1 //! Finds crate binaries and loads their metadata
3 //! Might I be the first to welcome you to a world of platform differences,
4 //! version requirements, dependency graphs, conflicting desires, and fun! This
5 //! is the major guts (along with metadata::creader) of the compiler for loading
6 //! crates and resolving dependencies. Let's take a tour!
10 //! Each invocation of the compiler is immediately concerned with one primary
11 //! problem, to connect a set of crates to resolved crates on the filesystem.
12 //! Concretely speaking, the compiler follows roughly these steps to get here:
14 //! 1. Discover a set of `extern crate` statements.
15 //! 2. Transform these directives into crate names. If the directive does not
16 //! have an explicit name, then the identifier is the name.
17 //! 3. For each of these crate names, find a corresponding crate on the
20 //! Sounds easy, right? Let's walk into some of the nuances.
22 //! ## Transitive Dependencies
24 //! Let's say we've got three crates: A, B, and C. A depends on B, and B depends
25 //! on C. When we're compiling A, we primarily need to find and locate B, but we
26 //! also end up needing to find and locate C as well.
28 //! The reason for this is that any of B's types could be composed of C's types,
29 //! any function in B could return a type from C, etc. To be able to guarantee
30 //! that we can always type-check/translate any function, we have to have
31 //! complete knowledge of the whole ecosystem, not just our immediate
34 //! So now as part of the "find a corresponding crate on the filesystem" step
35 //! above, this involves also finding all crates for *all upstream
36 //! dependencies*. This includes all dependencies transitively.
38 //! ## Rlibs and Dylibs
40 //! The compiler has two forms of intermediate dependencies. These are dubbed
41 //! rlibs and dylibs for the static and dynamic variants, respectively. An rlib
42 //! is a rustc-defined file format (currently just an ar archive) while a dylib
43 //! is a platform-defined dynamic library. Each library has a metadata somewhere
46 //! A third kind of dependency is an rmeta file. These are metadata files and do
47 //! not contain any code, etc. To a first approximation, these are treated in the
48 //! same way as rlibs. Where there is both an rlib and an rmeta file, the rlib
49 //! gets priority (even if the rmeta file is newer). An rmeta file is only
50 //! useful for checking a downstream crate, attempting to link one will cause an
53 //! When translating a crate name to a crate on the filesystem, we all of a
54 //! sudden need to take into account both rlibs and dylibs! Linkage later on may
55 //! use either one of these files, as each has their pros/cons. The job of crate
56 //! loading is to discover what's possible by finding all candidates.
58 //! Most parts of this loading systems keep the dylib/rlib as just separate
63 //! We can't exactly scan your whole hard drive when looking for dependencies,
64 //! so we need to places to look. Currently the compiler will implicitly add the
65 //! target lib search path ($prefix/lib/rustlib/$target/lib) to any compilation,
66 //! and otherwise all -L flags are added to the search paths.
68 //! ## What criterion to select on?
70 //! This a pretty tricky area of loading crates. Given a file, how do we know
71 //! whether it's the right crate? Currently, the rules look along these lines:
73 //! 1. Does the filename match an rlib/dylib pattern? That is to say, does the
74 //! filename have the right prefix/suffix?
75 //! 2. Does the filename have the right prefix for the crate name being queried?
76 //! This is filtering for files like `libfoo*.rlib` and such. If the crate
77 //! we're looking for was originally compiled with -C extra-filename, the
78 //! extra filename will be included in this prefix to reduce reading
79 //! metadata from crates that would otherwise share our prefix.
80 //! 3. Is the file an actual rust library? This is done by loading the metadata
81 //! from the library and making sure it's actually there.
82 //! 4. Does the name in the metadata agree with the name of the library?
83 //! 5. Does the target in the metadata agree with the current target?
84 //! 6. Does the SVH match? (more on this later)
86 //! If the file answers `yes` to all these questions, then the file is
87 //! considered as being *candidate* for being accepted. It is illegal to have
88 //! more than two candidates as the compiler has no method by which to resolve
89 //! this conflict. Additionally, rlib/dylib candidates are considered
92 //! After all this has happened, we have 1 or two files as candidates. These
93 //! represent the rlib/dylib file found for a library, and they're returned as
96 //! ### What about versions?
98 //! A lot of effort has been put forth to remove versioning from the compiler.
99 //! There have been forays in the past to have versioning baked in, but it was
100 //! largely always deemed insufficient to the point that it was recognized that
101 //! it's probably something the compiler shouldn't do anyway due to its
102 //! complicated nature and the state of the half-baked solutions.
104 //! With a departure from versioning, the primary criterion for loading crates
105 //! is just the name of a crate. If we stopped here, it would imply that you
106 //! could never link two crates of the same name from different sources
107 //! together, which is clearly a bad state to be in.
109 //! To resolve this problem, we come to the next section!
113 //! A number of flags have been added to the compiler to solve the "version
114 //! problem" in the previous section, as well as generally enabling more
115 //! powerful usage of the crate loading system of the compiler. The goal of
116 //! these flags and options are to enable third-party tools to drive the
117 //! compiler with prior knowledge about how the world should look.
119 //! ## The `--extern` flag
121 //! The compiler accepts a flag of this form a number of times:
124 //! --extern crate-name=path/to/the/crate.rlib
127 //! This flag is basically the following letter to the compiler:
131 //! > When you are attempting to load the immediate dependency `crate-name`, I
132 //! > would like you to assume that the library is located at
133 //! > `path/to/the/crate.rlib`, and look nowhere else. Also, please do not
134 //! > assume that the path I specified has the name `crate-name`.
136 //! This flag basically overrides most matching logic except for validating that
137 //! the file is indeed a rust library. The same `crate-name` can be specified
138 //! twice to specify the rlib/dylib pair.
140 //! ## Enabling "multiple versions"
142 //! This basically boils down to the ability to specify arbitrary packages to
143 //! the compiler. For example, if crate A wanted to use Bv1 and Bv2, then it
144 //! would look something like:
146 //! ```compile_fail,E0463
153 //! and the compiler would be invoked as:
156 //! rustc a.rs --extern b1=path/to/libb1.rlib --extern b2=path/to/libb2.rlib
159 //! In this scenario there are two crates named `b` and the compiler must be
160 //! manually driven to be informed where each crate is.
162 //! ## Frobbing symbols
164 //! One of the immediate problems with linking the same library together twice
165 //! in the same problem is dealing with duplicate symbols. The primary way to
166 //! deal with this in rustc is to add hashes to the end of each symbol.
168 //! In order to force hashes to change between versions of a library, if
169 //! desired, the compiler exposes an option `-C metadata=foo`, which is used to
170 //! initially seed each symbol hash. The string `foo` is prepended to each
171 //! string-to-hash to ensure that symbols change over time.
173 //! ## Loading transitive dependencies
175 //! Dealing with same-named-but-distinct crates is not just a local problem, but
176 //! one that also needs to be dealt with for transitive dependencies. Note that
177 //! in the letter above `--extern` flags only apply to the *local* set of
178 //! dependencies, not the upstream transitive dependencies. Consider this
179 //! dependency graph:
191 //! In this scenario, when we compile `D`, we need to be able to distinctly
192 //! resolve `A.1` and `A.2`, but an `--extern` flag cannot apply to these
193 //! transitive dependencies.
195 //! Note that the key idea here is that `B` and `C` are both *already compiled*.
196 //! That is, they have already resolved their dependencies. Due to unrelated
197 //! technical reasons, when a library is compiled, it is only compatible with
198 //! the *exact same* version of the upstream libraries it was compiled against.
199 //! We use the "Strict Version Hash" to identify the exact copy of an upstream
202 //! With this knowledge, we know that `B` and `C` will depend on `A` with
203 //! different SVH values, so we crawl the normal `-L` paths looking for
204 //! `liba*.rlib` and filter based on the contained SVH.
206 //! In the end, this ends up not needing `--extern` to specify upstream
207 //! transitive dependencies.
211 //! That's the general overview of loading crates in the compiler, but it's by
212 //! no means all of the necessary details. Take a look at the rest of
213 //! metadata::locator or metadata::creader for all the juicy details!
215 use crate::creader::Library;
216 use crate::rmeta::{rustc_version, MetadataBlob, METADATA_HEADER};
218 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
219 use rustc_data_structures::memmap::Mmap;
220 use rustc_data_structures::owning_ref::OwningRef;
221 use rustc_data_structures::svh::Svh;
222 use rustc_data_structures::sync::MetadataRef;
223 use rustc_errors::struct_span_err;
224 use rustc_session::config::{self, CrateType};
225 use rustc_session::cstore::{CrateSource, MetadataLoader};
226 use rustc_session::filesearch::{FileDoesntMatch, FileMatches, FileSearch};
227 use rustc_session::search_paths::PathKind;
228 use rustc_session::utils::CanonicalizedPath;
229 use rustc_session::Session;
230 use rustc_span::symbol::{sym, Symbol};
231 use rustc_span::Span;
232 use rustc_target::spec::{Target, TargetTriple};
234 use snap::read::FrameDecoder;
235 use std::fmt::Write as _;
236 use std::io::{Read, Result as IoResult, Write};
237 use std::path::{Path, PathBuf};
238 use std::{cmp, fmt, fs};
239 use tracing::{debug, info, warn};
242 crate struct CrateLocator<'a> {
243 // Immutable per-session configuration.
244 only_needs_metadata: bool,
246 metadata_loader: &'a dyn MetadataLoader,
248 // Immutable per-search configuration.
250 exact_paths: Vec<CanonicalizedPath>,
251 pub hash: Option<Svh>,
252 extra_filename: Option<&'a str>,
253 pub target: &'a Target,
254 pub triple: TargetTriple,
255 pub filesearch: FileSearch<'a>,
256 pub is_proc_macro: bool,
258 // Mutable in-progress state or output.
259 crate_rejections: CrateRejections,
263 crate struct CratePaths {
269 crate fn new(name: Symbol, source: CrateSource) -> CratePaths {
270 CratePaths { name, source }
274 #[derive(Copy, Clone, PartialEq)]
275 crate enum CrateFlavor {
281 impl fmt::Display for CrateFlavor {
282 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
283 f.write_str(match *self {
284 CrateFlavor::Rlib => "rlib",
285 CrateFlavor::Rmeta => "rmeta",
286 CrateFlavor::Dylib => "dylib",
291 impl<'a> CrateLocator<'a> {
294 metadata_loader: &'a dyn MetadataLoader,
297 extra_filename: Option<&'a str>,
300 ) -> CrateLocator<'a> {
301 // The all loop is because `--crate-type=rlib --crate-type=rlib` is
302 // legal and produces both inside this type.
303 let is_rlib = sess.crate_types().iter().all(|c| *c == CrateType::Rlib);
304 let needs_object_code = sess.opts.output_types.should_codegen();
305 // If we're producing an rlib, then we don't need object code.
306 // Or, if we're not producing object code, then we don't need it either
307 // (e.g., if we're a cdylib but emitting just metadata).
308 let only_needs_metadata = is_rlib || !needs_object_code;
312 sysroot: &sess.sysroot,
315 exact_paths: if hash.is_none() {
318 .get(&crate_name.as_str())
320 .filter_map(|entry| entry.files())
325 // SVH being specified means this is a transitive dependency,
326 // so `--extern` options do not apply.
331 target: if is_host { &sess.host } else { &sess.target },
333 TargetTriple::from_triple(config::host_triple())
335 sess.opts.target_triple.clone()
337 filesearch: if is_host {
338 sess.host_filesearch(path_kind)
340 sess.target_filesearch(path_kind)
342 is_proc_macro: false,
343 crate_rejections: CrateRejections::default(),
347 crate fn reset(&mut self) {
348 self.crate_rejections.via_hash.clear();
349 self.crate_rejections.via_triple.clear();
350 self.crate_rejections.via_kind.clear();
351 self.crate_rejections.via_version.clear();
352 self.crate_rejections.via_filename.clear();
355 crate fn maybe_load_library_crate(&mut self) -> Result<Option<Library>, CrateError> {
356 if !self.exact_paths.is_empty() {
357 return self.find_commandline_library();
359 let mut seen_paths = FxHashSet::default();
360 if let Some(extra_filename) = self.extra_filename {
361 if let library @ Some(_) = self.find_library_crate(extra_filename, &mut seen_paths)? {
365 self.find_library_crate("", &mut seen_paths)
368 fn find_library_crate(
371 seen_paths: &mut FxHashSet<PathBuf>,
372 ) -> Result<Option<Library>, CrateError> {
373 // want: crate_name.dir_part() + prefix + crate_name.file_part + "-"
374 let dylib_prefix = format!("{}{}{}", self.target.dll_prefix, self.crate_name, extra_prefix);
375 let rlib_prefix = format!("lib{}{}", self.crate_name, extra_prefix);
376 let staticlib_prefix =
377 format!("{}{}{}", self.target.staticlib_prefix, self.crate_name, extra_prefix);
379 let mut candidates: FxHashMap<_, (FxHashMap<_, _>, FxHashMap<_, _>, FxHashMap<_, _>)> =
381 let mut staticlibs = vec![];
383 // First, find all possible candidate rlibs and dylibs purely based on
384 // the name of the files themselves. We're trying to match against an
385 // exact crate name and a possibly an exact hash.
387 // During this step, we can filter all found libraries based on the
388 // name and id found in the crate id (we ignore the path portion for
389 // filename matching), as well as the exact hash (if specified). If we
390 // end up having many candidates, we must look at the metadata to
391 // perform exact matches against hashes/crate ids. Note that opening up
392 // the metadata is where we do an exact match against the full contents
393 // of the crate id (path/name/id).
395 // The goal of this step is to look at as little metadata as possible.
396 self.filesearch.search(|spf, kind| {
397 let file = match &spf.file_name_str {
398 None => return FileDoesntMatch,
401 let (hash, found_kind) = if file.starts_with(&rlib_prefix) && file.ends_with(".rlib") {
402 (&file[(rlib_prefix.len())..(file.len() - ".rlib".len())], CrateFlavor::Rlib)
403 } else if file.starts_with(&rlib_prefix) && file.ends_with(".rmeta") {
404 (&file[(rlib_prefix.len())..(file.len() - ".rmeta".len())], CrateFlavor::Rmeta)
405 } else if file.starts_with(&dylib_prefix) && file.ends_with(&self.target.dll_suffix) {
407 &file[(dylib_prefix.len())..(file.len() - self.target.dll_suffix.len())],
411 if file.starts_with(&staticlib_prefix)
412 && file.ends_with(&self.target.staticlib_suffix)
415 .push(CrateMismatch { path: spf.path.clone(), got: "static".to_string() });
417 return FileDoesntMatch;
420 info!("lib candidate: {}", spf.path.display());
422 let (rlibs, rmetas, dylibs) = candidates.entry(hash.to_string()).or_default();
423 let path = fs::canonicalize(&spf.path).unwrap_or_else(|_| spf.path.clone());
424 if seen_paths.contains(&path) {
425 return FileDoesntMatch;
427 seen_paths.insert(path.clone());
429 CrateFlavor::Rlib => rlibs.insert(path, kind),
430 CrateFlavor::Rmeta => rmetas.insert(path, kind),
431 CrateFlavor::Dylib => dylibs.insert(path, kind),
435 self.crate_rejections.via_kind.extend(staticlibs);
437 // We have now collected all known libraries into a set of candidates
438 // keyed of the filename hash listed. For each filename, we also have a
439 // list of rlibs/dylibs that apply. Here, we map each of these lists
440 // (per hash), to a Library candidate for returning.
442 // A Library candidate is created if the metadata for the set of
443 // libraries corresponds to the crate id and hash criteria that this
444 // search is being performed for.
445 let mut libraries = FxHashMap::default();
446 for (_hash, (rlibs, rmetas, dylibs)) in candidates {
447 if let Some((svh, lib)) = self.extract_lib(rlibs, rmetas, dylibs)? {
448 libraries.insert(svh, lib);
452 // Having now translated all relevant found hashes into libraries, see
453 // what we've got and figure out if we found multiple candidates for
455 match libraries.len() {
457 1 => Ok(Some(libraries.into_iter().next().unwrap().1)),
458 _ => Err(CrateError::MultipleMatchingCrates(self.crate_name, libraries)),
464 rlibs: FxHashMap<PathBuf, PathKind>,
465 rmetas: FxHashMap<PathBuf, PathKind>,
466 dylibs: FxHashMap<PathBuf, PathKind>,
467 ) -> Result<Option<(Svh, Library)>, CrateError> {
469 // Order here matters, rmeta should come first. See comment in
470 // `extract_one` below.
471 let source = CrateSource {
472 rmeta: self.extract_one(rmetas, CrateFlavor::Rmeta, &mut slot)?,
473 rlib: self.extract_one(rlibs, CrateFlavor::Rlib, &mut slot)?,
474 dylib: self.extract_one(dylibs, CrateFlavor::Dylib, &mut slot)?,
476 Ok(slot.map(|(svh, metadata)| (svh, Library { source, metadata })))
479 fn needs_crate_flavor(&self, flavor: CrateFlavor) -> bool {
480 if flavor == CrateFlavor::Dylib && self.is_proc_macro {
484 if self.only_needs_metadata {
485 flavor == CrateFlavor::Rmeta
487 // we need all flavors (perhaps not true, but what we do for now)
492 // Attempts to extract *one* library from the set `m`. If the set has no
493 // elements, `None` is returned. If the set has more than one element, then
494 // the errors and notes are emitted about the set of libraries.
496 // With only one library in the set, this function will extract it, and then
497 // read the metadata from it if `*slot` is `None`. If the metadata couldn't
498 // be read, it is assumed that the file isn't a valid rust library (no
499 // errors are emitted).
502 m: FxHashMap<PathBuf, PathKind>,
504 slot: &mut Option<(Svh, MetadataBlob)>,
505 ) -> Result<Option<(PathBuf, PathKind)>, CrateError> {
506 // If we are producing an rlib, and we've already loaded metadata, then
507 // we should not attempt to discover further crate sources (unless we're
508 // locating a proc macro; exact logic is in needs_crate_flavor). This means
509 // that under -Zbinary-dep-depinfo we will not emit a dependency edge on
510 // the *unused* rlib, and by returning `None` here immediately we
511 // guarantee that we do indeed not use it.
513 // See also #68149 which provides more detail on why emitting the
514 // dependency on the rlib is a bad thing.
516 // We currently do not verify that these other sources are even in sync,
517 // and this is arguably a bug (see #10786), but because reading metadata
518 // is quite slow (especially from dylibs) we currently do not read it
519 // from the other crate sources.
521 if m.is_empty() || !self.needs_crate_flavor(flavor) {
523 } else if m.len() == 1 {
524 return Ok(Some(m.into_iter().next().unwrap()));
528 let mut ret: Option<(PathBuf, PathKind)> = None;
529 let mut err_data: Option<Vec<PathBuf>> = None;
530 for (lib, kind) in m {
531 info!("{} reading metadata from: {}", flavor, lib.display());
532 if flavor == CrateFlavor::Rmeta && lib.metadata().map_or(false, |m| m.len() == 0) {
533 // Empty files will cause get_metadata_section to fail. Rmeta
534 // files can be empty, for example with binaries (which can
535 // often appear with `cargo check` when checking a library as
536 // a unittest). We don't want to emit a user-visible warning
537 // in this case as it is not a real problem.
538 debug!("skipping empty file");
541 let (hash, metadata) =
542 match get_metadata_section(self.target, flavor, &lib, self.metadata_loader) {
544 if let Some(h) = self.crate_matches(&blob, &lib) {
547 info!("metadata mismatch");
552 warn!("no metadata found: {}", err);
556 // If we see multiple hashes, emit an error about duplicate candidates.
557 if slot.as_ref().map_or(false, |s| s.0 != hash) {
558 if let Some(candidates) = err_data {
559 return Err(CrateError::MultipleCandidates(
565 err_data = Some(vec![ret.as_ref().unwrap().0.clone()]);
568 if let Some(candidates) = &mut err_data {
569 candidates.push(lib);
573 // Ok so at this point we've determined that `(lib, kind)` above is
574 // a candidate crate to load, and that `slot` is either none (this
575 // is the first crate of its kind) or if some the previous path has
576 // the exact same hash (e.g., it's the exact same crate).
578 // In principle these two candidate crates are exactly the same so
579 // we can choose either of them to link. As a stupidly gross hack,
580 // however, we favor crate in the sysroot.
582 // You can find more info in rust-lang/rust#39518 and various linked
583 // issues, but the general gist is that during testing libstd the
584 // compilers has two candidates to choose from: one in the sysroot
585 // and one in the deps folder. These two crates are the exact same
586 // crate but if the compiler chooses the one in the deps folder
587 // it'll cause spurious errors on Windows.
589 // As a result, we favor the sysroot crate here. Note that the
590 // candidates are all canonicalized, so we canonicalize the sysroot
592 if let Some((prev, _)) = &ret {
593 let sysroot = self.sysroot;
594 let sysroot = sysroot.canonicalize().unwrap_or_else(|_| sysroot.to_path_buf());
595 if prev.starts_with(&sysroot) {
599 *slot = Some((hash, metadata));
600 ret = Some((lib, kind));
603 if let Some(candidates) = err_data {
604 Err(CrateError::MultipleCandidates(self.crate_name, flavor, candidates))
610 fn crate_matches(&mut self, metadata: &MetadataBlob, libpath: &Path) -> Option<Svh> {
611 let rustc_version = rustc_version();
612 let found_version = metadata.get_rustc_version();
613 if found_version != rustc_version {
614 info!("Rejecting via version: expected {} got {}", rustc_version, found_version);
615 self.crate_rejections
617 .push(CrateMismatch { path: libpath.to_path_buf(), got: found_version });
621 let root = metadata.get_root();
622 if root.is_proc_macro_crate() != self.is_proc_macro {
624 "Rejecting via proc macro: expected {} got {}",
626 root.is_proc_macro_crate(),
631 if self.exact_paths.is_empty() && self.crate_name != root.name() {
632 info!("Rejecting via crate name");
636 if root.triple() != &self.triple {
637 info!("Rejecting via crate triple: expected {} got {}", self.triple, root.triple());
638 self.crate_rejections.via_triple.push(CrateMismatch {
639 path: libpath.to_path_buf(),
640 got: root.triple().to_string(),
645 let hash = root.hash();
646 if let Some(expected_hash) = self.hash {
647 if hash != expected_hash {
648 info!("Rejecting via hash: expected {} got {}", expected_hash, hash);
649 self.crate_rejections
651 .push(CrateMismatch { path: libpath.to_path_buf(), got: hash.to_string() });
659 fn find_commandline_library(&mut self) -> Result<Option<Library>, CrateError> {
660 // First, filter out all libraries that look suspicious. We only accept
661 // files which actually exist that have the correct naming scheme for
663 let mut rlibs = FxHashMap::default();
664 let mut rmetas = FxHashMap::default();
665 let mut dylibs = FxHashMap::default();
666 for loc in &self.exact_paths {
667 if !loc.canonicalized().exists() {
668 return Err(CrateError::ExternLocationNotExist(
670 loc.original().clone(),
673 let file = match loc.original().file_name().and_then(|s| s.to_str()) {
676 return Err(CrateError::ExternLocationNotFile(
678 loc.original().clone(),
683 if file.starts_with("lib") && (file.ends_with(".rlib") || file.ends_with(".rmeta"))
684 || file.starts_with(&self.target.dll_prefix)
685 && file.ends_with(&self.target.dll_suffix)
687 // Make sure there's at most one rlib and at most one dylib.
688 // Note to take care and match against the non-canonicalized name:
689 // some systems save build artifacts into content-addressed stores
690 // that do not preserve extensions, and then link to them using
691 // e.g. symbolic links. If we canonicalize too early, we resolve
692 // the symlink, the file type is lost and we might treat rlibs and
694 let loc_canon = loc.canonicalized().clone();
695 let loc = loc.original();
696 if loc.file_name().unwrap().to_str().unwrap().ends_with(".rlib") {
697 rlibs.insert(loc_canon, PathKind::ExternFlag);
698 } else if loc.file_name().unwrap().to_str().unwrap().ends_with(".rmeta") {
699 rmetas.insert(loc_canon, PathKind::ExternFlag);
701 dylibs.insert(loc_canon, PathKind::ExternFlag);
704 self.crate_rejections
706 .push(CrateMismatch { path: loc.original().clone(), got: String::new() });
710 // Extract the dylib/rlib/rmeta triple.
711 Ok(self.extract_lib(rlibs, rmetas, dylibs)?.map(|(_, lib)| lib))
714 crate fn into_error(self, root: Option<CratePaths>) -> CrateError {
715 CrateError::LocatorCombined(CombinedLocatorError {
716 crate_name: self.crate_name,
719 dll_prefix: self.target.dll_prefix.clone(),
720 dll_suffix: self.target.dll_suffix.clone(),
721 crate_rejections: self.crate_rejections,
726 fn get_metadata_section(
730 loader: &dyn MetadataLoader,
731 ) -> Result<MetadataBlob, String> {
732 if !filename.exists() {
733 return Err(format!("no such file: '{}'", filename.display()));
735 let raw_bytes: MetadataRef = match flavor {
736 CrateFlavor::Rlib => loader.get_rlib_metadata(target, filename)?,
737 CrateFlavor::Dylib => {
738 let buf = loader.get_dylib_metadata(target, filename)?;
739 // The header is uncompressed
740 let header_len = METADATA_HEADER.len();
741 debug!("checking {} bytes of metadata-version stamp", header_len);
742 let header = &buf[..cmp::min(header_len, buf.len())];
743 if header != METADATA_HEADER {
745 "incompatible metadata version found: '{}'",
750 // Header is okay -> inflate the actual metadata
751 let compressed_bytes = &buf[header_len..];
752 debug!("inflating {} bytes of compressed metadata", compressed_bytes.len());
753 // Assume the decompressed data will be at least the size of the compressed data, so we
754 // don't have to grow the buffer as much.
755 let mut inflated = Vec::with_capacity(compressed_bytes.len());
756 match FrameDecoder::new(compressed_bytes).read_to_end(&mut inflated) {
757 Ok(_) => rustc_erase_owner!(OwningRef::new(inflated).map_owner_box()),
759 return Err(format!("failed to decompress metadata: {}", filename.display()));
763 CrateFlavor::Rmeta => {
764 // mmap the file, because only a small fraction of it is read.
765 let file = std::fs::File::open(filename)
766 .map_err(|_| format!("failed to open rmeta metadata: '{}'", filename.display()))?;
767 let mmap = unsafe { Mmap::map(file) };
769 .map_err(|_| format!("failed to mmap rmeta metadata: '{}'", filename.display()))?;
771 rustc_erase_owner!(OwningRef::new(mmap).map_owner_box())
774 let blob = MetadataBlob::new(raw_bytes);
775 if blob.is_compatible() {
778 Err(format!("incompatible metadata version found: '{}'", filename.display()))
782 /// Look for a plugin registrar. Returns its library path and crate disambiguator.
783 pub fn find_plugin_registrar(
785 metadata_loader: &dyn MetadataLoader,
789 match find_plugin_registrar_impl(sess, metadata_loader, name) {
791 // `core` is always available if we got as far as loading plugins.
792 Err(err) => err.report(sess, span, false),
796 fn find_plugin_registrar_impl<'a>(
798 metadata_loader: &dyn MetadataLoader,
800 ) -> Result<PathBuf, CrateError> {
801 info!("find plugin registrar `{}`", name);
802 let mut locator = CrateLocator::new(
807 None, // extra_filename
812 match locator.maybe_load_library_crate()? {
813 Some(library) => match library.source.dylib {
814 Some(dylib) => Ok(dylib.0),
815 None => Err(CrateError::NonDylibPlugin(name)),
817 None => Err(locator.into_error(None)),
821 /// A diagnostic function for dumping crate metadata to an output stream.
822 pub fn list_file_metadata(
825 metadata_loader: &dyn MetadataLoader,
828 let filename = path.file_name().unwrap().to_str().unwrap();
829 let flavor = if filename.ends_with(".rlib") {
831 } else if filename.ends_with(".rmeta") {
836 match get_metadata_section(target, flavor, path, metadata_loader) {
837 Ok(metadata) => metadata.list_crate_metadata(out),
838 Err(msg) => write!(out, "{}\n", msg),
842 // ------------------------------------------ Error reporting -------------------------------------
845 struct CrateMismatch {
850 #[derive(Clone, Default)]
851 struct CrateRejections {
852 via_hash: Vec<CrateMismatch>,
853 via_triple: Vec<CrateMismatch>,
854 via_kind: Vec<CrateMismatch>,
855 via_version: Vec<CrateMismatch>,
856 via_filename: Vec<CrateMismatch>,
859 /// Candidate rejection reasons collected during crate search.
860 /// If no candidate is accepted, then these reasons are presented to the user,
861 /// otherwise they are ignored.
862 crate struct CombinedLocatorError {
864 root: Option<CratePaths>,
865 triple: TargetTriple,
868 crate_rejections: CrateRejections,
871 crate enum CrateError {
872 NonAsciiName(Symbol),
873 ExternLocationNotExist(Symbol, PathBuf),
874 ExternLocationNotFile(Symbol, PathBuf),
875 MultipleCandidates(Symbol, CrateFlavor, Vec<PathBuf>),
876 MultipleMatchingCrates(Symbol, FxHashMap<Svh, Library>),
877 SymbolConflictsCurrent(Symbol),
878 SymbolConflictsOthers(Symbol),
879 StableCrateIdCollision(Symbol, Symbol),
882 LocatorCombined(CombinedLocatorError),
883 NonDylibPlugin(Symbol),
887 crate fn report(self, sess: &Session, span: Span, missing_core: bool) -> ! {
888 let mut err = match self {
889 CrateError::NonAsciiName(crate_name) => sess.struct_span_err(
891 &format!("cannot load a crate with a non-ascii name `{}`", crate_name),
893 CrateError::ExternLocationNotExist(crate_name, loc) => sess.struct_span_err(
895 &format!("extern location for {} does not exist: {}", crate_name, loc.display()),
897 CrateError::ExternLocationNotFile(crate_name, loc) => sess.struct_span_err(
899 &format!("extern location for {} is not a file: {}", crate_name, loc.display()),
901 CrateError::MultipleCandidates(crate_name, flavor, candidates) => {
902 let mut err = struct_span_err!(
906 "multiple {} candidates for `{}` found",
910 for (i, candidate) in candidates.iter().enumerate() {
911 err.span_note(span, &format!("candidate #{}: {}", i + 1, candidate.display()));
915 CrateError::MultipleMatchingCrates(crate_name, libraries) => {
916 let mut err = struct_span_err!(
920 "multiple matching crates for `{}`",
923 let mut libraries: Vec<_> = libraries.into_values().collect();
924 // Make ordering of candidates deterministic.
925 // This has to `clone()` to work around lifetime restrictions with `sort_by_key()`.
926 // `sort_by()` could be used instead, but this is in the error path,
927 // so the performance shouldn't matter.
928 libraries.sort_by_cached_key(|lib| lib.source.paths().next().unwrap().clone());
929 let candidates = libraries
932 let crate_name = &lib.metadata.get_root().name().as_str();
933 let mut paths = lib.source.paths();
935 // This `unwrap()` should be okay because there has to be at least one
936 // source file. `CrateSource`'s docs confirm that too.
940 paths.next().unwrap().display()
942 let padding = 8 + crate_name.len();
944 write!(s, "\n{:>padding$}", path.display(), padding = padding).unwrap();
948 .collect::<String>();
949 err.note(&format!("candidates:{}", candidates));
952 CrateError::SymbolConflictsCurrent(root_name) => struct_span_err!(
956 "the current crate is indistinguishable from one of its dependencies: it has the \
957 same crate-name `{}` and was compiled with the same `-C metadata` arguments. \
958 This will result in symbol conflicts between the two.",
961 CrateError::SymbolConflictsOthers(root_name) => struct_span_err!(
965 "found two different crates with name `{}` that are not distinguished by differing \
966 `-C metadata`. This will result in symbol conflicts between the two.",
969 CrateError::StableCrateIdCollision(crate_name0, crate_name1) => {
971 "found crates (`{}` and `{}`) with colliding StableCrateId values.",
972 crate_name0, crate_name1
974 sess.struct_span_err(span, &msg)
976 CrateError::DlOpen(s) | CrateError::DlSym(s) => sess.struct_span_err(span, &s),
977 CrateError::LocatorCombined(locator) => {
978 let crate_name = locator.crate_name;
979 let add = match &locator.root {
980 None => String::new(),
981 Some(r) => format!(" which `{}` depends on", r.name),
983 let mut msg = "the following crate versions were found:".to_string();
984 let mut err = if !locator.crate_rejections.via_hash.is_empty() {
985 let mut err = struct_span_err!(
989 "found possibly newer version of crate `{}`{}",
993 err.note("perhaps that crate needs to be recompiled?");
994 let mismatches = locator.crate_rejections.via_hash.iter();
995 for CrateMismatch { path, .. } in mismatches {
996 msg.push_str(&format!("\ncrate `{}`: {}", crate_name, path.display()));
998 if let Some(r) = locator.root {
999 for path in r.source.paths() {
1000 msg.push_str(&format!("\ncrate `{}`: {}", r.name, path.display()));
1005 } else if !locator.crate_rejections.via_triple.is_empty() {
1006 let mut err = struct_span_err!(
1010 "couldn't find crate `{}` with expected target triple {}{}",
1015 let mismatches = locator.crate_rejections.via_triple.iter();
1016 for CrateMismatch { path, got } in mismatches {
1017 msg.push_str(&format!(
1018 "\ncrate `{}`, target triple {}: {}",
1026 } else if !locator.crate_rejections.via_kind.is_empty() {
1027 let mut err = struct_span_err!(
1031 "found staticlib `{}` instead of rlib or dylib{}",
1035 err.help("please recompile that crate using --crate-type lib");
1036 let mismatches = locator.crate_rejections.via_kind.iter();
1037 for CrateMismatch { path, .. } in mismatches {
1038 msg.push_str(&format!("\ncrate `{}`: {}", crate_name, path.display()));
1042 } else if !locator.crate_rejections.via_version.is_empty() {
1043 let mut err = struct_span_err!(
1047 "found crate `{}` compiled by an incompatible version of rustc{}",
1052 "please recompile that crate using this compiler ({}) \
1053 (consider running `cargo clean` first)",
1056 let mismatches = locator.crate_rejections.via_version.iter();
1057 for CrateMismatch { path, got } in mismatches {
1058 msg.push_str(&format!(
1059 "\ncrate `{}` compiled by {}: {}",
1068 let mut err = struct_span_err!(
1072 "can't find crate for `{}`{}",
1077 if (crate_name == sym::std || crate_name == sym::core)
1078 && locator.triple != TargetTriple::from_triple(config::host_triple())
1082 "the `{}` target may not be installed",
1087 "the `{}` target may not support the standard library",
1091 // NOTE: this suggests using rustup, even though the user may not have it installed.
1092 // That's because they could choose to install it; or this may give them a hint which
1093 // target they need to install from their distro.
1096 "consider downloading the target with `rustup target add {}`",
1100 // Suggest using #![no_std]. #[no_core] is unstable and not really supported anyway.
1101 // NOTE: this is a dummy span if `extern crate std` was injected by the compiler.
1102 // If it's not a dummy, that means someone added `extern crate std` explicitly and `#![no_std]` won't help.
1103 if !missing_core && span.is_dummy() {
1105 sess.opts.crate_name.as_deref().unwrap_or("<unknown>");
1107 "`std` is required by `{}` because it does not declare `#![no_std]`",
1111 if sess.is_nightly_build() {
1112 err.help("consider building the standard library from source with `cargo build -Zbuild-std`");
1114 } else if crate_name
1115 == Symbol::intern(&sess.opts.debugging_opts.profiler_runtime)
1117 err.note(&"the compiler may have been built without the profiler runtime");
1118 } else if crate_name.as_str().starts_with("rustc_") {
1120 "maybe you need to install the missing components with: \
1121 `rustup component add rust-src rustc-dev llvm-tools-preview`",
1124 err.span_label(span, "can't find crate");
1128 if !locator.crate_rejections.via_filename.is_empty() {
1129 let mismatches = locator.crate_rejections.via_filename.iter();
1130 for CrateMismatch { path, .. } in mismatches {
1132 "extern location for {} is of an unknown type: {}",
1137 "file name should be lib*.rlib or {}*.{}",
1138 locator.dll_prefix, locator.dll_suffix
1144 CrateError::NonDylibPlugin(crate_name) => struct_span_err!(
1148 "plugin `{}` only found in rlib format, but must be available in dylib format",
1154 sess.abort_if_errors();