1 //! Finds crate binaries and loads their metadata
2 //!
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!
7 //!
8 //! # The problem
9 //!
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:
13 //!
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
18 //! filesystem.
19 //!
20 //! Sounds easy, right? Let's walk into some of the nuances.
21 //!
22 //! ## Transitive Dependencies
23 //!
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.
27 //!
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
32 //! dependencies.
33 //!
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.
37 //!
38 //! ## Rlibs and Dylibs
39 //!
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
44 //! inside of it.
45 //!
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
51 //! error.
52 //!
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.
57 //!
58 //! Most parts of this loading systems keep the dylib/rlib as just separate
59 //! variables.
60 //!
61 //! ## Where to look?
62 //!
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.
67 //!
68 //! ## What criterion to select on?
69 //!
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:
72 //!
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)
85 //!
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
90 //! separately.
91 //!
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
94 //! being found.
95 //!
96 //! ### What about versions?
97 //!
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.
103 //!
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.
108 //!
109 //! To resolve this problem, we come to the next section!
110 //!
111 //! # Expert Mode
112 //!
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.
118 //!
119 //! ## The `--extern` flag
120 //!
121 //! The compiler accepts a flag of this form a number of times:
122 //!
123 //! ```text
124 //! --extern crate-name=path/to/the/crate.rlib
125 //! ```
126 //!
127 //! This flag is basically the following letter to the compiler:
128 //!
129 //! > Dear rustc,
130 //! >
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`.
135 //!
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.
139 //!
140 //! ## Enabling "multiple versions"
141 //!
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:
145 //!
146 //! ```compile_fail,E0463
147 //! extern crate b1;
148 //! extern crate b2;
149 //!
150 //! fn main() {}
151 //! ```
152 //!
153 //! and the compiler would be invoked as:
154 //!
155 //! ```text
156 //! rustc a.rs --extern b1=path/to/libb1.rlib --extern b2=path/to/libb2.rlib
157 //! ```
158 //!
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.
161 //!
162 //! ## Frobbing symbols
163 //!
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.
167 //!
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.
172 //!
173 //! ## Loading transitive dependencies
174 //!
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:
180 //!
181 //! ```text
182 //! A.1 A.2
183 //! | |
184 //! | |
185 //! B C
186 //! \ /
187 //! \ /
188 //! D
189 //! ```
190 //!
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.
194 //!
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
200 //! library.
201 //!
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.
205 //!
206 //! In the end, this ends up not needing `--extern` to specify upstream
207 //! transitive dependencies.
208 //!
209 //! # Wrapping up
210 //!
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!
214
215 use crate::creader::Library;
216 use crate::rmeta::{rustc_version, MetadataBlob, METADATA_HEADER};
217
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};
233
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};
240
241 #[derive(Clone)]
242 crate struct CrateLocator<'a> {
243 // Immutable per-session configuration.
244 only_needs_metadata: bool,
245 sysroot: &'a Path,
246 metadata_loader: &'a dyn MetadataLoader,
247
248 // Immutable per-search configuration.
249 crate_name: Symbol,
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,
257
258 // Mutable in-progress state or output.
259 crate_rejections: CrateRejections,
260 }
261
262 #[derive(Clone)]
263 crate struct CratePaths {
264 name: Symbol,
265 source: CrateSource,
266 }
267
268 impl CratePaths {
new(name: Symbol, source: CrateSource) -> CratePaths269 crate fn new(name: Symbol, source: CrateSource) -> CratePaths {
270 CratePaths { name, source }
271 }
272 }
273
274 #[derive(Copy, Clone, PartialEq)]
275 crate enum CrateFlavor {
276 Rlib,
277 Rmeta,
278 Dylib,
279 }
280
281 impl fmt::Display for CrateFlavor {
fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result282 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",
287 })
288 }
289 }
290
291 impl<'a> CrateLocator<'a> {
new( sess: &'a Session, metadata_loader: &'a dyn MetadataLoader, crate_name: Symbol, hash: Option<Svh>, extra_filename: Option<&'a str>, is_host: bool, path_kind: PathKind, ) -> CrateLocator<'a>292 crate fn new(
293 sess: &'a Session,
294 metadata_loader: &'a dyn MetadataLoader,
295 crate_name: Symbol,
296 hash: Option<Svh>,
297 extra_filename: Option<&'a str>,
298 is_host: bool,
299 path_kind: PathKind,
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;
309
310 CrateLocator {
311 only_needs_metadata,
312 sysroot: &sess.sysroot,
313 metadata_loader,
314 crate_name,
315 exact_paths: if hash.is_none() {
316 sess.opts
317 .externs
318 .get(&crate_name.as_str())
319 .into_iter()
320 .filter_map(|entry| entry.files())
321 .flatten()
322 .cloned()
323 .collect()
324 } else {
325 // SVH being specified means this is a transitive dependency,
326 // so `--extern` options do not apply.
327 Vec::new()
328 },
329 hash,
330 extra_filename,
331 target: if is_host { &sess.host } else { &sess.target },
332 triple: if is_host {
333 TargetTriple::from_triple(config::host_triple())
334 } else {
335 sess.opts.target_triple.clone()
336 },
337 filesearch: if is_host {
338 sess.host_filesearch(path_kind)
339 } else {
340 sess.target_filesearch(path_kind)
341 },
342 is_proc_macro: false,
343 crate_rejections: CrateRejections::default(),
344 }
345 }
346
reset(&mut self)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();
353 self.crate_rejections.via_invalid.clear();
354 }
355
maybe_load_library_crate(&mut self) -> Result<Option<Library>, CrateError>356 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();
359 }
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)? {
363 return Ok(library);
364 }
365 }
366 self.find_library_crate("", &mut seen_paths)
367 }
368
find_library_crate( &mut self, extra_prefix: &str, seen_paths: &mut FxHashSet<PathBuf>, ) -> Result<Option<Library>, CrateError>369 fn find_library_crate(
370 &mut self,
371 extra_prefix: &str,
372 seen_paths: &mut FxHashSet<PathBuf>,
373 ) -> Result<Option<Library>, CrateError> {
374 // want: crate_name.dir_part() + prefix + crate_name.file_part + "-"
375 let dylib_prefix = format!("{}{}{}", self.target.dll_prefix, self.crate_name, extra_prefix);
376 let rlib_prefix = format!("lib{}{}", self.crate_name, extra_prefix);
377 let staticlib_prefix =
378 format!("{}{}{}", self.target.staticlib_prefix, self.crate_name, extra_prefix);
379
380 let mut candidates: FxHashMap<_, (FxHashMap<_, _>, FxHashMap<_, _>, FxHashMap<_, _>)> =
381 Default::default();
382 let mut staticlibs = vec![];
383
384 // First, find all possible candidate rlibs and dylibs purely based on
385 // the name of the files themselves. We're trying to match against an
386 // exact crate name and a possibly an exact hash.
387 //
388 // During this step, we can filter all found libraries based on the
389 // name and id found in the crate id (we ignore the path portion for
390 // filename matching), as well as the exact hash (if specified). If we
391 // end up having many candidates, we must look at the metadata to
392 // perform exact matches against hashes/crate ids. Note that opening up
393 // the metadata is where we do an exact match against the full contents
394 // of the crate id (path/name/id).
395 //
396 // The goal of this step is to look at as little metadata as possible.
397 self.filesearch.search(|spf, kind| {
398 let file = match &spf.file_name_str {
399 None => return FileDoesntMatch,
400 Some(file) => file,
401 };
402 let (hash, found_kind) = if file.starts_with(&rlib_prefix) && file.ends_with(".rlib") {
403 (&file[(rlib_prefix.len())..(file.len() - ".rlib".len())], CrateFlavor::Rlib)
404 } else if file.starts_with(&rlib_prefix) && file.ends_with(".rmeta") {
405 (&file[(rlib_prefix.len())..(file.len() - ".rmeta".len())], CrateFlavor::Rmeta)
406 } else if file.starts_with(&dylib_prefix) && file.ends_with(&self.target.dll_suffix) {
407 (
408 &file[(dylib_prefix.len())..(file.len() - self.target.dll_suffix.len())],
409 CrateFlavor::Dylib,
410 )
411 } else {
412 if file.starts_with(&staticlib_prefix)
413 && file.ends_with(&self.target.staticlib_suffix)
414 {
415 staticlibs
416 .push(CrateMismatch { path: spf.path.clone(), got: "static".to_string() });
417 }
418 return FileDoesntMatch;
419 };
420
421 info!("lib candidate: {}", spf.path.display());
422
423 let (rlibs, rmetas, dylibs) = candidates.entry(hash.to_string()).or_default();
424 let path = fs::canonicalize(&spf.path).unwrap_or_else(|_| spf.path.clone());
425 if seen_paths.contains(&path) {
426 return FileDoesntMatch;
427 };
428 seen_paths.insert(path.clone());
429 match found_kind {
430 CrateFlavor::Rlib => rlibs.insert(path, kind),
431 CrateFlavor::Rmeta => rmetas.insert(path, kind),
432 CrateFlavor::Dylib => dylibs.insert(path, kind),
433 };
434 FileMatches
435 });
436 self.crate_rejections.via_kind.extend(staticlibs);
437
438 // We have now collected all known libraries into a set of candidates
439 // keyed of the filename hash listed. For each filename, we also have a
440 // list of rlibs/dylibs that apply. Here, we map each of these lists
441 // (per hash), to a Library candidate for returning.
442 //
443 // A Library candidate is created if the metadata for the set of
444 // libraries corresponds to the crate id and hash criteria that this
445 // search is being performed for.
446 let mut libraries = FxHashMap::default();
447 for (_hash, (rlibs, rmetas, dylibs)) in candidates {
448 if let Some((svh, lib)) = self.extract_lib(rlibs, rmetas, dylibs)? {
449 libraries.insert(svh, lib);
450 }
451 }
452
453 // Having now translated all relevant found hashes into libraries, see
454 // what we've got and figure out if we found multiple candidates for
455 // libraries or not.
456 match libraries.len() {
457 0 => Ok(None),
458 1 => Ok(Some(libraries.into_iter().next().unwrap().1)),
459 _ => Err(CrateError::MultipleMatchingCrates(self.crate_name, libraries)),
460 }
461 }
462
extract_lib( &mut self, rlibs: FxHashMap<PathBuf, PathKind>, rmetas: FxHashMap<PathBuf, PathKind>, dylibs: FxHashMap<PathBuf, PathKind>, ) -> Result<Option<(Svh, Library)>, CrateError>463 fn extract_lib(
464 &mut self,
465 rlibs: FxHashMap<PathBuf, PathKind>,
466 rmetas: FxHashMap<PathBuf, PathKind>,
467 dylibs: FxHashMap<PathBuf, PathKind>,
468 ) -> Result<Option<(Svh, Library)>, CrateError> {
469 let mut slot = None;
470 // Order here matters, rmeta should come first. See comment in
471 // `extract_one` below.
472 let source = CrateSource {
473 rmeta: self.extract_one(rmetas, CrateFlavor::Rmeta, &mut slot)?,
474 rlib: self.extract_one(rlibs, CrateFlavor::Rlib, &mut slot)?,
475 dylib: self.extract_one(dylibs, CrateFlavor::Dylib, &mut slot)?,
476 };
477 Ok(slot.map(|(svh, metadata)| (svh, Library { source, metadata })))
478 }
479
needs_crate_flavor(&self, flavor: CrateFlavor) -> bool480 fn needs_crate_flavor(&self, flavor: CrateFlavor) -> bool {
481 if flavor == CrateFlavor::Dylib && self.is_proc_macro {
482 return true;
483 }
484
485 if self.only_needs_metadata {
486 flavor == CrateFlavor::Rmeta
487 } else {
488 // we need all flavors (perhaps not true, but what we do for now)
489 true
490 }
491 }
492
493 // Attempts to extract *one* library from the set `m`. If the set has no
494 // elements, `None` is returned. If the set has more than one element, then
495 // the errors and notes are emitted about the set of libraries.
496 //
497 // With only one library in the set, this function will extract it, and then
498 // read the metadata from it if `*slot` is `None`. If the metadata couldn't
499 // be read, it is assumed that the file isn't a valid rust library (no
500 // errors are emitted).
extract_one( &mut self, m: FxHashMap<PathBuf, PathKind>, flavor: CrateFlavor, slot: &mut Option<(Svh, MetadataBlob)>, ) -> Result<Option<(PathBuf, PathKind)>, CrateError>501 fn extract_one(
502 &mut self,
503 m: FxHashMap<PathBuf, PathKind>,
504 flavor: CrateFlavor,
505 slot: &mut Option<(Svh, MetadataBlob)>,
506 ) -> Result<Option<(PathBuf, PathKind)>, CrateError> {
507 // If we are producing an rlib, and we've already loaded metadata, then
508 // we should not attempt to discover further crate sources (unless we're
509 // locating a proc macro; exact logic is in needs_crate_flavor). This means
510 // that under -Zbinary-dep-depinfo we will not emit a dependency edge on
511 // the *unused* rlib, and by returning `None` here immediately we
512 // guarantee that we do indeed not use it.
513 //
514 // See also #68149 which provides more detail on why emitting the
515 // dependency on the rlib is a bad thing.
516 //
517 // We currently do not verify that these other sources are even in sync,
518 // and this is arguably a bug (see #10786), but because reading metadata
519 // is quite slow (especially from dylibs) we currently do not read it
520 // from the other crate sources.
521 if slot.is_some() {
522 if m.is_empty() || !self.needs_crate_flavor(flavor) {
523 return Ok(None);
524 } else if m.len() == 1 {
525 return Ok(Some(m.into_iter().next().unwrap()));
526 }
527 }
528
529 let mut ret: Option<(PathBuf, PathKind)> = None;
530 let mut err_data: Option<Vec<PathBuf>> = None;
531 for (lib, kind) in m {
532 info!("{} reading metadata from: {}", flavor, lib.display());
533 if flavor == CrateFlavor::Rmeta && lib.metadata().map_or(false, |m| m.len() == 0) {
534 // Empty files will cause get_metadata_section to fail. Rmeta
535 // files can be empty, for example with binaries (which can
536 // often appear with `cargo check` when checking a library as
537 // a unittest). We don't want to emit a user-visible warning
538 // in this case as it is not a real problem.
539 debug!("skipping empty file");
540 continue;
541 }
542 let (hash, metadata) =
543 match get_metadata_section(self.target, flavor, &lib, self.metadata_loader) {
544 Ok(blob) => {
545 if let Some(h) = self.crate_matches(&blob, &lib) {
546 (h, blob)
547 } else {
548 info!("metadata mismatch");
549 continue;
550 }
551 }
552 Err(MetadataError::LoadFailure(err)) => {
553 info!("no metadata found: {}", err);
554 // The file was present and created by the same compiler version, but we
555 // couldn't load it for some reason. Give a hard error instead of silently
556 // ignoring it, but only if we would have given an error anyway.
557 self.crate_rejections
558 .via_invalid
559 .push(CrateMismatch { path: lib, got: err });
560 continue;
561 }
562 Err(err @ MetadataError::NotPresent(_)) => {
563 info!("no metadata found: {}", err);
564 continue;
565 }
566 };
567 // If we see multiple hashes, emit an error about duplicate candidates.
568 if slot.as_ref().map_or(false, |s| s.0 != hash) {
569 if let Some(candidates) = err_data {
570 return Err(CrateError::MultipleCandidates(
571 self.crate_name,
572 flavor,
573 candidates,
574 ));
575 }
576 err_data = Some(vec![ret.as_ref().unwrap().0.clone()]);
577 *slot = None;
578 }
579 if let Some(candidates) = &mut err_data {
580 candidates.push(lib);
581 continue;
582 }
583
584 // Ok so at this point we've determined that `(lib, kind)` above is
585 // a candidate crate to load, and that `slot` is either none (this
586 // is the first crate of its kind) or if some the previous path has
587 // the exact same hash (e.g., it's the exact same crate).
588 //
589 // In principle these two candidate crates are exactly the same so
590 // we can choose either of them to link. As a stupidly gross hack,
591 // however, we favor crate in the sysroot.
592 //
593 // You can find more info in rust-lang/rust#39518 and various linked
594 // issues, but the general gist is that during testing libstd the
595 // compilers has two candidates to choose from: one in the sysroot
596 // and one in the deps folder. These two crates are the exact same
597 // crate but if the compiler chooses the one in the deps folder
598 // it'll cause spurious errors on Windows.
599 //
600 // As a result, we favor the sysroot crate here. Note that the
601 // candidates are all canonicalized, so we canonicalize the sysroot
602 // as well.
603 if let Some((prev, _)) = &ret {
604 let sysroot = self.sysroot;
605 let sysroot = sysroot.canonicalize().unwrap_or_else(|_| sysroot.to_path_buf());
606 if prev.starts_with(&sysroot) {
607 continue;
608 }
609 }
610 *slot = Some((hash, metadata));
611 ret = Some((lib, kind));
612 }
613
614 if let Some(candidates) = err_data {
615 Err(CrateError::MultipleCandidates(self.crate_name, flavor, candidates))
616 } else {
617 Ok(ret)
618 }
619 }
620
crate_matches(&mut self, metadata: &MetadataBlob, libpath: &Path) -> Option<Svh>621 fn crate_matches(&mut self, metadata: &MetadataBlob, libpath: &Path) -> Option<Svh> {
622 let rustc_version = rustc_version();
623 let found_version = metadata.get_rustc_version();
624 if found_version != rustc_version {
625 info!("Rejecting via version: expected {} got {}", rustc_version, found_version);
626 self.crate_rejections
627 .via_version
628 .push(CrateMismatch { path: libpath.to_path_buf(), got: found_version });
629 return None;
630 }
631
632 let root = metadata.get_root();
633 if root.is_proc_macro_crate() != self.is_proc_macro {
634 info!(
635 "Rejecting via proc macro: expected {} got {}",
636 self.is_proc_macro,
637 root.is_proc_macro_crate(),
638 );
639 return None;
640 }
641
642 if self.exact_paths.is_empty() && self.crate_name != root.name() {
643 info!("Rejecting via crate name");
644 return None;
645 }
646
647 if root.triple() != &self.triple {
648 info!("Rejecting via crate triple: expected {} got {}", self.triple, root.triple());
649 self.crate_rejections.via_triple.push(CrateMismatch {
650 path: libpath.to_path_buf(),
651 got: root.triple().to_string(),
652 });
653 return None;
654 }
655
656 let hash = root.hash();
657 if let Some(expected_hash) = self.hash {
658 if hash != expected_hash {
659 info!("Rejecting via hash: expected {} got {}", expected_hash, hash);
660 self.crate_rejections
661 .via_hash
662 .push(CrateMismatch { path: libpath.to_path_buf(), got: hash.to_string() });
663 return None;
664 }
665 }
666
667 Some(hash)
668 }
669
find_commandline_library(&mut self) -> Result<Option<Library>, CrateError>670 fn find_commandline_library(&mut self) -> Result<Option<Library>, CrateError> {
671 // First, filter out all libraries that look suspicious. We only accept
672 // files which actually exist that have the correct naming scheme for
673 // rlibs/dylibs.
674 let mut rlibs = FxHashMap::default();
675 let mut rmetas = FxHashMap::default();
676 let mut dylibs = FxHashMap::default();
677 for loc in &self.exact_paths {
678 if !loc.canonicalized().exists() {
679 return Err(CrateError::ExternLocationNotExist(
680 self.crate_name,
681 loc.original().clone(),
682 ));
683 }
684 let file = match loc.original().file_name().and_then(|s| s.to_str()) {
685 Some(file) => file,
686 None => {
687 return Err(CrateError::ExternLocationNotFile(
688 self.crate_name,
689 loc.original().clone(),
690 ));
691 }
692 };
693
694 if file.starts_with("lib") && (file.ends_with(".rlib") || file.ends_with(".rmeta"))
695 || file.starts_with(&self.target.dll_prefix)
696 && file.ends_with(&self.target.dll_suffix)
697 {
698 // Make sure there's at most one rlib and at most one dylib.
699 // Note to take care and match against the non-canonicalized name:
700 // some systems save build artifacts into content-addressed stores
701 // that do not preserve extensions, and then link to them using
702 // e.g. symbolic links. If we canonicalize too early, we resolve
703 // the symlink, the file type is lost and we might treat rlibs and
704 // rmetas as dylibs.
705 let loc_canon = loc.canonicalized().clone();
706 let loc = loc.original();
707 if loc.file_name().unwrap().to_str().unwrap().ends_with(".rlib") {
708 rlibs.insert(loc_canon, PathKind::ExternFlag);
709 } else if loc.file_name().unwrap().to_str().unwrap().ends_with(".rmeta") {
710 rmetas.insert(loc_canon, PathKind::ExternFlag);
711 } else {
712 dylibs.insert(loc_canon, PathKind::ExternFlag);
713 }
714 } else {
715 self.crate_rejections
716 .via_filename
717 .push(CrateMismatch { path: loc.original().clone(), got: String::new() });
718 }
719 }
720
721 // Extract the dylib/rlib/rmeta triple.
722 Ok(self.extract_lib(rlibs, rmetas, dylibs)?.map(|(_, lib)| lib))
723 }
724
into_error(self, root: Option<CratePaths>) -> CrateError725 crate fn into_error(self, root: Option<CratePaths>) -> CrateError {
726 CrateError::LocatorCombined(CombinedLocatorError {
727 crate_name: self.crate_name,
728 root,
729 triple: self.triple,
730 dll_prefix: self.target.dll_prefix.clone(),
731 dll_suffix: self.target.dll_suffix.clone(),
732 crate_rejections: self.crate_rejections,
733 })
734 }
735 }
736
get_metadata_section( target: &Target, flavor: CrateFlavor, filename: &'p Path, loader: &dyn MetadataLoader, ) -> Result<MetadataBlob, MetadataError<'p>>737 fn get_metadata_section(
738 target: &Target,
739 flavor: CrateFlavor,
740 filename: &'p Path,
741 loader: &dyn MetadataLoader,
742 ) -> Result<MetadataBlob, MetadataError<'p>> {
743 if !filename.exists() {
744 return Err(MetadataError::NotPresent(filename));
745 }
746 let raw_bytes: MetadataRef = match flavor {
747 CrateFlavor::Rlib => {
748 loader.get_rlib_metadata(target, filename).map_err(MetadataError::LoadFailure)?
749 }
750 CrateFlavor::Dylib => {
751 let buf =
752 loader.get_dylib_metadata(target, filename).map_err(MetadataError::LoadFailure)?;
753 // The header is uncompressed
754 let header_len = METADATA_HEADER.len();
755 debug!("checking {} bytes of metadata-version stamp", header_len);
756 let header = &buf[..cmp::min(header_len, buf.len())];
757 if header != METADATA_HEADER {
758 return Err(MetadataError::LoadFailure(format!(
759 "invalid metadata version found: {}",
760 filename.display()
761 )));
762 }
763
764 // Header is okay -> inflate the actual metadata
765 let compressed_bytes = &buf[header_len..];
766 debug!("inflating {} bytes of compressed metadata", compressed_bytes.len());
767 // Assume the decompressed data will be at least the size of the compressed data, so we
768 // don't have to grow the buffer as much.
769 let mut inflated = Vec::with_capacity(compressed_bytes.len());
770 match FrameDecoder::new(compressed_bytes).read_to_end(&mut inflated) {
771 Ok(_) => rustc_erase_owner!(OwningRef::new(inflated).map_owner_box()),
772 Err(_) => {
773 return Err(MetadataError::LoadFailure(format!(
774 "failed to decompress metadata: {}",
775 filename.display()
776 )));
777 }
778 }
779 }
780 CrateFlavor::Rmeta => {
781 // mmap the file, because only a small fraction of it is read.
782 let file = std::fs::File::open(filename).map_err(|_| {
783 MetadataError::LoadFailure(format!(
784 "failed to open rmeta metadata: '{}'",
785 filename.display()
786 ))
787 })?;
788 let mmap = unsafe { Mmap::map(file) };
789 let mmap = mmap.map_err(|_| {
790 MetadataError::LoadFailure(format!(
791 "failed to mmap rmeta metadata: '{}'",
792 filename.display()
793 ))
794 })?;
795
796 rustc_erase_owner!(OwningRef::new(mmap).map_owner_box())
797 }
798 };
799 let blob = MetadataBlob::new(raw_bytes);
800 if blob.is_compatible() {
801 Ok(blob)
802 } else {
803 Err(MetadataError::LoadFailure(format!(
804 "invalid metadata version found: {}",
805 filename.display()
806 )))
807 }
808 }
809
810 /// Look for a plugin registrar. Returns its library path and crate disambiguator.
find_plugin_registrar( sess: &Session, metadata_loader: &dyn MetadataLoader, span: Span, name: Symbol, ) -> PathBuf811 pub fn find_plugin_registrar(
812 sess: &Session,
813 metadata_loader: &dyn MetadataLoader,
814 span: Span,
815 name: Symbol,
816 ) -> PathBuf {
817 match find_plugin_registrar_impl(sess, metadata_loader, name) {
818 Ok(res) => res,
819 // `core` is always available if we got as far as loading plugins.
820 Err(err) => err.report(sess, span, false),
821 }
822 }
823
find_plugin_registrar_impl<'a>( sess: &'a Session, metadata_loader: &dyn MetadataLoader, name: Symbol, ) -> Result<PathBuf, CrateError>824 fn find_plugin_registrar_impl<'a>(
825 sess: &'a Session,
826 metadata_loader: &dyn MetadataLoader,
827 name: Symbol,
828 ) -> Result<PathBuf, CrateError> {
829 info!("find plugin registrar `{}`", name);
830 let mut locator = CrateLocator::new(
831 sess,
832 metadata_loader,
833 name,
834 None, // hash
835 None, // extra_filename
836 true, // is_host
837 PathKind::Crate,
838 );
839
840 match locator.maybe_load_library_crate()? {
841 Some(library) => match library.source.dylib {
842 Some(dylib) => Ok(dylib.0),
843 None => Err(CrateError::NonDylibPlugin(name)),
844 },
845 None => Err(locator.into_error(None)),
846 }
847 }
848
849 /// A diagnostic function for dumping crate metadata to an output stream.
list_file_metadata( target: &Target, path: &Path, metadata_loader: &dyn MetadataLoader, out: &mut dyn Write, ) -> IoResult<()>850 pub fn list_file_metadata(
851 target: &Target,
852 path: &Path,
853 metadata_loader: &dyn MetadataLoader,
854 out: &mut dyn Write,
855 ) -> IoResult<()> {
856 let filename = path.file_name().unwrap().to_str().unwrap();
857 let flavor = if filename.ends_with(".rlib") {
858 CrateFlavor::Rlib
859 } else if filename.ends_with(".rmeta") {
860 CrateFlavor::Rmeta
861 } else {
862 CrateFlavor::Dylib
863 };
864 match get_metadata_section(target, flavor, path, metadata_loader) {
865 Ok(metadata) => metadata.list_crate_metadata(out),
866 Err(msg) => write!(out, "{}\n", msg),
867 }
868 }
869
870 // ------------------------------------------ Error reporting -------------------------------------
871
872 #[derive(Clone)]
873 struct CrateMismatch {
874 path: PathBuf,
875 got: String,
876 }
877
878 #[derive(Clone, Default)]
879 struct CrateRejections {
880 via_hash: Vec<CrateMismatch>,
881 via_triple: Vec<CrateMismatch>,
882 via_kind: Vec<CrateMismatch>,
883 via_version: Vec<CrateMismatch>,
884 via_filename: Vec<CrateMismatch>,
885 via_invalid: Vec<CrateMismatch>,
886 }
887
888 /// Candidate rejection reasons collected during crate search.
889 /// If no candidate is accepted, then these reasons are presented to the user,
890 /// otherwise they are ignored.
891 crate struct CombinedLocatorError {
892 crate_name: Symbol,
893 root: Option<CratePaths>,
894 triple: TargetTriple,
895 dll_prefix: String,
896 dll_suffix: String,
897 crate_rejections: CrateRejections,
898 }
899
900 crate enum CrateError {
901 NonAsciiName(Symbol),
902 ExternLocationNotExist(Symbol, PathBuf),
903 ExternLocationNotFile(Symbol, PathBuf),
904 MultipleCandidates(Symbol, CrateFlavor, Vec<PathBuf>),
905 MultipleMatchingCrates(Symbol, FxHashMap<Svh, Library>),
906 SymbolConflictsCurrent(Symbol),
907 SymbolConflictsOthers(Symbol),
908 StableCrateIdCollision(Symbol, Symbol),
909 DlOpen(String),
910 DlSym(String),
911 LocatorCombined(CombinedLocatorError),
912 NonDylibPlugin(Symbol),
913 }
914
915 enum MetadataError<'a> {
916 /// The file was missing.
917 NotPresent(&'a Path),
918 /// The file was present and invalid.
919 LoadFailure(String),
920 }
921
922 impl fmt::Display for MetadataError<'_> {
fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result923 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
924 match self {
925 MetadataError::NotPresent(filename) => {
926 f.write_str(&format!("no such file: '{}'", filename.display()))
927 }
928 MetadataError::LoadFailure(msg) => f.write_str(msg),
929 }
930 }
931 }
932
933 impl CrateError {
report(self, sess: &Session, span: Span, missing_core: bool) -> !934 crate fn report(self, sess: &Session, span: Span, missing_core: bool) -> ! {
935 let mut err = match self {
936 CrateError::NonAsciiName(crate_name) => sess.struct_span_err(
937 span,
938 &format!("cannot load a crate with a non-ascii name `{}`", crate_name),
939 ),
940 CrateError::ExternLocationNotExist(crate_name, loc) => sess.struct_span_err(
941 span,
942 &format!("extern location for {} does not exist: {}", crate_name, loc.display()),
943 ),
944 CrateError::ExternLocationNotFile(crate_name, loc) => sess.struct_span_err(
945 span,
946 &format!("extern location for {} is not a file: {}", crate_name, loc.display()),
947 ),
948 CrateError::MultipleCandidates(crate_name, flavor, candidates) => {
949 let mut err = struct_span_err!(
950 sess,
951 span,
952 E0465,
953 "multiple {} candidates for `{}` found",
954 flavor,
955 crate_name,
956 );
957 for (i, candidate) in candidates.iter().enumerate() {
958 err.span_note(span, &format!("candidate #{}: {}", i + 1, candidate.display()));
959 }
960 err
961 }
962 CrateError::MultipleMatchingCrates(crate_name, libraries) => {
963 let mut err = struct_span_err!(
964 sess,
965 span,
966 E0464,
967 "multiple matching crates for `{}`",
968 crate_name
969 );
970 let mut libraries: Vec<_> = libraries.into_values().collect();
971 // Make ordering of candidates deterministic.
972 // This has to `clone()` to work around lifetime restrictions with `sort_by_key()`.
973 // `sort_by()` could be used instead, but this is in the error path,
974 // so the performance shouldn't matter.
975 libraries.sort_by_cached_key(|lib| lib.source.paths().next().unwrap().clone());
976 let candidates = libraries
977 .iter()
978 .map(|lib| {
979 let crate_name = &lib.metadata.get_root().name().as_str();
980 let mut paths = lib.source.paths();
981
982 // This `unwrap()` should be okay because there has to be at least one
983 // source file. `CrateSource`'s docs confirm that too.
984 let mut s = format!(
985 "\ncrate `{}`: {}",
986 crate_name,
987 paths.next().unwrap().display()
988 );
989 let padding = 8 + crate_name.len();
990 for path in paths {
991 write!(s, "\n{:>padding$}", path.display(), padding = padding).unwrap();
992 }
993 s
994 })
995 .collect::<String>();
996 err.note(&format!("candidates:{}", candidates));
997 err
998 }
999 CrateError::SymbolConflictsCurrent(root_name) => struct_span_err!(
1000 sess,
1001 span,
1002 E0519,
1003 "the current crate is indistinguishable from one of its dependencies: it has the \
1004 same crate-name `{}` and was compiled with the same `-C metadata` arguments. \
1005 This will result in symbol conflicts between the two.",
1006 root_name,
1007 ),
1008 CrateError::SymbolConflictsOthers(root_name) => struct_span_err!(
1009 sess,
1010 span,
1011 E0523,
1012 "found two different crates with name `{}` that are not distinguished by differing \
1013 `-C metadata`. This will result in symbol conflicts between the two.",
1014 root_name,
1015 ),
1016 CrateError::StableCrateIdCollision(crate_name0, crate_name1) => {
1017 let msg = format!(
1018 "found crates (`{}` and `{}`) with colliding StableCrateId values.",
1019 crate_name0, crate_name1
1020 );
1021 sess.struct_span_err(span, &msg)
1022 }
1023 CrateError::DlOpen(s) | CrateError::DlSym(s) => sess.struct_span_err(span, &s),
1024 CrateError::LocatorCombined(locator) => {
1025 let crate_name = locator.crate_name;
1026 let add = match &locator.root {
1027 None => String::new(),
1028 Some(r) => format!(" which `{}` depends on", r.name),
1029 };
1030 let mut msg = "the following crate versions were found:".to_string();
1031 let mut err = if !locator.crate_rejections.via_hash.is_empty() {
1032 let mut err = struct_span_err!(
1033 sess,
1034 span,
1035 E0460,
1036 "found possibly newer version of crate `{}`{}",
1037 crate_name,
1038 add,
1039 );
1040 err.note("perhaps that crate needs to be recompiled?");
1041 let mismatches = locator.crate_rejections.via_hash.iter();
1042 for CrateMismatch { path, .. } in mismatches {
1043 msg.push_str(&format!("\ncrate `{}`: {}", crate_name, path.display()));
1044 }
1045 if let Some(r) = locator.root {
1046 for path in r.source.paths() {
1047 msg.push_str(&format!("\ncrate `{}`: {}", r.name, path.display()));
1048 }
1049 }
1050 err.note(&msg);
1051 err
1052 } else if !locator.crate_rejections.via_triple.is_empty() {
1053 let mut err = struct_span_err!(
1054 sess,
1055 span,
1056 E0461,
1057 "couldn't find crate `{}` with expected target triple {}{}",
1058 crate_name,
1059 locator.triple,
1060 add,
1061 );
1062 let mismatches = locator.crate_rejections.via_triple.iter();
1063 for CrateMismatch { path, got } in mismatches {
1064 msg.push_str(&format!(
1065 "\ncrate `{}`, target triple {}: {}",
1066 crate_name,
1067 got,
1068 path.display(),
1069 ));
1070 }
1071 err.note(&msg);
1072 err
1073 } else if !locator.crate_rejections.via_kind.is_empty() {
1074 let mut err = struct_span_err!(
1075 sess,
1076 span,
1077 E0462,
1078 "found staticlib `{}` instead of rlib or dylib{}",
1079 crate_name,
1080 add,
1081 );
1082 err.help("please recompile that crate using --crate-type lib");
1083 let mismatches = locator.crate_rejections.via_kind.iter();
1084 for CrateMismatch { path, .. } in mismatches {
1085 msg.push_str(&format!("\ncrate `{}`: {}", crate_name, path.display()));
1086 }
1087 err.note(&msg);
1088 err
1089 } else if !locator.crate_rejections.via_version.is_empty() {
1090 let mut err = struct_span_err!(
1091 sess,
1092 span,
1093 E0514,
1094 "found crate `{}` compiled by an incompatible version of rustc{}",
1095 crate_name,
1096 add,
1097 );
1098 err.help(&format!(
1099 "please recompile that crate using this compiler ({}) \
1100 (consider running `cargo clean` first)",
1101 rustc_version(),
1102 ));
1103 let mismatches = locator.crate_rejections.via_version.iter();
1104 for CrateMismatch { path, got } in mismatches {
1105 msg.push_str(&format!(
1106 "\ncrate `{}` compiled by {}: {}",
1107 crate_name,
1108 got,
1109 path.display(),
1110 ));
1111 }
1112 err.note(&msg);
1113 err
1114 } else if !locator.crate_rejections.via_invalid.is_empty() {
1115 let mut err = struct_span_err!(
1116 sess,
1117 span,
1118 E0786,
1119 "found invalid metadata files for crate `{}`{}",
1120 crate_name,
1121 add,
1122 );
1123 for CrateMismatch { path: _, got } in locator.crate_rejections.via_invalid {
1124 err.note(&got);
1125 }
1126 err
1127 } else {
1128 let mut err = struct_span_err!(
1129 sess,
1130 span,
1131 E0463,
1132 "can't find crate for `{}`{}",
1133 crate_name,
1134 add,
1135 );
1136
1137 if (crate_name == sym::std || crate_name == sym::core)
1138 && locator.triple != TargetTriple::from_triple(config::host_triple())
1139 {
1140 if missing_core {
1141 err.note(&format!(
1142 "the `{}` target may not be installed",
1143 locator.triple
1144 ));
1145 } else {
1146 err.note(&format!(
1147 "the `{}` target may not support the standard library",
1148 locator.triple
1149 ));
1150 }
1151 // NOTE: this suggests using rustup, even though the user may not have it installed.
1152 // That's because they could choose to install it; or this may give them a hint which
1153 // target they need to install from their distro.
1154 if missing_core {
1155 err.help(&format!(
1156 "consider downloading the target with `rustup target add {}`",
1157 locator.triple
1158 ));
1159 }
1160 // Suggest using #![no_std]. #[no_core] is unstable and not really supported anyway.
1161 // NOTE: this is a dummy span if `extern crate std` was injected by the compiler.
1162 // If it's not a dummy, that means someone added `extern crate std` explicitly and `#![no_std]` won't help.
1163 if !missing_core && span.is_dummy() {
1164 let current_crate =
1165 sess.opts.crate_name.as_deref().unwrap_or("<unknown>");
1166 err.note(&format!(
1167 "`std` is required by `{}` because it does not declare `#![no_std]`",
1168 current_crate
1169 ));
1170 }
1171 if sess.is_nightly_build() {
1172 err.help("consider building the standard library from source with `cargo build -Zbuild-std`");
1173 }
1174 } else if crate_name
1175 == Symbol::intern(&sess.opts.debugging_opts.profiler_runtime)
1176 {
1177 err.note(&"the compiler may have been built without the profiler runtime");
1178 } else if crate_name.as_str().starts_with("rustc_") {
1179 err.help(
1180 "maybe you need to install the missing components with: \
1181 `rustup component add rust-src rustc-dev llvm-tools-preview`",
1182 );
1183 }
1184 err.span_label(span, "can't find crate");
1185 err
1186 };
1187
1188 if !locator.crate_rejections.via_filename.is_empty() {
1189 let mismatches = locator.crate_rejections.via_filename.iter();
1190 for CrateMismatch { path, .. } in mismatches {
1191 err.note(&format!(
1192 "extern location for {} is of an unknown type: {}",
1193 crate_name,
1194 path.display(),
1195 ))
1196 .help(&format!(
1197 "file name should be lib*.rlib or {}*.{}",
1198 locator.dll_prefix, locator.dll_suffix
1199 ));
1200 }
1201 }
1202 err
1203 }
1204 CrateError::NonDylibPlugin(crate_name) => struct_span_err!(
1205 sess,
1206 span,
1207 E0457,
1208 "plugin `{}` only found in rlib format, but must be available in dylib format",
1209 crate_name,
1210 ),
1211 };
1212
1213 err.emit();
1214 sess.abort_if_errors();
1215 unreachable!();
1216 }
1217 }
1218