1use std::ffi::{OsStr, OsString};2use std::fs::{self, File};3use std::io::prelude::*;4use std::path::{Path, PathBuf};5use std::{env, iter, mem, str};67use find_msvc_tools;8use rustc_hir::attrs::WindowsSubsystemKind;9use rustc_hir::def_id::{CrateNum, LOCAL_CRATE};10use rustc_metadata::{11    find_native_static_library, try_find_native_dynamic_library, try_find_native_static_library,12};13use rustc_middle::bug;14use rustc_middle::middle::dependency_format::Linkage;15use rustc_middle::middle::exported_symbols::{16    self, ExportedSymbol, SymbolExportInfo, SymbolExportKind, SymbolExportLevel,17};18use rustc_middle::ty::TyCtxt;19use rustc_session::Session;20use rustc_session::config::{self, CrateType, DebugInfo, LinkerPluginLto, Lto, OptLevel, Strip};21use rustc_target::spec::{Arch, Cc, CfgAbi, LinkOutputKind, LinkerFlavor, Lld, Os};22use tracing::{debug, warn};2324use super::command::Command;25use super::symbol_export;26use crate::back::symbol_export::allocator_shim_symbols;27use crate::base::needs_allocator_shim_for_linking;28use crate::errors;2930#[cfg(test)]31mod tests;3233/// Disables non-English messages from localized linkers.34/// Such messages may cause issues with text encoding on Windows (#35785)35/// and prevent inspection of linker output in case of errors, which we occasionally do.36/// This should be acceptable because other messages from rustc are in English anyway,37/// and may also be desirable to improve searchability of the linker diagnostics.38pub(crate) fn disable_localization(linker: &mut Command) {39    // No harm in setting both env vars simultaneously.40    // Unix-style linkers.41    linker.env("LC_ALL", "C");42    // MSVC's `link.exe`.43    linker.env("VSLANG", "1033");44}4546/// The third parameter is for env vars, used on windows to set up the47/// path for MSVC to find its DLLs, and gcc to find its bundled48/// toolchain49pub(crate) fn get_linker<'a>(50    sess: &'a Session,51    linker: &Path,52    flavor: LinkerFlavor,53    self_contained: bool,54    target_cpu: &'a str,55    codegen_backend: &'static str,56) -> Box<dyn Linker + 'a> {57    let msvc_tool = find_msvc_tools::find_tool(sess.target.arch.desc(), "link.exe");5859    // If our linker looks like a batch script on Windows then to execute this60    // we'll need to spawn `cmd` explicitly. This is primarily done to handle61    // emscripten where the linker is `emcc.bat` and needs to be spawned as62    // `cmd /c emcc.bat ...`.63    //64    // This worked historically but is needed manually since #42436 (regression65    // was tagged as #42791) and some more info can be found on #44443 for66    // emscripten itself.67    let mut cmd = match linker.to_str() {68        Some(linker) if cfg!(windows) && linker.ends_with(".bat") => Command::bat_script(linker),69        _ => match flavor {70            LinkerFlavor::Gnu(Cc::No, Lld::Yes)71            | LinkerFlavor::Darwin(Cc::No, Lld::Yes)72            | LinkerFlavor::WasmLld(Cc::No)73            | LinkerFlavor::Msvc(Lld::Yes) => Command::lld(linker, flavor.lld_flavor()),74            LinkerFlavor::Msvc(Lld::No)75                if sess.opts.cg.linker.is_none() && sess.target.linker.is_none() =>76            {77                Command::new(msvc_tool.as_ref().map_or(linker, |t| t.path()))78            }79            _ => Command::new(linker),80        },81    };8283    // UWP apps have API restrictions enforced during Store submissions.84    // To comply with the Windows App Certification Kit,85    // MSVC needs to link with the Store versions of the runtime libraries (vcruntime, msvcrt, etc).86    let t = &sess.target;87    if matches!(flavor, LinkerFlavor::Msvc(..)) && t.cfg_abi == CfgAbi::Uwp {88        if let Some(ref tool) = msvc_tool {89            let original_path = tool.path();90            if let Some(root_lib_path) = original_path.ancestors().nth(4) {91                let arch = match t.arch {92                    Arch::X86_64 => Some("x64"),93                    Arch::X86 => Some("x86"),94                    Arch::AArch64 => Some("arm64"),95                    Arch::Arm => Some("arm"),96                    _ => None,97                };98                if let Some(ref a) = arch {99                    // FIXME: Move this to `fn linker_with_args`.100                    let mut arg = OsString::from("/LIBPATH:");101                    arg.push(format!("{}\\lib\\{}\\store", root_lib_path.display(), a));102                    cmd.arg(&arg);103                } else {104                    warn!("arch is not supported");105                }106            } else {107                warn!("MSVC root path lib location not found");108            }109        } else {110            warn!("link.exe not found");111        }112    }113114    // The compiler's sysroot often has some bundled tools, so add it to the115    // PATH for the child.116    let mut new_path = sess.get_tools_search_paths(self_contained);117    let mut msvc_changed_path = false;118    if sess.target.is_like_msvc119        && let Some(ref tool) = msvc_tool120    {121        for (k, v) in tool.env() {122            if k == "PATH" {123                new_path.extend(env::split_paths(v));124                msvc_changed_path = true;125            } else {126                cmd.env(k, v);127            }128        }129    }130131    if !msvc_changed_path && let Some(path) = env::var_os("PATH") {132        new_path.extend(env::split_paths(&path));133    }134    cmd.env("PATH", env::join_paths(new_path).unwrap());135136    // FIXME: Move `/LIBPATH` addition for uwp targets from the linker construction137    // to the linker args construction.138    assert!(cmd.get_args().is_empty() || sess.target.cfg_abi == CfgAbi::Uwp);139    match flavor {140        LinkerFlavor::Unix(Cc::No) if sess.target.os == Os::L4Re => {141            Box::new(L4Bender::new(cmd, sess)) as Box<dyn Linker>142        }143        LinkerFlavor::Unix(Cc::No) if sess.target.os == Os::Aix => {144            Box::new(AixLinker::new(cmd, sess)) as Box<dyn Linker>145        }146        LinkerFlavor::WasmLld(Cc::No) => Box::new(WasmLd::new(cmd, sess)) as Box<dyn Linker>,147        LinkerFlavor::Gnu(cc, _)148        | LinkerFlavor::Darwin(cc, _)149        | LinkerFlavor::WasmLld(cc)150        | LinkerFlavor::Unix(cc) => Box::new(GccLinker {151            cmd,152            sess,153            target_cpu,154            hinted_static: None,155            is_ld: cc == Cc::No,156            is_gnu: flavor.is_gnu(),157            uses_lld: flavor.uses_lld(),158            codegen_backend,159        }) as Box<dyn Linker>,160        LinkerFlavor::Msvc(..) => Box::new(MsvcLinker { cmd, sess }) as Box<dyn Linker>,161        LinkerFlavor::EmCc => Box::new(EmLinker { cmd, sess }) as Box<dyn Linker>,162        LinkerFlavor::Bpf => Box::new(BpfLinker { cmd, sess }) as Box<dyn Linker>,163        LinkerFlavor::Llbc => Box::new(LlbcLinker { cmd, sess }) as Box<dyn Linker>,164        LinkerFlavor::Ptx => Box::new(PtxLinker { cmd, sess }) as Box<dyn Linker>,165    }166}167168// Note: Ideally neither these helper function, nor the macro-generated inherent methods below169// would exist, and these functions would live in `trait Linker`.170// Unfortunately, adding these functions to `trait Linker` make it `dyn`-incompatible.171// If the methods are added to the trait with `where Self: Sized` bounds, then even a separate172// implementation of them for `dyn Linker {}` wouldn't work due to a conflict with those173// uncallable methods in the trait.174175/// Just pass the arguments to the linker as is.176/// It is assumed that they are correctly prepared in advance.177fn verbatim_args<L: Linker + ?Sized>(178    l: &mut L,179    args: impl IntoIterator<Item: AsRef<OsStr>>,180) -> &mut L {181    for arg in args {182        l.cmd().arg(arg);183    }184    l185}186/// Add underlying linker arguments to C compiler command, by wrapping them in187/// `-Wl` or `-Xlinker`.188fn convert_link_args_to_cc_args(cmd: &mut Command, args: impl IntoIterator<Item: AsRef<OsStr>>) {189    let mut combined_arg = OsString::from("-Wl");190    for arg in args {191        // If the argument itself contains a comma, we need to emit it192        // as `-Xlinker`, otherwise we can use `-Wl`.193        if arg.as_ref().as_encoded_bytes().contains(&b',') {194            // Emit current `-Wl` argument, if any has been built.195            if combined_arg != OsStr::new("-Wl") {196                cmd.arg(combined_arg);197                // Begin next `-Wl` argument.198                combined_arg = OsString::from("-Wl");199            }200201            // Emit `-Xlinker` argument.202            cmd.arg("-Xlinker");203            cmd.arg(arg);204        } else {205            // Append to `-Wl` argument.206            combined_arg.push(",");207            combined_arg.push(arg);208        }209    }210    // Emit final `-Wl` argument.211    if combined_arg != OsStr::new("-Wl") {212        cmd.arg(combined_arg);213    }214}215/// Arguments for the underlying linker.216/// Add options to pass them through cc wrapper if `Linker` is a cc wrapper.217fn link_args<L: Linker + ?Sized>(l: &mut L, args: impl IntoIterator<Item: AsRef<OsStr>>) -> &mut L {218    if !l.is_cc() {219        verbatim_args(l, args);220    } else {221        convert_link_args_to_cc_args(l.cmd(), args);222    }223    l224}225/// Arguments for the cc wrapper specifically.226/// Check that it's indeed a cc wrapper and pass verbatim.227fn cc_args<L: Linker + ?Sized>(l: &mut L, args: impl IntoIterator<Item: AsRef<OsStr>>) -> &mut L {228    assert!(l.is_cc());229    verbatim_args(l, args)230}231/// Arguments supported by both underlying linker and cc wrapper, pass verbatim.232fn link_or_cc_args<L: Linker + ?Sized>(233    l: &mut L,234    args: impl IntoIterator<Item: AsRef<OsStr>>,235) -> &mut L {236    verbatim_args(l, args)237}238239macro_rules! generate_arg_methods {240    ($($ty:ty)*) => { $(241        impl $ty {242            #[allow(unused)]243            pub(crate) fn verbatim_args(&mut self, args: impl IntoIterator<Item: AsRef<OsStr>>) -> &mut Self {244                verbatim_args(self, args)245            }246            #[allow(unused)]247            pub(crate) fn verbatim_arg(&mut self, arg: impl AsRef<OsStr>) -> &mut Self {248                verbatim_args(self, iter::once(arg))249            }250            #[allow(unused)]251            pub(crate) fn link_args(&mut self, args: impl IntoIterator<Item: AsRef<OsStr>>) -> &mut Self {252                link_args(self, args)253            }254            #[allow(unused)]255            pub(crate) fn link_arg(&mut self, arg: impl AsRef<OsStr>) -> &mut Self {256                link_args(self, iter::once(arg))257            }258            #[allow(unused)]259            pub(crate) fn cc_args(&mut self, args: impl IntoIterator<Item: AsRef<OsStr>>) -> &mut Self {260                cc_args(self, args)261            }262            #[allow(unused)]263            pub(crate) fn cc_arg(&mut self, arg: impl AsRef<OsStr>) -> &mut Self {264                cc_args(self, iter::once(arg))265            }266            #[allow(unused)]267            pub(crate) fn link_or_cc_args(&mut self, args: impl IntoIterator<Item: AsRef<OsStr>>) -> &mut Self {268                link_or_cc_args(self, args)269            }270            #[allow(unused)]271            pub(crate) fn link_or_cc_arg(&mut self, arg: impl AsRef<OsStr>) -> &mut Self {272                link_or_cc_args(self, iter::once(arg))273            }274        }275    )* }276}277278generate_arg_methods! {279    GccLinker<'_>280    MsvcLinker<'_>281    EmLinker<'_>282    WasmLd<'_>283    L4Bender<'_>284    AixLinker<'_>285    LlbcLinker<'_>286    PtxLinker<'_>287    BpfLinker<'_>288    dyn Linker + '_289}290291/// Linker abstraction used by `back::link` to build up the command to invoke a292/// linker.293///294/// This trait is the total list of requirements needed by `back::link` and295/// represents the meaning of each option being passed down. This trait is then296/// used to dispatch on whether a GNU-like linker (generally `ld.exe`) or an297/// MSVC linker (e.g., `link.exe`) is being used.298pub(crate) trait Linker {299    fn cmd(&mut self) -> &mut Command;300    fn is_cc(&self) -> bool {301        false302    }303    fn set_output_kind(304        &mut self,305        output_kind: LinkOutputKind,306        crate_type: CrateType,307        out_filename: &Path,308    );309    fn link_dylib_by_name(&mut self, _name: &str, _verbatim: bool, _as_needed: bool) {310        bug!("dylib linked with unsupported linker")311    }312    fn link_dylib_by_path(&mut self, _path: &Path, _as_needed: bool) {313        bug!("dylib linked with unsupported linker")314    }315    fn link_framework_by_name(&mut self, _name: &str, _verbatim: bool, _as_needed: bool) {316        bug!("framework linked with unsupported linker")317    }318    fn link_staticlib_by_name(&mut self, name: &str, verbatim: bool, whole_archive: bool);319    fn link_staticlib_by_path(&mut self, path: &Path, whole_archive: bool);320    fn include_path(&mut self, path: &Path) {321        link_or_cc_args(link_or_cc_args(self, &["-L"]), &[path]);322    }323    fn framework_path(&mut self, _path: &Path) {324        bug!("framework path set with unsupported linker")325    }326    fn output_filename(&mut self, path: &Path) {327        link_or_cc_args(link_or_cc_args(self, &["-o"]), &[path]);328    }329    fn add_object(&mut self, path: &Path) {330        link_or_cc_args(self, &[path]);331    }332    fn gc_sections(&mut self, keep_metadata: bool);333    fn full_relro(&mut self);334    fn partial_relro(&mut self);335    fn no_relro(&mut self);336    fn optimize(&mut self);337    fn pgo_gen(&mut self);338    fn control_flow_guard(&mut self);339    fn ehcont_guard(&mut self);340    fn debuginfo(&mut self, strip: Strip, natvis_debugger_visualizers: &[PathBuf]);341    fn no_crt_objects(&mut self);342    fn no_default_libraries(&mut self);343    fn export_symbols(344        &mut self,345        tmpdir: &Path,346        crate_type: CrateType,347        symbols: &[(String, SymbolExportKind)],348    );349    fn windows_subsystem(&mut self, subsystem: WindowsSubsystemKind);350    fn linker_plugin_lto(&mut self);351    fn add_eh_frame_header(&mut self) {}352    fn add_no_exec(&mut self) {}353    fn add_as_needed(&mut self) {}354    fn reset_per_library_state(&mut self) {}355    fn enable_profiling(&mut self) {}356}357358impl dyn Linker + '_ {359    pub(crate) fn take_cmd(&mut self) -> Command {360        mem::replace(self.cmd(), Command::new(""))361    }362}363364struct GccLinker<'a> {365    cmd: Command,366    sess: &'a Session,367    target_cpu: &'a str,368    hinted_static: Option<bool>, // Keeps track of the current hinting mode.369    // Link as ld370    is_ld: bool,371    is_gnu: bool,372    uses_lld: bool,373    codegen_backend: &'static str,374}375376impl<'a> GccLinker<'a> {377    fn takes_hints(&self) -> bool {378        // Really this function only returns true if the underlying linker379        // configured for a compiler is binutils `ld.bfd` and `ld.gold`. We380        // don't really have a foolproof way to detect that, so rule out some381        // platforms where currently this is guaranteed to *not* be the case:382        //383        // * On OSX they have their own linker, not binutils'384        // * For WebAssembly the only functional linker is LLD, which doesn't385        //   support hint flags386        !self.sess.target.is_like_darwin && !self.sess.target.is_like_wasm387    }388389    // Some platforms take hints about whether a library is static or dynamic.390    // For those that support this, we ensure we pass the option if the library391    // was flagged "static" (most defaults are dynamic) to ensure that if392    // libfoo.a and libfoo.so both exist that the right one is chosen.393    fn hint_static(&mut self) {394        if !self.takes_hints() {395            return;396        }397        if self.hinted_static != Some(true) {398            self.link_arg("-Bstatic");399            self.hinted_static = Some(true);400        }401    }402403    fn hint_dynamic(&mut self) {404        if !self.takes_hints() {405            return;406        }407        if self.hinted_static != Some(false) {408            self.link_arg("-Bdynamic");409            self.hinted_static = Some(false);410        }411    }412413    fn push_linker_plugin_lto_args(&mut self, plugin_path: Option<&OsStr>) {414        if let Some(plugin_path) = plugin_path {415            let mut arg = OsString::from("-plugin=");416            arg.push(plugin_path);417            self.link_arg(&arg);418        }419420        let opt_level = match self.sess.opts.optimize {421            config::OptLevel::No => "O0",422            config::OptLevel::Less => "O1",423            config::OptLevel::More | config::OptLevel::Size | config::OptLevel::SizeMin => "O2",424            config::OptLevel::Aggressive => "O3",425        };426427        if let Some(path) = &self.sess.opts.unstable_opts.profile_sample_use {428            self.link_arg(&format!("-plugin-opt=sample-profile={}", path.display()));429        };430        let prefix = if self.codegen_backend == "gcc" {431            // The GCC linker plugin requires a leading dash.432            "-"433        } else {434            ""435        };436        self.link_args(&[437            &format!("-plugin-opt={prefix}{opt_level}"),438            &format!("-plugin-opt={prefix}mcpu={}", self.target_cpu),439        ]);440    }441442    fn build_dylib(&mut self, crate_type: CrateType, out_filename: &Path) {443        // On mac we need to tell the linker to let this library be rpathed444        if self.sess.target.is_like_darwin {445            if self.is_cc() {446                // `-dynamiclib` makes `cc` pass `-dylib` to the linker.447                self.cc_arg("-dynamiclib");448            } else {449                self.link_arg("-dylib");450                // Clang also sets `-dynamic`, but that's implied by `-dylib`, so unnecessary.451            }452453            // Note that the `osx_rpath_install_name` option here is a hack454            // purely to support bootstrap right now, we should get a more455            // principled solution at some point to force the compiler to pass456            // the right `-Wl,-install_name` with an `@rpath` in it.457            if self.sess.opts.cg.rpath || self.sess.opts.unstable_opts.osx_rpath_install_name {458                let mut rpath = OsString::from("@rpath/");459                rpath.push(out_filename.file_name().unwrap());460                self.link_arg("-install_name").link_arg(rpath);461            }462        } else {463            self.link_or_cc_arg("-shared");464            if let Some(name) = out_filename.file_name() {465                if self.sess.target.is_like_windows {466                    // The output filename already contains `dll_suffix` so467                    // the resulting import library will have a name in the468                    // form of libfoo.dll.a469                    let (prefix, suffix) = self.sess.staticlib_components(false);470                    let mut implib_name = OsString::from(prefix);471                    implib_name.push(name);472                    implib_name.push(suffix);473                    let mut out_implib = OsString::from("--out-implib=");474                    out_implib.push(out_filename.with_file_name(implib_name));475                    self.link_arg(out_implib);476                } else if crate_type == CrateType::Dylib {477                    // When dylibs are linked by a full path this value will get into `DT_NEEDED`478                    // instead of the full path, so the library can be later found in some other479                    // location than that specific path.480                    let mut soname = OsString::from("-soname=");481                    soname.push(name);482                    self.link_arg(soname);483                }484            }485        }486    }487488    fn with_as_needed(&mut self, as_needed: bool, f: impl FnOnce(&mut Self)) {489        if !as_needed {490            if self.sess.target.is_like_darwin {491                // FIXME(81490): ld64 doesn't support these flags but macOS 11492                // has -needed-l{} / -needed_library {}493                // but we have no way to detect that here.494                self.sess.dcx().emit_warn(errors::Ld64UnimplementedModifier);495            } else if self.is_gnu && !self.sess.target.is_like_windows {496                self.link_arg("--no-as-needed");497            } else {498                self.sess.dcx().emit_warn(errors::LinkerUnsupportedModifier);499            }500        }501502        f(self);503504        if !as_needed {505            if self.sess.target.is_like_darwin {506                // See above FIXME comment507            } else if self.is_gnu && !self.sess.target.is_like_windows {508                self.link_arg("--as-needed");509            }510        }511    }512}513514impl<'a> Linker for GccLinker<'a> {515    fn cmd(&mut self) -> &mut Command {516        &mut self.cmd517    }518519    fn is_cc(&self) -> bool {520        !self.is_ld521    }522523    fn set_output_kind(524        &mut self,525        output_kind: LinkOutputKind,526        crate_type: CrateType,527        out_filename: &Path,528    ) {529        match output_kind {530            LinkOutputKind::DynamicNoPicExe => {531                // noop on windows w/ gcc, warning w/ clang532                if !self.is_ld && self.is_gnu && !self.sess.target.is_like_windows {533                    self.cc_arg("-no-pie");534                }535            }536            LinkOutputKind::DynamicPicExe => {537                // noop on windows w/ gcc & ld, error w/ lld538                if !self.sess.target.is_like_windows {539                    // `-pie` works for both gcc wrapper and ld.540                    self.link_or_cc_arg("-pie");541                }542            }543            LinkOutputKind::StaticNoPicExe => {544                // `-static` works for both gcc wrapper and ld.545                self.link_or_cc_arg("-static");546                if !self.is_ld && self.is_gnu {547                    self.cc_arg("-no-pie");548                }549            }550            LinkOutputKind::StaticPicExe => {551                if !self.is_ld {552                    // Note that combination `-static -pie` doesn't work as expected553                    // for the gcc wrapper, `-static` in that case suppresses `-pie`.554                    self.cc_arg("-static-pie");555                } else {556                    // `--no-dynamic-linker` and `-z text` are not strictly necessary for producing557                    // a static pie, but currently passed because gcc and clang pass them.558                    // The former suppresses the `INTERP` ELF header specifying dynamic linker,559                    // which is otherwise implicitly injected by ld (but not lld).560                    // The latter doesn't change anything, only ensures that everything is pic.561                    self.link_args(&["-static", "-pie", "--no-dynamic-linker", "-z", "text"]);562                }563            }564            LinkOutputKind::DynamicDylib => self.build_dylib(crate_type, out_filename),565            LinkOutputKind::StaticDylib => {566                self.link_or_cc_arg("-static");567                self.build_dylib(crate_type, out_filename);568            }569            LinkOutputKind::WasiReactorExe => {570                self.link_args(&["--entry", "_initialize"]);571            }572        }573574        // VxWorks compiler driver introduced `--static-crt` flag specifically for rustc,575        // it switches linking for libc and similar system libraries to static without using576        // any `#[link]` attributes in the `libc` crate, see #72782 for details.577        // FIXME: Switch to using `#[link]` attributes in the `libc` crate578        // similarly to other targets.579        if self.sess.target.os == Os::VxWorks580            && matches!(581                output_kind,582                LinkOutputKind::StaticNoPicExe583                    | LinkOutputKind::StaticPicExe584                    | LinkOutputKind::StaticDylib585            )586        {587            self.cc_arg("--static-crt");588        }589590        // avr-none doesn't have default ISA, users must specify which specific591        // CPU (well, microcontroller) they are targetting using `-Ctarget-cpu`.592        //593        // Currently this makes sense only when using avr-gcc as a linker, since594        // it brings a couple of hand-written important intrinsics from libgcc.595        if self.sess.target.arch == Arch::Avr && !self.uses_lld {596            self.verbatim_arg(format!("-mmcu={}", self.target_cpu));597        }598    }599600    fn link_dylib_by_name(&mut self, name: &str, verbatim: bool, as_needed: bool) {601        if self.sess.target.os == Os::Illumos && name == "c" {602            // libc will be added via late_link_args on illumos so that it will603            // appear last in the library search order.604            // FIXME: This should be replaced by a more complete and generic605            // mechanism for controlling the order of library arguments passed606            // to the linker.607            return;608        }609        self.hint_dynamic();610        self.with_as_needed(as_needed, |this| {611            let colon = if verbatim && this.is_gnu { ":" } else { "" };612            this.link_or_cc_arg(format!("-l{colon}{name}"));613        });614    }615616    fn link_dylib_by_path(&mut self, path: &Path, as_needed: bool) {617        self.hint_dynamic();618        self.with_as_needed(as_needed, |this| {619            this.link_or_cc_arg(path);620        })621    }622623    fn link_framework_by_name(&mut self, name: &str, _verbatim: bool, as_needed: bool) {624        self.hint_dynamic();625        if !as_needed {626            // FIXME(81490): ld64 as of macOS 11 supports the -needed_framework627            // flag but we have no way to detect that here.628            // self.link_or_cc_arg("-needed_framework").link_or_cc_arg(name);629            self.sess.dcx().emit_warn(errors::Ld64UnimplementedModifier);630        }631        self.link_or_cc_args(&["-framework", name]);632    }633634    fn link_staticlib_by_name(&mut self, name: &str, verbatim: bool, whole_archive: bool) {635        self.hint_static();636        let colon = if verbatim && self.is_gnu { ":" } else { "" };637        if !whole_archive {638            self.link_or_cc_arg(format!("-l{colon}{name}"));639        } else if self.sess.target.is_like_darwin {640            // -force_load is the macOS equivalent of --whole-archive, but it641            // involves passing the full path to the library to link.642            self.link_arg("-force_load");643            self.link_arg(find_native_static_library(name, verbatim, self.sess));644        } else {645            self.link_arg("--whole-archive")646                .link_or_cc_arg(format!("-l{colon}{name}"))647                .link_arg("--no-whole-archive");648        }649    }650651    fn link_staticlib_by_path(&mut self, path: &Path, whole_archive: bool) {652        self.hint_static();653        if !whole_archive {654            self.link_or_cc_arg(path);655        } else if self.sess.target.is_like_darwin {656            self.link_arg("-force_load").link_arg(path);657        } else {658            self.link_arg("--whole-archive").link_arg(path).link_arg("--no-whole-archive");659        }660    }661662    fn framework_path(&mut self, path: &Path) {663        self.link_or_cc_arg("-F").link_or_cc_arg(path);664    }665    fn full_relro(&mut self) {666        self.link_args(&["-z", "relro", "-z", "now"]);667    }668    fn partial_relro(&mut self) {669        self.link_args(&["-z", "relro"]);670    }671    fn no_relro(&mut self) {672        self.link_args(&["-z", "norelro"]);673    }674675    fn gc_sections(&mut self, keep_metadata: bool) {676        // The dead_strip option to the linker specifies that functions and data677        // unreachable by the entry point will be removed. This is quite useful678        // with Rust's compilation model of compiling libraries at a time into679        // one object file. For example, this brings hello world from 1.7MB to680        // 458K.681        //682        // Note that this is done for both executables and dynamic libraries. We683        // won't get much benefit from dylibs because LLVM will have already684        // stripped away as much as it could. This has not been seen to impact685        // link times negatively.686        //687        // -dead_strip can't be part of the pre_link_args because it's also used688        // for partial linking when using multiple codegen units (-r). So we689        // insert it here.690        if self.sess.target.is_like_darwin {691            self.link_arg("-dead_strip");692693        // If we're building a dylib, we don't use --gc-sections because LLVM694        // has already done the best it can do, and we also don't want to695        // eliminate the metadata. If we're building an executable, however,696        // --gc-sections drops the size of hello world from 1.8MB to 597K, a 67%697        // reduction.698        } else if (self.is_gnu || self.sess.target.is_like_wasm) && !keep_metadata {699            self.link_arg("--gc-sections");700        }701    }702703    fn optimize(&mut self) {704        if !self.is_gnu && !self.sess.target.is_like_wasm {705            return;706        }707708        // GNU-style linkers support optimization with -O. GNU ld doesn't709        // need a numeric argument, but other linkers do.710        if self.sess.opts.optimize == config::OptLevel::More711            || self.sess.opts.optimize == config::OptLevel::Aggressive712        {713            self.link_arg("-O1");714        }715    }716717    fn pgo_gen(&mut self) {718        if !self.is_gnu {719            return;720        }721722        // If we're doing PGO generation stuff and on a GNU-like linker, use the723        // "-u" flag to properly pull in the profiler runtime bits.724        //725        // This is because LLVM otherwise won't add the needed initialization726        // for us on Linux (though the extra flag should be harmless if it727        // does).728        //729        // See https://reviews.llvm.org/D14033 and https://reviews.llvm.org/D14030.730        //731        // Though it may be worth to try to revert those changes upstream, since732        // the overhead of the initialization should be minor.733        self.link_or_cc_args(&["-u", "__llvm_profile_runtime"]);734    }735736    fn enable_profiling(&mut self) {737        // This flag is also used when linking to choose target specific738        // libraries needed to enable profiling.739        if !self.is_ld {740            self.cc_arg("-pg");741            // On windows-gnu targets, libgmon also needs to be linked, and this742            // requires readding libraries to satisfy its dependencies.743            if self.sess.target.is_like_windows {744                self.cc_arg("-lgmon");745                self.cc_arg("-lkernel32");746                self.cc_arg("-lmsvcrt");747            }748        }749    }750751    fn control_flow_guard(&mut self) {}752753    fn ehcont_guard(&mut self) {}754755    fn debuginfo(&mut self, strip: Strip, _: &[PathBuf]) {756        // MacOS linker doesn't support stripping symbols directly anymore.757        if self.sess.target.is_like_darwin {758            return;759        }760761        match strip {762            Strip::None => {}763            Strip::Debuginfo => {764                // The illumos linker does not support --strip-debug although765                // it does support --strip-all as a compatibility alias for -s.766                // The --strip-debug case is handled by running an external767                // `strip` utility as a separate step after linking.768                if !self.sess.target.is_like_solaris {769                    self.link_arg("--strip-debug");770                }771            }772            Strip::Symbols => {773                self.link_arg("--strip-all");774            }775        }776        match self.sess.opts.unstable_opts.debuginfo_compression {777            config::DebugInfoCompression::None => {}778            config::DebugInfoCompression::Zlib => {779                self.link_arg("--compress-debug-sections=zlib");780            }781            config::DebugInfoCompression::Zstd => {782                self.link_arg("--compress-debug-sections=zstd");783            }784        }785    }786787    fn no_crt_objects(&mut self) {788        if !self.is_ld {789            self.cc_arg("-nostartfiles");790        }791    }792793    fn no_default_libraries(&mut self) {794        if !self.is_ld {795            self.cc_arg("-nodefaultlibs");796        }797    }798799    fn export_symbols(800        &mut self,801        tmpdir: &Path,802        crate_type: CrateType,803        symbols: &[(String, SymbolExportKind)],804    ) {805        // Symbol visibility in object files typically takes care of this.806        if crate_type == CrateType::Executable {807            let should_export_executable_symbols =808                self.sess.opts.unstable_opts.export_executable_symbols;809            if self.sess.target.override_export_symbols.is_none()810                && !should_export_executable_symbols811            {812                return;813            }814        }815816        // We manually create a list of exported symbols to ensure we don't expose any more.817        // The object files have far more public symbols than we actually want to export,818        // so we hide them all here.819820        if !self.sess.target.limit_rdylib_exports {821            return;822        }823824        let path = tmpdir.join(if self.sess.target.is_like_windows { "list.def" } else { "list" });825        debug!("EXPORTED SYMBOLS:");826827        if self.sess.target.is_like_darwin {828            // Write a plain, newline-separated list of symbols829            let res = try {830                let mut f = File::create_buffered(&path)?;831                for (sym, _) in symbols {832                    debug!("  _{sym}");833                    writeln!(f, "_{sym}")?;834                }835            };836            if let Err(error) = res {837                self.sess.dcx().emit_fatal(errors::LibDefWriteFailure { error });838            }839            self.link_arg("-exported_symbols_list").link_arg(path);840        } else if self.sess.target.is_like_windows {841            let res = try {842                let mut f = File::create_buffered(&path)?;843844                // .def file similar to MSVC one but without LIBRARY section845                // because LD doesn't like when it's empty846                writeln!(f, "EXPORTS")?;847                for (symbol, kind) in symbols {848                    let kind_marker = if *kind == SymbolExportKind::Data { " DATA" } else { "" };849                    debug!("  _{symbol}");850                    // Quote the name in case it's reserved by linker in some way851                    // (this accounts for names with dots in particular).852                    writeln!(f, "  \"{symbol}\"{kind_marker}")?;853                }854            };855            if let Err(error) = res {856                self.sess.dcx().emit_fatal(errors::LibDefWriteFailure { error });857            }858            self.link_arg(path);859        } else if self.sess.target.is_like_wasm {860            self.link_arg("--no-export-dynamic");861            for (sym, _) in symbols {862                self.link_arg("--export").link_arg(sym);863            }864        } else if crate_type == CrateType::Executable && !self.sess.target.is_like_solaris {865            let res = try {866                let mut f = File::create_buffered(&path)?;867                writeln!(f, "{{")?;868                for (sym, _) in symbols {869                    debug!(sym);870                    writeln!(f, "  {sym};")?;871                }872                writeln!(f, "}};")?;873            };874            if let Err(error) = res {875                self.sess.dcx().emit_fatal(errors::VersionScriptWriteFailure { error });876            }877            self.link_arg("--dynamic-list").link_arg(path);878        } else {879            // Write an LD version script880            let res = try {881                let mut f = File::create_buffered(&path)?;882                writeln!(f, "{{")?;883                if !symbols.is_empty() {884                    writeln!(f, "  global:")?;885                    for (sym, _) in symbols {886                        debug!("    {sym};");887                        writeln!(f, "    {sym};")?;888                    }889                }890                writeln!(f, "\n  local:\n    *;\n}};")?;891            };892            if let Err(error) = res {893                self.sess.dcx().emit_fatal(errors::VersionScriptWriteFailure { error });894            }895            if self.sess.target.is_like_solaris {896                self.link_arg("-M").link_arg(path);897            } else {898                let mut arg = OsString::from("--version-script=");899                arg.push(path);900                self.link_arg(arg).link_arg("--no-undefined-version");901            }902        }903    }904905    fn windows_subsystem(&mut self, subsystem: WindowsSubsystemKind) {906        self.link_args(&["--subsystem", subsystem.as_str()]);907    }908909    fn reset_per_library_state(&mut self) {910        self.hint_dynamic(); // Reset to default before returning the composed command line.911    }912913    fn linker_plugin_lto(&mut self) {914        match self.sess.opts.cg.linker_plugin_lto {915            LinkerPluginLto::Disabled => {916                // Nothing to do917            }918            LinkerPluginLto::LinkerPluginAuto => {919                self.push_linker_plugin_lto_args(None);920            }921            LinkerPluginLto::LinkerPlugin(ref path) => {922                self.push_linker_plugin_lto_args(Some(path.as_os_str()));923            }924        }925    }926927    // Add the `GNU_EH_FRAME` program header which is required to locate unwinding information.928    // Some versions of `gcc` add it implicitly, some (e.g. `musl-gcc`) don't,929    // so we just always add it.930    fn add_eh_frame_header(&mut self) {931        self.link_arg("--eh-frame-hdr");932    }933934    fn add_no_exec(&mut self) {935        if self.sess.target.is_like_windows {936            self.link_arg("--nxcompat");937        } else if self.is_gnu {938            self.link_args(&["-z", "noexecstack"]);939        }940    }941942    fn add_as_needed(&mut self) {943        if self.is_gnu && !self.sess.target.is_like_windows {944            self.link_arg("--as-needed");945        } else if self.sess.target.is_like_solaris {946            // -z ignore is the Solaris equivalent to the GNU ld --as-needed option947            self.link_args(&["-z", "ignore"]);948        }949    }950}951952struct MsvcLinker<'a> {953    cmd: Command,954    sess: &'a Session,955}956957impl<'a> Linker for MsvcLinker<'a> {958    fn cmd(&mut self) -> &mut Command {959        &mut self.cmd960    }961962    fn set_output_kind(963        &mut self,964        output_kind: LinkOutputKind,965        _crate_type: CrateType,966        out_filename: &Path,967    ) {968        match output_kind {969            LinkOutputKind::DynamicNoPicExe970            | LinkOutputKind::DynamicPicExe971            | LinkOutputKind::StaticNoPicExe972            | LinkOutputKind::StaticPicExe => {}973            LinkOutputKind::DynamicDylib | LinkOutputKind::StaticDylib => {974                self.link_arg("/DLL");975                let mut arg: OsString = "/IMPLIB:".into();976                arg.push(out_filename.with_extension("dll.lib"));977                self.link_arg(arg);978            }979            LinkOutputKind::WasiReactorExe => {980                panic!("can't link as reactor on non-wasi target");981            }982        }983    }984985    fn link_dylib_by_name(&mut self, name: &str, verbatim: bool, _as_needed: bool) {986        // On MSVC-like targets rustc supports import libraries using alternative naming987        // scheme (`libfoo.a`) unsupported by linker, search for such libraries manually.988        if let Some(path) = try_find_native_dynamic_library(self.sess, name, verbatim) {989            self.link_arg(path);990        } else {991            self.link_arg(format!("{}{}", name, if verbatim { "" } else { ".lib" }));992        }993    }994995    fn link_dylib_by_path(&mut self, path: &Path, _as_needed: bool) {996        // When producing a dll, MSVC linker may not emit an implib file if the dll doesn't export997        // any symbols, so we skip linking if the implib file is not present.998        let implib_path = path.with_extension("dll.lib");999        if implib_path.exists() {1000            self.link_or_cc_arg(implib_path);1001        }1002    }10031004    fn link_staticlib_by_name(&mut self, name: &str, verbatim: bool, whole_archive: bool) {1005        // On MSVC-like targets rustc supports static libraries using alternative naming1006        // scheme (`libfoo.a`) unsupported by linker, search for such libraries manually.1007        if let Some(path) = try_find_native_static_library(self.sess, name, verbatim) {1008            self.link_staticlib_by_path(&path, whole_archive);1009        } else {1010            let opts = if whole_archive { "/WHOLEARCHIVE:" } else { "" };1011            let (prefix, suffix) = self.sess.staticlib_components(verbatim);1012            self.link_arg(format!("{opts}{prefix}{name}{suffix}"));1013        }1014    }10151016    fn link_staticlib_by_path(&mut self, path: &Path, whole_archive: bool) {1017        if !whole_archive {1018            self.link_arg(path);1019        } else {1020            let mut arg = OsString::from("/WHOLEARCHIVE:");1021            arg.push(path);1022            self.link_arg(arg);1023        }1024    }10251026    fn gc_sections(&mut self, _keep_metadata: bool) {1027        // MSVC's ICF (Identical COMDAT Folding) link optimization is1028        // slow for Rust and thus we disable it by default when not in1029        // optimization build.1030        if self.sess.opts.optimize != config::OptLevel::No {1031            self.link_arg("/OPT:REF,ICF");1032        } else {1033            // It is necessary to specify NOICF here, because /OPT:REF1034            // implies ICF by default.1035            self.link_arg("/OPT:REF,NOICF");1036        }1037    }10381039    fn full_relro(&mut self) {1040        // noop1041    }10421043    fn partial_relro(&mut self) {1044        // noop1045    }10461047    fn no_relro(&mut self) {1048        // noop1049    }10501051    fn no_crt_objects(&mut self) {1052        // noop1053    }10541055    fn no_default_libraries(&mut self) {1056        self.link_arg("/NODEFAULTLIB");1057    }10581059    fn include_path(&mut self, path: &Path) {1060        let mut arg = OsString::from("/LIBPATH:");1061        arg.push(path);1062        self.link_arg(&arg);1063    }10641065    fn output_filename(&mut self, path: &Path) {1066        let mut arg = OsString::from("/OUT:");1067        arg.push(path);1068        self.link_arg(&arg);1069    }10701071    fn optimize(&mut self) {1072        // Needs more investigation of `/OPT` arguments1073    }10741075    fn pgo_gen(&mut self) {1076        // Nothing needed here.1077    }10781079    fn control_flow_guard(&mut self) {1080        self.link_arg("/guard:cf");1081    }10821083    fn ehcont_guard(&mut self) {1084        if self.sess.target.pointer_width == 64 {1085            self.link_arg("/guard:ehcont");1086        }1087    }10881089    fn debuginfo(&mut self, _strip: Strip, natvis_debugger_visualizers: &[PathBuf]) {1090        // This will cause the Microsoft linker to generate a PDB file1091        // from the CodeView line tables in the object files.1092        self.link_arg("/DEBUG");10931094        // Default to emitting only the file name of the PDB file into1095        // the binary instead of the full path. Emitting the full path1096        // may leak private information (such as user names).1097        // See https://github.com/rust-lang/rust/issues/87825.1098        //1099        // This default behavior can be overridden by explicitly passing1100        // `-Clink-arg=/PDBALTPATH:...` to rustc.1101        self.link_arg("/PDBALTPATH:%_PDB%");11021103        // This will cause the Microsoft linker to embed .natvis info into the PDB file1104        let natvis_dir_path = self.sess.opts.sysroot.path().join("lib\\rustlib\\etc");1105        if let Ok(natvis_dir) = fs::read_dir(&natvis_dir_path) {1106            for entry in natvis_dir {1107                match entry {1108                    Ok(entry) => {1109                        let path = entry.path();1110                        if path.extension() == Some("natvis".as_ref()) {1111                            let mut arg = OsString::from("/NATVIS:");1112                            arg.push(path);1113                            self.link_arg(arg);1114                        }1115                    }1116                    Err(error) => {1117                        self.sess.dcx().emit_warn(errors::NoNatvisDirectory { error });1118                    }1119                }1120            }1121        }11221123        // This will cause the Microsoft linker to embed .natvis info for all crates into the PDB file1124        for path in natvis_debugger_visualizers {1125            let mut arg = OsString::from("/NATVIS:");1126            arg.push(path);1127            self.link_arg(arg);1128        }1129    }11301131    // Currently the compiler doesn't use `dllexport` (an LLVM attribute) to1132    // export symbols from a dynamic library. When building a dynamic library,1133    // however, we're going to want some symbols exported, so this function1134    // generates a DEF file which lists all the symbols.1135    //1136    // The linker will read this `*.def` file and export all the symbols from1137    // the dynamic library. Note that this is not as simple as just exporting1138    // all the symbols in the current crate (as specified by `codegen.reachable`)1139    // but rather we also need to possibly export the symbols of upstream1140    // crates. Upstream rlibs may be linked statically to this dynamic library,1141    // in which case they may continue to transitively be used and hence need1142    // their symbols exported.1143    fn export_symbols(1144        &mut self,1145        tmpdir: &Path,1146        crate_type: CrateType,1147        symbols: &[(String, SymbolExportKind)],1148    ) {1149        // Symbol visibility takes care of this typically1150        if crate_type == CrateType::Executable {1151            let should_export_executable_symbols =1152                self.sess.opts.unstable_opts.export_executable_symbols;1153            if !should_export_executable_symbols {1154                return;1155            }1156        }11571158        let path = tmpdir.join("lib.def");1159        let res = try {1160            let mut f = File::create_buffered(&path)?;11611162            // Start off with the standard module name header and then go1163            // straight to exports.1164            writeln!(f, "LIBRARY")?;1165            writeln!(f, "EXPORTS")?;1166            for (symbol, kind) in symbols {1167                let kind_marker = if *kind == SymbolExportKind::Data { " DATA" } else { "" };1168                debug!("  _{symbol}");1169                writeln!(f, "  {symbol}{kind_marker}")?;1170            }1171        };1172        if let Err(error) = res {1173            self.sess.dcx().emit_fatal(errors::LibDefWriteFailure { error });1174        }1175        let mut arg = OsString::from("/DEF:");1176        arg.push(path);1177        self.link_arg(&arg);1178    }11791180    fn windows_subsystem(&mut self, subsystem: WindowsSubsystemKind) {1181        let subsystem = subsystem.as_str();1182        self.link_arg(&format!("/SUBSYSTEM:{subsystem}"));11831184        // Windows has two subsystems we're interested in right now, the console1185        // and windows subsystems. These both implicitly have different entry1186        // points (starting symbols). The console entry point starts with1187        // `mainCRTStartup` and the windows entry point starts with1188        // `WinMainCRTStartup`. These entry points, defined in system libraries,1189        // will then later probe for either `main` or `WinMain`, respectively to1190        // start the application.1191        //1192        // In Rust we just always generate a `main` function so we want control1193        // to always start there, so we force the entry point on the windows1194        // subsystem to be `mainCRTStartup` to get everything booted up1195        // correctly.1196        //1197        // For more information see RFC #16651198        if subsystem == "windows" {1199            self.link_arg("/ENTRY:mainCRTStartup");1200        }1201    }12021203    fn linker_plugin_lto(&mut self) {1204        // Do nothing1205    }12061207    fn add_no_exec(&mut self) {1208        self.link_arg("/NXCOMPAT");1209    }1210}12111212struct EmLinker<'a> {1213    cmd: Command,1214    sess: &'a Session,1215}12161217impl<'a> Linker for EmLinker<'a> {1218    fn cmd(&mut self) -> &mut Command {1219        &mut self.cmd1220    }12211222    fn is_cc(&self) -> bool {1223        true1224    }12251226    fn set_output_kind(1227        &mut self,1228        output_kind: LinkOutputKind,1229        _crate_type: CrateType,1230        _out_filename: &Path,1231    ) {1232        match output_kind {1233            LinkOutputKind::DynamicNoPicExe | LinkOutputKind::DynamicPicExe => {1234                self.cmd.arg("-sMAIN_MODULE=2");1235            }1236            LinkOutputKind::DynamicDylib | LinkOutputKind::StaticDylib => {1237                self.cmd.arg("-sSIDE_MODULE=2");1238            }1239            // -fno-pie is the default on Emscripten.1240            LinkOutputKind::StaticNoPicExe | LinkOutputKind::StaticPicExe => {}1241            LinkOutputKind::WasiReactorExe => {1242                unreachable!();1243            }1244        }1245    }12461247    fn link_dylib_by_name(&mut self, name: &str, _verbatim: bool, _as_needed: bool) {1248        // Emscripten always links statically1249        self.link_or_cc_args(&["-l", name]);1250    }12511252    fn link_dylib_by_path(&mut self, path: &Path, _as_needed: bool) {1253        self.link_or_cc_arg(path);1254    }12551256    fn link_staticlib_by_name(&mut self, name: &str, _verbatim: bool, _whole_archive: bool) {1257        self.link_or_cc_args(&["-l", name]);1258    }12591260    fn link_staticlib_by_path(&mut self, path: &Path, _whole_archive: bool) {1261        self.link_or_cc_arg(path);1262    }12631264    fn full_relro(&mut self) {1265        // noop1266    }12671268    fn partial_relro(&mut self) {1269        // noop1270    }12711272    fn no_relro(&mut self) {1273        // noop1274    }12751276    fn gc_sections(&mut self, _keep_metadata: bool) {1277        // noop1278    }12791280    fn optimize(&mut self) {1281        // Emscripten performs own optimizations1282        self.cc_arg(match self.sess.opts.optimize {1283            OptLevel::No => "-O0",1284            OptLevel::Less => "-O1",1285            OptLevel::More => "-O2",1286            OptLevel::Aggressive => "-O3",1287            OptLevel::Size => "-Os",1288            OptLevel::SizeMin => "-Oz",1289        });1290    }12911292    fn pgo_gen(&mut self) {1293        // noop, but maybe we need something like the gnu linker?1294    }12951296    fn control_flow_guard(&mut self) {}12971298    fn ehcont_guard(&mut self) {}12991300    fn debuginfo(&mut self, _strip: Strip, _: &[PathBuf]) {1301        // Preserve names or generate source maps depending on debug info1302        // For more information see https://emscripten.org/docs/tools_reference/emcc.html#emcc-g1303        self.cc_arg(match self.sess.opts.debuginfo {1304            DebugInfo::None => "-g0",1305            DebugInfo::Limited | DebugInfo::LineTablesOnly | DebugInfo::LineDirectivesOnly => {1306                "--profiling-funcs"1307            }1308            DebugInfo::Full => "-g",1309        });1310    }13111312    fn no_crt_objects(&mut self) {}13131314    fn no_default_libraries(&mut self) {1315        self.cc_arg("-nodefaultlibs");1316    }13171318    fn export_symbols(1319        &mut self,1320        _tmpdir: &Path,1321        _crate_type: CrateType,1322        symbols: &[(String, SymbolExportKind)],1323    ) {1324        debug!("EXPORTED SYMBOLS:");13251326        self.cc_arg("-s");13271328        let mut arg = OsString::from("EXPORTED_FUNCTIONS=");1329        let encoded = serde_json::to_string(1330            &symbols.iter().map(|(sym, _)| "_".to_owned() + sym).collect::<Vec<_>>(),1331        )1332        .unwrap();1333        debug!("{encoded}");13341335        arg.push(encoded);13361337        self.cc_arg(arg);1338    }13391340    fn windows_subsystem(&mut self, _subsystem: WindowsSubsystemKind) {1341        // noop1342    }13431344    fn linker_plugin_lto(&mut self) {1345        // Do nothing1346    }1347}13481349struct WasmLd<'a> {1350    cmd: Command,1351    sess: &'a Session,1352}13531354impl<'a> WasmLd<'a> {1355    fn new(cmd: Command, sess: &'a Session) -> WasmLd<'a> {1356        WasmLd { cmd, sess }1357    }1358}13591360impl<'a> Linker for WasmLd<'a> {1361    fn cmd(&mut self) -> &mut Command {1362        &mut self.cmd1363    }13641365    fn set_output_kind(1366        &mut self,1367        output_kind: LinkOutputKind,1368        _crate_type: CrateType,1369        _out_filename: &Path,1370    ) {1371        match output_kind {1372            LinkOutputKind::DynamicNoPicExe1373            | LinkOutputKind::DynamicPicExe1374            | LinkOutputKind::StaticNoPicExe1375            | LinkOutputKind::StaticPicExe => {}1376            LinkOutputKind::DynamicDylib | LinkOutputKind::StaticDylib => {1377                self.link_arg("--no-entry");1378            }1379            LinkOutputKind::WasiReactorExe => {1380                self.link_args(&["--entry", "_initialize"]);1381            }1382        }1383    }13841385    fn link_dylib_by_name(&mut self, name: &str, _verbatim: bool, _as_needed: bool) {1386        self.link_or_cc_args(&["-l", name]);1387    }13881389    fn link_dylib_by_path(&mut self, path: &Path, _as_needed: bool) {1390        self.link_or_cc_arg(path);1391    }13921393    fn link_staticlib_by_name(&mut self, name: &str, _verbatim: bool, whole_archive: bool) {1394        if !whole_archive {1395            self.link_or_cc_args(&["-l", name]);1396        } else {1397            self.link_arg("--whole-archive")1398                .link_or_cc_args(&["-l", name])1399                .link_arg("--no-whole-archive");1400        }1401    }14021403    fn link_staticlib_by_path(&mut self, path: &Path, whole_archive: bool) {1404        if !whole_archive {1405            self.link_or_cc_arg(path);1406        } else {1407            self.link_arg("--whole-archive").link_or_cc_arg(path).link_arg("--no-whole-archive");1408        }1409    }14101411    fn full_relro(&mut self) {}14121413    fn partial_relro(&mut self) {}14141415    fn no_relro(&mut self) {}14161417    fn gc_sections(&mut self, _keep_metadata: bool) {1418        self.link_arg("--gc-sections");1419    }14201421    fn optimize(&mut self) {1422        // The -O flag is, as of late 2023, only used for merging of strings and debuginfo, and1423        // only differentiates -O0 and -O1. It does not apply to LTO.1424        self.link_arg(match self.sess.opts.optimize {1425            OptLevel::No => "-O0",1426            OptLevel::Less => "-O1",1427            OptLevel::More => "-O2",1428            OptLevel::Aggressive => "-O3",1429            // Currently LLD doesn't support `Os` and `Oz`, so pass through `O2`1430            // instead.1431            OptLevel::Size => "-O2",1432            OptLevel::SizeMin => "-O2",1433        });1434    }14351436    fn pgo_gen(&mut self) {}14371438    fn debuginfo(&mut self, strip: Strip, _: &[PathBuf]) {1439        match strip {1440            Strip::None => {}1441            Strip::Debuginfo => {1442                self.link_arg("--strip-debug");1443            }1444            Strip::Symbols => {1445                self.link_arg("--strip-all");1446            }1447        }1448    }14491450    fn control_flow_guard(&mut self) {}14511452    fn ehcont_guard(&mut self) {}14531454    fn no_crt_objects(&mut self) {}14551456    fn no_default_libraries(&mut self) {}14571458    fn export_symbols(1459        &mut self,1460        _tmpdir: &Path,1461        _crate_type: CrateType,1462        symbols: &[(String, SymbolExportKind)],1463    ) {1464        for (sym, _) in symbols {1465            self.link_args(&["--export", sym]);1466        }14671468        // LLD will hide these otherwise-internal symbols since it only exports1469        // symbols explicitly passed via the `--export` flags above and hides all1470        // others. Various bits and pieces of wasm32-unknown-unknown tooling use1471        // this, so be sure these symbols make their way out of the linker as well.1472        if matches!(self.sess.target.os, Os::Unknown | Os::None) {1473            self.link_args(&["--export=__heap_base", "--export=__data_end"]);1474        }1475    }14761477    fn windows_subsystem(&mut self, _subsystem: WindowsSubsystemKind) {}14781479    fn linker_plugin_lto(&mut self) {1480        match self.sess.opts.cg.linker_plugin_lto {1481            LinkerPluginLto::Disabled => {1482                // Nothing to do1483            }1484            LinkerPluginLto::LinkerPluginAuto => {1485                self.push_linker_plugin_lto_args();1486            }1487            LinkerPluginLto::LinkerPlugin(_) => {1488                self.push_linker_plugin_lto_args();1489            }1490        }1491    }1492}14931494impl<'a> WasmLd<'a> {1495    fn push_linker_plugin_lto_args(&mut self) {1496        let opt_level = match self.sess.opts.optimize {1497            config::OptLevel::No => "O0",1498            config::OptLevel::Less => "O1",1499            config::OptLevel::More => "O2",1500            config::OptLevel::Aggressive => "O3",1501            // wasm-ld only handles integer LTO opt levels. Use O21502            config::OptLevel::Size | config::OptLevel::SizeMin => "O2",1503        };1504        self.link_arg(&format!("--lto-{opt_level}"));1505    }1506}15071508/// Linker shepherd script for L4Re (Fiasco)1509struct L4Bender<'a> {1510    cmd: Command,1511    sess: &'a Session,1512    hinted_static: bool,1513}15141515impl<'a> Linker for L4Bender<'a> {1516    fn cmd(&mut self) -> &mut Command {1517        &mut self.cmd1518    }15191520    fn set_output_kind(1521        &mut self,1522        _output_kind: LinkOutputKind,1523        _crate_type: CrateType,1524        _out_filename: &Path,1525    ) {1526    }15271528    fn link_staticlib_by_name(&mut self, name: &str, _verbatim: bool, whole_archive: bool) {1529        self.hint_static();1530        if !whole_archive {1531            self.link_arg(format!("-PC{name}"));1532        } else {1533            self.link_arg("--whole-archive")1534                .link_or_cc_arg(format!("-l{name}"))1535                .link_arg("--no-whole-archive");1536        }1537    }15381539    fn link_staticlib_by_path(&mut self, path: &Path, whole_archive: bool) {1540        self.hint_static();1541        if !whole_archive {1542            self.link_or_cc_arg(path);1543        } else {1544            self.link_arg("--whole-archive").link_or_cc_arg(path).link_arg("--no-whole-archive");1545        }1546    }15471548    fn full_relro(&mut self) {1549        self.link_args(&["-z", "relro", "-z", "now"]);1550    }15511552    fn partial_relro(&mut self) {1553        self.link_args(&["-z", "relro"]);1554    }15551556    fn no_relro(&mut self) {1557        self.link_args(&["-z", "norelro"]);1558    }15591560    fn gc_sections(&mut self, keep_metadata: bool) {1561        if !keep_metadata {1562            self.link_arg("--gc-sections");1563        }1564    }15651566    fn optimize(&mut self) {1567        // GNU-style linkers support optimization with -O. GNU ld doesn't1568        // need a numeric argument, but other linkers do.1569        if self.sess.opts.optimize == config::OptLevel::More1570            || self.sess.opts.optimize == config::OptLevel::Aggressive1571        {1572            self.link_arg("-O1");1573        }1574    }15751576    fn pgo_gen(&mut self) {}15771578    fn debuginfo(&mut self, strip: Strip, _: &[PathBuf]) {1579        match strip {1580            Strip::None => {}1581            Strip::Debuginfo => {1582                self.link_arg("--strip-debug");1583            }1584            Strip::Symbols => {1585                self.link_arg("--strip-all");1586            }1587        }1588    }15891590    fn no_default_libraries(&mut self) {1591        self.cc_arg("-nostdlib");1592    }15931594    fn export_symbols(&mut self, _: &Path, _: CrateType, _: &[(String, SymbolExportKind)]) {1595        // ToDo, not implemented, copy from GCC1596        self.sess.dcx().emit_warn(errors::L4BenderExportingSymbolsUnimplemented);1597    }15981599    fn windows_subsystem(&mut self, subsystem: WindowsSubsystemKind) {1600        let subsystem = subsystem.as_str();1601        self.link_arg(&format!("--subsystem {subsystem}"));1602    }16031604    fn reset_per_library_state(&mut self) {1605        self.hint_static(); // Reset to default before returning the composed command line.1606    }16071608    fn linker_plugin_lto(&mut self) {}16091610    fn control_flow_guard(&mut self) {}16111612    fn ehcont_guard(&mut self) {}16131614    fn no_crt_objects(&mut self) {}1615}16161617impl<'a> L4Bender<'a> {1618    fn new(cmd: Command, sess: &'a Session) -> L4Bender<'a> {1619        L4Bender { cmd, sess, hinted_static: false }1620    }16211622    fn hint_static(&mut self) {1623        if !self.hinted_static {1624            self.link_or_cc_arg("-static");1625            self.hinted_static = true;1626        }1627    }1628}16291630/// Linker for AIX.1631struct AixLinker<'a> {1632    cmd: Command,1633    sess: &'a Session,1634    hinted_static: Option<bool>,1635}16361637impl<'a> AixLinker<'a> {1638    fn new(cmd: Command, sess: &'a Session) -> AixLinker<'a> {1639        AixLinker { cmd, sess, hinted_static: None }1640    }16411642    fn hint_static(&mut self) {1643        if self.hinted_static != Some(true) {1644            self.link_arg("-bstatic");1645            self.hinted_static = Some(true);1646        }1647    }16481649    fn hint_dynamic(&mut self) {1650        if self.hinted_static != Some(false) {1651            self.link_arg("-bdynamic");1652            self.hinted_static = Some(false);1653        }1654    }16551656    fn build_dylib(&mut self, _out_filename: &Path) {1657        self.link_args(&["-bM:SRE", "-bnoentry"]);1658        // FIXME: Use CreateExportList utility to create export list1659        // and remove -bexpfull.1660        self.link_arg("-bexpfull");1661    }1662}16631664impl<'a> Linker for AixLinker<'a> {1665    fn cmd(&mut self) -> &mut Command {1666        &mut self.cmd1667    }16681669    fn set_output_kind(1670        &mut self,1671        output_kind: LinkOutputKind,1672        _crate_type: CrateType,1673        out_filename: &Path,1674    ) {1675        match output_kind {1676            LinkOutputKind::DynamicDylib => {1677                self.hint_dynamic();1678                self.build_dylib(out_filename);1679            }1680            LinkOutputKind::StaticDylib => {1681                self.hint_static();1682                self.build_dylib(out_filename);1683            }1684            _ => {}1685        }1686    }16871688    fn link_dylib_by_name(&mut self, name: &str, verbatim: bool, _as_needed: bool) {1689        self.hint_dynamic();1690        self.link_or_cc_arg(if verbatim { String::from(name) } else { format!("-l{name}") });1691    }16921693    fn link_dylib_by_path(&mut self, path: &Path, _as_needed: bool) {1694        self.hint_dynamic();1695        self.link_or_cc_arg(path);1696    }16971698    fn link_staticlib_by_name(&mut self, name: &str, verbatim: bool, whole_archive: bool) {1699        self.hint_static();1700        if !whole_archive {1701            self.link_or_cc_arg(if verbatim { String::from(name) } else { format!("-l{name}") });1702        } else {1703            let mut arg = OsString::from("-bkeepfile:");1704            arg.push(find_native_static_library(name, verbatim, self.sess));1705            self.link_or_cc_arg(arg);1706        }1707    }17081709    fn link_staticlib_by_path(&mut self, path: &Path, whole_archive: bool) {1710        self.hint_static();1711        if !whole_archive {1712            self.link_or_cc_arg(path);1713        } else {1714            let mut arg = OsString::from("-bkeepfile:");1715            arg.push(path);1716            self.link_arg(arg);1717        }1718    }17191720    fn full_relro(&mut self) {}17211722    fn partial_relro(&mut self) {}17231724    fn no_relro(&mut self) {}17251726    fn gc_sections(&mut self, _keep_metadata: bool) {1727        self.link_arg("-bgc");1728    }17291730    fn optimize(&mut self) {}17311732    fn pgo_gen(&mut self) {1733        self.link_arg("-bdbg:namedsects:ss");1734        self.link_arg("-u");1735        self.link_arg("__llvm_profile_runtime");1736    }17371738    fn control_flow_guard(&mut self) {}17391740    fn ehcont_guard(&mut self) {}17411742    fn debuginfo(&mut self, _: Strip, _: &[PathBuf]) {}17431744    fn no_crt_objects(&mut self) {}17451746    fn no_default_libraries(&mut self) {}17471748    fn export_symbols(1749        &mut self,1750        tmpdir: &Path,1751        _crate_type: CrateType,1752        symbols: &[(String, SymbolExportKind)],1753    ) {1754        let path = tmpdir.join("list.exp");1755        let res = try {1756            let mut f = File::create_buffered(&path)?;1757            // FIXME: use llvm-nm to generate export list.1758            for (symbol, _) in symbols {1759                debug!("  _{symbol}");1760                writeln!(f, "  {symbol}")?;1761            }1762        };1763        if let Err(e) = res {1764            self.sess.dcx().fatal(format!("failed to write export file: {e}"));1765        }1766        self.link_arg(format!("-bE:{}", path.to_str().unwrap()));1767    }17681769    fn windows_subsystem(&mut self, _subsystem: WindowsSubsystemKind) {}17701771    fn reset_per_library_state(&mut self) {1772        self.hint_dynamic();1773    }17741775    fn linker_plugin_lto(&mut self) {}17761777    fn add_eh_frame_header(&mut self) {}17781779    fn add_no_exec(&mut self) {}17801781    fn add_as_needed(&mut self) {}1782}17831784fn for_each_exported_symbols_include_dep<'tcx>(1785    tcx: TyCtxt<'tcx>,1786    crate_type: CrateType,1787    mut callback: impl FnMut(ExportedSymbol<'tcx>, SymbolExportInfo, CrateNum),1788) {1789    let formats = tcx.dependency_formats(());1790    let deps = &formats[&crate_type];17911792    for (cnum, dep_format) in deps.iter_enumerated() {1793        // For each dependency that we are linking to statically ...1794        if *dep_format == Linkage::Static {1795            for &(symbol, info) in tcx.exported_non_generic_symbols(cnum).iter() {1796                callback(symbol, info, cnum);1797            }1798            for &(symbol, info) in tcx.exported_generic_symbols(cnum).iter() {1799                callback(symbol, info, cnum);1800            }1801        }1802    }1803}18041805pub(crate) fn exported_symbols(1806    tcx: TyCtxt<'_>,1807    crate_type: CrateType,1808) -> Vec<(String, SymbolExportKind)> {1809    if let Some(ref exports) = tcx.sess.target.override_export_symbols {1810        return exports1811            .iter()1812            .map(|name| {1813                (1814                    name.to_string(),1815                    // FIXME use the correct export kind for this symbol. override_export_symbols1816                    // can't directly specify the SymbolExportKind as it is defined in rustc_middle1817                    // which rustc_target can't depend on.1818                    SymbolExportKind::Text,1819                )1820            })1821            .collect();1822    }18231824    let mut symbols = if let CrateType::ProcMacro = crate_type {1825        exported_symbols_for_proc_macro_crate(tcx)1826    } else {1827        exported_symbols_for_non_proc_macro(tcx, crate_type)1828    };18291830    if crate_type == CrateType::Dylib || crate_type == CrateType::ProcMacro {1831        let metadata_symbol_name = exported_symbols::metadata_symbol_name(tcx);1832        symbols.push((metadata_symbol_name, SymbolExportKind::Data));1833    }18341835    symbols1836}18371838fn exported_symbols_for_non_proc_macro(1839    tcx: TyCtxt<'_>,1840    crate_type: CrateType,1841) -> Vec<(String, SymbolExportKind)> {1842    let mut symbols = Vec::new();1843    let export_threshold = symbol_export::crates_export_threshold(&[crate_type]);1844    for_each_exported_symbols_include_dep(tcx, crate_type, |symbol, info, cnum| {1845        // Do not export mangled symbols from cdylibs and don't attempt to export compiler-builtins1846        // from any dylib. The latter doesn't work anyway as we use hidden visibility for1847        // compiler-builtins. Most linkers silently ignore it, but ld64 gives a warning.1848        if info.level.is_below_threshold(export_threshold) && !tcx.is_compiler_builtins(cnum) {1849            symbols.push((1850                symbol_export::exporting_symbol_name_for_instance_in_crate(tcx, symbol, cnum),1851                info.kind,1852            ));1853            symbol_export::extend_exported_symbols(&mut symbols, tcx, symbol, cnum);1854        }1855    });18561857    // Mark allocator shim symbols as exported only if they were generated.1858    if export_threshold == SymbolExportLevel::Rust1859        && needs_allocator_shim_for_linking(tcx.dependency_formats(()), crate_type)1860        && let Some(kind) = tcx.allocator_kind(())1861    {1862        symbols.extend(allocator_shim_symbols(tcx, kind));1863    }18641865    symbols1866}18671868fn exported_symbols_for_proc_macro_crate(tcx: TyCtxt<'_>) -> Vec<(String, SymbolExportKind)> {1869    // `exported_symbols` will be empty when !should_codegen.1870    if !tcx.sess.opts.output_types.should_codegen() {1871        return Vec::new();1872    }18731874    let stable_crate_id = tcx.stable_crate_id(LOCAL_CRATE);1875    let proc_macro_decls_name = tcx.sess.generate_proc_macro_decls_symbol(stable_crate_id);18761877    vec![(proc_macro_decls_name, SymbolExportKind::Data)]1878}18791880pub(crate) fn linked_symbols(1881    tcx: TyCtxt<'_>,1882    crate_type: CrateType,1883) -> Vec<(String, SymbolExportKind)> {1884    match crate_type {1885        CrateType::Executable1886        | CrateType::ProcMacro1887        | CrateType::Cdylib1888        | CrateType::Dylib1889        | CrateType::Sdylib => (),1890        CrateType::StaticLib | CrateType::Rlib => {1891            // These are not linked, so no need to generate symbols.o for them.1892            return Vec::new();1893        }1894    }18951896    match tcx.sess.lto() {1897        Lto::No | Lto::ThinLocal => {}1898        Lto::Thin | Lto::Fat => {1899            // We really only need symbols from upstream rlibs to end up in the linked symbols list.1900            // The rest are in separate object files which the linker will always link in and1901            // doesn't have rules around the order in which they need to appear.1902            // When doing LTO, some of the symbols in the linked symbols list happen to be1903            // internalized by LTO, which then prevents referencing them from symbols.o. When doing1904            // LTO, all object files that get linked in will be local object files rather than1905            // pulled in from rlibs, so an empty linked symbols list works fine to avoid referencing1906            // all those internalized symbols from symbols.o.1907            return Vec::new();1908        }1909    }19101911    let mut symbols = Vec::new();19121913    let export_threshold = symbol_export::crates_export_threshold(&[crate_type]);1914    for_each_exported_symbols_include_dep(tcx, crate_type, |symbol, info, cnum| {1915        if info.level.is_below_threshold(export_threshold) && !tcx.is_compiler_builtins(cnum)1916            || info.used1917            || info.rustc_std_internal_symbol1918        {1919            symbols.push((1920                symbol_export::linking_symbol_name_for_instance_in_crate(1921                    tcx, symbol, info.kind, cnum,1922                ),1923                info.kind,1924            ));1925        }1926    });19271928    symbols1929}19301931/// Much simplified and explicit CLI for the NVPTX linker. The linker operates1932/// with bitcode and uses LLVM backend to generate a PTX assembly.1933struct PtxLinker<'a> {1934    cmd: Command,1935    sess: &'a Session,1936}19371938impl<'a> Linker for PtxLinker<'a> {1939    fn cmd(&mut self) -> &mut Command {1940        &mut self.cmd1941    }19421943    fn set_output_kind(1944        &mut self,1945        _output_kind: LinkOutputKind,1946        _crate_type: CrateType,1947        _out_filename: &Path,1948    ) {1949    }19501951    fn link_staticlib_by_name(&mut self, _name: &str, _verbatim: bool, _whole_archive: bool) {1952        panic!("staticlibs not supported")1953    }19541955    fn link_staticlib_by_path(&mut self, path: &Path, _whole_archive: bool) {1956        self.link_arg("--rlib").link_arg(path);1957    }19581959    fn debuginfo(&mut self, _strip: Strip, _: &[PathBuf]) {1960        self.link_arg("--debug");1961    }19621963    fn add_object(&mut self, path: &Path) {1964        self.link_arg("--bitcode").link_arg(path);1965    }19661967    fn optimize(&mut self) {1968        match self.sess.lto() {1969            Lto::Thin | Lto::Fat | Lto::ThinLocal => {1970                self.link_arg("-Olto");1971            }19721973            Lto::No => {}1974        }1975    }19761977    fn full_relro(&mut self) {}19781979    fn partial_relro(&mut self) {}19801981    fn no_relro(&mut self) {}19821983    fn gc_sections(&mut self, _keep_metadata: bool) {}19841985    fn pgo_gen(&mut self) {}19861987    fn no_crt_objects(&mut self) {}19881989    fn no_default_libraries(&mut self) {}19901991    fn control_flow_guard(&mut self) {}19921993    fn ehcont_guard(&mut self) {}19941995    fn export_symbols(1996        &mut self,1997        _tmpdir: &Path,1998        _crate_type: CrateType,1999        _symbols: &[(String, SymbolExportKind)],2000    ) {