rustc_codegen_ssa/back/
linker.rs

1use std::ffi::{OsStr, OsString};
2use std::fs::{self, File};
3use std::io::prelude::*;
4use std::path::{Path, PathBuf};
5use std::{env, io, iter, mem, str};
6
7use cc::windows_registry;
8use rustc_hir::def_id::{CrateNum, LOCAL_CRATE};
9use rustc_metadata::{
10    find_native_static_library, try_find_native_dynamic_library, try_find_native_static_library,
11};
12use rustc_middle::bug;
13use rustc_middle::middle::dependency_format::Linkage;
14use rustc_middle::middle::exported_symbols;
15use rustc_middle::middle::exported_symbols::{ExportedSymbol, SymbolExportInfo, SymbolExportKind};
16use rustc_middle::ty::TyCtxt;
17use rustc_session::Session;
18use rustc_session::config::{self, CrateType, DebugInfo, LinkerPluginLto, Lto, OptLevel, Strip};
19use rustc_span::sym;
20use rustc_target::spec::{Cc, LinkOutputKind, LinkerFlavor, Lld};
21use tracing::{debug, warn};
22
23use super::command::Command;
24use super::symbol_export;
25use crate::errors;
26
27#[cfg(test)]
28mod tests;
29
30/// Disables non-English messages from localized linkers.
31/// Such messages may cause issues with text encoding on Windows (#35785)
32/// and prevent inspection of linker output in case of errors, which we occasionally do.
33/// This should be acceptable because other messages from rustc are in English anyway,
34/// and may also be desirable to improve searchability of the linker diagnostics.
35pub(crate) fn disable_localization(linker: &mut Command) {
36    // No harm in setting both env vars simultaneously.
37    // Unix-style linkers.
38    linker.env("LC_ALL", "C");
39    // MSVC's `link.exe`.
40    linker.env("VSLANG", "1033");
41}
42
43/// The third parameter is for env vars, used on windows to set up the
44/// path for MSVC to find its DLLs, and gcc to find its bundled
45/// toolchain
46pub(crate) fn get_linker<'a>(
47    sess: &'a Session,
48    linker: &Path,
49    flavor: LinkerFlavor,
50    self_contained: bool,
51    target_cpu: &'a str,
52) -> Box<dyn Linker + 'a> {
53    let msvc_tool = windows_registry::find_tool(&sess.target.arch, "link.exe");
54
55    // If our linker looks like a batch script on Windows then to execute this
56    // we'll need to spawn `cmd` explicitly. This is primarily done to handle
57    // emscripten where the linker is `emcc.bat` and needs to be spawned as
58    // `cmd /c emcc.bat ...`.
59    //
60    // This worked historically but is needed manually since #42436 (regression
61    // was tagged as #42791) and some more info can be found on #44443 for
62    // emscripten itself.
63    let mut cmd = match linker.to_str() {
64        Some(linker) if cfg!(windows) && linker.ends_with(".bat") => Command::bat_script(linker),
65        _ => match flavor {
66            LinkerFlavor::Gnu(Cc::No, Lld::Yes)
67            | LinkerFlavor::Darwin(Cc::No, Lld::Yes)
68            | LinkerFlavor::WasmLld(Cc::No)
69            | LinkerFlavor::Msvc(Lld::Yes) => Command::lld(linker, flavor.lld_flavor()),
70            LinkerFlavor::Msvc(Lld::No)
71                if sess.opts.cg.linker.is_none() && sess.target.linker.is_none() =>
72            {
73                Command::new(msvc_tool.as_ref().map_or(linker, |t| t.path()))
74            }
75            _ => Command::new(linker),
76        },
77    };
78
79    // UWP apps have API restrictions enforced during Store submissions.
80    // To comply with the Windows App Certification Kit,
81    // MSVC needs to link with the Store versions of the runtime libraries (vcruntime, msvcrt, etc).
82    let t = &sess.target;
83    if matches!(flavor, LinkerFlavor::Msvc(..)) && t.vendor == "uwp" {
84        if let Some(ref tool) = msvc_tool {
85            let original_path = tool.path();
86            if let Some(root_lib_path) = original_path.ancestors().nth(4) {
87                let arch = match t.arch.as_ref() {
88                    "x86_64" => Some("x64"),
89                    "x86" => Some("x86"),
90                    "aarch64" => Some("arm64"),
91                    "arm" => Some("arm"),
92                    _ => None,
93                };
94                if let Some(ref a) = arch {
95                    // FIXME: Move this to `fn linker_with_args`.
96                    let mut arg = OsString::from("/LIBPATH:");
97                    arg.push(format!("{}\\lib\\{}\\store", root_lib_path.display(), a));
98                    cmd.arg(&arg);
99                } else {
100                    warn!("arch is not supported");
101                }
102            } else {
103                warn!("MSVC root path lib location not found");
104            }
105        } else {
106            warn!("link.exe not found");
107        }
108    }
109
110    // The compiler's sysroot often has some bundled tools, so add it to the
111    // PATH for the child.
112    let mut new_path = sess.get_tools_search_paths(self_contained);
113    let mut msvc_changed_path = false;
114    if sess.target.is_like_msvc
115        && let Some(ref tool) = msvc_tool
116    {
117        cmd.args(tool.args());
118        for (k, v) in tool.env() {
119            if k == "PATH" {
120                new_path.extend(env::split_paths(v));
121                msvc_changed_path = true;
122            } else {
123                cmd.env(k, v);
124            }
125        }
126    }
127
128    if !msvc_changed_path && let Some(path) = env::var_os("PATH") {
129        new_path.extend(env::split_paths(&path));
130    }
131    cmd.env("PATH", env::join_paths(new_path).unwrap());
132
133    // FIXME: Move `/LIBPATH` addition for uwp targets from the linker construction
134    // to the linker args construction.
135    assert!(cmd.get_args().is_empty() || sess.target.vendor == "uwp");
136    match flavor {
137        LinkerFlavor::Unix(Cc::No) if sess.target.os == "l4re" => {
138            Box::new(L4Bender::new(cmd, sess)) as Box<dyn Linker>
139        }
140        LinkerFlavor::Unix(Cc::No) if sess.target.os == "aix" => {
141            Box::new(AixLinker::new(cmd, sess)) as Box<dyn Linker>
142        }
143        LinkerFlavor::WasmLld(Cc::No) => Box::new(WasmLd::new(cmd, sess)) as Box<dyn Linker>,
144        LinkerFlavor::Gnu(cc, _)
145        | LinkerFlavor::Darwin(cc, _)
146        | LinkerFlavor::WasmLld(cc)
147        | LinkerFlavor::Unix(cc) => Box::new(GccLinker {
148            cmd,
149            sess,
150            target_cpu,
151            hinted_static: None,
152            is_ld: cc == Cc::No,
153            is_gnu: flavor.is_gnu(),
154            uses_lld: flavor.uses_lld(),
155        }) as Box<dyn Linker>,
156        LinkerFlavor::Msvc(..) => Box::new(MsvcLinker { cmd, sess }) as Box<dyn Linker>,
157        LinkerFlavor::EmCc => Box::new(EmLinker { cmd, sess }) as Box<dyn Linker>,
158        LinkerFlavor::Bpf => Box::new(BpfLinker { cmd, sess }) as Box<dyn Linker>,
159        LinkerFlavor::Llbc => Box::new(LlbcLinker { cmd, sess }) as Box<dyn Linker>,
160        LinkerFlavor::Ptx => Box::new(PtxLinker { cmd, sess }) as Box<dyn Linker>,
161    }
162}
163
164// Note: Ideally neither these helper function, nor the macro-generated inherent methods below
165// would exist, and these functions would live in `trait Linker`.
166// Unfortunately, adding these functions to `trait Linker` make it `dyn`-incompatible.
167// If the methods are added to the trait with `where Self: Sized` bounds, then even a separate
168// implementation of them for `dyn Linker {}` wouldn't work due to a conflict with those
169// uncallable methods in the trait.
170
171/// Just pass the arguments to the linker as is.
172/// It is assumed that they are correctly prepared in advance.
173fn verbatim_args<L: Linker + ?Sized>(
174    l: &mut L,
175    args: impl IntoIterator<Item: AsRef<OsStr>>,
176) -> &mut L {
177    for arg in args {
178        l.cmd().arg(arg);
179    }
180    l
181}
182/// Add underlying linker arguments to C compiler command, by wrapping them in
183/// `-Wl` or `-Xlinker`.
184fn convert_link_args_to_cc_args(cmd: &mut Command, args: impl IntoIterator<Item: AsRef<OsStr>>) {
185    let mut combined_arg = OsString::from("-Wl");
186    for arg in args {
187        // If the argument itself contains a comma, we need to emit it
188        // as `-Xlinker`, otherwise we can use `-Wl`.
189        if arg.as_ref().as_encoded_bytes().contains(&b',') {
190            // Emit current `-Wl` argument, if any has been built.
191            if combined_arg != OsStr::new("-Wl") {
192                cmd.arg(combined_arg);
193                // Begin next `-Wl` argument.
194                combined_arg = OsString::from("-Wl");
195            }
196
197            // Emit `-Xlinker` argument.
198            cmd.arg("-Xlinker");
199            cmd.arg(arg);
200        } else {
201            // Append to `-Wl` argument.
202            combined_arg.push(",");
203            combined_arg.push(arg);
204        }
205    }
206    // Emit final `-Wl` argument.
207    if combined_arg != OsStr::new("-Wl") {
208        cmd.arg(combined_arg);
209    }
210}
211/// Arguments for the underlying linker.
212/// Add options to pass them through cc wrapper if `Linker` is a cc wrapper.
213fn link_args<L: Linker + ?Sized>(l: &mut L, args: impl IntoIterator<Item: AsRef<OsStr>>) -> &mut L {
214    if !l.is_cc() {
215        verbatim_args(l, args);
216    } else {
217        convert_link_args_to_cc_args(l.cmd(), args);
218    }
219    l
220}
221/// Arguments for the cc wrapper specifically.
222/// Check that it's indeed a cc wrapper and pass verbatim.
223fn cc_args<L: Linker + ?Sized>(l: &mut L, args: impl IntoIterator<Item: AsRef<OsStr>>) -> &mut L {
224    assert!(l.is_cc());
225    verbatim_args(l, args)
226}
227/// Arguments supported by both underlying linker and cc wrapper, pass verbatim.
228fn link_or_cc_args<L: Linker + ?Sized>(
229    l: &mut L,
230    args: impl IntoIterator<Item: AsRef<OsStr>>,
231) -> &mut L {
232    verbatim_args(l, args)
233}
234
235macro_rules! generate_arg_methods {
236    ($($ty:ty)*) => { $(
237        impl $ty {
238            #[allow(unused)]
239            pub(crate) fn verbatim_args(&mut self, args: impl IntoIterator<Item: AsRef<OsStr>>) -> &mut Self {
240                verbatim_args(self, args)
241            }
242            #[allow(unused)]
243            pub(crate) fn verbatim_arg(&mut self, arg: impl AsRef<OsStr>) -> &mut Self {
244                verbatim_args(self, iter::once(arg))
245            }
246            #[allow(unused)]
247            pub(crate) fn link_args(&mut self, args: impl IntoIterator<Item: AsRef<OsStr>>) -> &mut Self {
248                link_args(self, args)
249            }
250            #[allow(unused)]
251            pub(crate) fn link_arg(&mut self, arg: impl AsRef<OsStr>) -> &mut Self {
252                link_args(self, iter::once(arg))
253            }
254            #[allow(unused)]
255            pub(crate) fn cc_args(&mut self, args: impl IntoIterator<Item: AsRef<OsStr>>) -> &mut Self {
256                cc_args(self, args)
257            }
258            #[allow(unused)]
259            pub(crate) fn cc_arg(&mut self, arg: impl AsRef<OsStr>) -> &mut Self {
260                cc_args(self, iter::once(arg))
261            }
262            #[allow(unused)]
263            pub(crate) fn link_or_cc_args(&mut self, args: impl IntoIterator<Item: AsRef<OsStr>>) -> &mut Self {
264                link_or_cc_args(self, args)
265            }
266            #[allow(unused)]
267            pub(crate) fn link_or_cc_arg(&mut self, arg: impl AsRef<OsStr>) -> &mut Self {
268                link_or_cc_args(self, iter::once(arg))
269            }
270        }
271    )* }
272}
273
274generate_arg_methods! {
275    GccLinker<'_>
276    MsvcLinker<'_>
277    EmLinker<'_>
278    WasmLd<'_>
279    L4Bender<'_>
280    AixLinker<'_>
281    LlbcLinker<'_>
282    PtxLinker<'_>
283    BpfLinker<'_>
284    dyn Linker + '_
285}
286
287/// Linker abstraction used by `back::link` to build up the command to invoke a
288/// linker.
289///
290/// This trait is the total list of requirements needed by `back::link` and
291/// represents the meaning of each option being passed down. This trait is then
292/// used to dispatch on whether a GNU-like linker (generally `ld.exe`) or an
293/// MSVC linker (e.g., `link.exe`) is being used.
294pub(crate) trait Linker {
295    fn cmd(&mut self) -> &mut Command;
296    fn is_cc(&self) -> bool {
297        false
298    }
299    fn set_output_kind(
300        &mut self,
301        output_kind: LinkOutputKind,
302        crate_type: CrateType,
303        out_filename: &Path,
304    );
305    fn link_dylib_by_name(&mut self, _name: &str, _verbatim: bool, _as_needed: bool) {
306        bug!("dylib linked with unsupported linker")
307    }
308    fn link_dylib_by_path(&mut self, _path: &Path, _as_needed: bool) {
309        bug!("dylib linked with unsupported linker")
310    }
311    fn link_framework_by_name(&mut self, _name: &str, _verbatim: bool, _as_needed: bool) {
312        bug!("framework linked with unsupported linker")
313    }
314    fn link_staticlib_by_name(&mut self, name: &str, verbatim: bool, whole_archive: bool);
315    fn link_staticlib_by_path(&mut self, path: &Path, whole_archive: bool);
316    fn include_path(&mut self, path: &Path) {
317        link_or_cc_args(link_or_cc_args(self, &["-L"]), &[path]);
318    }
319    fn framework_path(&mut self, _path: &Path) {
320        bug!("framework path set with unsupported linker")
321    }
322    fn output_filename(&mut self, path: &Path) {
323        link_or_cc_args(link_or_cc_args(self, &["-o"]), &[path]);
324    }
325    fn add_object(&mut self, path: &Path) {
326        link_or_cc_args(self, &[path]);
327    }
328    fn gc_sections(&mut self, keep_metadata: bool);
329    fn no_gc_sections(&mut self);
330    fn full_relro(&mut self);
331    fn partial_relro(&mut self);
332    fn no_relro(&mut self);
333    fn optimize(&mut self);
334    fn pgo_gen(&mut self);
335    fn control_flow_guard(&mut self);
336    fn ehcont_guard(&mut self);
337    fn debuginfo(&mut self, strip: Strip, natvis_debugger_visualizers: &[PathBuf]);
338    fn no_crt_objects(&mut self);
339    fn no_default_libraries(&mut self);
340    fn export_symbols(&mut self, tmpdir: &Path, crate_type: CrateType, symbols: &[String]);
341    fn subsystem(&mut self, subsystem: &str);
342    fn linker_plugin_lto(&mut self);
343    fn add_eh_frame_header(&mut self) {}
344    fn add_no_exec(&mut self) {}
345    fn add_as_needed(&mut self) {}
346    fn reset_per_library_state(&mut self) {}
347}
348
349impl dyn Linker + '_ {
350    pub(crate) fn take_cmd(&mut self) -> Command {
351        mem::replace(self.cmd(), Command::new(""))
352    }
353}
354
355struct GccLinker<'a> {
356    cmd: Command,
357    sess: &'a Session,
358    target_cpu: &'a str,
359    hinted_static: Option<bool>, // Keeps track of the current hinting mode.
360    // Link as ld
361    is_ld: bool,
362    is_gnu: bool,
363    uses_lld: bool,
364}
365
366impl<'a> GccLinker<'a> {
367    fn takes_hints(&self) -> bool {
368        // Really this function only returns true if the underlying linker
369        // configured for a compiler is binutils `ld.bfd` and `ld.gold`. We
370        // don't really have a foolproof way to detect that, so rule out some
371        // platforms where currently this is guaranteed to *not* be the case:
372        //
373        // * On OSX they have their own linker, not binutils'
374        // * For WebAssembly the only functional linker is LLD, which doesn't
375        //   support hint flags
376        !self.sess.target.is_like_darwin && !self.sess.target.is_like_wasm
377    }
378
379    // Some platforms take hints about whether a library is static or dynamic.
380    // For those that support this, we ensure we pass the option if the library
381    // was flagged "static" (most defaults are dynamic) to ensure that if
382    // libfoo.a and libfoo.so both exist that the right one is chosen.
383    fn hint_static(&mut self) {
384        if !self.takes_hints() {
385            return;
386        }
387        if self.hinted_static != Some(true) {
388            self.link_arg("-Bstatic");
389            self.hinted_static = Some(true);
390        }
391    }
392
393    fn hint_dynamic(&mut self) {
394        if !self.takes_hints() {
395            return;
396        }
397        if self.hinted_static != Some(false) {
398            self.link_arg("-Bdynamic");
399            self.hinted_static = Some(false);
400        }
401    }
402
403    fn push_linker_plugin_lto_args(&mut self, plugin_path: Option<&OsStr>) {
404        if let Some(plugin_path) = plugin_path {
405            let mut arg = OsString::from("-plugin=");
406            arg.push(plugin_path);
407            self.link_arg(&arg);
408        }
409
410        let opt_level = match self.sess.opts.optimize {
411            config::OptLevel::No => "O0",
412            config::OptLevel::Less => "O1",
413            config::OptLevel::More | config::OptLevel::Size | config::OptLevel::SizeMin => "O2",
414            config::OptLevel::Aggressive => "O3",
415        };
416
417        if let Some(path) = &self.sess.opts.unstable_opts.profile_sample_use {
418            self.link_arg(&format!("-plugin-opt=sample-profile={}", path.display()));
419        };
420        self.link_args(&[
421            &format!("-plugin-opt={opt_level}"),
422            &format!("-plugin-opt=mcpu={}", self.target_cpu),
423        ]);
424    }
425
426    fn build_dylib(&mut self, crate_type: CrateType, out_filename: &Path) {
427        // On mac we need to tell the linker to let this library be rpathed
428        if self.sess.target.is_like_darwin {
429            if self.is_cc() {
430                // `-dynamiclib` makes `cc` pass `-dylib` to the linker.
431                self.cc_arg("-dynamiclib");
432            } else {
433                self.link_arg("-dylib");
434                // Clang also sets `-dynamic`, but that's implied by `-dylib`, so unnecessary.
435            }
436
437            // Note that the `osx_rpath_install_name` option here is a hack
438            // purely to support bootstrap right now, we should get a more
439            // principled solution at some point to force the compiler to pass
440            // the right `-Wl,-install_name` with an `@rpath` in it.
441            if self.sess.opts.cg.rpath || self.sess.opts.unstable_opts.osx_rpath_install_name {
442                let mut rpath = OsString::from("@rpath/");
443                rpath.push(out_filename.file_name().unwrap());
444                self.link_arg("-install_name").link_arg(rpath);
445            }
446        } else {
447            self.link_or_cc_arg("-shared");
448            if let Some(name) = out_filename.file_name() {
449                if self.sess.target.is_like_windows {
450                    // The output filename already contains `dll_suffix` so
451                    // the resulting import library will have a name in the
452                    // form of libfoo.dll.a
453                    let (prefix, suffix) = self.sess.staticlib_components(false);
454                    let mut implib_name = OsString::from(prefix);
455                    implib_name.push(name);
456                    implib_name.push(suffix);
457                    let mut out_implib = OsString::from("--out-implib=");
458                    out_implib.push(out_filename.with_file_name(implib_name));
459                    self.link_arg(out_implib);
460                } else if crate_type == CrateType::Dylib {
461                    // When dylibs are linked by a full path this value will get into `DT_NEEDED`
462                    // instead of the full path, so the library can be later found in some other
463                    // location than that specific path.
464                    let mut soname = OsString::from("-soname=");
465                    soname.push(name);
466                    self.link_arg(soname);
467                }
468            }
469        }
470    }
471
472    fn with_as_needed(&mut self, as_needed: bool, f: impl FnOnce(&mut Self)) {
473        if !as_needed {
474            if self.sess.target.is_like_darwin {
475                // FIXME(81490): ld64 doesn't support these flags but macOS 11
476                // has -needed-l{} / -needed_library {}
477                // but we have no way to detect that here.
478                self.sess.dcx().emit_warn(errors::Ld64UnimplementedModifier);
479            } else if self.is_gnu && !self.sess.target.is_like_windows {
480                self.link_arg("--no-as-needed");
481            } else {
482                self.sess.dcx().emit_warn(errors::LinkerUnsupportedModifier);
483            }
484        }
485
486        f(self);
487
488        if !as_needed {
489            if self.sess.target.is_like_darwin {
490                // See above FIXME comment
491            } else if self.is_gnu && !self.sess.target.is_like_windows {
492                self.link_arg("--as-needed");
493            }
494        }
495    }
496}
497
498impl<'a> Linker for GccLinker<'a> {
499    fn cmd(&mut self) -> &mut Command {
500        &mut self.cmd
501    }
502
503    fn is_cc(&self) -> bool {
504        !self.is_ld
505    }
506
507    fn set_output_kind(
508        &mut self,
509        output_kind: LinkOutputKind,
510        crate_type: CrateType,
511        out_filename: &Path,
512    ) {
513        match output_kind {
514            LinkOutputKind::DynamicNoPicExe => {
515                if !self.is_ld && self.is_gnu {
516                    self.cc_arg("-no-pie");
517                }
518            }
519            LinkOutputKind::DynamicPicExe => {
520                // noop on windows w/ gcc & ld, error w/ lld
521                if !self.sess.target.is_like_windows {
522                    // `-pie` works for both gcc wrapper and ld.
523                    self.link_or_cc_arg("-pie");
524                }
525            }
526            LinkOutputKind::StaticNoPicExe => {
527                // `-static` works for both gcc wrapper and ld.
528                self.link_or_cc_arg("-static");
529                if !self.is_ld && self.is_gnu {
530                    self.cc_arg("-no-pie");
531                }
532            }
533            LinkOutputKind::StaticPicExe => {
534                if !self.is_ld {
535                    // Note that combination `-static -pie` doesn't work as expected
536                    // for the gcc wrapper, `-static` in that case suppresses `-pie`.
537                    self.cc_arg("-static-pie");
538                } else {
539                    // `--no-dynamic-linker` and `-z text` are not strictly necessary for producing
540                    // a static pie, but currently passed because gcc and clang pass them.
541                    // The former suppresses the `INTERP` ELF header specifying dynamic linker,
542                    // which is otherwise implicitly injected by ld (but not lld).
543                    // The latter doesn't change anything, only ensures that everything is pic.
544                    self.link_args(&["-static", "-pie", "--no-dynamic-linker", "-z", "text"]);
545                }
546            }
547            LinkOutputKind::DynamicDylib => self.build_dylib(crate_type, out_filename),
548            LinkOutputKind::StaticDylib => {
549                self.link_or_cc_arg("-static");
550                self.build_dylib(crate_type, out_filename);
551            }
552            LinkOutputKind::WasiReactorExe => {
553                self.link_args(&["--entry", "_initialize"]);
554            }
555        }
556
557        // VxWorks compiler driver introduced `--static-crt` flag specifically for rustc,
558        // it switches linking for libc and similar system libraries to static without using
559        // any `#[link]` attributes in the `libc` crate, see #72782 for details.
560        // FIXME: Switch to using `#[link]` attributes in the `libc` crate
561        // similarly to other targets.
562        if self.sess.target.os == "vxworks"
563            && matches!(
564                output_kind,
565                LinkOutputKind::StaticNoPicExe
566                    | LinkOutputKind::StaticPicExe
567                    | LinkOutputKind::StaticDylib
568            )
569        {
570            self.cc_arg("--static-crt");
571        }
572
573        // avr-none doesn't have default ISA, users must specify which specific
574        // CPU (well, microcontroller) they are targetting using `-Ctarget-cpu`.
575        //
576        // Currently this makes sense only when using avr-gcc as a linker, since
577        // it brings a couple of hand-written important intrinsics from libgcc.
578        if self.sess.target.arch == "avr" && !self.uses_lld {
579            self.verbatim_arg(format!("-mmcu={}", self.target_cpu));
580        }
581    }
582
583    fn link_dylib_by_name(&mut self, name: &str, verbatim: bool, as_needed: bool) {
584        if self.sess.target.os == "illumos" && name == "c" {
585            // libc will be added via late_link_args on illumos so that it will
586            // appear last in the library search order.
587            // FIXME: This should be replaced by a more complete and generic
588            // mechanism for controlling the order of library arguments passed
589            // to the linker.
590            return;
591        }
592        self.hint_dynamic();
593        self.with_as_needed(as_needed, |this| {
594            let colon = if verbatim && this.is_gnu { ":" } else { "" };
595            this.link_or_cc_arg(format!("-l{colon}{name}"));
596        });
597    }
598
599    fn link_dylib_by_path(&mut self, path: &Path, as_needed: bool) {
600        self.hint_dynamic();
601        self.with_as_needed(as_needed, |this| {
602            this.link_or_cc_arg(path);
603        })
604    }
605
606    fn link_framework_by_name(&mut self, name: &str, _verbatim: bool, as_needed: bool) {
607        self.hint_dynamic();
608        if !as_needed {
609            // FIXME(81490): ld64 as of macOS 11 supports the -needed_framework
610            // flag but we have no way to detect that here.
611            // self.link_or_cc_arg("-needed_framework").link_or_cc_arg(name);
612            self.sess.dcx().emit_warn(errors::Ld64UnimplementedModifier);
613        }
614        self.link_or_cc_args(&["-framework", name]);
615    }
616
617    fn link_staticlib_by_name(&mut self, name: &str, verbatim: bool, whole_archive: bool) {
618        self.hint_static();
619        let colon = if verbatim && self.is_gnu { ":" } else { "" };
620        if !whole_archive {
621            self.link_or_cc_arg(format!("-l{colon}{name}"));
622        } else if self.sess.target.is_like_darwin {
623            // -force_load is the macOS equivalent of --whole-archive, but it
624            // involves passing the full path to the library to link.
625            self.link_arg("-force_load");
626            self.link_arg(find_native_static_library(name, verbatim, self.sess));
627        } else {
628            self.link_arg("--whole-archive")
629                .link_or_cc_arg(format!("-l{colon}{name}"))
630                .link_arg("--no-whole-archive");
631        }
632    }
633
634    fn link_staticlib_by_path(&mut self, path: &Path, whole_archive: bool) {
635        self.hint_static();
636        if !whole_archive {
637            self.link_or_cc_arg(path);
638        } else if self.sess.target.is_like_darwin {
639            self.link_arg("-force_load").link_arg(path);
640        } else {
641            self.link_arg("--whole-archive").link_arg(path).link_arg("--no-whole-archive");
642        }
643    }
644
645    fn framework_path(&mut self, path: &Path) {
646        self.link_or_cc_arg("-F").link_or_cc_arg(path);
647    }
648    fn full_relro(&mut self) {
649        self.link_args(&["-z", "relro", "-z", "now"]);
650    }
651    fn partial_relro(&mut self) {
652        self.link_args(&["-z", "relro"]);
653    }
654    fn no_relro(&mut self) {
655        self.link_args(&["-z", "norelro"]);
656    }
657
658    fn gc_sections(&mut self, keep_metadata: bool) {
659        // The dead_strip option to the linker specifies that functions and data
660        // unreachable by the entry point will be removed. This is quite useful
661        // with Rust's compilation model of compiling libraries at a time into
662        // one object file. For example, this brings hello world from 1.7MB to
663        // 458K.
664        //
665        // Note that this is done for both executables and dynamic libraries. We
666        // won't get much benefit from dylibs because LLVM will have already
667        // stripped away as much as it could. This has not been seen to impact
668        // link times negatively.
669        //
670        // -dead_strip can't be part of the pre_link_args because it's also used
671        // for partial linking when using multiple codegen units (-r). So we
672        // insert it here.
673        if self.sess.target.is_like_darwin {
674            self.link_arg("-dead_strip");
675
676        // If we're building a dylib, we don't use --gc-sections because LLVM
677        // has already done the best it can do, and we also don't want to
678        // eliminate the metadata. If we're building an executable, however,
679        // --gc-sections drops the size of hello world from 1.8MB to 597K, a 67%
680        // reduction.
681        } else if (self.is_gnu || self.sess.target.is_like_wasm) && !keep_metadata {
682            self.link_arg("--gc-sections");
683        }
684    }
685
686    fn no_gc_sections(&mut self) {
687        if self.is_gnu || self.sess.target.is_like_wasm {
688            self.link_arg("--no-gc-sections");
689        }
690    }
691
692    fn optimize(&mut self) {
693        if !self.is_gnu && !self.sess.target.is_like_wasm {
694            return;
695        }
696
697        // GNU-style linkers support optimization with -O. GNU ld doesn't
698        // need a numeric argument, but other linkers do.
699        if self.sess.opts.optimize == config::OptLevel::More
700            || self.sess.opts.optimize == config::OptLevel::Aggressive
701        {
702            self.link_arg("-O1");
703        }
704    }
705
706    fn pgo_gen(&mut self) {
707        if !self.is_gnu {
708            return;
709        }
710
711        // If we're doing PGO generation stuff and on a GNU-like linker, use the
712        // "-u" flag to properly pull in the profiler runtime bits.
713        //
714        // This is because LLVM otherwise won't add the needed initialization
715        // for us on Linux (though the extra flag should be harmless if it
716        // does).
717        //
718        // See https://reviews.llvm.org/D14033 and https://reviews.llvm.org/D14030.
719        //
720        // Though it may be worth to try to revert those changes upstream, since
721        // the overhead of the initialization should be minor.
722        self.link_or_cc_args(&["-u", "__llvm_profile_runtime"]);
723    }
724
725    fn control_flow_guard(&mut self) {}
726
727    fn ehcont_guard(&mut self) {}
728
729    fn debuginfo(&mut self, strip: Strip, _: &[PathBuf]) {
730        // MacOS linker doesn't support stripping symbols directly anymore.
731        if self.sess.target.is_like_darwin {
732            return;
733        }
734
735        match strip {
736            Strip::None => {}
737            Strip::Debuginfo => {
738                // The illumos linker does not support --strip-debug although
739                // it does support --strip-all as a compatibility alias for -s.
740                // The --strip-debug case is handled by running an external
741                // `strip` utility as a separate step after linking.
742                if !self.sess.target.is_like_solaris {
743                    self.link_arg("--strip-debug");
744                }
745            }
746            Strip::Symbols => {
747                self.link_arg("--strip-all");
748            }
749        }
750        match self.sess.opts.unstable_opts.debuginfo_compression {
751            config::DebugInfoCompression::None => {}
752            config::DebugInfoCompression::Zlib => {
753                self.link_arg("--compress-debug-sections=zlib");
754            }
755            config::DebugInfoCompression::Zstd => {
756                self.link_arg("--compress-debug-sections=zstd");
757            }
758        }
759    }
760
761    fn no_crt_objects(&mut self) {
762        if !self.is_ld {
763            self.cc_arg("-nostartfiles");
764        }
765    }
766
767    fn no_default_libraries(&mut self) {
768        if !self.is_ld {
769            self.cc_arg("-nodefaultlibs");
770        }
771    }
772
773    fn export_symbols(&mut self, tmpdir: &Path, crate_type: CrateType, symbols: &[String]) {
774        // Symbol visibility in object files typically takes care of this.
775        if crate_type == CrateType::Executable {
776            let should_export_executable_symbols =
777                self.sess.opts.unstable_opts.export_executable_symbols;
778            if self.sess.target.override_export_symbols.is_none()
779                && !should_export_executable_symbols
780            {
781                return;
782            }
783        }
784
785        // We manually create a list of exported symbols to ensure we don't expose any more.
786        // The object files have far more public symbols than we actually want to export,
787        // so we hide them all here.
788
789        if !self.sess.target.limit_rdylib_exports {
790            return;
791        }
792
793        let is_windows = self.sess.target.is_like_windows;
794        let path = tmpdir.join(if is_windows { "list.def" } else { "list" });
795
796        debug!("EXPORTED SYMBOLS:");
797
798        if self.sess.target.is_like_darwin {
799            // Write a plain, newline-separated list of symbols
800            let res: io::Result<()> = try {
801                let mut f = File::create_buffered(&path)?;
802                for sym in symbols {
803                    debug!("  _{sym}");
804                    writeln!(f, "_{sym}")?;
805                }
806            };
807            if let Err(error) = res {
808                self.sess.dcx().emit_fatal(errors::LibDefWriteFailure { error });
809            }
810        } else if is_windows {
811            let res: io::Result<()> = try {
812                let mut f = File::create_buffered(&path)?;
813
814                // .def file similar to MSVC one but without LIBRARY section
815                // because LD doesn't like when it's empty
816                writeln!(f, "EXPORTS")?;
817                for symbol in symbols {
818                    debug!("  _{symbol}");
819                    // Quote the name in case it's reserved by linker in some way
820                    // (this accounts for names with dots in particular).
821                    writeln!(f, "  \"{symbol}\"")?;
822                }
823            };
824            if let Err(error) = res {
825                self.sess.dcx().emit_fatal(errors::LibDefWriteFailure { error });
826            }
827        } else {
828            // Write an LD version script
829            let res: io::Result<()> = try {
830                let mut f = File::create_buffered(&path)?;
831                writeln!(f, "{{")?;
832                if !symbols.is_empty() {
833                    writeln!(f, "  global:")?;
834                    for sym in symbols {
835                        debug!("    {sym};");
836                        writeln!(f, "    {sym};")?;
837                    }
838                }
839                writeln!(f, "\n  local:\n    *;\n}};")?;
840            };
841            if let Err(error) = res {
842                self.sess.dcx().emit_fatal(errors::VersionScriptWriteFailure { error });
843            }
844        }
845
846        if self.sess.target.is_like_darwin {
847            self.link_arg("-exported_symbols_list").link_arg(path);
848        } else if self.sess.target.is_like_solaris {
849            self.link_arg("-M").link_arg(path);
850        } else if is_windows {
851            self.link_arg(path);
852        } else {
853            let mut arg = OsString::from("--version-script=");
854            arg.push(path);
855            self.link_arg(arg).link_arg("--no-undefined-version");
856        }
857    }
858
859    fn subsystem(&mut self, subsystem: &str) {
860        self.link_args(&["--subsystem", subsystem]);
861    }
862
863    fn reset_per_library_state(&mut self) {
864        self.hint_dynamic(); // Reset to default before returning the composed command line.
865    }
866
867    fn linker_plugin_lto(&mut self) {
868        match self.sess.opts.cg.linker_plugin_lto {
869            LinkerPluginLto::Disabled => {
870                // Nothing to do
871            }
872            LinkerPluginLto::LinkerPluginAuto => {
873                self.push_linker_plugin_lto_args(None);
874            }
875            LinkerPluginLto::LinkerPlugin(ref path) => {
876                self.push_linker_plugin_lto_args(Some(path.as_os_str()));
877            }
878        }
879    }
880
881    // Add the `GNU_EH_FRAME` program header which is required to locate unwinding information.
882    // Some versions of `gcc` add it implicitly, some (e.g. `musl-gcc`) don't,
883    // so we just always add it.
884    fn add_eh_frame_header(&mut self) {
885        self.link_arg("--eh-frame-hdr");
886    }
887
888    fn add_no_exec(&mut self) {
889        if self.sess.target.is_like_windows {
890            self.link_arg("--nxcompat");
891        } else if self.is_gnu {
892            self.link_args(&["-z", "noexecstack"]);
893        }
894    }
895
896    fn add_as_needed(&mut self) {
897        if self.is_gnu && !self.sess.target.is_like_windows {
898            self.link_arg("--as-needed");
899        } else if self.sess.target.is_like_solaris {
900            // -z ignore is the Solaris equivalent to the GNU ld --as-needed option
901            self.link_args(&["-z", "ignore"]);
902        }
903    }
904}
905
906struct MsvcLinker<'a> {
907    cmd: Command,
908    sess: &'a Session,
909}
910
911impl<'a> Linker for MsvcLinker<'a> {
912    fn cmd(&mut self) -> &mut Command {
913        &mut self.cmd
914    }
915
916    fn set_output_kind(
917        &mut self,
918        output_kind: LinkOutputKind,
919        _crate_type: CrateType,
920        out_filename: &Path,
921    ) {
922        match output_kind {
923            LinkOutputKind::DynamicNoPicExe
924            | LinkOutputKind::DynamicPicExe
925            | LinkOutputKind::StaticNoPicExe
926            | LinkOutputKind::StaticPicExe => {}
927            LinkOutputKind::DynamicDylib | LinkOutputKind::StaticDylib => {
928                self.link_arg("/DLL");
929                let mut arg: OsString = "/IMPLIB:".into();
930                arg.push(out_filename.with_extension("dll.lib"));
931                self.link_arg(arg);
932            }
933            LinkOutputKind::WasiReactorExe => {
934                panic!("can't link as reactor on non-wasi target");
935            }
936        }
937    }
938
939    fn link_dylib_by_name(&mut self, name: &str, verbatim: bool, _as_needed: bool) {
940        // On MSVC-like targets rustc supports import libraries using alternative naming
941        // scheme (`libfoo.a`) unsupported by linker, search for such libraries manually.
942        if let Some(path) = try_find_native_dynamic_library(self.sess, name, verbatim) {
943            self.link_arg(path);
944        } else {
945            self.link_arg(format!("{}{}", name, if verbatim { "" } else { ".lib" }));
946        }
947    }
948
949    fn link_dylib_by_path(&mut self, path: &Path, _as_needed: bool) {
950        // When producing a dll, MSVC linker may not emit an implib file if the dll doesn't export
951        // any symbols, so we skip linking if the implib file is not present.
952        let implib_path = path.with_extension("dll.lib");
953        if implib_path.exists() {
954            self.link_or_cc_arg(implib_path);
955        }
956    }
957
958    fn link_staticlib_by_name(&mut self, name: &str, verbatim: bool, whole_archive: bool) {
959        // On MSVC-like targets rustc supports static libraries using alternative naming
960        // scheme (`libfoo.a`) unsupported by linker, search for such libraries manually.
961        if let Some(path) = try_find_native_static_library(self.sess, name, verbatim) {
962            self.link_staticlib_by_path(&path, whole_archive);
963        } else {
964            let opts = if whole_archive { "/WHOLEARCHIVE:" } else { "" };
965            let (prefix, suffix) = self.sess.staticlib_components(verbatim);
966            self.link_arg(format!("{opts}{prefix}{name}{suffix}"));
967        }
968    }
969
970    fn link_staticlib_by_path(&mut self, path: &Path, whole_archive: bool) {
971        if !whole_archive {
972            self.link_arg(path);
973        } else {
974            let mut arg = OsString::from("/WHOLEARCHIVE:");
975            arg.push(path);
976            self.link_arg(arg);
977        }
978    }
979
980    fn gc_sections(&mut self, _keep_metadata: bool) {
981        // MSVC's ICF (Identical COMDAT Folding) link optimization is
982        // slow for Rust and thus we disable it by default when not in
983        // optimization build.
984        if self.sess.opts.optimize != config::OptLevel::No {
985            self.link_arg("/OPT:REF,ICF");
986        } else {
987            // It is necessary to specify NOICF here, because /OPT:REF
988            // implies ICF by default.
989            self.link_arg("/OPT:REF,NOICF");
990        }
991    }
992
993    fn no_gc_sections(&mut self) {
994        self.link_arg("/OPT:NOREF,NOICF");
995    }
996
997    fn full_relro(&mut self) {
998        // noop
999    }
1000
1001    fn partial_relro(&mut self) {
1002        // noop
1003    }
1004
1005    fn no_relro(&mut self) {
1006        // noop
1007    }
1008
1009    fn no_crt_objects(&mut self) {
1010        // noop
1011    }
1012
1013    fn no_default_libraries(&mut self) {
1014        self.link_arg("/NODEFAULTLIB");
1015    }
1016
1017    fn include_path(&mut self, path: &Path) {
1018        let mut arg = OsString::from("/LIBPATH:");
1019        arg.push(path);
1020        self.link_arg(&arg);
1021    }
1022
1023    fn output_filename(&mut self, path: &Path) {
1024        let mut arg = OsString::from("/OUT:");
1025        arg.push(path);
1026        self.link_arg(&arg);
1027    }
1028
1029    fn optimize(&mut self) {
1030        // Needs more investigation of `/OPT` arguments
1031    }
1032
1033    fn pgo_gen(&mut self) {
1034        // Nothing needed here.
1035    }
1036
1037    fn control_flow_guard(&mut self) {
1038        self.link_arg("/guard:cf");
1039    }
1040
1041    fn ehcont_guard(&mut self) {
1042        if self.sess.target.pointer_width == 64 {
1043            self.link_arg("/guard:ehcont");
1044        }
1045    }
1046
1047    fn debuginfo(&mut self, _strip: Strip, natvis_debugger_visualizers: &[PathBuf]) {
1048        // This will cause the Microsoft linker to generate a PDB file
1049        // from the CodeView line tables in the object files.
1050        self.link_arg("/DEBUG");
1051
1052        // Default to emitting only the file name of the PDB file into
1053        // the binary instead of the full path. Emitting the full path
1054        // may leak private information (such as user names).
1055        // See https://github.com/rust-lang/rust/issues/87825.
1056        //
1057        // This default behavior can be overridden by explicitly passing
1058        // `-Clink-arg=/PDBALTPATH:...` to rustc.
1059        self.link_arg("/PDBALTPATH:%_PDB%");
1060
1061        // This will cause the Microsoft linker to embed .natvis info into the PDB file
1062        let natvis_dir_path = self.sess.sysroot.join("lib\\rustlib\\etc");
1063        if let Ok(natvis_dir) = fs::read_dir(&natvis_dir_path) {
1064            for entry in natvis_dir {
1065                match entry {
1066                    Ok(entry) => {
1067                        let path = entry.path();
1068                        if path.extension() == Some("natvis".as_ref()) {
1069                            let mut arg = OsString::from("/NATVIS:");
1070                            arg.push(path);
1071                            self.link_arg(arg);
1072                        }
1073                    }
1074                    Err(error) => {
1075                        self.sess.dcx().emit_warn(errors::NoNatvisDirectory { error });
1076                    }
1077                }
1078            }
1079        }
1080
1081        // This will cause the Microsoft linker to embed .natvis info for all crates into the PDB file
1082        for path in natvis_debugger_visualizers {
1083            let mut arg = OsString::from("/NATVIS:");
1084            arg.push(path);
1085            self.link_arg(arg);
1086        }
1087    }
1088
1089    // Currently the compiler doesn't use `dllexport` (an LLVM attribute) to
1090    // export symbols from a dynamic library. When building a dynamic library,
1091    // however, we're going to want some symbols exported, so this function
1092    // generates a DEF file which lists all the symbols.
1093    //
1094    // The linker will read this `*.def` file and export all the symbols from
1095    // the dynamic library. Note that this is not as simple as just exporting
1096    // all the symbols in the current crate (as specified by `codegen.reachable`)
1097    // but rather we also need to possibly export the symbols of upstream
1098    // crates. Upstream rlibs may be linked statically to this dynamic library,
1099    // in which case they may continue to transitively be used and hence need
1100    // their symbols exported.
1101    fn export_symbols(&mut self, tmpdir: &Path, crate_type: CrateType, symbols: &[String]) {
1102        // Symbol visibility takes care of this typically
1103        if crate_type == CrateType::Executable {
1104            let should_export_executable_symbols =
1105                self.sess.opts.unstable_opts.export_executable_symbols;
1106            if !should_export_executable_symbols {
1107                return;
1108            }
1109        }
1110
1111        let path = tmpdir.join("lib.def");
1112        let res: io::Result<()> = try {
1113            let mut f = File::create_buffered(&path)?;
1114
1115            // Start off with the standard module name header and then go
1116            // straight to exports.
1117            writeln!(f, "LIBRARY")?;
1118            writeln!(f, "EXPORTS")?;
1119            for symbol in symbols {
1120                debug!("  _{symbol}");
1121                writeln!(f, "  {symbol}")?;
1122            }
1123        };
1124        if let Err(error) = res {
1125            self.sess.dcx().emit_fatal(errors::LibDefWriteFailure { error });
1126        }
1127        let mut arg = OsString::from("/DEF:");
1128        arg.push(path);
1129        self.link_arg(&arg);
1130    }
1131
1132    fn subsystem(&mut self, subsystem: &str) {
1133        // Note that previous passes of the compiler validated this subsystem,
1134        // so we just blindly pass it to the linker.
1135        self.link_arg(&format!("/SUBSYSTEM:{subsystem}"));
1136
1137        // Windows has two subsystems we're interested in right now, the console
1138        // and windows subsystems. These both implicitly have different entry
1139        // points (starting symbols). The console entry point starts with
1140        // `mainCRTStartup` and the windows entry point starts with
1141        // `WinMainCRTStartup`. These entry points, defined in system libraries,
1142        // will then later probe for either `main` or `WinMain`, respectively to
1143        // start the application.
1144        //
1145        // In Rust we just always generate a `main` function so we want control
1146        // to always start there, so we force the entry point on the windows
1147        // subsystem to be `mainCRTStartup` to get everything booted up
1148        // correctly.
1149        //
1150        // For more information see RFC #1665
1151        if subsystem == "windows" {
1152            self.link_arg("/ENTRY:mainCRTStartup");
1153        }
1154    }
1155
1156    fn linker_plugin_lto(&mut self) {
1157        // Do nothing
1158    }
1159
1160    fn add_no_exec(&mut self) {
1161        self.link_arg("/NXCOMPAT");
1162    }
1163}
1164
1165struct EmLinker<'a> {
1166    cmd: Command,
1167    sess: &'a Session,
1168}
1169
1170impl<'a> Linker for EmLinker<'a> {
1171    fn cmd(&mut self) -> &mut Command {
1172        &mut self.cmd
1173    }
1174
1175    fn is_cc(&self) -> bool {
1176        true
1177    }
1178
1179    fn set_output_kind(
1180        &mut self,
1181        _output_kind: LinkOutputKind,
1182        _crate_type: CrateType,
1183        _out_filename: &Path,
1184    ) {
1185    }
1186
1187    fn link_dylib_by_name(&mut self, name: &str, _verbatim: bool, _as_needed: bool) {
1188        // Emscripten always links statically
1189        self.link_or_cc_args(&["-l", name]);
1190    }
1191
1192    fn link_dylib_by_path(&mut self, path: &Path, _as_needed: bool) {
1193        self.link_or_cc_arg(path);
1194    }
1195
1196    fn link_staticlib_by_name(&mut self, name: &str, _verbatim: bool, _whole_archive: bool) {
1197        self.link_or_cc_args(&["-l", name]);
1198    }
1199
1200    fn link_staticlib_by_path(&mut self, path: &Path, _whole_archive: bool) {
1201        self.link_or_cc_arg(path);
1202    }
1203
1204    fn full_relro(&mut self) {
1205        // noop
1206    }
1207
1208    fn partial_relro(&mut self) {
1209        // noop
1210    }
1211
1212    fn no_relro(&mut self) {
1213        // noop
1214    }
1215
1216    fn gc_sections(&mut self, _keep_metadata: bool) {
1217        // noop
1218    }
1219
1220    fn no_gc_sections(&mut self) {
1221        // noop
1222    }
1223
1224    fn optimize(&mut self) {
1225        // Emscripten performs own optimizations
1226        self.cc_arg(match self.sess.opts.optimize {
1227            OptLevel::No => "-O0",
1228            OptLevel::Less => "-O1",
1229            OptLevel::More => "-O2",
1230            OptLevel::Aggressive => "-O3",
1231            OptLevel::Size => "-Os",
1232            OptLevel::SizeMin => "-Oz",
1233        });
1234    }
1235
1236    fn pgo_gen(&mut self) {
1237        // noop, but maybe we need something like the gnu linker?
1238    }
1239
1240    fn control_flow_guard(&mut self) {}
1241
1242    fn ehcont_guard(&mut self) {}
1243
1244    fn debuginfo(&mut self, _strip: Strip, _: &[PathBuf]) {
1245        // Preserve names or generate source maps depending on debug info
1246        // For more information see https://emscripten.org/docs/tools_reference/emcc.html#emcc-g
1247        self.cc_arg(match self.sess.opts.debuginfo {
1248            DebugInfo::None => "-g0",
1249            DebugInfo::Limited | DebugInfo::LineTablesOnly | DebugInfo::LineDirectivesOnly => {
1250                "--profiling-funcs"
1251            }
1252            DebugInfo::Full => "-g",
1253        });
1254    }
1255
1256    fn no_crt_objects(&mut self) {}
1257
1258    fn no_default_libraries(&mut self) {
1259        self.cc_arg("-nodefaultlibs");
1260    }
1261
1262    fn export_symbols(&mut self, _tmpdir: &Path, _crate_type: CrateType, symbols: &[String]) {
1263        debug!("EXPORTED SYMBOLS:");
1264
1265        self.cc_arg("-s");
1266
1267        let mut arg = OsString::from("EXPORTED_FUNCTIONS=");
1268        let encoded = serde_json::to_string(
1269            &symbols.iter().map(|sym| "_".to_owned() + sym).collect::<Vec<_>>(),
1270        )
1271        .unwrap();
1272        debug!("{encoded}");
1273
1274        arg.push(encoded);
1275
1276        self.cc_arg(arg);
1277    }
1278
1279    fn subsystem(&mut self, _subsystem: &str) {
1280        // noop
1281    }
1282
1283    fn linker_plugin_lto(&mut self) {
1284        // Do nothing
1285    }
1286}
1287
1288struct WasmLd<'a> {
1289    cmd: Command,
1290    sess: &'a Session,
1291}
1292
1293impl<'a> WasmLd<'a> {
1294    fn new(cmd: Command, sess: &'a Session) -> WasmLd<'a> {
1295        // If the atomics feature is enabled for wasm then we need a whole bunch
1296        // of flags:
1297        //
1298        // * `--shared-memory` - the link won't even succeed without this, flags
1299        //   the one linear memory as `shared`
1300        //
1301        // * `--max-memory=1G` - when specifying a shared memory this must also
1302        //   be specified. We conservatively choose 1GB but users should be able
1303        //   to override this with `-C link-arg`.
1304        //
1305        // * `--import-memory` - it doesn't make much sense for memory to be
1306        //   exported in a threaded module because typically you're
1307        //   sharing memory and instantiating the module multiple times. As a
1308        //   result if it were exported then we'd just have no sharing.
1309        //
1310        // On wasm32-unknown-unknown, we also export symbols for glue code to use:
1311        //    * `--export=*tls*` - when `#[thread_local]` symbols are used these
1312        //      symbols are how the TLS segments are initialized and configured.
1313        let mut wasm_ld = WasmLd { cmd, sess };
1314        if sess.target_features.contains(&sym::atomics) {
1315            wasm_ld.link_args(&["--shared-memory", "--max-memory=1073741824", "--import-memory"]);
1316            if sess.target.os == "unknown" || sess.target.os == "none" {
1317                wasm_ld.link_args(&[
1318                    "--export=__wasm_init_tls",
1319                    "--export=__tls_size",
1320                    "--export=__tls_align",
1321                    "--export=__tls_base",
1322                ]);
1323            }
1324        }
1325        wasm_ld
1326    }
1327}
1328
1329impl<'a> Linker for WasmLd<'a> {
1330    fn cmd(&mut self) -> &mut Command {
1331        &mut self.cmd
1332    }
1333
1334    fn set_output_kind(
1335        &mut self,
1336        output_kind: LinkOutputKind,
1337        _crate_type: CrateType,
1338        _out_filename: &Path,
1339    ) {
1340        match output_kind {
1341            LinkOutputKind::DynamicNoPicExe
1342            | LinkOutputKind::DynamicPicExe
1343            | LinkOutputKind::StaticNoPicExe
1344            | LinkOutputKind::StaticPicExe => {}
1345            LinkOutputKind::DynamicDylib | LinkOutputKind::StaticDylib => {
1346                self.link_arg("--no-entry");
1347            }
1348            LinkOutputKind::WasiReactorExe => {
1349                self.link_args(&["--entry", "_initialize"]);
1350            }
1351        }
1352    }
1353
1354    fn link_dylib_by_name(&mut self, name: &str, _verbatim: bool, _as_needed: bool) {
1355        self.link_or_cc_args(&["-l", name]);
1356    }
1357
1358    fn link_dylib_by_path(&mut self, path: &Path, _as_needed: bool) {
1359        self.link_or_cc_arg(path);
1360    }
1361
1362    fn link_staticlib_by_name(&mut self, name: &str, _verbatim: bool, whole_archive: bool) {
1363        if !whole_archive {
1364            self.link_or_cc_args(&["-l", name]);
1365        } else {
1366            self.link_arg("--whole-archive")
1367                .link_or_cc_args(&["-l", name])
1368                .link_arg("--no-whole-archive");
1369        }
1370    }
1371
1372    fn link_staticlib_by_path(&mut self, path: &Path, whole_archive: bool) {
1373        if !whole_archive {
1374            self.link_or_cc_arg(path);
1375        } else {
1376            self.link_arg("--whole-archive").link_or_cc_arg(path).link_arg("--no-whole-archive");
1377        }
1378    }
1379
1380    fn full_relro(&mut self) {}
1381
1382    fn partial_relro(&mut self) {}
1383
1384    fn no_relro(&mut self) {}
1385
1386    fn gc_sections(&mut self, _keep_metadata: bool) {
1387        self.link_arg("--gc-sections");
1388    }
1389
1390    fn no_gc_sections(&mut self) {
1391        self.link_arg("--no-gc-sections");
1392    }
1393
1394    fn optimize(&mut self) {
1395        // The -O flag is, as of late 2023, only used for merging of strings and debuginfo, and
1396        // only differentiates -O0 and -O1. It does not apply to LTO.
1397        self.link_arg(match self.sess.opts.optimize {
1398            OptLevel::No => "-O0",
1399            OptLevel::Less => "-O1",
1400            OptLevel::More => "-O2",
1401            OptLevel::Aggressive => "-O3",
1402            // Currently LLD doesn't support `Os` and `Oz`, so pass through `O2`
1403            // instead.
1404            OptLevel::Size => "-O2",
1405            OptLevel::SizeMin => "-O2",
1406        });
1407    }
1408
1409    fn pgo_gen(&mut self) {}
1410
1411    fn debuginfo(&mut self, strip: Strip, _: &[PathBuf]) {
1412        match strip {
1413            Strip::None => {}
1414            Strip::Debuginfo => {
1415                self.link_arg("--strip-debug");
1416            }
1417            Strip::Symbols => {
1418                self.link_arg("--strip-all");
1419            }
1420        }
1421    }
1422
1423    fn control_flow_guard(&mut self) {}
1424
1425    fn ehcont_guard(&mut self) {}
1426
1427    fn no_crt_objects(&mut self) {}
1428
1429    fn no_default_libraries(&mut self) {}
1430
1431    fn export_symbols(&mut self, _tmpdir: &Path, _crate_type: CrateType, symbols: &[String]) {
1432        for sym in symbols {
1433            self.link_args(&["--export", sym]);
1434        }
1435
1436        // LLD will hide these otherwise-internal symbols since it only exports
1437        // symbols explicitly passed via the `--export` flags above and hides all
1438        // others. Various bits and pieces of wasm32-unknown-unknown tooling use
1439        // this, so be sure these symbols make their way out of the linker as well.
1440        if self.sess.target.os == "unknown" || self.sess.target.os == "none" {
1441            self.link_args(&["--export=__heap_base", "--export=__data_end"]);
1442        }
1443    }
1444
1445    fn subsystem(&mut self, _subsystem: &str) {}
1446
1447    fn linker_plugin_lto(&mut self) {
1448        match self.sess.opts.cg.linker_plugin_lto {
1449            LinkerPluginLto::Disabled => {
1450                // Nothing to do
1451            }
1452            LinkerPluginLto::LinkerPluginAuto => {
1453                self.push_linker_plugin_lto_args();
1454            }
1455            LinkerPluginLto::LinkerPlugin(_) => {
1456                self.push_linker_plugin_lto_args();
1457            }
1458        }
1459    }
1460}
1461
1462impl<'a> WasmLd<'a> {
1463    fn push_linker_plugin_lto_args(&mut self) {
1464        let opt_level = match self.sess.opts.optimize {
1465            config::OptLevel::No => "O0",
1466            config::OptLevel::Less => "O1",
1467            config::OptLevel::More => "O2",
1468            config::OptLevel::Aggressive => "O3",
1469            // wasm-ld only handles integer LTO opt levels. Use O2
1470            config::OptLevel::Size | config::OptLevel::SizeMin => "O2",
1471        };
1472        self.link_arg(&format!("--lto-{opt_level}"));
1473    }
1474}
1475
1476/// Linker shepherd script for L4Re (Fiasco)
1477struct L4Bender<'a> {
1478    cmd: Command,
1479    sess: &'a Session,
1480    hinted_static: bool,
1481}
1482
1483impl<'a> Linker for L4Bender<'a> {
1484    fn cmd(&mut self) -> &mut Command {
1485        &mut self.cmd
1486    }
1487
1488    fn set_output_kind(
1489        &mut self,
1490        _output_kind: LinkOutputKind,
1491        _crate_type: CrateType,
1492        _out_filename: &Path,
1493    ) {
1494    }
1495
1496    fn link_staticlib_by_name(&mut self, name: &str, _verbatim: bool, whole_archive: bool) {
1497        self.hint_static();
1498        if !whole_archive {
1499            self.link_arg(format!("-PC{name}"));
1500        } else {
1501            self.link_arg("--whole-archive")
1502                .link_or_cc_arg(format!("-l{name}"))
1503                .link_arg("--no-whole-archive");
1504        }
1505    }
1506
1507    fn link_staticlib_by_path(&mut self, path: &Path, whole_archive: bool) {
1508        self.hint_static();
1509        if !whole_archive {
1510            self.link_or_cc_arg(path);
1511        } else {
1512            self.link_arg("--whole-archive").link_or_cc_arg(path).link_arg("--no-whole-archive");
1513        }
1514    }
1515
1516    fn full_relro(&mut self) {
1517        self.link_args(&["-z", "relro", "-z", "now"]);
1518    }
1519
1520    fn partial_relro(&mut self) {
1521        self.link_args(&["-z", "relro"]);
1522    }
1523
1524    fn no_relro(&mut self) {
1525        self.link_args(&["-z", "norelro"]);
1526    }
1527
1528    fn gc_sections(&mut self, keep_metadata: bool) {
1529        if !keep_metadata {
1530            self.link_arg("--gc-sections");
1531        }
1532    }
1533
1534    fn no_gc_sections(&mut self) {
1535        self.link_arg("--no-gc-sections");
1536    }
1537
1538    fn optimize(&mut self) {
1539        // GNU-style linkers support optimization with -O. GNU ld doesn't
1540        // need a numeric argument, but other linkers do.
1541        if self.sess.opts.optimize == config::OptLevel::More
1542            || self.sess.opts.optimize == config::OptLevel::Aggressive
1543        {
1544            self.link_arg("-O1");
1545        }
1546    }
1547
1548    fn pgo_gen(&mut self) {}
1549
1550    fn debuginfo(&mut self, strip: Strip, _: &[PathBuf]) {
1551        match strip {
1552            Strip::None => {}
1553            Strip::Debuginfo => {
1554                self.link_arg("--strip-debug");
1555            }
1556            Strip::Symbols => {
1557                self.link_arg("--strip-all");
1558            }
1559        }
1560    }
1561
1562    fn no_default_libraries(&mut self) {
1563        self.cc_arg("-nostdlib");
1564    }
1565
1566    fn export_symbols(&mut self, _: &Path, _: CrateType, _: &[String]) {
1567        // ToDo, not implemented, copy from GCC
1568        self.sess.dcx().emit_warn(errors::L4BenderExportingSymbolsUnimplemented);
1569    }
1570
1571    fn subsystem(&mut self, subsystem: &str) {
1572        self.link_arg(&format!("--subsystem {subsystem}"));
1573    }
1574
1575    fn reset_per_library_state(&mut self) {
1576        self.hint_static(); // Reset to default before returning the composed command line.
1577    }
1578
1579    fn linker_plugin_lto(&mut self) {}
1580
1581    fn control_flow_guard(&mut self) {}
1582
1583    fn ehcont_guard(&mut self) {}
1584
1585    fn no_crt_objects(&mut self) {}
1586}
1587
1588impl<'a> L4Bender<'a> {
1589    fn new(cmd: Command, sess: &'a Session) -> L4Bender<'a> {
1590        L4Bender { cmd, sess, hinted_static: false }
1591    }
1592
1593    fn hint_static(&mut self) {
1594        if !self.hinted_static {
1595            self.link_or_cc_arg("-static");
1596            self.hinted_static = true;
1597        }
1598    }
1599}
1600
1601/// Linker for AIX.
1602struct AixLinker<'a> {
1603    cmd: Command,
1604    sess: &'a Session,
1605    hinted_static: Option<bool>,
1606}
1607
1608impl<'a> AixLinker<'a> {
1609    fn new(cmd: Command, sess: &'a Session) -> AixLinker<'a> {
1610        AixLinker { cmd, sess, hinted_static: None }
1611    }
1612
1613    fn hint_static(&mut self) {
1614        if self.hinted_static != Some(true) {
1615            self.link_arg("-bstatic");
1616            self.hinted_static = Some(true);
1617        }
1618    }
1619
1620    fn hint_dynamic(&mut self) {
1621        if self.hinted_static != Some(false) {
1622            self.link_arg("-bdynamic");
1623            self.hinted_static = Some(false);
1624        }
1625    }
1626
1627    fn build_dylib(&mut self, _out_filename: &Path) {
1628        self.link_args(&["-bM:SRE", "-bnoentry"]);
1629        // FIXME: Use CreateExportList utility to create export list
1630        // and remove -bexpfull.
1631        self.link_arg("-bexpfull");
1632    }
1633}
1634
1635impl<'a> Linker for AixLinker<'a> {
1636    fn cmd(&mut self) -> &mut Command {
1637        &mut self.cmd
1638    }
1639
1640    fn set_output_kind(
1641        &mut self,
1642        output_kind: LinkOutputKind,
1643        _crate_type: CrateType,
1644        out_filename: &Path,
1645    ) {
1646        match output_kind {
1647            LinkOutputKind::DynamicDylib => {
1648                self.hint_dynamic();
1649                self.build_dylib(out_filename);
1650            }
1651            LinkOutputKind::StaticDylib => {
1652                self.hint_static();
1653                self.build_dylib(out_filename);
1654            }
1655            _ => {}
1656        }
1657    }
1658
1659    fn link_dylib_by_name(&mut self, name: &str, verbatim: bool, _as_needed: bool) {
1660        self.hint_dynamic();
1661        self.link_or_cc_arg(if verbatim { String::from(name) } else { format!("-l{name}") });
1662    }
1663
1664    fn link_dylib_by_path(&mut self, path: &Path, _as_needed: bool) {
1665        self.hint_dynamic();
1666        self.link_or_cc_arg(path);
1667    }
1668
1669    fn link_staticlib_by_name(&mut self, name: &str, verbatim: bool, whole_archive: bool) {
1670        self.hint_static();
1671        if !whole_archive {
1672            self.link_or_cc_arg(if verbatim { String::from(name) } else { format!("-l{name}") });
1673        } else {
1674            let mut arg = OsString::from("-bkeepfile:");
1675            arg.push(find_native_static_library(name, verbatim, self.sess));
1676            self.link_or_cc_arg(arg);
1677        }
1678    }
1679
1680    fn link_staticlib_by_path(&mut self, path: &Path, whole_archive: bool) {
1681        self.hint_static();
1682        if !whole_archive {
1683            self.link_or_cc_arg(path);
1684        } else {
1685            let mut arg = OsString::from("-bkeepfile:");
1686            arg.push(path);
1687            self.link_arg(arg);
1688        }
1689    }
1690
1691    fn full_relro(&mut self) {}
1692
1693    fn partial_relro(&mut self) {}
1694
1695    fn no_relro(&mut self) {}
1696
1697    fn gc_sections(&mut self, _keep_metadata: bool) {
1698        self.link_arg("-bgc");
1699    }
1700
1701    fn no_gc_sections(&mut self) {
1702        self.link_arg("-bnogc");
1703    }
1704
1705    fn optimize(&mut self) {}
1706
1707    fn pgo_gen(&mut self) {
1708        self.link_arg("-bdbg:namedsects:ss");
1709        self.link_arg("-u");
1710        self.link_arg("__llvm_profile_runtime");
1711    }
1712
1713    fn control_flow_guard(&mut self) {}
1714
1715    fn ehcont_guard(&mut self) {}
1716
1717    fn debuginfo(&mut self, _: Strip, _: &[PathBuf]) {}
1718
1719    fn no_crt_objects(&mut self) {}
1720
1721    fn no_default_libraries(&mut self) {}
1722
1723    fn export_symbols(&mut self, tmpdir: &Path, _crate_type: CrateType, symbols: &[String]) {
1724        let path = tmpdir.join("list.exp");
1725        let res: io::Result<()> = try {
1726            let mut f = File::create_buffered(&path)?;
1727            // FIXME: use llvm-nm to generate export list.
1728            for symbol in symbols {
1729                debug!("  _{symbol}");
1730                writeln!(f, "  {symbol}")?;
1731            }
1732        };
1733        if let Err(e) = res {
1734            self.sess.dcx().fatal(format!("failed to write export file: {e}"));
1735        }
1736        self.link_arg(format!("-bE:{}", path.to_str().unwrap()));
1737    }
1738
1739    fn subsystem(&mut self, _subsystem: &str) {}
1740
1741    fn reset_per_library_state(&mut self) {
1742        self.hint_dynamic();
1743    }
1744
1745    fn linker_plugin_lto(&mut self) {}
1746
1747    fn add_eh_frame_header(&mut self) {}
1748
1749    fn add_no_exec(&mut self) {}
1750
1751    fn add_as_needed(&mut self) {}
1752}
1753
1754fn for_each_exported_symbols_include_dep<'tcx>(
1755    tcx: TyCtxt<'tcx>,
1756    crate_type: CrateType,
1757    mut callback: impl FnMut(ExportedSymbol<'tcx>, SymbolExportInfo, CrateNum),
1758) {
1759    let formats = tcx.dependency_formats(());
1760    let deps = &formats[&crate_type];
1761
1762    for (cnum, dep_format) in deps.iter_enumerated() {
1763        // For each dependency that we are linking to statically ...
1764        if *dep_format == Linkage::Static {
1765            for &(symbol, info) in tcx.exported_symbols(cnum).iter() {
1766                callback(symbol, info, cnum);
1767            }
1768        }
1769    }
1770}
1771
1772pub(crate) fn exported_symbols(tcx: TyCtxt<'_>, crate_type: CrateType) -> Vec<String> {
1773    if let Some(ref exports) = tcx.sess.target.override_export_symbols {
1774        return exports.iter().map(ToString::to_string).collect();
1775    }
1776
1777    if let CrateType::ProcMacro = crate_type {
1778        exported_symbols_for_proc_macro_crate(tcx)
1779    } else {
1780        exported_symbols_for_non_proc_macro(tcx, crate_type)
1781    }
1782}
1783
1784fn exported_symbols_for_non_proc_macro(tcx: TyCtxt<'_>, crate_type: CrateType) -> Vec<String> {
1785    let mut symbols = Vec::new();
1786    let export_threshold = symbol_export::crates_export_threshold(&[crate_type]);
1787    for_each_exported_symbols_include_dep(tcx, crate_type, |symbol, info, cnum| {
1788        // Do not export mangled symbols from cdylibs and don't attempt to export compiler-builtins
1789        // from any cdylib. The latter doesn't work anyway as we use hidden visibility for
1790        // compiler-builtins. Most linkers silently ignore it, but ld64 gives a warning.
1791        if info.level.is_below_threshold(export_threshold) && !tcx.is_compiler_builtins(cnum) {
1792            symbols.push(symbol_export::exporting_symbol_name_for_instance_in_crate(
1793                tcx, symbol, cnum,
1794            ));
1795            symbol_export::extend_exported_symbols(&mut symbols, tcx, symbol, cnum);
1796        }
1797    });
1798
1799    symbols
1800}
1801
1802fn exported_symbols_for_proc_macro_crate(tcx: TyCtxt<'_>) -> Vec<String> {
1803    // `exported_symbols` will be empty when !should_codegen.
1804    if !tcx.sess.opts.output_types.should_codegen() {
1805        return Vec::new();
1806    }
1807
1808    let stable_crate_id = tcx.stable_crate_id(LOCAL_CRATE);
1809    let proc_macro_decls_name = tcx.sess.generate_proc_macro_decls_symbol(stable_crate_id);
1810    let metadata_symbol_name = exported_symbols::metadata_symbol_name(tcx);
1811
1812    vec![proc_macro_decls_name, metadata_symbol_name]
1813}
1814
1815pub(crate) fn linked_symbols(
1816    tcx: TyCtxt<'_>,
1817    crate_type: CrateType,
1818) -> Vec<(String, SymbolExportKind)> {
1819    match crate_type {
1820        CrateType::Executable | CrateType::Cdylib | CrateType::Dylib | CrateType::Sdylib => (),
1821        CrateType::Staticlib | CrateType::ProcMacro | CrateType::Rlib => {
1822            return Vec::new();
1823        }
1824    }
1825
1826    let mut symbols = Vec::new();
1827
1828    let export_threshold = symbol_export::crates_export_threshold(&[crate_type]);
1829    for_each_exported_symbols_include_dep(tcx, crate_type, |symbol, info, cnum| {
1830        if info.level.is_below_threshold(export_threshold) && !tcx.is_compiler_builtins(cnum)
1831            || info.used
1832        {
1833            symbols.push((
1834                symbol_export::linking_symbol_name_for_instance_in_crate(tcx, symbol, cnum),
1835                info.kind,
1836            ));
1837        }
1838    });
1839
1840    symbols
1841}
1842
1843/// Much simplified and explicit CLI for the NVPTX linker. The linker operates
1844/// with bitcode and uses LLVM backend to generate a PTX assembly.
1845struct PtxLinker<'a> {
1846    cmd: Command,
1847    sess: &'a Session,
1848}
1849
1850impl<'a> Linker for PtxLinker<'a> {
1851    fn cmd(&mut self) -> &mut Command {
1852        &mut self.cmd
1853    }
1854
1855    fn set_output_kind(
1856        &mut self,
1857        _output_kind: LinkOutputKind,
1858        _crate_type: CrateType,
1859        _out_filename: &Path,
1860    ) {
1861    }
1862
1863    fn link_staticlib_by_name(&mut self, _name: &str, _verbatim: bool, _whole_archive: bool) {
1864        panic!("staticlibs not supported")
1865    }
1866
1867    fn link_staticlib_by_path(&mut self, path: &Path, _whole_archive: bool) {
1868        self.link_arg("--rlib").link_arg(path);
1869    }
1870
1871    fn debuginfo(&mut self, _strip: Strip, _: &[PathBuf]) {
1872        self.link_arg("--debug");
1873    }
1874
1875    fn add_object(&mut self, path: &Path) {
1876        self.link_arg("--bitcode").link_arg(path);
1877    }
1878
1879    fn optimize(&mut self) {
1880        match self.sess.lto() {
1881            Lto::Thin | Lto::Fat | Lto::ThinLocal => {
1882                self.link_arg("-Olto");
1883            }
1884
1885            Lto::No => {}
1886        }
1887    }
1888
1889    fn full_relro(&mut self) {}
1890
1891    fn partial_relro(&mut self) {}
1892
1893    fn no_relro(&mut self) {}
1894
1895    fn gc_sections(&mut self, _keep_metadata: bool) {}
1896
1897    fn no_gc_sections(&mut self) {}
1898
1899    fn pgo_gen(&mut self) {}
1900
1901    fn no_crt_objects(&mut self) {}
1902
1903    fn no_default_libraries(&mut self) {}
1904
1905    fn control_flow_guard(&mut self) {}
1906
1907    fn ehcont_guard(&mut self) {}
1908
1909    fn export_symbols(&mut self, _tmpdir: &Path, _crate_type: CrateType, _symbols: &[String]) {}
1910
1911    fn subsystem(&mut self, _subsystem: &str) {}
1912
1913    fn linker_plugin_lto(&mut self) {}
1914}
1915
1916/// The `self-contained` LLVM bitcode linker
1917struct LlbcLinker<'a> {
1918    cmd: Command,
1919    sess: &'a Session,
1920}
1921
1922impl<'a> Linker for LlbcLinker<'a> {
1923    fn cmd(&mut self) -> &mut Command {
1924        &mut self.cmd
1925    }
1926
1927    fn set_output_kind(
1928        &mut self,
1929        _output_kind: LinkOutputKind,
1930        _crate_type: CrateType,
1931        _out_filename: &Path,
1932    ) {
1933    }
1934
1935    fn link_staticlib_by_name(&mut self, _name: &str, _verbatim: bool, _whole_archive: bool) {
1936        panic!("staticlibs not supported")
1937    }
1938
1939    fn link_staticlib_by_path(&mut self, path: &Path, _whole_archive: bool) {
1940        self.link_or_cc_arg(path);
1941    }
1942
1943    fn debuginfo(&mut self, _strip: Strip, _: &[PathBuf]) {
1944        self.link_arg("--debug");
1945    }
1946
1947    fn optimize(&mut self) {
1948        self.link_arg(match self.sess.opts.optimize {
1949            OptLevel::No => "-O0",
1950            OptLevel::Less => "-O1",
1951            OptLevel::More => "-O2",
1952            OptLevel::Aggressive => "-O3",
1953            OptLevel::Size => "-Os",
1954            OptLevel::SizeMin => "-Oz",
1955        });
1956    }
1957
1958    fn full_relro(&mut self) {}
1959
1960    fn partial_relro(&mut self) {}
1961
1962    fn no_relro(&mut self) {}
1963
1964    fn gc_sections(&mut self, _keep_metadata: bool) {}
1965
1966    fn no_gc_sections(&mut self) {}
1967
1968    fn pgo_gen(&mut self) {}
1969
1970    fn no_crt_objects(&mut self) {}
1971
1972    fn no_default_libraries(&mut self) {}
1973
1974    fn control_flow_guard(&mut self) {}
1975
1976    fn ehcont_guard(&mut self) {}
1977
1978    fn export_symbols(&mut self, _tmpdir: &Path, _crate_type: CrateType, symbols: &[String]) {
1979        match _crate_type {
1980            CrateType::Cdylib => {
1981                for sym in symbols {
1982                    self.link_args(&["--export-symbol", sym]);
1983                }
1984            }
1985            _ => (),
1986        }
1987    }
1988
1989    fn subsystem(&mut self, _subsystem: &str) {}
1990
1991    fn linker_plugin_lto(&mut self) {}
1992}
1993
1994struct BpfLinker<'a> {
1995    cmd: Command,
1996    sess: &'a Session,
1997}
1998
1999impl<'a> Linker for BpfLinker<'a> {
2000    fn cmd(&mut self) -> &mut Command {
2001        &mut self.cmd
2002    }
2003
2004    fn set_output_kind(
2005        &mut self,
2006        _output_kind: LinkOutputKind,
2007        _crate_type: CrateType,
2008        _out_filename: &Path,
2009    ) {
2010    }
2011
2012    fn link_staticlib_by_name(&mut self, _name: &str, _verbatim: bool, _whole_archive: bool) {
2013        panic!("staticlibs not supported")
2014    }
2015
2016    fn link_staticlib_by_path(&mut self, path: &Path, _whole_archive: bool) {
2017        self.link_or_cc_arg(path);
2018    }
2019
2020    fn debuginfo(&mut self, _strip: Strip, _: &[PathBuf]) {
2021        self.link_arg("--debug");
2022    }
2023
2024    fn optimize(&mut self) {
2025        self.link_arg(match self.sess.opts.optimize {
2026            OptLevel::No => "-O0",
2027            OptLevel::Less => "-O1",
2028            OptLevel::More => "-O2",
2029            OptLevel::Aggressive => "-O3",
2030            OptLevel::Size => "-Os",
2031            OptLevel::SizeMin => "-Oz",
2032        });
2033    }
2034
2035    fn full_relro(&mut self) {}
2036
2037    fn partial_relro(&mut self) {}
2038
2039    fn no_relro(&mut self) {}
2040
2041    fn gc_sections(&mut self, _keep_metadata: bool) {}
2042
2043    fn no_gc_sections(&mut self) {}
2044
2045    fn pgo_gen(&mut self) {}
2046
2047    fn no_crt_objects(&mut self) {}
2048
2049    fn no_default_libraries(&mut self) {}
2050
2051    fn control_flow_guard(&mut self) {}
2052
2053    fn ehcont_guard(&mut self) {}
2054
2055    fn export_symbols(&mut self, tmpdir: &Path, _crate_type: CrateType, symbols: &[String]) {
2056        let path = tmpdir.join("symbols");
2057        let res: io::Result<()> = try {
2058            let mut f = File::create_buffered(&path)?;
2059            for sym in symbols {
2060                writeln!(f, "{sym}")?;
2061            }
2062        };
2063        if let Err(error) = res {
2064            self.sess.dcx().emit_fatal(errors::SymbolFileWriteFailure { error });
2065        } else {
2066            self.link_arg("--export-symbols").link_arg(&path);
2067        }
2068    }
2069
2070    fn subsystem(&mut self, _subsystem: &str) {}
2071
2072    fn linker_plugin_lto(&mut self) {}
2073}