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};
  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 = l.canonicalized();
 256                         source.dylib.as_ref().map(|(p, _)| p) == Some(l)
 257                             || source.rlib.as_ref().map(|(p, _)| p) == Some(l)
 258                             || source.rmeta.as_ref().map(|(p, _)| p) == Some(l)
 259                     }) {
 260                         ret = Some(cnum);
 261                     }
 262                 }
 263                 return;
 264             }
 265
 266             // Alright, so we've gotten this far which means that `data` has the
 267             // right name, we don't have a hash, and we don't have a --extern
 268             // pointing for ourselves. We're still not quite yet done because we
 269             // have to make sure that this crate was found in the crate lookup
 270             // path (this is a top-level dependency) as we don't want to
 271             // implicitly load anything inside the dependency lookup path.
 272             let prev_kind = source
 273                 .dylib
 274                 .as_ref()
 275                 .or(source.rlib.as_ref())
 276                 .or(source.rmeta.as_ref())
 277                 .expect("No sources for crate")
 278                 .1;
 279             if kind.matches(prev_kind) {
 280                 ret = Some(cnum);
 281             } else {
 282                 debug!(
 283                     "failed to load existing crate {}; kind {:?} did not match prev_kind {:?}",
 284                     name, kind, prev_kind
 285                 );
 286             }
 287         });
 288         ret
 289     }
 290
 291     fn verify_no_symbol_conflicts(&self, root: &CrateRoot<'_>) -> Result<(), CrateError> {
 292         // Check for (potential) conflicts with the local crate
 293         if self.local_crate_name == root.name()
 294             && self.sess.local_crate_disambiguator() == root.disambiguator()
 295         {
 296             return Err(CrateError::SymbolConflictsCurrent(root.name()));
 297         }
 298
 299         // Check for conflicts with any crate loaded so far
 300         let mut res = Ok(());
 301         self.cstore.iter_crate_data(|_, other| {
 302             if other.name() == root.name() && // same crate-name
 303                other.disambiguator() == root.disambiguator() && // same crate-disambiguator
 304                other.hash() != root.hash()
 305             {
 306                 // but different SVH
 307                 res = Err(CrateError::SymbolConflictsOthers(root.name()));
 308             }
 309         });
 310
 311         res
 312     }
 313
 314     fn register_crate(
 315         &mut self,
 316         host_lib: Option<Library>,
 317         root: Option<&CratePaths>,
 318         lib: Library,
 319         dep_kind: CrateDepKind,
 320         name: Symbol,
 321     ) -> Result<CrateNum, CrateError> {
 322         let _prof_timer = self.sess.prof.generic_activity("metadata_register_crate");
 323
 324         let Library { source, metadata } = lib;
 325         let crate_root = metadata.get_root();
 326         let host_hash = host_lib.as_ref().map(|lib| lib.metadata.get_root().hash());
 327         self.verify_no_symbol_conflicts(&crate_root)?;
 328
 329         let private_dep =
 330             self.sess.opts.externs.get(&name.as_str()).map_or(false, |e| e.is_private_dep);
 331
 332         // Claim this crate number and cache it
 333         let cnum = self.cstore.alloc_new_crate_num();
 334
 335         info!(
 336             "register crate `{}` (cnum = {}. private_dep = {})",
 337             crate_root.name(),
 338             cnum,
 339             private_dep
 340         );
 341
 342         // Maintain a reference to the top most crate.
 343         // Stash paths for top-most crate locally if necessary.
 344         let crate_paths;
 345         let root = if let Some(root) = root {
 346             root
 347         } else {
 348             crate_paths = CratePaths::new(crate_root.name(), source.clone());
 349             &crate_paths
 350         };
 351
 352         let cnum_map = self.resolve_crate_deps(root, &crate_root, &metadata, cnum, dep_kind)?;
 353
 354         let raw_proc_macros = if crate_root.is_proc_macro_crate() {
 355             let temp_root;
 356             let (dlsym_source, dlsym_root) = match &host_lib {
 357                 Some(host_lib) => (&host_lib.source, {
 358                     temp_root = host_lib.metadata.get_root();
 359                     &temp_root
 360                 }),
 361                 None => (&source, &crate_root),
 362             };
 363             let dlsym_dylib = dlsym_source.dylib.as_ref().expect("no dylib for a proc-macro crate");
 364             Some(self.dlsym_proc_macros(&dlsym_dylib.0, dlsym_root.disambiguator())?)
 365         } else {
 366             None
 367         };
 368
 369         let crate_metadata = CrateMetadata::new(
 370             self.sess,
 371             metadata,
 372             crate_root,
 373             raw_proc_macros,
 374             cnum,
 375             cnum_map,
 376             dep_kind,
 377             source,
 378             private_dep,
 379             host_hash,
 380         );
 381
 382         self.cstore.set_crate_data(cnum, crate_metadata);
 383
 384         Ok(cnum)
 385     }
 386
 387     fn load_proc_macro<'b>(
 388         &self,
 389         locator: &mut CrateLocator<'b>,
 390         path_kind: PathKind,
 391     ) -> Result<Option<(LoadResult, Option<Library>)>, CrateError>
 392     where
 393         'a: 'b,
 394     {
 395         // Use a new crate locator so trying to load a proc macro doesn't affect the error
 396         // message we emit
 397         let mut proc_macro_locator = locator.clone();
 398
 399         // Try to load a proc macro
 400         proc_macro_locator.is_proc_macro = Some(true);
 401
 402         // Load the proc macro crate for the target
 403         let (locator, target_result) = if self.sess.opts.debugging_opts.dual_proc_macros {
 404             proc_macro_locator.reset();
 405             let result = match self.load(&mut proc_macro_locator)? {
 406                 Some(LoadResult::Previous(cnum)) => {
 407                     return Ok(Some((LoadResult::Previous(cnum), None)));
 408                 }
 409                 Some(LoadResult::Loaded(library)) => Some(LoadResult::Loaded(library)),
 410                 None => return Ok(None),
 411             };
 412             locator.hash = locator.host_hash;
 413             // Use the locator when looking for the host proc macro crate, as that is required
 414             // so we want it to affect the error message
 415             (locator, result)
 416         } else {
 417             (&mut proc_macro_locator, None)
 418         };
 419
 420         // Load the proc macro crate for the host
 421
 422         locator.reset();
 423         locator.is_proc_macro = Some(true);
 424         locator.target = &self.sess.host;
 425         locator.triple = TargetTriple::from_triple(config::host_triple());
 426         locator.filesearch = self.sess.host_filesearch(path_kind);
 427
 428         let host_result = match self.load(locator)? {
 429             Some(host_result) => host_result,
 430             None => return Ok(None),
 431         };
 432
 433         Ok(Some(if self.sess.opts.debugging_opts.dual_proc_macros {
 434             let host_result = match host_result {
 435                 LoadResult::Previous(..) => {
 436                     panic!("host and target proc macros must be loaded in lock-step")
 437                 }
 438                 LoadResult::Loaded(library) => library,
 439             };
 440             (target_result.unwrap(), Some(host_result))
 441         } else {
 442             (host_result, None)
 443         }))
 444     }
 445
 446     fn resolve_crate<'b>(
 447         &'b mut self,
 448         name: Symbol,
 449         span: Span,
 450         dep_kind: CrateDepKind,
 451         dep: Option<(&'b CratePaths, &'b CrateDep)>,
 452     ) -> CrateNum {
 453         if dep.is_none() {
 454             self.used_extern_options.insert(name);
 455         }
 456         self.maybe_resolve_crate(name, dep_kind, dep)
 457             .unwrap_or_else(|err| err.report(self.sess, span))
 458     }
 459
 460     fn maybe_resolve_crate<'b>(
 461         &'b mut self,
 462         name: Symbol,
 463         mut dep_kind: CrateDepKind,
 464         dep: Option<(&'b CratePaths, &'b CrateDep)>,
 465     ) -> Result<CrateNum, CrateError> {
 466         info!("resolving crate `{}`", name);
 467         if !name.as_str().is_ascii() {
 468             return Err(CrateError::NonAsciiName(name));
 469         }
 470         let (root, hash, host_hash, extra_filename, path_kind) = match dep {
 471             Some((root, dep)) => (
 472                 Some(root),
 473                 Some(dep.hash),
 474                 dep.host_hash,
 475                 Some(&dep.extra_filename[..]),
 476                 PathKind::Dependency,
 477             ),
 478             None => (None, None, None, None, PathKind::Crate),
 479         };
 480         let result = if let Some(cnum) = self.existing_match(name, hash, path_kind) {
 481             (LoadResult::Previous(cnum), None)
 482         } else {
 483             info!("falling back to a load");
 484             let mut locator = CrateLocator::new(
 485                 self.sess,
 486                 self.metadata_loader,
 487                 name,
 488                 hash,
 489                 host_hash,
 490                 extra_filename,
 491                 false, // is_host
 492                 path_kind,
 493                 root,
 494                 Some(false), // is_proc_macro
 495             );
 496
 497             match self.load(&mut locator)? {
 498                 Some(res) => (res, None),
 499                 None => {
 500                     dep_kind = CrateDepKind::MacrosOnly;
 501                     match self.load_proc_macro(&mut locator, path_kind)? {
 502                         Some(res) => res,
 503                         None => return Err(locator.into_error()),
 504                     }
 505                 }
 506             }
 507         };
 508
 509         match result {
 510             (LoadResult::Previous(cnum), None) => {
 511                 let data = self.cstore.get_crate_data(cnum);
 512                 if data.is_proc_macro_crate() {
 513                     dep_kind = CrateDepKind::MacrosOnly;
 514                 }
 515                 data.update_dep_kind(|data_dep_kind| cmp::max(data_dep_kind, dep_kind));
 516                 Ok(cnum)
 517             }
 518             (LoadResult::Loaded(library), host_library) => {
 519                 self.register_crate(host_library, root, library, dep_kind, name)
 520             }
 521             _ => panic!(),
 522         }
 523     }
 524
 525     fn load(&self, locator: &mut CrateLocator<'_>) -> Result<Option<LoadResult>, CrateError> {
 526         let library = match locator.maybe_load_library_crate()? {
 527             Some(library) => library,
 528             None => return Ok(None),
 529         };
 530
 531         // In the case that we're loading a crate, but not matching
 532         // against a hash, we could load a crate which has the same hash
 533         // as an already loaded crate. If this is the case prevent
 534         // duplicates by just using the first crate.
 535         //
 536         // Note that we only do this for target triple crates, though, as we
 537         // don't want to match a host crate against an equivalent target one
 538         // already loaded.
 539         let root = library.metadata.get_root();
 540         Ok(Some(if locator.triple == self.sess.opts.target_triple {
 541             let mut result = LoadResult::Loaded(library);
 542             self.cstore.iter_crate_data(|cnum, data| {
 543                 if data.name() == root.name() && root.hash() == data.hash() {
 544                     assert!(locator.hash.is_none());
 545                     info!("load success, going to previous cnum: {}", cnum);
 546                     result = LoadResult::Previous(cnum);
 547                 }
 548             });
 549             result
 550         } else {
 551             LoadResult::Loaded(library)
 552         }))
 553     }
 554
 555     fn update_extern_crate(&self, cnum: CrateNum, extern_crate: ExternCrate) {
 556         let cmeta = self.cstore.get_crate_data(cnum);
 557         if cmeta.update_extern_crate(extern_crate) {
 558             // Propagate the extern crate info to dependencies if it was updated.
 559             let extern_crate = ExternCrate { dependency_of: cnum, ..extern_crate };
 560             for &dep_cnum in cmeta.dependencies().iter() {
 561                 self.update_extern_crate(dep_cnum, extern_crate);
 562             }
 563         }
 564     }
 565
 566     // Go through the crate metadata and load any crates that it references
 567     fn resolve_crate_deps(
 568         &mut self,
 569         root: &CratePaths,
 570         crate_root: &CrateRoot<'_>,
 571         metadata: &MetadataBlob,
 572         krate: CrateNum,
 573         dep_kind: CrateDepKind,
 574     ) -> Result<CrateNumMap, CrateError> {
 575         debug!("resolving deps of external crate");
 576         if crate_root.is_proc_macro_crate() {
 577             return Ok(CrateNumMap::new());
 578         }
 579
 580         // The map from crate numbers in the crate we're resolving to local crate numbers.
 581         // We map 0 and all other holes in the map to our parent crate. The "additional"
 582         // self-dependencies should be harmless.
 583         let deps = crate_root.decode_crate_deps(metadata);
 584         let mut crate_num_map = CrateNumMap::with_capacity(1 + deps.len());
 585         crate_num_map.push(krate);
 586         for dep in deps {
 587             info!(
 588                 "resolving dep crate {} hash: `{}` extra filename: `{}`",
 589                 dep.name, dep.hash, dep.extra_filename
 590             );
 591             let dep_kind = match dep_kind {
 592                 CrateDepKind::MacrosOnly => CrateDepKind::MacrosOnly,
 593                 _ => dep.kind,
 594             };
 595             let cnum = self.maybe_resolve_crate(dep.name, dep_kind, Some((root, &dep)))?;
 596             crate_num_map.push(cnum);
 597         }
 598
 599         debug!("resolve_crate_deps: cnum_map for {:?} is {:?}", krate, crate_num_map);
 600         Ok(crate_num_map)
 601     }
 602
 603     fn dlsym_proc_macros(
 604         &self,
 605         path: &Path,
 606         disambiguator: CrateDisambiguator,
 607     ) -> Result<&'static [ProcMacro], CrateError> {
 608         // Make sure the path contains a / or the linker will search for it.
 609         let path = env::current_dir().unwrap().join(path);
 610         let lib = match DynamicLibrary::open(&path) {
 611             Ok(lib) => lib,
 612             Err(s) => return Err(CrateError::DlOpen(s)),
 613         };
 614
 615         let sym = self.sess.generate_proc_macro_decls_symbol(disambiguator);
 616         let decls = unsafe {
 617             let sym = match lib.symbol(&sym) {
 618                 Ok(f) => f,
 619                 Err(s) => return Err(CrateError::DlSym(s)),
 620             };
 621             *(sym as *const &[ProcMacro])
 622         };
 623
 624         // Intentionally leak the dynamic library. We can't ever unload it
 625         // since the library can make things that will live arbitrarily long.
 626         std::mem::forget(lib);
 627
 628         Ok(decls)
 629     }
 630
 631     fn inject_panic_runtime(&mut self, krate: &ast::Crate) {
 632         // If we're only compiling an rlib, then there's no need to select a
 633         // panic runtime, so we just skip this section entirely.
 634         let any_non_rlib = self.sess.crate_types().iter().any(|ct| *ct != CrateType::Rlib);
 635         if !any_non_rlib {
 636             info!("panic runtime injection skipped, only generating rlib");
 637             return;
 638         }
 639
 640         // If we need a panic runtime, we try to find an existing one here. At
 641         // the same time we perform some general validation of the DAG we've got
 642         // going such as ensuring everything has a compatible panic strategy.
 643         //
 644         // The logic for finding the panic runtime here is pretty much the same
 645         // as the allocator case with the only addition that the panic strategy
 646         // compilation mode also comes into play.
 647         let desired_strategy = self.sess.panic_strategy();
 648         let mut runtime_found = false;
 649         let mut needs_panic_runtime =
 650             self.sess.contains_name(&krate.attrs, sym::needs_panic_runtime);
 651
 652         self.cstore.iter_crate_data(|cnum, data| {
 653             needs_panic_runtime = needs_panic_runtime || data.needs_panic_runtime();
 654             if data.is_panic_runtime() {
 655                 // Inject a dependency from all #![needs_panic_runtime] to this
 656                 // #![panic_runtime] crate.
 657                 self.inject_dependency_if(cnum, "a panic runtime", &|data| {
 658                     data.needs_panic_runtime()
 659                 });
 660                 runtime_found = runtime_found || data.dep_kind() == CrateDepKind::Explicit;
 661             }
 662         });
 663
 664         // If an explicitly linked and matching panic runtime was found, or if
 665         // we just don't need one at all, then we're done here and there's
 666         // nothing else to do.
 667         if !needs_panic_runtime || runtime_found {
 668             return;
 669         }
 670
 671         // By this point we know that we (a) need a panic runtime and (b) no
 672         // panic runtime was explicitly linked. Here we just load an appropriate
 673         // default runtime for our panic strategy and then inject the
 674         // dependencies.
 675         //
 676         // We may resolve to an already loaded crate (as the crate may not have
 677         // been explicitly linked prior to this) and we may re-inject
 678         // dependencies again, but both of those situations are fine.
 679         //
 680         // Also note that we have yet to perform validation of the crate graph
 681         // in terms of everyone has a compatible panic runtime format, that's
 682         // performed later as part of the `dependency_format` module.
 683         let name = match desired_strategy {
 684             PanicStrategy::Unwind => sym::panic_unwind,
 685             PanicStrategy::Abort => sym::panic_abort,
 686         };
 687         info!("panic runtime not found -- loading {}", name);
 688
 689         let cnum = self.resolve_crate(name, DUMMY_SP, CrateDepKind::Implicit, None);
 690         let data = self.cstore.get_crate_data(cnum);
 691
 692         // Sanity check the loaded crate to ensure it is indeed a panic runtime
 693         // and the panic strategy is indeed what we thought it was.
 694         if !data.is_panic_runtime() {
 695             self.sess.err(&format!("the crate `{}` is not a panic runtime", name));
 696         }
 697         if data.panic_strategy() != desired_strategy {
 698             self.sess.err(&format!(
 699                 "the crate `{}` does not have the panic \
 700                                     strategy `{}`",
 701                 name,
 702                 desired_strategy.desc()
 703             ));
 704         }
 705
 706         self.cstore.injected_panic_runtime = Some(cnum);
 707         self.inject_dependency_if(cnum, "a panic runtime", &|data| data.needs_panic_runtime());
 708     }
 709
 710     fn inject_profiler_runtime(&mut self, krate: &ast::Crate) {
 711         if (self.sess.opts.debugging_opts.instrument_coverage
 712             || self.sess.opts.debugging_opts.profile
 713             || self.sess.opts.cg.profile_generate.enabled())
 714             && !self.sess.opts.debugging_opts.no_profiler_runtime
 715         {
 716             info!("loading profiler");
 717
 718             if self.sess.contains_name(&krate.attrs, sym::no_core) {
 719                 self.sess.err(
 720                     "`profiler_builtins` crate (required by compiler options) \
 721                                is not compatible with crate attribute `#![no_core]`",
 722                 );
 723             }
 724
 725             let name = sym::profiler_builtins;
 726             let cnum = self.resolve_crate(name, DUMMY_SP, CrateDepKind::Implicit, None);
 727             let data = self.cstore.get_crate_data(cnum);
 728
 729             // Sanity check the loaded crate to ensure it is indeed a profiler runtime
 730             if !data.is_profiler_runtime() {
 731                 self.sess.err("the crate `profiler_builtins` is not a profiler runtime");
 732             }
 733         }
 734     }
 735
 736     fn inject_allocator_crate(&mut self, krate: &ast::Crate) {
 737         self.cstore.has_global_allocator = match &*global_allocator_spans(&self.sess, krate) {
 738             [span1, span2, ..] => {
 739                 self.sess
 740                     .struct_span_err(*span2, "cannot define multiple global allocators")
 741                     .span_label(*span2, "cannot define a new global allocator")
 742                     .span_label(*span1, "previous global allocator defined here")
 743                     .emit();
 744                 true
 745             }
 746             spans => !spans.is_empty(),
 747         };
 748
 749         // Check to see if we actually need an allocator. This desire comes
 750         // about through the `#![needs_allocator]` attribute and is typically
 751         // written down in liballoc.
 752         let mut needs_allocator = self.sess.contains_name(&krate.attrs, sym::needs_allocator);
 753         self.cstore.iter_crate_data(|_, data| {
 754             needs_allocator = needs_allocator || data.needs_allocator();
 755         });
 756         if !needs_allocator {
 757             return;
 758         }
 759
 760         // At this point we've determined that we need an allocator. Let's see
 761         // if our compilation session actually needs an allocator based on what
 762         // we're emitting.
 763         let all_rlib = self.sess.crate_types().iter().all(|ct| matches!(*ct, CrateType::Rlib));
 764         if all_rlib {
 765             return;
 766         }
 767
 768         // Ok, we need an allocator. Not only that but we're actually going to
 769         // create an artifact that needs one linked in. Let's go find the one
 770         // that we're going to link in.
 771         //
 772         // First up we check for global allocators. Look at the crate graph here
 773         // and see what's a global allocator, including if we ourselves are a
 774         // global allocator.
 775         let mut global_allocator =
 776             self.cstore.has_global_allocator.then(|| Symbol::intern("this crate"));
 777         self.cstore.iter_crate_data(|_, data| {
 778             if !data.has_global_allocator() {
 779                 return;
 780             }
 781             match global_allocator {
 782                 Some(other_crate) => {
 783                     self.sess.err(&format!(
 784                         "the `#[global_allocator]` in {} \
 785                                             conflicts with global \
 786                                             allocator in: {}",
 787                         other_crate,
 788                         data.name()
 789                     ));
 790                 }
 791                 None => global_allocator = Some(data.name()),
 792             }
 793         });
 794         if global_allocator.is_some() {
 795             self.cstore.allocator_kind = Some(AllocatorKind::Global);
 796             return;
 797         }
 798
 799         // Ok we haven't found a global allocator but we still need an
 800         // allocator. At this point our allocator request is typically fulfilled
 801         // by the standard library, denoted by the `#![default_lib_allocator]`
 802         // attribute.
 803         let mut has_default = self.sess.contains_name(&krate.attrs, sym::default_lib_allocator);
 804         self.cstore.iter_crate_data(|_, data| {
 805             if data.has_default_lib_allocator() {
 806                 has_default = true;
 807             }
 808         });
 809
 810         if !has_default {
 811             self.sess.err(
 812                 "no global memory allocator found but one is \
 813                            required; link to std or \
 814                            add `#[global_allocator]` to a static item \
 815                            that implements the GlobalAlloc trait.",
 816             );
 817         }
 818         self.cstore.allocator_kind = Some(AllocatorKind::Default);
 819     }
 820
 821     fn inject_dependency_if(
 822         &self,
 823         krate: CrateNum,
 824         what: &str,
 825         needs_dep: &dyn Fn(&CrateMetadata) -> bool,
 826     ) {
 827         // don't perform this validation if the session has errors, as one of
 828         // those errors may indicate a circular dependency which could cause
 829         // this to stack overflow.
 830         if self.sess.has_errors() {
 831             return;
 832         }
 833
 834         // Before we inject any dependencies, make sure we don't inject a
 835         // circular dependency by validating that this crate doesn't
 836         // transitively depend on any crates satisfying `needs_dep`.
 837         for dep in self.cstore.crate_dependencies_in_reverse_postorder(krate) {
 838             let data = self.cstore.get_crate_data(dep);
 839             if needs_dep(&data) {
 840                 self.sess.err(&format!(
 841                     "the crate `{}` cannot depend \
 842                                         on a crate that needs {}, but \
 843                                         it depends on `{}`",
 844                     self.cstore.get_crate_data(krate).name(),
 845                     what,
 846                     data.name()
 847                 ));
 848             }
 849         }
 850
 851         // All crates satisfying `needs_dep` do not explicitly depend on the
 852         // crate provided for this compile, but in order for this compilation to
 853         // be successfully linked we need to inject a dependency (to order the
 854         // crates on the command line correctly).
 855         self.cstore.iter_crate_data(|cnum, data| {
 856             if !needs_dep(data) {
 857                 return;
 858             }
 859
 860             info!("injecting a dep from {} to {}", cnum, krate);
 861             data.add_dependency(krate);
 862         });
 863     }
 864
 865     fn report_unused_deps(&mut self, krate: &ast::Crate) {
 866         // Make a point span rather than covering the whole file
 867         let span = krate.span.shrink_to_lo();
 868         // Complain about anything left over
 869         for (name, entry) in self.sess.opts.externs.iter() {
 870             if let ExternLocation::FoundInLibrarySearchDirectories = entry.location {
 871                 // Don't worry about pathless `--extern foo` sysroot references
 872                 continue;
 873             }
 874             if !self.used_extern_options.contains(&Symbol::intern(name)) {
 875                 self.sess.parse_sess.buffer_lint(
 876                     lint::builtin::UNUSED_CRATE_DEPENDENCIES,
 877                     span,
 878                     ast::CRATE_NODE_ID,
 879                     &format!(
 880                         "external crate `{}` unused in `{}`: remove the dependency or add `use {} as _;`",
 881                         name,
 882                         self.local_crate_name,
 883                         name),
 884                 );
 885             }
 886         }
 887     }
 888
 889     pub fn postprocess(&mut self, krate: &ast::Crate) {
 890         self.inject_profiler_runtime(krate);
 891         self.inject_allocator_crate(krate);
 892         self.inject_panic_runtime(krate);
 893
 894         info!("{:?}", CrateDump(&self.cstore));
 895
 896         self.report_unused_deps(krate);
 897     }
 898
 899     pub fn process_extern_crate(
 900         &mut self,
 901         item: &ast::Item,
 902         definitions: &Definitions,
 903         def_id: LocalDefId,
 904     ) -> CrateNum {
 905         match item.kind {
 906             ast::ItemKind::ExternCrate(orig_name) => {
 907                 debug!(
 908                     "resolving extern crate stmt. ident: {} orig_name: {:?}",
 909                     item.ident, orig_name
 910                 );
 911                 let name = match orig_name {
 912                     Some(orig_name) => {
 913                         validate_crate_name(self.sess, &orig_name.as_str(), Some(item.span));
 914                         orig_name
 915                     }
 916                     None => item.ident.name,
 917                 };
 918                 let dep_kind = if self.sess.contains_name(&item.attrs, sym::no_link) {
 919                     CrateDepKind::MacrosOnly
 920                 } else {
 921                     CrateDepKind::Explicit
 922                 };
 923
 924                 let cnum = self.resolve_crate(name, item.span, dep_kind, None);
 925
 926                 let path_len = definitions.def_path(def_id).data.len();
 927                 self.update_extern_crate(
 928                     cnum,
 929                     ExternCrate {
 930                         src: ExternCrateSource::Extern(def_id.to_def_id()),
 931                         span: item.span,
 932                         path_len,
 933                         dependency_of: LOCAL_CRATE,
 934                     },
 935                 );
 936                 cnum
 937             }
 938             _ => bug!(),
 939         }
 940     }
 941
 942     pub fn process_path_extern(&mut self, name: Symbol, span: Span) -> CrateNum {
 943         let cnum = self.resolve_crate(name, span, CrateDepKind::Explicit, None);
 944
 945         self.update_extern_crate(
 946             cnum,
 947             ExternCrate {
 948                 src: ExternCrateSource::Path,
 949                 span,
 950                 // to have the least priority in `update_extern_crate`
 951                 path_len: usize::MAX,
 952                 dependency_of: LOCAL_CRATE,
 953             },
 954         );
 955
 956         cnum
 957     }
 958
 959     pub fn maybe_process_path_extern(&mut self, name: Symbol) -> Option<CrateNum> {
 960         self.maybe_resolve_crate(name, CrateDepKind::Explicit, None).ok()
 961     }
 962 }
 963
 964 fn global_allocator_spans(sess: &Session, krate: &ast::Crate) -> Vec<Span> {
 965     struct Finder<'a> {
 966         sess: &'a Session,
 967         name: Symbol,
 968         spans: Vec<Span>,
 969     }
 970     impl<'ast, 'a> visit::Visitor<'ast> for Finder<'a> {
 971         fn visit_item(&mut self, item: &'ast ast::Item) {
 972             if item.ident.name == self.name
 973                 && self.sess.contains_name(&item.attrs, sym::rustc_std_internal_symbol)
 974             {
 975                 self.spans.push(item.span);
 976             }
 977             visit::walk_item(self, item)
 978         }
 979     }
 980
 981     let name = Symbol::intern(&AllocatorKind::Global.fn_name(sym::alloc));
 982     let mut f = Finder { sess, name, spans: Vec::new() };
 983     visit::walk_crate(&mut f, krate);
 984     f.spans
 985 }