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, FatalError};
224 use rustc_session::config::{self, CrateType};
225 use rustc_session::cstore::{CrateSource, MetadataLoader};
226 use rustc_session::filesearch::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};
242 pub(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 pub(crate) struct CratePaths {
269 pub(crate) fn new(name: Symbol, source: CrateSource) -> CratePaths {
270 CratePaths { name, source }
274 #[derive(Copy, Clone, PartialEq)]
275 pub(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 pub(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();
353 self.crate_rejections.via_invalid.clear();
356 pub(crate) fn maybe_load_library_crate(&mut self) -> Result<Option<Library>, CrateError> {
357 if !self.exact_paths.is_empty() {
358 return self.find_commandline_library();
360 let mut seen_paths = FxHashSet::default();
361 if let Some(extra_filename) = self.extra_filename {
362 if let library @ Some(_) = self.find_library_crate(extra_filename, &mut seen_paths)? {
366 self.find_library_crate("", &mut seen_paths)
369 fn find_library_crate(
372 seen_paths: &mut FxHashSet<PathBuf>,
373 ) -> Result<Option<Library>, CrateError> {
374 let rmeta_prefix = &format!("lib{}{}", self.crate_name, extra_prefix);
375 let rlib_prefix = rmeta_prefix;
377 &format!("{}{}{}", self.target.dll_prefix, self.crate_name, extra_prefix);
378 let staticlib_prefix =
379 &format!("{}{}{}", self.target.staticlib_prefix, self.crate_name, extra_prefix);
381 let rmeta_suffix = ".rmeta";
382 let rlib_suffix = ".rlib";
383 let dylib_suffix = &self.target.dll_suffix;
384 let staticlib_suffix = &self.target.staticlib_suffix;
386 let mut candidates: FxHashMap<_, (FxHashMap<_, _>, FxHashMap<_, _>, FxHashMap<_, _>)> =
389 // First, find all possible candidate rlibs and dylibs purely based on
390 // the name of the files themselves. We're trying to match against an
391 // exact crate name and a possibly an exact hash.
393 // During this step, we can filter all found libraries based on the
394 // name and id found in the crate id (we ignore the path portion for
395 // filename matching), as well as the exact hash (if specified). If we
396 // end up having many candidates, we must look at the metadata to
397 // perform exact matches against hashes/crate ids. Note that opening up
398 // the metadata is where we do an exact match against the full contents
399 // of the crate id (path/name/id).
401 // The goal of this step is to look at as little metadata as possible.
402 // Unfortunately, the prefix-based matching sometimes is over-eager.
403 // E.g. if `rlib_suffix` is `libstd` it'll match the file
404 // `libstd_detect-8d6701fb958915ad.rlib` (incorrect) as well as
405 // `libstd-f3ab5b1dea981f17.rlib` (correct). But this is hard to avoid
406 // given that `extra_filename` comes from the `-C extra-filename`
407 // option and thus can be anything, and the incorrect match will be
408 // handled safely in `extract_one`.
409 for search_path in self.filesearch.search_paths() {
410 debug!("searching {}", search_path.dir.display());
411 for spf in search_path.files.iter() {
412 debug!("testing {}", spf.path.display());
414 let f = &spf.file_name_str;
415 let (hash, kind) = if f.starts_with(rlib_prefix) && f.ends_with(rlib_suffix) {
416 (&f[rlib_prefix.len()..(f.len() - rlib_suffix.len())], CrateFlavor::Rlib)
417 } else if f.starts_with(rmeta_prefix) && f.ends_with(rmeta_suffix) {
418 (&f[rmeta_prefix.len()..(f.len() - rmeta_suffix.len())], CrateFlavor::Rmeta)
419 } else if f.starts_with(dylib_prefix) && f.ends_with(dylib_suffix.as_ref()) {
420 (&f[dylib_prefix.len()..(f.len() - dylib_suffix.len())], CrateFlavor::Dylib)
422 if f.starts_with(staticlib_prefix) && f.ends_with(staticlib_suffix.as_ref()) {
423 self.crate_rejections.via_kind.push(CrateMismatch {
424 path: spf.path.clone(),
425 got: "static".to_string(),
431 info!("lib candidate: {}", spf.path.display());
433 let (rlibs, rmetas, dylibs) = candidates.entry(hash.to_string()).or_default();
434 let path = fs::canonicalize(&spf.path).unwrap_or_else(|_| spf.path.clone());
435 if seen_paths.contains(&path) {
438 seen_paths.insert(path.clone());
440 CrateFlavor::Rlib => rlibs.insert(path, search_path.kind),
441 CrateFlavor::Rmeta => rmetas.insert(path, search_path.kind),
442 CrateFlavor::Dylib => dylibs.insert(path, search_path.kind),
447 // We have now collected all known libraries into a set of candidates
448 // keyed of the filename hash listed. For each filename, we also have a
449 // list of rlibs/dylibs that apply. Here, we map each of these lists
450 // (per hash), to a Library candidate for returning.
452 // A Library candidate is created if the metadata for the set of
453 // libraries corresponds to the crate id and hash criteria that this
454 // search is being performed for.
455 let mut libraries = FxHashMap::default();
456 for (_hash, (rlibs, rmetas, dylibs)) in candidates {
457 if let Some((svh, lib)) = self.extract_lib(rlibs, rmetas, dylibs)? {
458 libraries.insert(svh, lib);
462 // Having now translated all relevant found hashes into libraries, see
463 // what we've got and figure out if we found multiple candidates for
465 match libraries.len() {
467 1 => Ok(Some(libraries.into_iter().next().unwrap().1)),
468 _ => Err(CrateError::MultipleMatchingCrates(self.crate_name, libraries)),
474 rlibs: FxHashMap<PathBuf, PathKind>,
475 rmetas: FxHashMap<PathBuf, PathKind>,
476 dylibs: FxHashMap<PathBuf, PathKind>,
477 ) -> Result<Option<(Svh, Library)>, CrateError> {
479 // Order here matters, rmeta should come first. See comment in
480 // `extract_one` below.
481 let source = CrateSource {
482 rmeta: self.extract_one(rmetas, CrateFlavor::Rmeta, &mut slot)?,
483 rlib: self.extract_one(rlibs, CrateFlavor::Rlib, &mut slot)?,
484 dylib: self.extract_one(dylibs, CrateFlavor::Dylib, &mut slot)?,
486 Ok(slot.map(|(svh, metadata)| (svh, Library { source, metadata })))
489 fn needs_crate_flavor(&self, flavor: CrateFlavor) -> bool {
490 if flavor == CrateFlavor::Dylib && self.is_proc_macro {
494 if self.only_needs_metadata {
495 flavor == CrateFlavor::Rmeta
497 // we need all flavors (perhaps not true, but what we do for now)
502 // Attempts to extract *one* library from the set `m`. If the set has no
503 // elements, `None` is returned. If the set has more than one element, then
504 // the errors and notes are emitted about the set of libraries.
506 // With only one library in the set, this function will extract it, and then
507 // read the metadata from it if `*slot` is `None`. If the metadata couldn't
508 // be read, it is assumed that the file isn't a valid rust library (no
509 // errors are emitted).
512 m: FxHashMap<PathBuf, PathKind>,
514 slot: &mut Option<(Svh, MetadataBlob)>,
515 ) -> Result<Option<(PathBuf, PathKind)>, CrateError> {
516 // If we are producing an rlib, and we've already loaded metadata, then
517 // we should not attempt to discover further crate sources (unless we're
518 // locating a proc macro; exact logic is in needs_crate_flavor). This means
519 // that under -Zbinary-dep-depinfo we will not emit a dependency edge on
520 // the *unused* rlib, and by returning `None` here immediately we
521 // guarantee that we do indeed not use it.
523 // See also #68149 which provides more detail on why emitting the
524 // dependency on the rlib is a bad thing.
526 // We currently do not verify that these other sources are even in sync,
527 // and this is arguably a bug (see #10786), but because reading metadata
528 // is quite slow (especially from dylibs) we currently do not read it
529 // from the other crate sources.
531 if m.is_empty() || !self.needs_crate_flavor(flavor) {
533 } else if m.len() == 1 {
534 return Ok(Some(m.into_iter().next().unwrap()));
538 let mut ret: Option<(PathBuf, PathKind)> = None;
539 let mut err_data: Option<Vec<PathBuf>> = None;
540 for (lib, kind) in m {
541 info!("{} reading metadata from: {}", flavor, lib.display());
542 if flavor == CrateFlavor::Rmeta && lib.metadata().map_or(false, |m| m.len() == 0) {
543 // Empty files will cause get_metadata_section to fail. Rmeta
544 // files can be empty, for example with binaries (which can
545 // often appear with `cargo check` when checking a library as
546 // a unittest). We don't want to emit a user-visible warning
547 // in this case as it is not a real problem.
548 debug!("skipping empty file");
551 let (hash, metadata) =
552 match get_metadata_section(self.target, flavor, &lib, self.metadata_loader) {
554 if let Some(h) = self.crate_matches(&blob, &lib) {
557 info!("metadata mismatch");
561 Err(MetadataError::LoadFailure(err)) => {
562 info!("no metadata found: {}", err);
563 // The file was present and created by the same compiler version, but we
564 // couldn't load it for some reason. Give a hard error instead of silently
565 // ignoring it, but only if we would have given an error anyway.
566 self.crate_rejections
568 .push(CrateMismatch { path: lib, got: err });
571 Err(err @ MetadataError::NotPresent(_)) => {
572 info!("no metadata found: {}", err);
576 // If we see multiple hashes, emit an error about duplicate candidates.
577 if slot.as_ref().map_or(false, |s| s.0 != hash) {
578 if let Some(candidates) = err_data {
579 return Err(CrateError::MultipleCandidates(
585 err_data = Some(vec![ret.as_ref().unwrap().0.clone()]);
588 if let Some(candidates) = &mut err_data {
589 candidates.push(lib);
593 // Ok so at this point we've determined that `(lib, kind)` above is
594 // a candidate crate to load, and that `slot` is either none (this
595 // is the first crate of its kind) or if some the previous path has
596 // the exact same hash (e.g., it's the exact same crate).
598 // In principle these two candidate crates are exactly the same so
599 // we can choose either of them to link. As a stupidly gross hack,
600 // however, we favor crate in the sysroot.
602 // You can find more info in rust-lang/rust#39518 and various linked
603 // issues, but the general gist is that during testing libstd the
604 // compilers has two candidates to choose from: one in the sysroot
605 // and one in the deps folder. These two crates are the exact same
606 // crate but if the compiler chooses the one in the deps folder
607 // it'll cause spurious errors on Windows.
609 // As a result, we favor the sysroot crate here. Note that the
610 // candidates are all canonicalized, so we canonicalize the sysroot
612 if let Some((prev, _)) = &ret {
613 let sysroot = self.sysroot;
614 let sysroot = sysroot.canonicalize().unwrap_or_else(|_| sysroot.to_path_buf());
615 if prev.starts_with(&sysroot) {
619 *slot = Some((hash, metadata));
620 ret = Some((lib, kind));
623 if let Some(candidates) = err_data {
624 Err(CrateError::MultipleCandidates(self.crate_name, flavor, candidates))
630 fn crate_matches(&mut self, metadata: &MetadataBlob, libpath: &Path) -> Option<Svh> {
631 let rustc_version = rustc_version();
632 let found_version = metadata.get_rustc_version();
633 if found_version != rustc_version {
634 info!("Rejecting via version: expected {} got {}", rustc_version, found_version);
635 self.crate_rejections
637 .push(CrateMismatch { path: libpath.to_path_buf(), got: found_version });
641 let root = metadata.get_root();
642 if root.is_proc_macro_crate() != self.is_proc_macro {
644 "Rejecting via proc macro: expected {} got {}",
646 root.is_proc_macro_crate(),
651 if self.exact_paths.is_empty() && self.crate_name != root.name() {
652 info!("Rejecting via crate name");
656 if root.triple() != &self.triple {
657 info!("Rejecting via crate triple: expected {} got {}", self.triple, root.triple());
658 self.crate_rejections.via_triple.push(CrateMismatch {
659 path: libpath.to_path_buf(),
660 got: root.triple().to_string(),
665 let hash = root.hash();
666 if let Some(expected_hash) = self.hash {
667 if hash != expected_hash {
668 info!("Rejecting via hash: expected {} got {}", expected_hash, hash);
669 self.crate_rejections
671 .push(CrateMismatch { path: libpath.to_path_buf(), got: hash.to_string() });
679 fn find_commandline_library(&mut self) -> Result<Option<Library>, CrateError> {
680 // First, filter out all libraries that look suspicious. We only accept
681 // files which actually exist that have the correct naming scheme for
683 let mut rlibs = FxHashMap::default();
684 let mut rmetas = FxHashMap::default();
685 let mut dylibs = FxHashMap::default();
686 for loc in &self.exact_paths {
687 if !loc.canonicalized().exists() {
688 return Err(CrateError::ExternLocationNotExist(
690 loc.original().clone(),
693 let Some(file) = loc.original().file_name().and_then(|s| s.to_str()) else {
694 return Err(CrateError::ExternLocationNotFile(
696 loc.original().clone(),
700 if file.starts_with("lib") && (file.ends_with(".rlib") || file.ends_with(".rmeta"))
701 || file.starts_with(self.target.dll_prefix.as_ref())
702 && file.ends_with(self.target.dll_suffix.as_ref())
704 // Make sure there's at most one rlib and at most one dylib.
705 // Note to take care and match against the non-canonicalized name:
706 // some systems save build artifacts into content-addressed stores
707 // that do not preserve extensions, and then link to them using
708 // e.g. symbolic links. If we canonicalize too early, we resolve
709 // the symlink, the file type is lost and we might treat rlibs and
711 let loc_canon = loc.canonicalized().clone();
712 let loc = loc.original();
713 if loc.file_name().unwrap().to_str().unwrap().ends_with(".rlib") {
714 rlibs.insert(loc_canon, PathKind::ExternFlag);
715 } else if loc.file_name().unwrap().to_str().unwrap().ends_with(".rmeta") {
716 rmetas.insert(loc_canon, PathKind::ExternFlag);
718 dylibs.insert(loc_canon, PathKind::ExternFlag);
721 self.crate_rejections
723 .push(CrateMismatch { path: loc.original().clone(), got: String::new() });
727 // Extract the dylib/rlib/rmeta triple.
728 Ok(self.extract_lib(rlibs, rmetas, dylibs)?.map(|(_, lib)| lib))
731 pub(crate) fn into_error(self, root: Option<CratePaths>) -> CrateError {
732 CrateError::LocatorCombined(CombinedLocatorError {
733 crate_name: self.crate_name,
736 dll_prefix: self.target.dll_prefix.to_string(),
737 dll_suffix: self.target.dll_suffix.to_string(),
738 crate_rejections: self.crate_rejections,
743 fn get_metadata_section<'p>(
747 loader: &dyn MetadataLoader,
748 ) -> Result<MetadataBlob, MetadataError<'p>> {
749 if !filename.exists() {
750 return Err(MetadataError::NotPresent(filename));
752 let raw_bytes: MetadataRef = match flavor {
753 CrateFlavor::Rlib => {
754 loader.get_rlib_metadata(target, filename).map_err(MetadataError::LoadFailure)?
756 CrateFlavor::Dylib => {
758 loader.get_dylib_metadata(target, filename).map_err(MetadataError::LoadFailure)?;
759 // The header is uncompressed
760 let header_len = METADATA_HEADER.len();
761 debug!("checking {} bytes of metadata-version stamp", header_len);
762 let header = &buf[..cmp::min(header_len, buf.len())];
763 if header != METADATA_HEADER {
764 return Err(MetadataError::LoadFailure(format!(
765 "invalid metadata version found: {}",
770 // Header is okay -> inflate the actual metadata
771 let compressed_bytes = &buf[header_len..];
772 debug!("inflating {} bytes of compressed metadata", compressed_bytes.len());
773 // Assume the decompressed data will be at least the size of the compressed data, so we
774 // don't have to grow the buffer as much.
775 let mut inflated = Vec::with_capacity(compressed_bytes.len());
776 match FrameDecoder::new(compressed_bytes).read_to_end(&mut inflated) {
777 Ok(_) => rustc_erase_owner!(OwningRef::new(inflated).map_owner_box()),
779 return Err(MetadataError::LoadFailure(format!(
780 "failed to decompress metadata: {}",
786 CrateFlavor::Rmeta => {
787 // mmap the file, because only a small fraction of it is read.
788 let file = std::fs::File::open(filename).map_err(|_| {
789 MetadataError::LoadFailure(format!(
790 "failed to open rmeta metadata: '{}'",
794 let mmap = unsafe { Mmap::map(file) };
795 let mmap = mmap.map_err(|_| {
796 MetadataError::LoadFailure(format!(
797 "failed to mmap rmeta metadata: '{}'",
802 rustc_erase_owner!(OwningRef::new(mmap).map_owner_box())
805 let blob = MetadataBlob::new(raw_bytes);
806 if blob.is_compatible() {
809 Err(MetadataError::LoadFailure(format!(
810 "invalid metadata version found: {}",
816 /// Look for a plugin registrar. Returns its library path and crate disambiguator.
817 pub fn find_plugin_registrar(
819 metadata_loader: &dyn MetadataLoader,
823 find_plugin_registrar_impl(sess, metadata_loader, name).unwrap_or_else(|err| {
824 // `core` is always available if we got as far as loading plugins.
825 err.report(sess, span, false);
830 fn find_plugin_registrar_impl<'a>(
832 metadata_loader: &dyn MetadataLoader,
834 ) -> Result<PathBuf, CrateError> {
835 info!("find plugin registrar `{}`", name);
836 let mut locator = CrateLocator::new(
841 None, // extra_filename
846 match locator.maybe_load_library_crate()? {
847 Some(library) => match library.source.dylib {
848 Some(dylib) => Ok(dylib.0),
849 None => Err(CrateError::NonDylibPlugin(name)),
851 None => Err(locator.into_error(None)),
855 /// A diagnostic function for dumping crate metadata to an output stream.
856 pub fn list_file_metadata(
859 metadata_loader: &dyn MetadataLoader,
862 let filename = path.file_name().unwrap().to_str().unwrap();
863 let flavor = if filename.ends_with(".rlib") {
865 } else if filename.ends_with(".rmeta") {
870 match get_metadata_section(target, flavor, path, metadata_loader) {
871 Ok(metadata) => metadata.list_crate_metadata(out),
872 Err(msg) => write!(out, "{}\n", msg),
876 // ------------------------------------------ Error reporting -------------------------------------
879 struct CrateMismatch {
884 #[derive(Clone, Default)]
885 struct CrateRejections {
886 via_hash: Vec<CrateMismatch>,
887 via_triple: Vec<CrateMismatch>,
888 via_kind: Vec<CrateMismatch>,
889 via_version: Vec<CrateMismatch>,
890 via_filename: Vec<CrateMismatch>,
891 via_invalid: Vec<CrateMismatch>,
894 /// Candidate rejection reasons collected during crate search.
895 /// If no candidate is accepted, then these reasons are presented to the user,
896 /// otherwise they are ignored.
897 pub(crate) struct CombinedLocatorError {
899 root: Option<CratePaths>,
900 triple: TargetTriple,
903 crate_rejections: CrateRejections,
906 pub(crate) enum CrateError {
907 NonAsciiName(Symbol),
908 ExternLocationNotExist(Symbol, PathBuf),
909 ExternLocationNotFile(Symbol, PathBuf),
910 MultipleCandidates(Symbol, CrateFlavor, Vec<PathBuf>),
911 MultipleMatchingCrates(Symbol, FxHashMap<Svh, Library>),
912 SymbolConflictsCurrent(Symbol),
913 SymbolConflictsOthers(Symbol),
914 StableCrateIdCollision(Symbol, Symbol),
917 LocatorCombined(CombinedLocatorError),
918 NonDylibPlugin(Symbol),
921 enum MetadataError<'a> {
922 /// The file was missing.
923 NotPresent(&'a Path),
924 /// The file was present and invalid.
928 impl fmt::Display for MetadataError<'_> {
929 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
931 MetadataError::NotPresent(filename) => {
932 f.write_str(&format!("no such file: '{}'", filename.display()))
934 MetadataError::LoadFailure(msg) => f.write_str(msg),
940 pub(crate) fn report(self, sess: &Session, span: Span, missing_core: bool) {
941 let mut diag = match self {
942 CrateError::NonAsciiName(crate_name) => sess.struct_span_err(
944 &format!("cannot load a crate with a non-ascii name `{}`", crate_name),
946 CrateError::ExternLocationNotExist(crate_name, loc) => sess.struct_span_err(
948 &format!("extern location for {} does not exist: {}", crate_name, loc.display()),
950 CrateError::ExternLocationNotFile(crate_name, loc) => sess.struct_span_err(
952 &format!("extern location for {} is not a file: {}", crate_name, loc.display()),
954 CrateError::MultipleCandidates(crate_name, flavor, candidates) => {
955 let mut err = struct_span_err!(
959 "multiple {} candidates for `{}` found",
963 for (i, candidate) in candidates.iter().enumerate() {
964 err.span_note(span, &format!("candidate #{}: {}", i + 1, candidate.display()));
968 CrateError::MultipleMatchingCrates(crate_name, libraries) => {
969 let mut err = struct_span_err!(
973 "multiple matching crates for `{}`",
976 let mut libraries: Vec<_> = libraries.into_values().collect();
977 // Make ordering of candidates deterministic.
978 // This has to `clone()` to work around lifetime restrictions with `sort_by_key()`.
979 // `sort_by()` could be used instead, but this is in the error path,
980 // so the performance shouldn't matter.
981 libraries.sort_by_cached_key(|lib| lib.source.paths().next().unwrap().clone());
982 let candidates = libraries
985 let crate_name = lib.metadata.get_root().name();
986 let crate_name = crate_name.as_str();
987 let mut paths = lib.source.paths();
989 // This `unwrap()` should be okay because there has to be at least one
990 // source file. `CrateSource`'s docs confirm that too.
994 paths.next().unwrap().display()
996 let padding = 8 + crate_name.len();
998 write!(s, "\n{:>padding$}", path.display(), padding = padding).unwrap();
1002 .collect::<String>();
1003 err.note(&format!("candidates:{}", candidates));
1006 CrateError::SymbolConflictsCurrent(root_name) => struct_span_err!(
1010 "the current crate is indistinguishable from one of its dependencies: it has the \
1011 same crate-name `{}` and was compiled with the same `-C metadata` arguments. \
1012 This will result in symbol conflicts between the two.",
1015 CrateError::SymbolConflictsOthers(root_name) => struct_span_err!(
1019 "found two different crates with name `{}` that are not distinguished by differing \
1020 `-C metadata`. This will result in symbol conflicts between the two.",
1023 CrateError::StableCrateIdCollision(crate_name0, crate_name1) => {
1025 "found crates (`{}` and `{}`) with colliding StableCrateId values.",
1026 crate_name0, crate_name1
1028 sess.struct_span_err(span, &msg)
1030 CrateError::DlOpen(s) | CrateError::DlSym(s) => sess.struct_span_err(span, &s),
1031 CrateError::LocatorCombined(locator) => {
1032 let crate_name = locator.crate_name;
1033 let add = match &locator.root {
1034 None => String::new(),
1035 Some(r) => format!(" which `{}` depends on", r.name),
1037 let mut msg = "the following crate versions were found:".to_string();
1038 let mut err = if !locator.crate_rejections.via_hash.is_empty() {
1039 let mut err = struct_span_err!(
1043 "found possibly newer version of crate `{}`{}",
1047 err.note("perhaps that crate needs to be recompiled?");
1048 let mismatches = locator.crate_rejections.via_hash.iter();
1049 for CrateMismatch { path, .. } in mismatches {
1050 msg.push_str(&format!("\ncrate `{}`: {}", crate_name, path.display()));
1052 if let Some(r) = locator.root {
1053 for path in r.source.paths() {
1054 msg.push_str(&format!("\ncrate `{}`: {}", r.name, path.display()));
1059 } else if !locator.crate_rejections.via_triple.is_empty() {
1060 let mut err = struct_span_err!(
1064 "couldn't find crate `{}` with expected target triple {}{}",
1069 let mismatches = locator.crate_rejections.via_triple.iter();
1070 for CrateMismatch { path, got } in mismatches {
1071 msg.push_str(&format!(
1072 "\ncrate `{}`, target triple {}: {}",
1080 } else if !locator.crate_rejections.via_kind.is_empty() {
1081 let mut err = struct_span_err!(
1085 "found staticlib `{}` instead of rlib or dylib{}",
1089 err.help("please recompile that crate using --crate-type lib");
1090 let mismatches = locator.crate_rejections.via_kind.iter();
1091 for CrateMismatch { path, .. } in mismatches {
1092 msg.push_str(&format!("\ncrate `{}`: {}", crate_name, path.display()));
1096 } else if !locator.crate_rejections.via_version.is_empty() {
1097 let mut err = struct_span_err!(
1101 "found crate `{}` compiled by an incompatible version of rustc{}",
1106 "please recompile that crate using this compiler ({}) \
1107 (consider running `cargo clean` first)",
1110 let mismatches = locator.crate_rejections.via_version.iter();
1111 for CrateMismatch { path, got } in mismatches {
1112 msg.push_str(&format!(
1113 "\ncrate `{}` compiled by {}: {}",
1121 } else if !locator.crate_rejections.via_invalid.is_empty() {
1122 let mut err = struct_span_err!(
1126 "found invalid metadata files for crate `{}`{}",
1130 for CrateMismatch { path: _, got } in locator.crate_rejections.via_invalid {
1135 let mut err = struct_span_err!(
1139 "can't find crate for `{}`{}",
1144 if (crate_name == sym::std || crate_name == sym::core)
1145 && locator.triple != TargetTriple::from_triple(config::host_triple())
1149 "the `{}` target may not be installed",
1154 "the `{}` target may not support the standard library",
1158 // NOTE: this suggests using rustup, even though the user may not have it installed.
1159 // That's because they could choose to install it; or this may give them a hint which
1160 // target they need to install from their distro.
1163 "consider downloading the target with `rustup target add {}`",
1167 // Suggest using #![no_std]. #[no_core] is unstable and not really supported anyway.
1168 // NOTE: this is a dummy span if `extern crate std` was injected by the compiler.
1169 // If it's not a dummy, that means someone added `extern crate std` explicitly and `#![no_std]` won't help.
1170 if !missing_core && span.is_dummy() {
1172 sess.opts.crate_name.as_deref().unwrap_or("<unknown>");
1174 "`std` is required by `{}` because it does not declare `#![no_std]`",
1178 if sess.is_nightly_build() {
1179 err.help("consider building the standard library from source with `cargo build -Zbuild-std`");
1181 } else if crate_name
1182 == Symbol::intern(&sess.opts.debugging_opts.profiler_runtime)
1184 err.note("the compiler may have been built without the profiler runtime");
1185 } else if crate_name.as_str().starts_with("rustc_") {
1187 "maybe you need to install the missing components with: \
1188 `rustup component add rust-src rustc-dev llvm-tools-preview`",
1191 err.span_label(span, "can't find crate");
1195 if !locator.crate_rejections.via_filename.is_empty() {
1196 let mismatches = locator.crate_rejections.via_filename.iter();
1197 for CrateMismatch { path, .. } in mismatches {
1199 "extern location for {} is of an unknown type: {}",
1204 "file name should be lib*.rlib or {}*.{}",
1205 locator.dll_prefix, locator.dll_suffix
1211 CrateError::NonDylibPlugin(crate_name) => struct_span_err!(
1215 "plugin `{}` only found in rlib format, but must be available in dylib format",