compiler/rustc_metadata/src/creader.rs

   1 //! Validates all used crates and extern libraries and loads their metadata
   2
   3 use crate::dynamic_lib::DynamicLibrary;
   4 use crate::locator::{CrateError, CrateLocator, CratePaths};
   5 use crate::rmeta::{CrateDep, CrateMetadata, CrateNumMap, CrateRoot, MetadataBlob};
   6
   7 use rustc_ast::expand::allocator::AllocatorKind;
   8 use rustc_ast::{self as ast, *};
   9 use rustc_data_structures::fx::FxHashSet;
  10 use rustc_data_structures::svh::Svh;
  11 use rustc_data_structures::sync::Lrc;
  12 use rustc_expand::base::SyntaxExtension;
  13 use rustc_hir::def_id::{CrateNum, LocalDefId, LOCAL_CRATE};
  14 use rustc_hir::definitions::Definitions;
  15 use rustc_index::vec::IndexVec;
  16 use rustc_middle::middle::cstore::{CrateDepKind, CrateSource, ExternCrate};
  17 use rustc_middle::middle::cstore::{ExternCrateSource, MetadataLoaderDyn};
  18 use rustc_middle::ty::TyCtxt;
  19 use rustc_session::config::{self, CrateType, ExternLocation};
  20 use rustc_session::lint;
  21 use rustc_session::output::validate_crate_name;
  22 use rustc_session::search_paths::PathKind;
  23 use rustc_session::{CrateDisambiguator, Session};
  24 use rustc_span::edition::Edition;
  25 use rustc_span::symbol::{sym, Symbol};
  26 use rustc_span::{Span, DUMMY_SP};
  27 use rustc_target::spec::{PanicStrategy, TargetTriple};
  28
  29 use proc_macro::bridge::client::ProcMacro;
  30 use std::path::Path;
  31 use std::{cmp, env, fs};
  32 use tracing::{debug, info};
  33
  34 #[derive(Clone)]
  35 pub struct CStore {
  36     metas: IndexVec<CrateNum, Option<Lrc<CrateMetadata>>>,
  37     injected_panic_runtime: Option<CrateNum>,
  38     /// This crate needs an allocator and either provides it itself, or finds it in a dependency.
  39     /// If the above is true, then this field denotes the kind of the found allocator.
  40     allocator_kind: Option<AllocatorKind>,
  41     /// This crate has a `#[global_allocator]` item.
  42     has_global_allocator: bool,
  43 }
  44
  45 pub struct CrateLoader<'a> {
  46     // Immutable configuration.
  47     sess: &'a Session,
  48     metadata_loader: &'a MetadataLoaderDyn,
  49     local_crate_name: Symbol,
  50     // Mutable output.
  51     cstore: CStore,
  52     used_extern_options: FxHashSet<Symbol>,
  53 }
  54
  55 pub enum LoadedMacro {
  56     MacroDef(ast::Item, Edition),
  57     ProcMacro(SyntaxExtension),
  58 }
  59
  60 crate struct Library {
  61     pub source: CrateSource,
  62     pub metadata: MetadataBlob,
  63 }
  64
  65 enum LoadResult {
  66     Previous(CrateNum),
  67     Loaded(Library),
  68 }
  69
  70 /// A reference to `CrateMetadata` that can also give access to whole crate store when necessary.
  71 #[derive(Clone, Copy)]
  72 crate struct CrateMetadataRef<'a> {
  73     pub cdata: &'a CrateMetadata,
  74     pub cstore: &'a CStore,
  75 }
  76
  77 impl std::ops::Deref for CrateMetadataRef<'_> {
  78     type Target = CrateMetadata;
  79
  80     fn deref(&self) -> &Self::Target {
  81         self.cdata
  82     }
  83 }
  84
  85 struct CrateDump<'a>(&'a CStore);
  86
  87 impl<'a> std::fmt::Debug for CrateDump<'a> {
  88     fn fmt(&self, fmt: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
  89         writeln!(fmt, "resolved crates:")?;
  90         // `iter_crate_data` does not allow returning values. Thus we use a mutable variable here
  91         // that aggregates the value (and any errors that could happen).
  92         let mut res = Ok(());
  93         self.0.iter_crate_data(|cnum, data| {
  94             res = res.and(
  95                 try {
  96                     writeln!(fmt, "  name: {}", data.name())?;
  97                     writeln!(fmt, "  cnum: {}", cnum)?;
  98                     writeln!(fmt, "  hash: {}", data.hash())?;
  99                     writeln!(fmt, "  reqd: {:?}", data.dep_kind())?;
 100                     let CrateSource { dylib, rlib, rmeta } = data.source();
 101                     if let Some(dylib) = dylib {
 102                         writeln!(fmt, "  dylib: {}", dylib.0.display())?;
 103                     }
 104                     if let Some(rlib) = rlib {
 105                         writeln!(fmt, "   rlib: {}", rlib.0.display())?;
 106                     }
 107                     if let Some(rmeta) = rmeta {
 108                         writeln!(fmt, "   rmeta: {}", rmeta.0.display())?;
 109                     }
 110                 },
 111             );
 112         });
 113         res
 114     }
 115 }
 116
 117 impl CStore {
 118     crate fn from_tcx(tcx: TyCtxt<'_>) -> &CStore {
 119         tcx.cstore_as_any().downcast_ref::<CStore>().expect("`tcx.cstore` is not a `CStore`")
 120     }
 121
 122     fn alloc_new_crate_num(&mut self) -> CrateNum {
 123         self.metas.push(None);
 124         CrateNum::new(self.metas.len() - 1)
 125     }
 126
 127     crate fn get_crate_data(&self, cnum: CrateNum) -> CrateMetadataRef<'_> {
 128         let cdata = self.metas[cnum]
 129             .as_ref()
 130             .unwrap_or_else(|| panic!("Failed to get crate data for {:?}", cnum));
 131         CrateMetadataRef { cdata, cstore: self }
 132     }
 133
 134     fn set_crate_data(&mut self, cnum: CrateNum, data: CrateMetadata) {
 135         assert!(self.metas[cnum].is_none(), "Overwriting crate metadata entry");
 136         self.metas[cnum] = Some(Lrc::new(data));
 137     }
 138
 139     crate fn iter_crate_data(&self, mut f: impl FnMut(CrateNum, &CrateMetadata)) {
 140         for (cnum, data) in self.metas.iter_enumerated() {
 141             if let Some(data) = data {
 142                 f(cnum, data);
 143             }
 144         }
 145     }
 146
 147     fn push_dependencies_in_postorder(&self, deps: &mut Vec<CrateNum>, cnum: CrateNum) {
 148         if !deps.contains(&cnum) {
 149             let data = self.get_crate_data(cnum);
 150             for &dep in data.dependencies().iter() {
 151                 if dep != cnum {
 152                     self.push_dependencies_in_postorder(deps, dep);
 153                 }
 154             }
 155
 156             deps.push(cnum);
 157         }
 158     }
 159
 160     crate fn crate_dependencies_in_postorder(&self, cnum: CrateNum) -> Vec<CrateNum> {
 161         let mut deps = Vec::new();
 162         if cnum == LOCAL_CRATE {
 163             self.iter_crate_data(|cnum, _| self.push_dependencies_in_postorder(&mut deps, cnum));
 164         } else {
 165             self.push_dependencies_in_postorder(&mut deps, cnum);
 166         }
 167         deps
 168     }
 169
 170     fn crate_dependencies_in_reverse_postorder(&self, cnum: CrateNum) -> Vec<CrateNum> {
 171         let mut deps = self.crate_dependencies_in_postorder(cnum);
 172         deps.reverse();
 173         deps
 174     }
 175
 176     crate fn injected_panic_runtime(&self) -> Option<CrateNum> {
 177         self.injected_panic_runtime
 178     }
 179
 180     crate fn allocator_kind(&self) -> Option<AllocatorKind> {
 181         self.allocator_kind
 182     }
 183
 184     crate fn has_global_allocator(&self) -> bool {
 185         self.has_global_allocator
 186     }
 187 }
 188
 189 impl<'a> CrateLoader<'a> {
 190     pub fn new(
 191         sess: &'a Session,
 192         metadata_loader: &'a MetadataLoaderDyn,
 193         local_crate_name: &str,
 194     ) -> Self {
 195         CrateLoader {
 196             sess,
 197             metadata_loader,
 198             local_crate_name: Symbol::intern(local_crate_name),
 199             cstore: CStore {
 200                 // We add an empty entry for LOCAL_CRATE (which maps to zero) in
 201                 // order to make array indices in `metas` match with the
 202                 // corresponding `CrateNum`. This first entry will always remain
 203                 // `None`.
 204                 metas: IndexVec::from_elem_n(None, 1),
 205                 injected_panic_runtime: None,
 206                 allocator_kind: None,
 207                 has_global_allocator: false,
 208             },
 209             used_extern_options: Default::default(),
 210         }
 211     }
 212
 213     pub fn cstore(&self) -> &CStore {
 214         &self.cstore
 215     }
 216
 217     pub fn into_cstore(self) -> CStore {
 218         self.cstore
 219     }
 220
 221     fn existing_match(&self, name: Symbol, hash: Option<Svh>, kind: PathKind) -> Option<CrateNum> {
 222         let mut ret = None;
 223         self.cstore.iter_crate_data(|cnum, data| {
 224             if data.name() != name {
 225                 tracing::trace!("{} did not match {}", data.name(), name);
 226                 return;
 227             }
 228
 229             match hash {
 230                 Some(hash) if hash == data.hash() => {
 231                     ret = Some(cnum);
 232                     return;
 233                 }
 234                 Some(hash) => {
 235                     debug!("actual hash {} did not match expected {}", hash, data.hash());
 236                     return;
 237                 }
 238                 None => {}
 239             }
 240
 241             // When the hash is None we're dealing with a top-level dependency
 242             // in which case we may have a specification on the command line for
 243             // this library. Even though an upstream library may have loaded
 244             // something of the same name, we have to make sure it was loaded
 245             // from the exact same location as well.
 246             //
 247             // We're also sure to compare *paths*, not actual byte slices. The
 248             // `source` stores paths which are normalized which may be different
 249             // from the strings on the command line.
 250             let source = self.cstore.get_crate_data(cnum).cdata.source();
 251             if let Some(entry) = self.sess.opts.externs.get(&name.as_str()) {
 252                 // Only use `--extern crate_name=path` here, not `--extern crate_name`.
 253                 if let Some(mut files) = entry.files() {
 254                     if files.any(|l| {
 255                         let l = fs::canonicalize(l).unwrap_or(l.clone().into());
 256                         source.dylib.as_ref().map(|p| &p.0) == Some(&l)
 257                             || source.rlib.as_ref().map(|p| &p.0) == Some(&l)
 258                     }) {
 259                         ret = Some(cnum);
 260                     }
 261                 }
 262                 return;
 263             }
 264
 265             // Alright, so we've gotten this far which means that `data` has the
 266             // right name, we don't have a hash, and we don't have a --extern
 267             // pointing for ourselves. We're still not quite yet done because we
 268             // have to make sure that this crate was found in the crate lookup
 269             // path (this is a top-level dependency) as we don't want to
 270             // implicitly load anything inside the dependency lookup path.
 271             let prev_kind = source
 272                 .dylib
 273                 .as_ref()
 274                 .or(source.rlib.as_ref())
 275                 .or(source.rmeta.as_ref())
 276                 .expect("No sources for crate")
 277                 .1;
 278             if kind.matches(prev_kind) {
 279                 ret = Some(cnum);
 280             } else {
 281                 debug!(
 282                     "failed to load existing crate {}; kind {:?} did not match prev_kind {:?}",
 283                     name, kind, prev_kind
 284                 );
 285             }
 286         });
 287         ret
 288     }
 289
 290     fn verify_no_symbol_conflicts(&self, root: &CrateRoot<'_>) -> Result<(), CrateError> {
 291         // Check for (potential) conflicts with the local crate
 292         if self.local_crate_name == root.name()
 293             && self.sess.local_crate_disambiguator() == root.disambiguator()
 294         {
 295             return Err(CrateError::SymbolConflictsCurrent(root.name()));
 296         }
 297
 298         // Check for conflicts with any crate loaded so far
 299         let mut res = Ok(());
 300         self.cstore.iter_crate_data(|_, other| {
 301             if other.name() == root.name() && // same crate-name
 302                other.disambiguator() == root.disambiguator() && // same crate-disambiguator
 303                other.hash() != root.hash()
 304             {
 305                 // but different SVH
 306                 res = Err(CrateError::SymbolConflictsOthers(root.name()));
 307             }
 308         });
 309
 310         res
 311     }
 312
 313     fn register_crate(
 314         &mut self,
 315         host_lib: Option<Library>,
 316         root: Option<&CratePaths>,
 317         lib: Library,
 318         dep_kind: CrateDepKind,
 319         name: Symbol,
 320     ) -> Result<CrateNum, CrateError> {
 321         let _prof_timer = self.sess.prof.generic_activity("metadata_register_crate");
 322
 323         let Library { source, metadata } = lib;
 324         let crate_root = metadata.get_root();
 325         let host_hash = host_lib.as_ref().map(|lib| lib.metadata.get_root().hash());
 326         self.verify_no_symbol_conflicts(&crate_root)?;
 327
 328         let private_dep =
 329             self.sess.opts.externs.get(&name.as_str()).map(|e| e.is_private_dep).unwrap_or(false);
 330
 331         // Claim this crate number and cache it
 332         let cnum = self.cstore.alloc_new_crate_num();
 333
 334         info!(
 335             "register crate `{}` (cnum = {}. private_dep = {})",
 336             crate_root.name(),
 337             cnum,
 338             private_dep
 339         );
 340
 341         // Maintain a reference to the top most crate.
 342         // Stash paths for top-most crate locally if necessary.
 343         let crate_paths;
 344         let root = if let Some(root) = root {
 345             root
 346         } else {
 347             crate_paths = CratePaths::new(crate_root.name(), source.clone());
 348             &crate_paths
 349         };
 350
 351         let cnum_map = self.resolve_crate_deps(root, &crate_root, &metadata, cnum, dep_kind)?;
 352
 353         let raw_proc_macros = if crate_root.is_proc_macro_crate() {
 354             let temp_root;
 355             let (dlsym_source, dlsym_root) = match &host_lib {
 356                 Some(host_lib) => (&host_lib.source, {
 357                     temp_root = host_lib.metadata.get_root();
 358                     &temp_root
 359                 }),
 360                 None => (&source, &crate_root),
 361             };
 362             let dlsym_dylib = dlsym_source.dylib.as_ref().expect("no dylib for a proc-macro crate");
 363             Some(self.dlsym_proc_macros(&dlsym_dylib.0, dlsym_root.disambiguator())?)
 364         } else {
 365             None
 366         };
 367
 368         let crate_metadata = CrateMetadata::new(
 369             self.sess,
 370             metadata,
 371             crate_root,
 372             raw_proc_macros,
 373             cnum,
 374             cnum_map,
 375             dep_kind,
 376             source,
 377             private_dep,
 378             host_hash,
 379         );
 380
 381         self.cstore.set_crate_data(cnum, crate_metadata);
 382
 383         Ok(cnum)
 384     }
 385
 386     fn load_proc_macro<'b>(
 387         &self,
 388         locator: &mut CrateLocator<'b>,
 389         path_kind: PathKind,
 390     ) -> Result<Option<(LoadResult, Option<Library>)>, CrateError>
 391     where
 392         'a: 'b,
 393     {
 394         // Use a new crate locator so trying to load a proc macro doesn't affect the error
 395         // message we emit
 396         let mut proc_macro_locator = locator.clone();
 397
 398         // Try to load a proc macro
 399         proc_macro_locator.is_proc_macro = Some(true);
 400
 401         // Load the proc macro crate for the target
 402         let (locator, target_result) = if self.sess.opts.debugging_opts.dual_proc_macros {
 403             proc_macro_locator.reset();
 404             let result = match self.load(&mut proc_macro_locator)? {
 405                 Some(LoadResult::Previous(cnum)) => {
 406                     return Ok(Some((LoadResult::Previous(cnum), None)));
 407                 }
 408                 Some(LoadResult::Loaded(library)) => Some(LoadResult::Loaded(library)),
 409                 None => return Ok(None),
 410             };
 411             locator.hash = locator.host_hash;
 412             // Use the locator when looking for the host proc macro crate, as that is required
 413             // so we want it to affect the error message
 414             (locator, result)
 415         } else {
 416             (&mut proc_macro_locator, None)
 417         };
 418
 419         // Load the proc macro crate for the host
 420
 421         locator.reset();
 422         locator.is_proc_macro = Some(true);
 423         locator.target = &self.sess.host;
 424         locator.triple = TargetTriple::from_triple(config::host_triple());
 425         locator.filesearch = self.sess.host_filesearch(path_kind);
 426
 427         let host_result = match self.load(locator)? {
 428             Some(host_result) => host_result,
 429             None => return Ok(None),
 430         };
 431
 432         Ok(Some(if self.sess.opts.debugging_opts.dual_proc_macros {
 433             let host_result = match host_result {
 434                 LoadResult::Previous(..) => {
 435                     panic!("host and target proc macros must be loaded in lock-step")
 436                 }
 437                 LoadResult::Loaded(library) => library,
 438             };
 439             (target_result.unwrap(), Some(host_result))
 440         } else {
 441             (host_result, None)
 442         }))
 443     }
 444
 445     fn resolve_crate<'b>(
 446         &'b mut self,
 447         name: Symbol,
 448         span: Span,
 449         dep_kind: CrateDepKind,
 450         dep: Option<(&'b CratePaths, &'b CrateDep)>,
 451     ) -> CrateNum {
 452         if dep.is_none() {
 453             self.used_extern_options.insert(name);
 454         }
 455         self.maybe_resolve_crate(name, dep_kind, dep)
 456             .unwrap_or_else(|err| err.report(self.sess, span))
 457     }
 458
 459     fn maybe_resolve_crate<'b>(
 460         &'b mut self,
 461         name: Symbol,
 462         mut dep_kind: CrateDepKind,
 463         dep: Option<(&'b CratePaths, &'b CrateDep)>,
 464     ) -> Result<CrateNum, CrateError> {
 465         info!("resolving crate `{}`", name);
 466         if !name.as_str().is_ascii() {
 467             return Err(CrateError::NonAsciiName(name));
 468         }
 469         let (root, hash, host_hash, extra_filename, path_kind) = match dep {
 470             Some((root, dep)) => (
 471                 Some(root),
 472                 Some(dep.hash),
 473                 dep.host_hash,
 474                 Some(&dep.extra_filename[..]),
 475                 PathKind::Dependency,
 476             ),
 477             None => (None, None, None, None, PathKind::Crate),
 478         };
 479         let result = if let Some(cnum) = self.existing_match(name, hash, path_kind) {
 480             (LoadResult::Previous(cnum), None)
 481         } else {
 482             info!("falling back to a load");
 483             let mut locator = CrateLocator::new(
 484                 self.sess,
 485                 self.metadata_loader,
 486                 name,
 487                 hash,
 488                 host_hash,
 489                 extra_filename,
 490                 false, // is_host
 491                 path_kind,
 492                 root,
 493                 Some(false), // is_proc_macro
 494             );
 495
 496             match self.load(&mut locator)? {
 497                 Some(res) => (res, None),
 498                 None => {
 499                     dep_kind = CrateDepKind::MacrosOnly;
 500                     match self.load_proc_macro(&mut locator, path_kind)? {
 501                         Some(res) => res,
 502                         None => return Err(locator.into_error()),
 503                     }
 504                 }
 505             }
 506         };
 507
 508         match result {
 509             (LoadResult::Previous(cnum), None) => {
 510                 let data = self.cstore.get_crate_data(cnum);
 511                 if data.is_proc_macro_crate() {
 512                     dep_kind = CrateDepKind::MacrosOnly;
 513                 }
 514                 data.update_dep_kind(|data_dep_kind| cmp::max(data_dep_kind, dep_kind));
 515                 Ok(cnum)
 516             }
 517             (LoadResult::Loaded(library), host_library) => {
 518                 self.register_crate(host_library, root, library, dep_kind, name)
 519             }
 520             _ => panic!(),
 521         }
 522     }
 523
 524     fn load(&self, locator: &mut CrateLocator<'_>) -> Result<Option<LoadResult>, CrateError> {
 525         let library = match locator.maybe_load_library_crate()? {
 526             Some(library) => library,
 527             None => return Ok(None),
 528         };
 529
 530         // In the case that we're loading a crate, but not matching
 531         // against a hash, we could load a crate which has the same hash
 532         // as an already loaded crate. If this is the case prevent
 533         // duplicates by just using the first crate.
 534         //
 535         // Note that we only do this for target triple crates, though, as we
 536         // don't want to match a host crate against an equivalent target one
 537         // already loaded.
 538         let root = library.metadata.get_root();
 539         Ok(Some(if locator.triple == self.sess.opts.target_triple {
 540             let mut result = LoadResult::Loaded(library);
 541             self.cstore.iter_crate_data(|cnum, data| {
 542                 if data.name() == root.name() && root.hash() == data.hash() {
 543                     assert!(locator.hash.is_none());
 544                     info!("load success, going to previous cnum: {}", cnum);
 545                     result = LoadResult::Previous(cnum);
 546                 }
 547             });
 548             result
 549         } else {
 550             LoadResult::Loaded(library)
 551         }))
 552     }
 553
 554     fn update_extern_crate(&self, cnum: CrateNum, extern_crate: ExternCrate) {
 555         let cmeta = self.cstore.get_crate_data(cnum);
 556         if cmeta.update_extern_crate(extern_crate) {
 557             // Propagate the extern crate info to dependencies if it was updated.
 558             let extern_crate = ExternCrate { dependency_of: cnum, ..extern_crate };
 559             for &dep_cnum in cmeta.dependencies().iter() {
 560                 self.update_extern_crate(dep_cnum, extern_crate);
 561             }
 562         }
 563     }
 564
 565     // Go through the crate metadata and load any crates that it references
 566     fn resolve_crate_deps(
 567         &mut self,
 568         root: &CratePaths,
 569         crate_root: &CrateRoot<'_>,
 570         metadata: &MetadataBlob,
 571         krate: CrateNum,
 572         dep_kind: CrateDepKind,
 573     ) -> Result<CrateNumMap, CrateError> {
 574         debug!("resolving deps of external crate");
 575         if crate_root.is_proc_macro_crate() {
 576             return Ok(CrateNumMap::new());
 577         }
 578
 579         // The map from crate numbers in the crate we're resolving to local crate numbers.
 580         // We map 0 and all other holes in the map to our parent crate. The "additional"
 581         // self-dependencies should be harmless.
 582         let deps = crate_root.decode_crate_deps(metadata);
 583         let mut crate_num_map = CrateNumMap::with_capacity(1 + deps.len());
 584         crate_num_map.push(krate);
 585         for dep in deps {
 586             info!(
 587                 "resolving dep crate {} hash: `{}` extra filename: `{}`",
 588                 dep.name, dep.hash, dep.extra_filename
 589             );
 590             let dep_kind = match dep_kind {
 591                 CrateDepKind::MacrosOnly => CrateDepKind::MacrosOnly,
 592                 _ => dep.kind,
 593             };
 594             let cnum = self.maybe_resolve_crate(dep.name, dep_kind, Some((root, &dep)))?;
 595             crate_num_map.push(cnum);
 596         }
 597
 598         debug!("resolve_crate_deps: cnum_map for {:?} is {:?}", krate, crate_num_map);
 599         Ok(crate_num_map)
 600     }
 601
 602     fn dlsym_proc_macros(
 603         &self,
 604         path: &Path,
 605         disambiguator: CrateDisambiguator,
 606     ) -> Result<&'static [ProcMacro], CrateError> {
 607         // Make sure the path contains a / or the linker will search for it.
 608         let path = env::current_dir().unwrap().join(path);
 609         let lib = match DynamicLibrary::open(&path) {
 610             Ok(lib) => lib,
 611             Err(s) => return Err(CrateError::DlOpen(s)),
 612         };
 613
 614         let sym = self.sess.generate_proc_macro_decls_symbol(disambiguator);
 615         let decls = unsafe {
 616             let sym = match lib.symbol(&sym) {
 617                 Ok(f) => f,
 618                 Err(s) => return Err(CrateError::DlSym(s)),
 619             };
 620             *(sym as *const &[ProcMacro])
 621         };
 622
 623         // Intentionally leak the dynamic library. We can't ever unload it
 624         // since the library can make things that will live arbitrarily long.
 625         std::mem::forget(lib);
 626
 627         Ok(decls)
 628     }
 629
 630     fn inject_panic_runtime(&mut self, krate: &ast::Crate) {
 631         // If we're only compiling an rlib, then there's no need to select a
 632         // panic runtime, so we just skip this section entirely.
 633         let any_non_rlib = self.sess.crate_types().iter().any(|ct| *ct != CrateType::Rlib);
 634         if !any_non_rlib {
 635             info!("panic runtime injection skipped, only generating rlib");
 636             return;
 637         }
 638
 639         // If we need a panic runtime, we try to find an existing one here. At
 640         // the same time we perform some general validation of the DAG we've got
 641         // going such as ensuring everything has a compatible panic strategy.
 642         //
 643         // The logic for finding the panic runtime here is pretty much the same
 644         // as the allocator case with the only addition that the panic strategy
 645         // compilation mode also comes into play.
 646         let desired_strategy = self.sess.panic_strategy();
 647         let mut runtime_found = false;
 648         let mut needs_panic_runtime =
 649             self.sess.contains_name(&krate.attrs, sym::needs_panic_runtime);
 650
 651         self.cstore.iter_crate_data(|cnum, data| {
 652             needs_panic_runtime = needs_panic_runtime || data.needs_panic_runtime();
 653             if data.is_panic_runtime() {
 654                 // Inject a dependency from all #![needs_panic_runtime] to this
 655                 // #![panic_runtime] crate.
 656                 self.inject_dependency_if(cnum, "a panic runtime", &|data| {
 657                     data.needs_panic_runtime()
 658                 });
 659                 runtime_found = runtime_found || data.dep_kind() == CrateDepKind::Explicit;
 660             }
 661         });
 662
 663         // If an explicitly linked and matching panic runtime was found, or if
 664         // we just don't need one at all, then we're done here and there's
 665         // nothing else to do.
 666         if !needs_panic_runtime || runtime_found {
 667             return;
 668         }
 669
 670         // By this point we know that we (a) need a panic runtime and (b) no
 671         // panic runtime was explicitly linked. Here we just load an appropriate
 672         // default runtime for our panic strategy and then inject the
 673         // dependencies.
 674         //
 675         // We may resolve to an already loaded crate (as the crate may not have
 676         // been explicitly linked prior to this) and we may re-inject
 677         // dependencies again, but both of those situations are fine.
 678         //
 679         // Also note that we have yet to perform validation of the crate graph
 680         // in terms of everyone has a compatible panic runtime format, that's
 681         // performed later as part of the `dependency_format` module.
 682         let name = match desired_strategy {
 683             PanicStrategy::Unwind => sym::panic_unwind,
 684             PanicStrategy::Abort => sym::panic_abort,
 685         };
 686         info!("panic runtime not found -- loading {}", name);
 687
 688         let cnum = self.resolve_crate(name, DUMMY_SP, CrateDepKind::Implicit, None);
 689         let data = self.cstore.get_crate_data(cnum);
 690
 691         // Sanity check the loaded crate to ensure it is indeed a panic runtime
 692         // and the panic strategy is indeed what we thought it was.
 693         if !data.is_panic_runtime() {
 694             self.sess.err(&format!("the crate `{}` is not a panic runtime", name));
 695         }
 696         if data.panic_strategy() != desired_strategy {
 697             self.sess.err(&format!(
 698                 "the crate `{}` does not have the panic \
 699                                     strategy `{}`",
 700                 name,
 701                 desired_strategy.desc()
 702             ));
 703         }
 704
 705         self.cstore.injected_panic_runtime = Some(cnum);
 706         self.inject_dependency_if(cnum, "a panic runtime", &|data| data.needs_panic_runtime());
 707     }
 708
 709     fn inject_profiler_runtime(&mut self) {
 710         if (self.sess.opts.debugging_opts.instrument_coverage
 711             || self.sess.opts.debugging_opts.profile
 712             || self.sess.opts.cg.profile_generate.enabled())
 713             && !self.sess.opts.debugging_opts.no_profiler_runtime
 714         {
 715             info!("loading profiler");
 716
 717             let name = sym::profiler_builtins;
 718             let cnum = self.resolve_crate(name, DUMMY_SP, CrateDepKind::Implicit, None);
 719             let data = self.cstore.get_crate_data(cnum);
 720
 721             // Sanity check the loaded crate to ensure it is indeed a profiler runtime
 722             if !data.is_profiler_runtime() {
 723                 self.sess.err("the crate `profiler_builtins` is not a profiler runtime");
 724             }
 725         }
 726     }
 727
 728     fn inject_allocator_crate(&mut self, krate: &ast::Crate) {
 729         self.cstore.has_global_allocator = match &*global_allocator_spans(&self.sess, krate) {
 730             [span1, span2, ..] => {
 731                 self.sess
 732                     .struct_span_err(*span2, "cannot define multiple global allocators")
 733                     .span_label(*span2, "cannot define a new global allocator")
 734                     .span_label(*span1, "previous global allocator defined here")
 735                     .emit();
 736                 true
 737             }
 738             spans => !spans.is_empty(),
 739         };
 740
 741         // Check to see if we actually need an allocator. This desire comes
 742         // about through the `#![needs_allocator]` attribute and is typically
 743         // written down in liballoc.
 744         let mut needs_allocator = self.sess.contains_name(&krate.attrs, sym::needs_allocator);
 745         self.cstore.iter_crate_data(|_, data| {
 746             needs_allocator = needs_allocator || data.needs_allocator();
 747         });
 748         if !needs_allocator {
 749             return;
 750         }
 751
 752         // At this point we've determined that we need an allocator. Let's see
 753         // if our compilation session actually needs an allocator based on what
 754         // we're emitting.
 755         let all_rlib = self.sess.crate_types().iter().all(|ct| match *ct {
 756             CrateType::Rlib => true,
 757             _ => false,
 758         });
 759         if all_rlib {
 760             return;
 761         }
 762
 763         // Ok, we need an allocator. Not only that but we're actually going to
 764         // create an artifact that needs one linked in. Let's go find the one
 765         // that we're going to link in.
 766         //
 767         // First up we check for global allocators. Look at the crate graph here
 768         // and see what's a global allocator, including if we ourselves are a
 769         // global allocator.
 770         let mut global_allocator =
 771             self.cstore.has_global_allocator.then(|| Symbol::intern("this crate"));
 772         self.cstore.iter_crate_data(|_, data| {
 773             if !data.has_global_allocator() {
 774                 return;
 775             }
 776             match global_allocator {
 777                 Some(other_crate) => {
 778                     self.sess.err(&format!(
 779                         "the `#[global_allocator]` in {} \
 780                                             conflicts with global \
 781                                             allocator in: {}",
 782                         other_crate,
 783                         data.name()
 784                     ));
 785                 }
 786                 None => global_allocator = Some(data.name()),
 787             }
 788         });
 789         if global_allocator.is_some() {
 790             self.cstore.allocator_kind = Some(AllocatorKind::Global);
 791             return;
 792         }
 793
 794         // Ok we haven't found a global allocator but we still need an
 795         // allocator. At this point our allocator request is typically fulfilled
 796         // by the standard library, denoted by the `#![default_lib_allocator]`
 797         // attribute.
 798         let mut has_default = self.sess.contains_name(&krate.attrs, sym::default_lib_allocator);
 799         self.cstore.iter_crate_data(|_, data| {
 800             if data.has_default_lib_allocator() {
 801                 has_default = true;
 802             }
 803         });
 804
 805         if !has_default {
 806             self.sess.err(
 807                 "no global memory allocator found but one is \
 808                            required; link to std or \
 809                            add `#[global_allocator]` to a static item \
 810                            that implements the GlobalAlloc trait.",
 811             );
 812         }
 813         self.cstore.allocator_kind = Some(AllocatorKind::Default);
 814     }
 815
 816     fn inject_dependency_if(
 817         &self,
 818         krate: CrateNum,
 819         what: &str,
 820         needs_dep: &dyn Fn(&CrateMetadata) -> bool,
 821     ) {
 822         // don't perform this validation if the session has errors, as one of
 823         // those errors may indicate a circular dependency which could cause
 824         // this to stack overflow.
 825         if self.sess.has_errors() {
 826             return;
 827         }
 828
 829         // Before we inject any dependencies, make sure we don't inject a
 830         // circular dependency by validating that this crate doesn't
 831         // transitively depend on any crates satisfying `needs_dep`.
 832         for dep in self.cstore.crate_dependencies_in_reverse_postorder(krate) {
 833             let data = self.cstore.get_crate_data(dep);
 834             if needs_dep(&data) {
 835                 self.sess.err(&format!(
 836                     "the crate `{}` cannot depend \
 837                                         on a crate that needs {}, but \
 838                                         it depends on `{}`",
 839                     self.cstore.get_crate_data(krate).name(),
 840                     what,
 841                     data.name()
 842                 ));
 843             }
 844         }
 845
 846         // All crates satisfying `needs_dep` do not explicitly depend on the
 847         // crate provided for this compile, but in order for this compilation to
 848         // be successfully linked we need to inject a dependency (to order the
 849         // crates on the command line correctly).
 850         self.cstore.iter_crate_data(|cnum, data| {
 851             if !needs_dep(data) {
 852                 return;
 853             }
 854
 855             info!("injecting a dep from {} to {}", cnum, krate);
 856             data.add_dependency(krate);
 857         });
 858     }
 859
 860     fn report_unused_deps(&mut self, krate: &ast::Crate) {
 861         // Make a point span rather than covering the whole file
 862         let span = krate.span.shrink_to_lo();
 863         // Complain about anything left over
 864         for (name, entry) in self.sess.opts.externs.iter() {
 865             if let ExternLocation::FoundInLibrarySearchDirectories = entry.location {
 866                 // Don't worry about pathless `--extern foo` sysroot references
 867                 continue;
 868             }
 869             if !self.used_extern_options.contains(&Symbol::intern(name)) {
 870                 self.sess.parse_sess.buffer_lint(
 871                     lint::builtin::UNUSED_CRATE_DEPENDENCIES,
 872                     span,
 873                     ast::CRATE_NODE_ID,
 874                     &format!(
 875                         "external crate `{}` unused in `{}`: remove the dependency or add `use {} as _;`",
 876                         name,
 877                         self.local_crate_name,
 878                         name),
 879                 );
 880             }
 881         }
 882     }
 883
 884     pub fn postprocess(&mut self, krate: &ast::Crate) {
 885         self.inject_profiler_runtime();
 886         self.inject_allocator_crate(krate);
 887         self.inject_panic_runtime(krate);
 888
 889         info!("{:?}", CrateDump(&self.cstore));
 890
 891         self.report_unused_deps(krate);
 892     }
 893
 894     pub fn process_extern_crate(
 895         &mut self,
 896         item: &ast::Item,
 897         definitions: &Definitions,
 898         def_id: LocalDefId,
 899     ) -> CrateNum {
 900         match item.kind {
 901             ast::ItemKind::ExternCrate(orig_name) => {
 902                 debug!(
 903                     "resolving extern crate stmt. ident: {} orig_name: {:?}",
 904                     item.ident, orig_name
 905                 );
 906                 let name = match orig_name {
 907                     Some(orig_name) => {
 908                         validate_crate_name(self.sess, &orig_name.as_str(), Some(item.span));
 909                         orig_name
 910                     }
 911                     None => item.ident.name,
 912                 };
 913                 let dep_kind = if self.sess.contains_name(&item.attrs, sym::no_link) {
 914                     CrateDepKind::MacrosOnly
 915                 } else {
 916                     CrateDepKind::Explicit
 917                 };
 918
 919                 let cnum = self.resolve_crate(name, item.span, dep_kind, None);
 920
 921                 let path_len = definitions.def_path(def_id).data.len();
 922                 self.update_extern_crate(
 923                     cnum,
 924                     ExternCrate {
 925                         src: ExternCrateSource::Extern(def_id.to_def_id()),
 926                         span: item.span,
 927                         path_len,
 928                         dependency_of: LOCAL_CRATE,
 929                     },
 930                 );
 931                 cnum
 932             }
 933             _ => bug!(),
 934         }
 935     }
 936
 937     pub fn process_path_extern(&mut self, name: Symbol, span: Span) -> CrateNum {
 938         let cnum = self.resolve_crate(name, span, CrateDepKind::Explicit, None);
 939
 940         self.update_extern_crate(
 941             cnum,
 942             ExternCrate {
 943                 src: ExternCrateSource::Path,
 944                 span,
 945                 // to have the least priority in `update_extern_crate`
 946                 path_len: usize::MAX,
 947                 dependency_of: LOCAL_CRATE,
 948             },
 949         );
 950
 951         cnum
 952     }
 953
 954     pub fn maybe_process_path_extern(&mut self, name: Symbol) -> Option<CrateNum> {
 955         self.maybe_resolve_crate(name, CrateDepKind::Explicit, None).ok()
 956     }
 957 }
 958
 959 fn global_allocator_spans(sess: &Session, krate: &ast::Crate) -> Vec<Span> {
 960     struct Finder<'a> {
 961         sess: &'a Session,
 962         name: Symbol,
 963         spans: Vec<Span>,
 964     }
 965     impl<'ast, 'a> visit::Visitor<'ast> for Finder<'a> {
 966         fn visit_item(&mut self, item: &'ast ast::Item) {
 967             if item.ident.name == self.name
 968                 && self.sess.contains_name(&item.attrs, sym::rustc_std_internal_symbol)
 969             {
 970                 self.spans.push(item.span);
 971             }
 972             visit::walk_item(self, item)
 973         }
 974     }
 975
 976     let name = Symbol::intern(&AllocatorKind::Global.fn_name(sym::alloc));
 977     let mut f = Finder { sess, name, spans: Vec::new() };
 978     visit::walk_crate(&mut f, krate);
 979     f.spans
 980 }