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::cstore::{MetadataRef, MetadataBlob};
216 use crate::creader::Library;
217 use crate::schema::{METADATA_HEADER, rustc_version};
219 use rustc_data_structures::fx::FxHashSet;
220 use rustc_data_structures::svh::Svh;
221 use rustc::middle::cstore::MetadataLoader;
222 use rustc::session::{config, Session};
223 use rustc::session::filesearch::{FileSearch, FileMatches, FileDoesntMatch};
224 use rustc::session::search_paths::PathKind;
225 use rustc::util::nodemap::FxHashMap;
227 use errors::DiagnosticBuilder;
228 use syntax::symbol::{Symbol, sym};
229 use syntax::struct_span_err;
230 use syntax_pos::Span;
231 use rustc_target::spec::{Target, TargetTriple};
236 use std::io::{self, Read};
238 use std::path::{Path, PathBuf};
239 use std::time::Instant;
241 use flate2::read::DeflateDecoder;
243 use rustc_data_structures::owning_ref::OwningRef;
245 use log::{debug, info, warn};
248 pub struct CrateMismatch {
254 pub struct Context<'a> {
255 pub sess: &'a Session,
257 pub crate_name: Symbol,
258 pub hash: Option<&'a Svh>,
259 pub extra_filename: Option<&'a str>,
260 // points to either self.sess.target.target or self.sess.host, must match triple
261 pub target: &'a Target,
262 pub triple: TargetTriple,
263 pub filesearch: FileSearch<'a>,
264 pub root: Option<&'a CratePaths>,
265 pub rejected_via_hash: Vec<CrateMismatch>,
266 pub rejected_via_triple: Vec<CrateMismatch>,
267 pub rejected_via_kind: Vec<CrateMismatch>,
268 pub rejected_via_version: Vec<CrateMismatch>,
269 pub rejected_via_filename: Vec<CrateMismatch>,
270 pub should_match_name: bool,
271 pub is_proc_macro: Option<bool>,
272 pub metadata_loader: &'a dyn MetadataLoader,
275 pub struct CratePaths {
277 pub dylib: Option<PathBuf>,
278 pub rlib: Option<PathBuf>,
279 pub rmeta: Option<PathBuf>,
282 #[derive(Copy, Clone, PartialEq)]
289 impl fmt::Display for CrateFlavor {
290 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
291 f.write_str(match *self {
292 CrateFlavor::Rlib => "rlib",
293 CrateFlavor::Rmeta => "rmeta",
294 CrateFlavor::Dylib => "dylib",
300 fn paths(&self) -> Vec<PathBuf> {
301 self.dylib.iter().chain(self.rlib.iter()).chain(self.rmeta.iter()).cloned().collect()
305 impl<'a> Context<'a> {
306 pub fn reset(&mut self) {
307 self.rejected_via_hash.clear();
308 self.rejected_via_triple.clear();
309 self.rejected_via_kind.clear();
310 self.rejected_via_version.clear();
311 self.rejected_via_filename.clear();
314 pub fn maybe_load_library_crate(&mut self) -> Option<Library> {
315 let mut seen_paths = FxHashSet::default();
316 match self.extra_filename {
317 Some(s) => self.find_library_crate(s, &mut seen_paths)
318 .or_else(|| self.find_library_crate("", &mut seen_paths)),
319 None => self.find_library_crate("", &mut seen_paths)
323 pub fn report_errs(self) -> ! {
324 let add = match self.root {
325 None => String::new(),
326 Some(r) => format!(" which `{}` depends on", r.ident),
328 let mut msg = "the following crate versions were found:".to_string();
329 let mut err = if !self.rejected_via_hash.is_empty() {
330 let mut err = struct_span_err!(self.sess,
333 "found possibly newer version of crate `{}`{}",
336 err.note("perhaps that crate needs to be recompiled?");
337 let mismatches = self.rejected_via_hash.iter();
338 for &CrateMismatch { ref path, .. } in mismatches {
339 msg.push_str(&format!("\ncrate `{}`: {}", self.crate_name, path.display()));
344 for path in r.paths().iter() {
345 msg.push_str(&format!("\ncrate `{}`: {}", r.ident, path.display()));
351 } else if !self.rejected_via_triple.is_empty() {
352 let mut err = struct_span_err!(self.sess,
355 "couldn't find crate `{}` \
356 with expected target triple {}{}",
360 let mismatches = self.rejected_via_triple.iter();
361 for &CrateMismatch { ref path, ref got } in mismatches {
362 msg.push_str(&format!("\ncrate `{}`, target triple {}: {}",
369 } else if !self.rejected_via_kind.is_empty() {
370 let mut err = struct_span_err!(self.sess,
373 "found staticlib `{}` instead of rlib or dylib{}",
376 err.help("please recompile that crate using --crate-type lib");
377 let mismatches = self.rejected_via_kind.iter();
378 for &CrateMismatch { ref path, .. } in mismatches {
379 msg.push_str(&format!("\ncrate `{}`: {}", self.crate_name, path.display()));
383 } else if !self.rejected_via_version.is_empty() {
384 let mut err = struct_span_err!(self.sess,
387 "found crate `{}` compiled by an incompatible version \
391 err.help(&format!("please recompile that crate using this compiler ({})",
393 let mismatches = self.rejected_via_version.iter();
394 for &CrateMismatch { ref path, ref got } in mismatches {
395 msg.push_str(&format!("\ncrate `{}` compiled by {}: {}",
403 let mut err = struct_span_err!(self.sess,
406 "can't find crate for `{}`{}",
410 if (self.crate_name == sym::std || self.crate_name == sym::core)
411 && self.triple != TargetTriple::from_triple(config::host_triple()) {
412 err.note(&format!("the `{}` target may not be installed", self.triple));
414 err.span_label(self.span, "can't find crate");
418 if !self.rejected_via_filename.is_empty() {
419 let dylibname = self.dylibname();
420 let mismatches = self.rejected_via_filename.iter();
421 for &CrateMismatch { ref path, .. } in mismatches {
422 err.note(&format!("extern location for {} is of an unknown type: {}",
425 .help(&format!("file name should be lib*.rlib or {}*.{}",
432 self.sess.abort_if_errors();
436 fn find_library_crate(&mut self,
438 seen_paths: &mut FxHashSet<PathBuf>)
440 // If an SVH is specified, then this is a transitive dependency that
441 // must be loaded via -L plus some filtering.
442 if self.hash.is_none() {
443 self.should_match_name = false;
444 if let Some(entry) = self.sess.opts.externs.get(&self.crate_name.as_str()) {
445 // Only use `--extern crate_name=path` here, not `--extern crate_name`.
446 if entry.locations.iter().any(|l| l.is_some()) {
447 return self.find_commandline_library(
448 entry.locations.iter().filter_map(|l| l.as_ref()),
452 self.should_match_name = true;
455 let dypair = self.dylibname();
456 let staticpair = self.staticlibname();
458 // want: crate_name.dir_part() + prefix + crate_name.file_part + "-"
459 let dylib_prefix = format!("{}{}{}", dypair.0, self.crate_name, extra_prefix);
460 let rlib_prefix = format!("lib{}{}", self.crate_name, extra_prefix);
461 let staticlib_prefix = format!("{}{}{}", staticpair.0, self.crate_name, extra_prefix);
463 let mut candidates: FxHashMap<
465 (FxHashMap<_, _>, FxHashMap<_, _>, FxHashMap<_, _>),
466 > = Default::default();
467 let mut staticlibs = vec![];
469 // First, find all possible candidate rlibs and dylibs purely based on
470 // the name of the files themselves. We're trying to match against an
471 // exact crate name and a possibly an exact hash.
473 // During this step, we can filter all found libraries based on the
474 // name and id found in the crate id (we ignore the path portion for
475 // filename matching), as well as the exact hash (if specified). If we
476 // end up having many candidates, we must look at the metadata to
477 // perform exact matches against hashes/crate ids. Note that opening up
478 // the metadata is where we do an exact match against the full contents
479 // of the crate id (path/name/id).
481 // The goal of this step is to look at as little metadata as possible.
482 self.filesearch.search(|path, kind| {
483 let file = match path.file_name().and_then(|s| s.to_str()) {
484 None => return FileDoesntMatch,
487 let (hash, found_kind) =
488 if file.starts_with(&rlib_prefix) && file.ends_with(".rlib") {
489 (&file[(rlib_prefix.len())..(file.len() - ".rlib".len())], CrateFlavor::Rlib)
490 } else if file.starts_with(&rlib_prefix) && file.ends_with(".rmeta") {
491 (&file[(rlib_prefix.len())..(file.len() - ".rmeta".len())], CrateFlavor::Rmeta)
492 } else if file.starts_with(&dylib_prefix) &&
493 file.ends_with(&dypair.1) {
494 (&file[(dylib_prefix.len())..(file.len() - dypair.1.len())], CrateFlavor::Dylib)
496 if file.starts_with(&staticlib_prefix) && file.ends_with(&staticpair.1) {
497 staticlibs.push(CrateMismatch {
498 path: path.to_path_buf(),
499 got: "static".to_string(),
502 return FileDoesntMatch;
505 info!("lib candidate: {}", path.display());
507 let hash_str = hash.to_string();
508 let slot = candidates.entry(hash_str).or_default();
509 let (ref mut rlibs, ref mut rmetas, ref mut dylibs) = *slot;
510 fs::canonicalize(path)
512 if seen_paths.contains(&p) {
513 return FileDoesntMatch
515 seen_paths.insert(p.clone());
517 CrateFlavor::Rlib => { rlibs.insert(p, kind); }
518 CrateFlavor::Rmeta => { rmetas.insert(p, kind); }
519 CrateFlavor::Dylib => { dylibs.insert(p, kind); }
523 .unwrap_or(FileDoesntMatch)
525 self.rejected_via_kind.extend(staticlibs);
527 // We have now collected all known libraries into a set of candidates
528 // keyed of the filename hash listed. For each filename, we also have a
529 // list of rlibs/dylibs that apply. Here, we map each of these lists
530 // (per hash), to a Library candidate for returning.
532 // A Library candidate is created if the metadata for the set of
533 // libraries corresponds to the crate id and hash criteria that this
534 // search is being performed for.
535 let mut libraries = FxHashMap::default();
536 for (_hash, (rlibs, rmetas, dylibs)) in candidates {
538 let rlib = self.extract_one(rlibs, CrateFlavor::Rlib, &mut slot);
539 let rmeta = self.extract_one(rmetas, CrateFlavor::Rmeta, &mut slot);
540 let dylib = self.extract_one(dylibs, CrateFlavor::Dylib, &mut slot);
541 if let Some((h, m)) = slot {
552 // Having now translated all relevant found hashes into libraries, see
553 // what we've got and figure out if we found multiple candidates for
555 match libraries.len() {
557 1 => Some(libraries.into_iter().next().unwrap().1),
559 let mut err = struct_span_err!(self.sess,
562 "multiple matching crates for `{}`",
564 let candidates = libraries.iter().filter_map(|(_, lib)| {
565 let crate_name = &lib.metadata.get_root().name.as_str();
566 match &(&lib.dylib, &lib.rlib) {
567 &(&Some((ref pd, _)), &Some((ref pr, _))) => {
568 Some(format!("\ncrate `{}`: {}\n{:>padding$}",
572 padding=8 + crate_name.len()))
574 &(&Some((ref p, _)), &None) | &(&None, &Some((ref p, _))) => {
575 Some(format!("\ncrate `{}`: {}", crate_name, p.display()))
577 &(&None, &None) => None,
579 }).collect::<String>();
580 err.note(&format!("candidates:{}", candidates));
587 // Attempts to extract *one* library from the set `m`. If the set has no
588 // elements, `None` is returned. If the set has more than one element, then
589 // the errors and notes are emitted about the set of libraries.
591 // With only one library in the set, this function will extract it, and then
592 // read the metadata from it if `*slot` is `None`. If the metadata couldn't
593 // be read, it is assumed that the file isn't a valid rust library (no
594 // errors are emitted).
595 fn extract_one(&mut self,
596 m: FxHashMap<PathBuf, PathKind>,
598 slot: &mut Option<(Svh, MetadataBlob)>)
599 -> Option<(PathBuf, PathKind)> {
600 let mut ret: Option<(PathBuf, PathKind)> = None;
604 // FIXME(#10786): for an optimization, we only read one of the
605 // libraries' metadata sections. In theory we should
606 // read both, but reading dylib metadata is quite
610 } else if m.len() == 1 {
611 return Some(m.into_iter().next().unwrap());
615 let mut err: Option<DiagnosticBuilder<'_>> = None;
616 for (lib, kind) in m {
617 info!("{} reading metadata from: {}", flavor, lib.display());
618 let (hash, metadata) =
619 match get_metadata_section(self.target, flavor, &lib, self.metadata_loader) {
621 if let Some(h) = self.crate_matches(&blob, &lib) {
624 info!("metadata mismatch");
629 warn!("no metadata found: {}", err);
633 // If we see multiple hashes, emit an error about duplicate candidates.
634 if slot.as_ref().map_or(false, |s| s.0 != hash) {
635 let mut e = struct_span_err!(self.sess,
638 "multiple {} candidates for `{}` found",
641 e.span_note(self.span,
642 &format!(r"candidate #1: {}",
647 if let Some(ref mut e) = err {
656 err.as_mut().unwrap().span_note(self.span,
657 &format!(r"candidate #{}: {}",
663 // Ok so at this point we've determined that `(lib, kind)` above is
664 // a candidate crate to load, and that `slot` is either none (this
665 // is the first crate of its kind) or if some the previous path has
666 // the exact same hash (e.g., it's the exact same crate).
668 // In principle these two candidate crates are exactly the same so
669 // we can choose either of them to link. As a stupidly gross hack,
670 // however, we favor crate in the sysroot.
672 // You can find more info in rust-lang/rust#39518 and various linked
673 // issues, but the general gist is that during testing libstd the
674 // compilers has two candidates to choose from: one in the sysroot
675 // and one in the deps folder. These two crates are the exact same
676 // crate but if the compiler chooses the one in the deps folder
677 // it'll cause spurious errors on Windows.
679 // As a result, we favor the sysroot crate here. Note that the
680 // candidates are all canonicalized, so we canonicalize the sysroot
682 if let Some((ref prev, _)) = ret {
683 let sysroot = &self.sess.sysroot;
684 let sysroot = sysroot.canonicalize()
685 .unwrap_or_else(|_| sysroot.to_path_buf());
686 if prev.starts_with(&sysroot) {
690 *slot = Some((hash, metadata));
691 ret = Some((lib, kind));
702 fn crate_matches(&mut self, metadata: &MetadataBlob, libpath: &Path) -> Option<Svh> {
703 let rustc_version = rustc_version();
704 let found_version = metadata.get_rustc_version();
705 if found_version != rustc_version {
706 info!("Rejecting via version: expected {} got {}",
709 self.rejected_via_version.push(CrateMismatch {
710 path: libpath.to_path_buf(),
716 let root = metadata.get_root();
717 if let Some(is_proc_macro) = self.is_proc_macro {
718 if root.proc_macro_data.is_some() != is_proc_macro {
719 info!("Rejecting via proc macro: expected {} got {}",
720 is_proc_macro, root.proc_macro_data.is_some());
725 if self.should_match_name {
726 if self.crate_name != root.name {
727 info!("Rejecting via crate name");
732 if root.triple != self.triple {
733 info!("Rejecting via crate triple: expected {} got {}",
736 self.rejected_via_triple.push(CrateMismatch {
737 path: libpath.to_path_buf(),
738 got: root.triple.to_string(),
743 if let Some(myhash) = self.hash {
744 if *myhash != root.hash {
745 info!("Rejecting via hash: expected {} got {}", *myhash, root.hash);
746 self.rejected_via_hash.push(CrateMismatch {
747 path: libpath.to_path_buf(),
748 got: myhash.to_string(),
758 // Returns the corresponding (prefix, suffix) that files need to have for
760 fn dylibname(&self) -> (String, String) {
761 let t = &self.target;
762 (t.options.dll_prefix.clone(), t.options.dll_suffix.clone())
765 // Returns the corresponding (prefix, suffix) that files need to have for
767 fn staticlibname(&self) -> (String, String) {
768 let t = &self.target;
769 (t.options.staticlib_prefix.clone(), t.options.staticlib_suffix.clone())
772 fn find_commandline_library<'b, LOCS>(&mut self, locs: LOCS) -> Option<Library>
773 where LOCS: Iterator<Item = &'b String>
775 // First, filter out all libraries that look suspicious. We only accept
776 // files which actually exist that have the correct naming scheme for
778 let sess = self.sess;
779 let dylibname = self.dylibname();
780 let mut rlibs = FxHashMap::default();
781 let mut rmetas = FxHashMap::default();
782 let mut dylibs = FxHashMap::default();
784 let locs = locs.map(|l| PathBuf::from(l)).filter(|loc| {
786 sess.err(&format!("extern location for {} does not exist: {}",
791 let file = match loc.file_name().and_then(|s| s.to_str()) {
794 sess.err(&format!("extern location for {} is not a file: {}",
800 if file.starts_with("lib") &&
801 (file.ends_with(".rlib") || file.ends_with(".rmeta")) {
804 let (ref prefix, ref suffix) = dylibname;
805 if file.starts_with(&prefix[..]) && file.ends_with(&suffix[..]) {
810 self.rejected_via_filename.push(CrateMismatch {
818 // Now that we have an iterator of good candidates, make sure
819 // there's at most one rlib and at most one dylib.
821 if loc.file_name().unwrap().to_str().unwrap().ends_with(".rlib") {
822 rlibs.insert(fs::canonicalize(&loc).unwrap(), PathKind::ExternFlag);
823 } else if loc.file_name().unwrap().to_str().unwrap().ends_with(".rmeta") {
824 rmetas.insert(fs::canonicalize(&loc).unwrap(), PathKind::ExternFlag);
826 dylibs.insert(fs::canonicalize(&loc).unwrap(), PathKind::ExternFlag);
831 // Extract the rlib/dylib pair.
833 let rlib = self.extract_one(rlibs, CrateFlavor::Rlib, &mut slot);
834 let rmeta = self.extract_one(rmetas, CrateFlavor::Rmeta, &mut slot);
835 let dylib = self.extract_one(dylibs, CrateFlavor::Dylib, &mut slot);
837 if rlib.is_none() && rmeta.is_none() && dylib.is_none() {
840 slot.map(|(_, metadata)|
851 // Just a small wrapper to time how long reading metadata takes.
852 fn get_metadata_section(target: &Target,
855 loader: &dyn MetadataLoader)
856 -> Result<MetadataBlob, String> {
857 let start = Instant::now();
858 let ret = get_metadata_section_imp(target, flavor, filename, loader);
859 info!("reading {:?} => {:?}",
860 filename.file_name().unwrap(),
865 /// A trivial wrapper for `Mmap` that implements `StableDeref`.
866 struct StableDerefMmap(memmap::Mmap);
868 impl Deref for StableDerefMmap {
871 fn deref(&self) -> &[u8] {
876 unsafe impl stable_deref_trait::StableDeref for StableDerefMmap {}
878 fn get_metadata_section_imp(target: &Target,
881 loader: &dyn MetadataLoader)
882 -> Result<MetadataBlob, String> {
883 if !filename.exists() {
884 return Err(format!("no such file: '{}'", filename.display()));
886 let raw_bytes: MetadataRef = match flavor {
887 CrateFlavor::Rlib => loader.get_rlib_metadata(target, filename)?,
888 CrateFlavor::Dylib => {
889 let buf = loader.get_dylib_metadata(target, filename)?;
890 // The header is uncompressed
891 let header_len = METADATA_HEADER.len();
892 debug!("checking {} bytes of metadata-version stamp", header_len);
893 let header = &buf[..cmp::min(header_len, buf.len())];
894 if header != METADATA_HEADER {
895 return Err(format!("incompatible metadata version found: '{}'",
896 filename.display()));
899 // Header is okay -> inflate the actual metadata
900 let compressed_bytes = &buf[header_len..];
901 debug!("inflating {} bytes of compressed metadata", compressed_bytes.len());
902 let mut inflated = Vec::new();
903 match DeflateDecoder::new(compressed_bytes).read_to_end(&mut inflated) {
905 rustc_erase_owner!(OwningRef::new(inflated).map_owner_box())
908 return Err(format!("failed to decompress metadata: {}", filename.display()));
912 CrateFlavor::Rmeta => {
913 // mmap the file, because only a small fraction of it is read.
914 let file = std::fs::File::open(filename).map_err(|_|
915 format!("failed to open rmeta metadata: '{}'", filename.display()))?;
916 let mmap = unsafe { memmap::Mmap::map(&file) };
917 let mmap = mmap.map_err(|_|
918 format!("failed to mmap rmeta metadata: '{}'", filename.display()))?;
920 rustc_erase_owner!(OwningRef::new(StableDerefMmap(mmap)).map_owner_box())
923 let blob = MetadataBlob(raw_bytes);
924 if blob.is_compatible() {
927 Err(format!("incompatible metadata version found: '{}'", filename.display()))
931 /// A diagnostic function for dumping crate metadata to an output stream.
932 pub fn list_file_metadata(target: &Target,
934 loader: &dyn MetadataLoader,
935 out: &mut dyn io::Write)
937 let filename = path.file_name().unwrap().to_str().unwrap();
938 let flavor = if filename.ends_with(".rlib") {
940 } else if filename.ends_with(".rmeta") {
945 match get_metadata_section(target, flavor, path, loader) {
946 Ok(metadata) => metadata.list_crate_metadata(out),
947 Err(msg) => write!(out, "{}\n", msg),