposite defaults on some
-        // section garbage-collection features. For example, the somewhat popular `linkme` crate and
-        // its dependents rely in practice on this difference: when using lld, they need `-z
-        // nostart-stop-gc` to prevent encapsulation symbols and sections from being
-        // garbage-collected.
-        //
-        // More information about all this can be found in:
-        // - https://maskray.me/blog/2021-01-31-metadata-sections-comdat-and-shf-link-order
-        // - https://lld.llvm.org/ELF/start-stop-gc
-        //
-        // So when using lld, we restore, for now, the traditional behavior to help migration, but
-        // will remove it in the future.
-        // Since this only disables an optimization, it shouldn't create issues, but is in theory
-        // slightly suboptimal. However, it:
-        // - doesn't have any visible impact on our benchmarks
-        // - reduces the need to disable lld for the crates that depend on this
-        //
-        // Note that lld can detect some cases where this difference is relied on, and emits a
-        // dedicated error to add this link arg. We could make use of this error to emit an FCW. As
-        // of writing this, we don't do it, because lld is already enabled by default on nightly
-        // without this mitigation: no working project would see the FCW, so we do this to help
-        // stabilization.
-        //
-        // FIXME: emit an FCW if linking fails due its absence, and then remove this link-arg in the
-        // future.
-        if sess.target.llvm_target == "x86_64-unknown-linux-gnu" {
-            cmd.link_arg("-znostart-stop-gc");
-        }
     }
 
     if !flavor.is_gnu() {

compiler/rustc_session/src/config.rs

@@ -370,12 +370,34 @@ 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 has_minus_linker = self.disabled_components.is_linker_enabled();
+        if has_minus_linker && target_tuple.tuple() != "x86_64-unknown-linux-gnu" {
+            return Err(format!(
+                "`-C link-self-contained=-linker` is unstable on the `{target_tuple}` \
+                    target. The `-Z unstable-options` flag must also be passed to use it on this target",
+            ));
+        }
+
+        // Any `+linker` or other component used is unstable, and that's an error.
+        let unstable_enabled = self.enabled_components;
+        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` \
+                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
@@ -402,7 +424,7 @@ 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
@@ -442,6 +464,39 @@ 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 has_minus_lld = self.disabled.is_lld_enabled();
+        if has_minus_lld && target_tuple.tuple() != "x86_64-unknown-linux-gnu" {
+            return Err(format!(
+                "`-C linker-features=-lld` is unstable on the `{target_tuple}` \
+                    target. The `-Z unstable-options` flag must also be passed to use it on this target",
+            ));
+        }
+
+        // Any `+lld` or non-lld feature used is unstable, and that's an error.
+        let unstable_enabled = self.enabled;
+        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!(
+                "`-C linker-features={}` is unstable, and also requires the \
+                `-Z unstable-options` flag to be used",
+                unstable_features.join(","),
+            ));
+        }
+
+        Ok(())
+    }
 }
 
 /// Used with `-Z assert-incr-state`.
@@ -2638,26 +2693,21 @@ 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 {
@@ -2697,7 +2747,6 @@ pub fn build_session_options(early_dcx: &mut EarlyDiagCtxt, matches: &getopts::M
 
     let cg = cg;
 
-    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`)
@@ -2706,6 +2755,12 @@ 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.

compiler/rustc_session/src/options.rs

@@ -2015,6 +2015,8 @@ 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,
@@ -2307,8 +2309,6 @@ 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],

compiler/rustc_target/src/spec/mod.rs

@@ -725,7 +725,7 @@ 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
@@ -756,7 +756,7 @@ 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,
@@ -765,6 +765,17 @@ 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)

src/bootstrap/src/core/build_steps/compile.rs

@@ -1369,9 +1369,7 @@ 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");
     }
 

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) {
@@ -1812,7 +1824,7 @@ 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;
 

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);
             }
         }
 
@@ -209,7 +209,7 @@ 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;
 
@@ -264,7 +264,12 @@ impl Cargo {
             }
         }
 
-        for arg in linker_args(builder, compiler.host, LldThreads::Yes) {
+        // We use the snapshot compiler when building host code (build scripts/proc macros) of
+        // `Mode::Std` tools, so we need to determine the current stage here to pass the proper
+        // linker args (e.g. -C vs -Z).
+        // 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);
         }
 
@@ -274,10 +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);
         }
 

src/bootstrap/src/core/builder/mod.rs

@@ -1599,7 +1599,7 @@ You have to build a stage1 compiler for `{}` first, and then use it to build a s
             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
     }
 

src/bootstrap/src/core/config/toml/rust.rs

@@ -619,7 +619,6 @@ 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
@@ -628,9 +627,7 @@ 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 self.host_target.triple == "x86_64-unknown-linux-gnu"
-            && self.hosts == [self.host_target]
-            && (self.channel == "dev" || self.channel == "nightly")
+        if self.host_target.triple == "x86_64-unknown-linux-gnu" && self.hosts == [self.host_target]
         {
             let no_llvm_config = self
                 .target_config

src/bootstrap/src/utils/helpers.rs

@@ -404,8 +404,9 @@ pub fn linker_args(
     builder: &Builder<'_>,
     target: TargetSelection,
     lld_threads: LldThreads,
+    stage: u32,
 ) -> Vec<String> {
-    let mut args = linker_flags(builder, target, lld_threads);
+    let mut args = linker_flags(builder, target, lld_threads, stage);
 
     if let Some(linker) = builder.linker(target) {
         args.push(format!("-Clinker={}", linker.display()));
@@ -420,19 +421,30 @@ pub fn linker_flags(
     builder: &Builder<'_>,
     target: TargetSelection,
     lld_threads: LldThreads,
+    stage: u32,
 ) -> Vec<String> {
     let mut args = vec![];
     if !builder.is_lld_direct_linker(target) && builder.config.lld_mode.is_used() {
         match builder.config.lld_mode {
             LldMode::External => {
-                args.push("-Zlinker-features=+lld".to_string());
-                // FIXME(kobzol): remove this flag once MCP510 gets stabilized
+                // cfg(bootstrap) - remove the stage 0 check after updating the bootstrap compiler:
+                // `-Clinker-features` has been stabilized.
+                if stage == 0 {
+                    args.push("-Zlinker-features=+lld".to_string());
+                } else {
+                    args.push("-Clinker-features=+lld".to_string());
+                }
                 args.push("-Zunstable-options".to_string());
             }
             LldMode::SelfContained => {
-                args.push("-Zlinker-features=+lld".to_string());
+                // cfg(bootstrap) - remove the stage 0 check after updating the bootstrap compiler:
+                // `-Clinker-features` has been stabilized.
+                if stage == 0 {
+                    args.push("-Zlinker-features=+lld".to_string());
+                } else {
+                    args.push("-Clinker-features=+lld".to_string());
+                }
                 args.push("-Clink-self-contained=+linker".to_string());
-                // FIXME(kobzol): remove this flag once MCP510 gets stabilized
                 args.push("-Zunstable-options".to_string());
             }
             LldMode::Unused => unreachable!(),
@@ -453,8 +465,9 @@ pub fn add_rustdoc_cargo_linker_args(
     builder: &Builder<'_>,
     target: TargetSelection,
     lld_threads: LldThreads,
+    stage: u32,
 ) {
-    let args = linker_args(builder, target, lld_threads);
+    let args = linker_args(builder, target, lld_threads, stage);
     let mut flags = cmd
         .get_envs()
         .find_map(|(k, v)| if k == OsStr::new("RUSTDOCFLAGS") { v } else { None })

src/doc/rustc/src/codegen-options/index.md

@@ -235,15 +235,33 @@ coverage measurement. Its use is not recommended.
 
 ## link-self-contained
 
-On `windows-gnu`, `linux-musl`, and `wasi` targets, this flag controls whether the
-linker will use libraries and objects shipped with Rust instead of those in the system.
-It takes one of the following values:
+This flag controls whether the linker will use libraries and objects shipped with Rust instead of
+those in the system.  It also controls which binary is used for the linker itself. This allows
+overriding cases when detection fails or the user wants to use shipped libraries.
+
+You can enable or disable the usage of any self-contained components using one of the following values:
 
 * no value: rustc will use heuristic to disable self-contained mode if system has necessary tools.
 * `y`, `yes`, `on`, `true`: use only libraries/objects shipped with Rust.
 * `n`, `no`, `off` or `false`: rely on the user or the linker to provide non-Rust libraries/objects.
 
-This allows overriding cases when detection fails or user wants to use shipped libraries.
+It is also possible to enable or disable specific self-contained components in a more granular way.
+You can pass a comma-separated list of self-contained components, individually enabled
+(`+component`) or disabled (`-component`).
+
+Currently, only the `linker` granular option is stabilized, and only on the `x86_64-unknown-linux-gnu` target:
+- `linker`: toggle the usage of self-contained linker binaries (linker, dlltool, and their necessary libraries)
+
+Note that only the `-linker` opt-out is stable on the `x86_64-unknown-linux-gnu` target: `+linker` is
+already the default on this target.
+
+#### Implementation notes
+
+On the `x86_64-unknown-linux-gnu` target, when using the default linker flavor (using `cc` as the
+linker driver) and linker features (to try using `lld`), `rustc` will try to use the self-contained
+linker by passing a `-B /path/to/sysroot/` link argument to the driver to find `rust-lld` in the
+sysroot. For backwards-compatibility, and to limit name and `PATH` collisions, this is done using a
+shim executable (the `lld-wrapper` tool) that forwards execution to the `rust-lld` executable itself.
 
 ## linker
 
@@ -256,6 +274,39 @@ Note that on Unix-like targets (for example, `*-unknown-linux-gnu` or `*-unknown
 the C compiler (for example `cc` or `clang`) is used as the "linker" here, serving as a linker driver.
 It will invoke the actual linker with all the necessary flags to be able to link against the system libraries like libc.
 
+## linker-features
+
+The `-Clinker-features` flag allows enabling or disabling specific features used during linking.
+
+These feature flags are a flexible extension mechanism that is complementary to linker flavors,
+designed to avoid the combinatorial explosion of having to create a new set of flavors for each
+linker feature we'd want to use.
+
+The flag accepts a comma-separated list of features, individually enabled (`+feature`) or disabled
+(`-feature`).
+
+Currently only one is stable, and only on the `x86_64-unknown-linux-gnu` target:
+- `lld`: to toggle trying to use the lld linker, either the system-installed binary, or the self-contained
+  `rust-lld` linker (via the [`-Clink-self-contained=+linker`](#link-self-contained) flag).
+
+For example, use:
+- `-Clinker-features=+lld` to opt into using the `lld` linker, when possible (see the Implementation notes below)
+- `-Clinker-features=-lld` to opt out instead, for targets where it is configured as the default linker
+
+Note that only the `-lld` opt-out is stable on the `x86_64-unknown-linux-gnu` target: `+lld` is
+already the default on this target.
+
+#### Implementation notes
+
+On the `x86_64-unknown-linux-gnu` target, when using the default linker flavor (using `cc` as the
+linker driver), `rustc` will try to use lld by passing a `-fuse-ld=lld` link argument to the driver.
+`rustc` will also try to detect if that _causes_ an error during linking (for example, if GCC is too
+old to understand the flag, and returns an error) and will then retry linking without this argument,
+as a fallback.
+
+If the user _also_ passes a `-Clink-arg=-fuse-ld=$value`, both will be given to the linker
+driver but the user's will be passed last, and would generally have priority over `rustc`'s.
+
 ## linker-flavor
 
 This flag controls the linker flavor used by `rustc`. If a linker is given with

src/doc/unstable-book/src/compiler-flags/codegen-options.md

@@ -51,10 +51,10 @@ instead of those in the system. The stable boolean values for this flag are coar
 - `mingw`: other MinGW libs and Windows import libs
 
 Out of the above self-contained linking components, `linker` is the only one currently implemented
-(beyond parsing the CLI options).
+(beyond parsing the CLI options) and stabilized.
 
 It refers to the LLD linker, built from the same LLVM revision used by rustc (named `rust-lld` to
 avoid naming conflicts), that is distributed via `rustup` with the compiler (and is used by default
-for the wasm targets). One can also opt-in to use it by combining this flag with an appropriate
-linker flavor: for example, `-Clinker-flavor=gnu-lld-cc -Clink-self-contained=+linker` will use the
-toolchain's `rust-lld` as the linker.
+for the wasm targets). One can also opt into using it by combining this flag with the appropriate
+linker feature: for example, `-Clinker-features=+lld -Clink-self-contained=+linker` will use the
+toolchain's `rust-lld` as the linker instead of the system's lld with `-Clinker-features=+lld` only.

src/tools/opt-dist/src/tests.rs

@@ -106,7 +106,10 @@ llvm-config = "{llvm_config}"
             "tests/incremental",
             "tests/mir-opt",
             "tests/pretty",
+            // Make sure that we don't use too new GLIBC symbols on x64
             "tests/run-make/glibc-symbols-x86_64-unknown-linux-gnu",
+            // Make sure that we use LLD by default on x64
+            "tests/run-make/rust-lld-x86_64-unknown-linux-gnu-dist",
             "tests/ui",
             "tests/crashes",
         ];

tests/run-make/compressed-debuginfo-zstd/rmake.rs

@@ -26,7 +26,7 @@ fn prepare_and_check<F: FnOnce(&mut Rustc) -> &mut Rustc>(to_find: &str, prepare
     run_in_tmpdir(|| {
         let mut rustc = Rustc::new();
         rustc
-            .arg("-Zlinker-features=+lld")
+            .arg("-Clinker-features=+lld")
             .arg("-Clink-self-contained=+linker")
             .arg("-Zunstable-options")
             .arg("-Cdebuginfo=full")

tests/run-make/rust-lld-custom-target/rmake.rs

@@ -23,7 +23,8 @@ fn main() {
         rustc()
             .crate_type("cdylib")
             .target("custom-target.json")
-            .arg("-Zlinker-features=-lld")
+            .arg("-Clinker-features=-lld")
+            .arg("-Zunstable-options")
             .input("lib.rs"),
     );
 }

tests/run-make/rust-lld-link-script-provide/rmake.rs

@@ -10,7 +10,7 @@ use run_make_support::rustc;
 fn main() {
     rustc()
         .input("main.rs")
-        .arg("-Zlinker-features=+lld")
+        .arg("-Clinker-features=+lld")
         .arg("-Clink-self-contained=+linker")
         .arg("-Zunstable-options")
         .link_arg("-Tscript.t")

tests/run-make/rust-lld-by-default-nightly/rmake.rs → tests/run-make/rust-lld-x86_64-unknown-linux-gnu-dist/rmake.rs

@@ -1,19 +1,16 @@
-// Ensure that rust-lld is used as the default linker on `x86_64-unknown-linux-gnu` on the nightly
-// channel, and that it can also be turned off with a CLI flag.
+// Ensure that rust-lld is used as the default linker on `x86_64-unknown-linux-gnu`
+// dist artifacts and that it can also be turned off with a CLI flag.
 
-//@ needs-rust-lld
-//@ ignore-beta
-//@ ignore-stable
+//@ only-dist
 //@ only-x86_64-unknown-linux-gnu
 
 use run_make_support::linker::{assert_rustc_doesnt_use_lld, assert_rustc_uses_lld};
 use run_make_support::rustc;
 
 fn main() {
-    // A regular compilation should use rust-lld by default. We'll check that by asking the linker
-    // to display its version number with a link-arg.
+    // A regular compilation should use rust-lld by default.
     assert_rustc_uses_lld(rustc().input("main.rs"));
 
     // But it can still be disabled by turning the linker feature off.
-    assert_rustc_doesnt_use_lld(rustc().arg("-Zlinker-features=-lld").input("main.rs"));
+    assert_rustc_doesnt_use_lld(rustc().arg("-Clinker-features=-lld").input("main.rs"));
 }

tests/run-make/rust-lld-x86_64-unknown-linux-gnu/main.rs

@@ -0,0 +1,5 @@
+// Test linking using `cc` with `rust-lld`, which is on by default on the x86_64-unknown-linux-gnu
+// target.
+// See https://github.com/rust-lang/compiler-team/issues/510 for more info
+
+fn main() {}

tests/run-make/rust-lld-x86_64-unknown-linux-gnu/rmake.rs

@@ -0,0 +1,20 @@
+// Ensure that rust-lld is used as the default linker on `x86_64-unknown-linux-gnu`
+// and that it can also be turned off with a CLI flag.
+//
+// This version of the test checks that LLD is used by default when LLD is enabled in the
+// toolchain. There is a separate test that checks that LLD is used for dist artifacts
+// unconditionally.
+
+//@ needs-rust-lld
+//@ only-x86_64-unknown-linux-gnu
+
+use run_make_support::linker::{assert_rustc_doesnt_use_lld, assert_rustc_uses_lld};
+use run_make_support::rustc;
+
+fn main() {
+    // A regular compilation should use rust-lld by default.
+    assert_rustc_uses_lld(rustc().input("main.rs"));
+
+    // But it can still be disabled by turning the linker feature off.
+    assert_rustc_doesnt_use_lld(rustc().arg("-Clinker-features=-lld").input("main.rs"));
+}

tests/run-make/rust-lld/rmake.rs

@@ -1,5 +1,5 @@
-// Test linking using `cc` with `rust-lld`, using the unstable CLI described in MCP 510
-// see https://github.com/rust-lang/compiler-team/issues/510 for more info
+// Test linking using `cc` with `rust-lld`, using the `-Clinker-features` and
+// `-Clink-self-contained` CLI flags.
 
 //@ needs-rust-lld
 //@ ignore-s390x lld does not yet support s390x as target
@@ -12,24 +12,26 @@ fn main() {
     // asking the linker to display its version number with a link-arg.
     assert_rustc_uses_lld(
         rustc()
-            .arg("-Zlinker-features=+lld")
+            .arg("-Clinker-features=+lld")
             .arg("-Clink-self-contained=+linker")
-            .arg("-Zunstable-options")
+            .arg("-Zunstable-options") // the opt-ins are unstable
             .input("main.rs"),
     );
 
     // It should not be used when we explicitly opt out of lld.
-    assert_rustc_doesnt_use_lld(rustc().arg("-Zlinker-features=-lld").input("main.rs"));
+    assert_rustc_doesnt_use_lld(
+        rustc().arg("-Clinker-features=-lld").arg("-Zunstable-options").input("main.rs"),
+    );
 
     // While we're here, also check that the last linker feature flag "wins" when passed multiple
     // times to rustc.
     assert_rustc_uses_lld(
         rustc()
             .arg("-Clink-self-contained=+linker")
             .arg("-Zunstable-options")
-            .arg("-Zlinker-features=-lld")
-            .arg("-Zlinker-features=+lld")
-            .arg("-Zlinker-features=-lld,+lld")
+            .arg("-Clinker-features=-lld")
+            .arg("-Clinker-features=+lld")
+            .arg("-Clinker-features=-lld,+lld")
             .input("main.rs"),
     );
 }

tests/ui/linking/link-self-contained-consistency.rs

@@ -1,7 +1,6 @@
 // Checks that self-contained linking components cannot be both enabled and disabled at the same
 // time on the CLI.
 
-//@ check-fail
 //@ revisions: one many
 //@ [one] compile-flags: -Clink-self-contained=-linker -Clink-self-contained=+linker -Zunstable-options
 //@ [many] compile-flags: -Clink-self-contained=+linker,+crto -Clink-self-contained=-linker,-crto -Zunstable-options

tests/ui/linking/link-self-contained-linker-disallowed.rs

@@ -0,0 +1,18 @@
+// Check that only `-C link-self-contained=-linker` is stable on x64 linux. Any other value or
+// target, needs `-Z unstable-options`.
+
+// ignore-tidy-linelength
+
+//@ revisions: unstable_target_positive unstable_target_negative unstable_positive
+//@ [unstable_target_negative] compile-flags: --target=x86_64-unknown-linux-musl -C link-self-contained=-linker --crate-type=rlib
+//@ [unstable_target_negative] needs-llvm-components: x86
+//@ [unstable_target_positive] compile-flags: --target=x86_64-unknown-linux-musl -C link-self-contained=+linker --crate-type=rlib
+//@ [unstable_target_positive] needs-llvm-components: x86
+//@ [unstable_positive] compile-flags: --target=x86_64-unknown-linux-gnu -C link-self-contained=+linker --crate-type=rlib
+//@ [unstable_positive] needs-llvm-components: x86
+
+#![feature(no_core)]
+#![no_core]
+
+//[unstable_target_negative]~? ERROR `-C link-self-contained=-linker` is unstable on the `x86_64-unknown-linux-musl` target
+//[unstable_target_positive,unstable_positive]~? ERROR only `-C link-self-contained` values `y`/`yes`/`on`/`n`/`no`/`off`/`-linker` are stable

tests/ui/linking/link-self-contained-linker-disallowed.unstable_positive.stderr

@@ -0,0 +1,2 @@
+error: only `-C link-self-contained` values `y`/`yes`/`on`/`n`/`no`/`off`/`-linker` are stable, the `-Z unstable-options` flag must also be passed to use the unstable values
+

tests/ui/linking/link-self-contained-linker-disallowed.unstable_target_negative.stderr

@@ -0,0 +1,2 @@
+error: `-C link-self-contained=-linker` is unstable on the `x86_64-unknown-linux-musl` target. The `-Z unstable-options` flag must also be passed to use it on this target
+

tests/ui/linking/link-self-contained-linker-disallowed.unstable_target_positive.stderr

@@ -0,0 +1,2 @@
+error: only `-C link-self-contained` values `y`/`yes`/`on`/`n`/`no`/`off`/`-linker` are stable, the `-Z unstable-options` flag must also be passed to use the unstable values
+

tests/ui/linking/link-self-contained-unstable.crto.stderr

@@ -0,0 +1,2 @@
+error: only `-C link-self-contained` values `y`/`yes`/`on`/`n`/`no`/`off`/`-linker` are stable, the `-Z unstable-options` flag must also be passed to use the unstable values
+

tests/ui/linking/link-self-contained-unstable.libc.stderr

@@ -0,0 +1,2 @@
+error: only `-C link-self-contained` values `y`/`yes`/`on`/`n`/`no`/`off`/`-linker` are stable, the `-Z unstable-options` flag must also be passed to use the unstable values
+

tests/ui/linking/link-self-contained-unstable.mingw.stderr

@@ -0,0 +1,2 @@
+error: only `-C link-self-contained` values `y`/`yes`/`on`/`n`/`no`/`off`/`-linker` are stable, the `-Z unstable-options` flag must also be passed to use the unstable values
+

tests/ui/linking/link-self-contained-unstable.rs

@@ -0,0 +1,13 @@
+// Checks that values for `-Clink-self-contained` other than the blanket enable/disable and
+// `-linker` require `-Zunstable-options`.
+
+//@ revisions: crto libc unwind sanitizers mingw
+//@ [crto] compile-flags: -Clink-self-contained=+crto
+//@ [libc] compile-flags: -Clink-self-contained=-libc
+//@ [unwind] compile-flags: -Clink-self-contained=+unwind
+//@ [sanitizers] compile-flags: -Clink-self-contained=-sanitizers
+//@ [mingw] compile-flags: -Clink-self-contained=+mingw
+
+fn main() {}
+
+//~? ERROR only `-C link-self-contained` values `y`/`yes`/`on`/`n`/`no`/`off`/`-linker` are stable

tests/ui/linking/link-self-contained-unstable.sanitizers.stderr

@@ -0,0 +1,2 @@
+error: only `-C link-self-contained` values `y`/`yes`/`on`/`n`/`no`/`off`/`-linker` are stable, the `-Z unstable-options` flag must also be passed to use the unstable values
+

tests/ui/linking/link-self-contained-unstable.unwind.stderr

@@ -0,0 +1,2 @@
+error: only `-C link-self-contained` values `y`/`yes`/`on`/`n`/`no`/`off`/`-linker` are stable, the `-Z unstable-options` flag must also be passed to use the unstable values
+

tests/ui/linking/linker-features-lld-disallowed.rs

@@ -0,0 +1,19 @@
+// Check that only `-C linker-features=-lld` is stable on x64 linux. Any other value or target,
+// needs `-Z unstable-options`.
+
+// ignore-tidy-linelength
+
+//@ revisions: unstable_target_positive unstable_target_negative unstable_positive
+//@ [unstable_target_negative] compile-flags: --target=x86_64-unknown-linux-musl -C linker-features=-lld --crate-type=rlib
+//@ [unstable_target_negative] needs-llvm-components: x86
+//@ [unstable_target_positive] compile-flags: --target=x86_64-unknown-linux-musl -C linker-features=+lld --crate-type=rlib
+//@ [unstable_target_positive] needs-llvm-components: x86
+//@ [unstable_positive] compile-flags: --target=x86_64-unknown-linux-gnu -C linker-features=+lld --crate-type=rlib
+//@ [unstable_positive] needs-llvm-components: x86
+
+
+#![feature(no_core)]
+#![no_core]
+
+//[unstable_target_negative]~? ERROR `-C linker-features=-lld` is unstable on the `x86_64-unknown-linux-musl` target
+//[unstable_target_positive,unstable_positive]~? ERROR `-C linker-features=+lld` is unstable, and also requires the `-Z unstable-options`

tests/ui/linking/linker-features-lld-disallowed.unstable_positive.stderr

@@ -0,0 +1,2 @@
+error: `-C linker-features=+lld` is unstable, and also requires the `-Z unstable-options` flag to be used
+

tests/ui/linking/linker-features-lld-disallowed.unstable_target_negative.stderr

@@ -0,0 +1,2 @@
+error: `-C linker-features=-lld` is unstable on the `x86_64-unknown-linux-musl` target. The `-Z unstable-options` flag must also be passed to use it on this target
+

tests/ui/linking/linker-features-lld-disallowed.unstable_target_positive.stderr

@@ -0,0 +1,2 @@
+error: `-C linker-features=+lld` is unstable, and also requires the `-Z unstable-options` flag to be used
+

tests/ui/linking/linker-features-malformed.invalid_modifier.stderr

@@ -1,2 +1,2 @@
-error: incorrect value `*lld` for unstable option `linker-features` - a list of enabled (`+` prefix) and disabled (`-` prefix) features: `lld` was expected
+error: incorrect value `*lld` for codegen option `linker-features` - a list of enabled (`+` prefix) and disabled (`-` prefix) features: `lld` was expected
 

tests/ui/linking/linker-features-malformed.invalid_separator.stderr

@@ -1,2 +1,2 @@
-error: incorrect value `-lld@+lld` for unstable option `linker-features` - a list of enabled (`+` prefix) and disabled (`-` prefix) features: `lld` was expected
+error: incorrect value `-lld@+lld` for codegen option `linker-features` - a list of enabled (`+` prefix) and disabled (`-` prefix) features: `lld` was expected
 

tests/ui/linking/linker-features-malformed.no_value.stderr

@@ -1,2 +1,2 @@
-error: incorrect value `` for unstable option `linker-features` - a list of enabled (`+` prefix) and disabled (`-` prefix) features: `lld` was expected
+error: incorrect value `` for codegen option `linker-features` - a list of enabled (`+` prefix) and disabled (`-` prefix) features: `lld` was expected
 

tests/ui/linking/linker-features-malformed.rs

@@ -1,27 +1,27 @@
-//! Check that malformed `-Zlinker-features` flags are properly rejected.
+//! Check that malformed `-Clinker-features` flags are properly rejected.
 
 //@ revisions: no_value
-//@[no_value] compile-flags: -Zlinker-features=
-//[no_value]~? ERROR incorrect value `` for unstable option `linker-features`
+//@[no_value] compile-flags: -Clinker-features=
+//[no_value]~? ERROR incorrect value `` for codegen option `linker-features`
 
 //@ revisions: invalid_modifier
-//@[invalid_modifier] compile-flags: -Zlinker-features=*lld
-//[invalid_modifier]~? ERROR incorrect value `*lld` for unstable option `linker-features`
+//@[invalid_modifier] compile-flags: -Clinker-features=*lld
+//[invalid_modifier]~? ERROR incorrect value `*lld` for codegen option `linker-features`
 
 //@ revisions: unknown_value
-//@[unknown_value] compile-flags: -Zlinker-features=unknown
-//[unknown_value]~? ERROR incorrect value `unknown` for unstable option `linker-features`
+//@[unknown_value] compile-flags: -Clinker-features=unknown
+//[unknown_value]~? ERROR incorrect value `unknown` for codegen option `linker-features`
 
 //@ revisions: unknown_modifier_value
-//@[unknown_modifier_value] compile-flags: -Zlinker-features=-unknown
-//[unknown_modifier_value]~? ERROR incorrect value `-unknown` for unstable option `linker-features`
+//@[unknown_modifier_value] compile-flags: -Clinker-features=-unknown
+//[unknown_modifier_value]~? ERROR incorrect value `-unknown` for codegen option `linker-features`
 
 //@ revisions: unknown_boolean
-//@[unknown_boolean] compile-flags: -Zlinker-features=maybe
-//[unknown_boolean]~? ERROR incorrect value `maybe` for unstable option `linker-features`
+//@[unknown_boolean] compile-flags: -Clinker-features=maybe
+//[unknown_boolean]~? ERROR incorrect value `maybe` for codegen option `linker-features`
 
 //@ revisions: invalid_separator
-//@[invalid_separator] compile-flags: -Zlinker-features=-lld@+lld
-//[invalid_separator]~? ERROR incorrect value `-lld@+lld` for unstable option `linker-features`
+//@[invalid_separator] compile-flags: -Clinker-features=-lld@+lld
+//[invalid_separator]~? ERROR incorrect value `-lld@+lld` for codegen option `linker-features`
 
 fn main() {}

tests/ui/linking/linker-features-malformed.unknown_boolean.stderr

@@ -1,2 +1,2 @@
-error: incorrect value `maybe` for unstable option `linker-features` - a list of enabled (`+` prefix) and disabled (`-` prefix) features: `lld` was expected
+error: incorrect value `maybe` for codegen option `linker-features` - a list of enabled (`+` prefix) and disabled (`-` prefix) features: `lld` was expected
 

tests/ui/linking/linker-features-malformed.unknown_modifier_value.stderr

@@ -1,2 +1,2 @@
-error: incorrect value `-unknown` for unstable option `linker-features` - a list of enabled (`+` prefix) and disabled (`-` prefix) features: `lld` was expected
+error: incorrect value `-unknown` for codegen option `linker-features` - a list of enabled (`+` prefix) and disabled (`-` prefix) features: `lld` was expected
 

tests/ui/linking/linker-features-malformed.unknown_value.stderr

@@ -1,2 +1,2 @@
-error: incorrect value `unknown` for unstable option `linker-features` - a list of enabled (`+` prefix) and disabled (`-` prefix) features: `lld` was expected
+error: incorrect value `unknown` for codegen option `linker-features` - a list of enabled (`+` prefix) and disabled (`-` prefix) features: `lld` was expected
 

tests/ui/linking/linker-features-unstable-cc.rs

@@ -0,0 +1,13 @@
+// Check that only `-C linker-features=-lld` is stable on x64 linux, and that other linker
+// features require using `-Z unstable-options`.
+//
+// Note that, currently, only `lld` is parsed on the CLI, but that other linker features can exist
+// internally (`cc`).
+//
+//@ compile-flags: --target=x86_64-unknown-linux-gnu -C linker-features=+cc --crate-type=rlib
+//@ needs-llvm-components: x86
+
+#![feature(no_core)]
+#![no_core]
+
+//~? ERROR incorrect value `+cc` for codegen option `linker-features`

tests/ui/linking/linker-features-unstable-cc.stderr

@@ -0,0 +1,2 @@
+error: incorrect value `+cc` for codegen option `linker-features` - a list of enabled (`+` prefix) and disabled (`-` prefix) features: `lld` was expected
+