1//===--- PrecompiledPreamble.cpp - Build precompiled preambles --*- C++ -*-===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8//
9// Helper class to build precompiled preamble.
10//
11//===----------------------------------------------------------------------===//
12
13#include "clang/Frontend/PrecompiledPreamble.h"
14#include "clang/AST/DeclObjC.h"
15#include "clang/Basic/FileManager.h"
16#include "clang/Basic/LangStandard.h"
17#include "clang/Basic/TargetInfo.h"
18#include "clang/Frontend/CompilerInstance.h"
19#include "clang/Frontend/CompilerInvocation.h"
20#include "clang/Frontend/FrontendActions.h"
21#include "clang/Frontend/FrontendOptions.h"
22#include "clang/Lex/HeaderSearch.h"
23#include "clang/Lex/Lexer.h"
24#include "clang/Lex/Preprocessor.h"
25#include "clang/Lex/PreprocessorOptions.h"
26#include "clang/Serialization/ASTWriter.h"
27#include "llvm/ADT/SmallString.h"
28#include "llvm/ADT/StringExtras.h"
29#include "llvm/ADT/StringSet.h"
30#include "llvm/ADT/iterator_range.h"
31#include "llvm/Config/llvm-config.h"
32#include "llvm/Support/CrashRecoveryContext.h"
33#include "llvm/Support/FileSystem.h"
34#include "llvm/Support/Path.h"
35#include "llvm/Support/Process.h"
36#include "llvm/Support/VirtualFileSystem.h"
37#include <limits>
38#include <mutex>
39#include <utility>
40
41using namespace clang;
42
43namespace {
44
45StringRef getInMemoryPreamblePath() {
46#if defined(LLVM_ON_UNIX)
47  return "/__clang_tmp/___clang_inmemory_preamble___";
48#elif defined(_WIN32)
49  return "C:\\__clang_tmp\\___clang_inmemory_preamble___";
50#else
51#warning "Unknown platform. Defaulting to UNIX-style paths for in-memory PCHs"
52  return "/__clang_tmp/___clang_inmemory_preamble___";
53#endif
54}
55
56IntrusiveRefCntPtr<llvm::vfs::FileSystem>
57createVFSOverlayForPreamblePCH(StringRef PCHFilename,
58                               std::unique_ptr<llvm::MemoryBuffer> PCHBuffer,
59                               IntrusiveRefCntPtr<llvm::vfs::FileSystem> VFS) {
60  // We want only the PCH file from the real filesystem to be available,
61  // so we create an in-memory VFS with just that and overlay it on top.
62  IntrusiveRefCntPtr<llvm::vfs::InMemoryFileSystem> PCHFS(
63      new llvm::vfs::InMemoryFileSystem());
64  PCHFS->addFile(PCHFilename, 0, std::move(PCHBuffer));
65  IntrusiveRefCntPtr<llvm::vfs::OverlayFileSystem> Overlay(
66      new llvm::vfs::OverlayFileSystem(VFS));
67  Overlay->pushOverlay(PCHFS);
68  return Overlay;
69}
70
71class PreambleDependencyCollector : public DependencyCollector {
72public:
73  // We want to collect all dependencies for correctness. Avoiding the real
74  // system dependencies (e.g. stl from /usr/lib) would probably be a good idea,
75  // but there is no way to distinguish between those and the ones that can be
76  // spuriously added by '-isystem' (e.g. to suppress warnings from those
77  // headers).
78  bool needSystemDependencies() override { return true; }
79};
80
81// Collects files whose existence would invalidate the preamble.
82// Collecting *all* of these would make validating it too slow though, so we
83// just find all the candidates for 'file not found' diagnostics.
84//
85// A caveat that may be significant for generated files: we'll omit files under
86// search path entries whose roots don't exist when the preamble is built.
87// These are pruned by InitHeaderSearch and so we don't see the search path.
88// It would be nice to include them but we don't want to duplicate all the rest
89// of the InitHeaderSearch logic to reconstruct them.
90class MissingFileCollector : public PPCallbacks {
91  llvm::StringSet<> &Out;
92  const HeaderSearch &Search;
93  const SourceManager &SM;
94
95public:
96  MissingFileCollector(llvm::StringSet<> &Out, const HeaderSearch &Search,
97                       const SourceManager &SM)
98      : Out(Out), Search(Search), SM(SM) {}
99
100  void InclusionDirective(SourceLocation HashLoc, const Token &IncludeTok,
101                          StringRef FileName, bool IsAngled,
102                          CharSourceRange FilenameRange, const FileEntry *File,
103                          StringRef SearchPath, StringRef RelativePath,
104                          const Module *Imported,
105                          SrcMgr::CharacteristicKind FileType) override {
106    // File is null if it wasn't found.
107    // (We have some false negatives if PP recovered e.g. <foo> -> "foo")
108    if (File != nullptr)
109      return;
110
111    // If it's a rare absolute include, we know the full path already.
112    if (llvm::sys::path::is_absolute(FileName)) {
113      Out.insert(FileName);
114      return;
115    }
116
117    // Reconstruct the filenames that would satisfy this directive...
118    llvm::SmallString<256> Buf;
119    auto NotFoundRelativeTo = [&](const DirectoryEntry *DE) {
120      Buf = DE->getName();
121      llvm::sys::path::append(Buf, FileName);
122      llvm::sys::path::remove_dots(Buf, /*remove_dot_dot=*/true);
123      Out.insert(Buf);
124    };
125    // ...relative to the including file.
126    if (!IsAngled) {
127      if (const FileEntry *IncludingFile =
128              SM.getFileEntryForID(SM.getFileID(IncludeTok.getLocation())))
129        if (IncludingFile->getDir())
130          NotFoundRelativeTo(IncludingFile->getDir());
131    }
132    // ...relative to the search paths.
133    for (const auto &Dir : llvm::make_range(
134             IsAngled ? Search.angled_dir_begin() : Search.search_dir_begin(),
135             Search.search_dir_end())) {
136      // No support for frameworks or header maps yet.
137      if (Dir.isNormalDir())
138        NotFoundRelativeTo(Dir.getDir());
139    }
140  }
141};
142
143/// Keeps a track of files to be deleted in destructor.
144class TemporaryFiles {
145public:
146  // A static instance to be used by all clients.
147  static TemporaryFiles &getInstance();
148
149private:
150  // Disallow constructing the class directly.
151  TemporaryFiles() = default;
152  // Disallow copy.
153  TemporaryFiles(const TemporaryFiles &) = delete;
154
155public:
156  ~TemporaryFiles();
157
158  /// Adds \p File to a set of tracked files.
159  void addFile(StringRef File);
160
161  /// Remove \p File from disk and from the set of tracked files.
162  void removeFile(StringRef File);
163
164private:
165  std::mutex Mutex;
166  llvm::StringSet<> Files;
167};
168
169TemporaryFiles &TemporaryFiles::getInstance() {
170  static TemporaryFiles Instance;
171  return Instance;
172}
173
174TemporaryFiles::~TemporaryFiles() {
175  std::lock_guard<std::mutex> Guard(Mutex);
176  for (const auto &File : Files)
177    llvm::sys::fs::remove(File.getKey());
178}
179
180void TemporaryFiles::addFile(StringRef File) {
181  std::lock_guard<std::mutex> Guard(Mutex);
182  auto IsInserted = Files.insert(File).second;
183  (void)IsInserted;
184  assert(IsInserted && "File has already been added");
185}
186
187void TemporaryFiles::removeFile(StringRef File) {
188  std::lock_guard<std::mutex> Guard(Mutex);
189  auto WasPresent = Files.erase(File);
190  (void)WasPresent;
191  assert(WasPresent && "File was not tracked");
192  llvm::sys::fs::remove(File);
193}
194
195class PrecompilePreambleAction : public ASTFrontendAction {
196public:
197  PrecompilePreambleAction(std::string *InMemStorage,
198                           PreambleCallbacks &Callbacks)
199      : InMemStorage(InMemStorage), Callbacks(Callbacks) {}
200
201  std::unique_ptr<ASTConsumer> CreateASTConsumer(CompilerInstance &CI,
202                                                 StringRef InFile) override;
203
204  bool hasEmittedPreamblePCH() const { return HasEmittedPreamblePCH; }
205
206  void setEmittedPreamblePCH(ASTWriter &Writer) {
207    this->HasEmittedPreamblePCH = true;
208    Callbacks.AfterPCHEmitted(Writer);
209  }
210
211  bool BeginSourceFileAction(CompilerInstance &CI) override {
212    assert(CI.getLangOpts().CompilingPCH);
213    return ASTFrontendAction::BeginSourceFileAction(CI);
214  }
215
216  bool shouldEraseOutputFiles() override { return !hasEmittedPreamblePCH(); }
217  bool hasCodeCompletionSupport() const override { return false; }
218  bool hasASTFileSupport() const override { return false; }
219  TranslationUnitKind getTranslationUnitKind() override { return TU_Prefix; }
220
221private:
222  friend class PrecompilePreambleConsumer;
223
224  bool HasEmittedPreamblePCH = false;
225  std::string *InMemStorage;
226  PreambleCallbacks &Callbacks;
227};
228
229class PrecompilePreambleConsumer : public PCHGenerator {
230public:
231  PrecompilePreambleConsumer(PrecompilePreambleAction &Action,
232                             const Preprocessor &PP,
233                             InMemoryModuleCache &ModuleCache,
234                             StringRef isysroot,
235                             std::unique_ptr<raw_ostream> Out)
236      : PCHGenerator(PP, ModuleCache, "", isysroot,
237                     std::make_shared<PCHBuffer>(),
238                     ArrayRef<std::shared_ptr<ModuleFileExtension>>(),
239                     /*AllowASTWithErrors=*/true),
240        Action(Action), Out(std::move(Out)) {}
241
242  bool HandleTopLevelDecl(DeclGroupRef DG) override {
243    Action.Callbacks.HandleTopLevelDecl(DG);
244    return true;
245  }
246
247  void HandleTranslationUnit(ASTContext &Ctx) override {
248    PCHGenerator::HandleTranslationUnit(Ctx);
249    if (!hasEmittedPCH())
250      return;
251
252    // Write the generated bitstream to "Out".
253    *Out << getPCH();
254    // Make sure it hits disk now.
255    Out->flush();
256    // Free the buffer.
257    llvm::SmallVector<char, 0> Empty;
258    getPCH() = std::move(Empty);
259
260    Action.setEmittedPreamblePCH(getWriter());
261  }
262
263  bool shouldSkipFunctionBody(Decl *D) override {
264    return Action.Callbacks.shouldSkipFunctionBody(D);
265  }
266
267private:
268  PrecompilePreambleAction &Action;
269  std::unique_ptr<raw_ostream> Out;
270};
271
272std::unique_ptr<ASTConsumer>
273PrecompilePreambleAction::CreateASTConsumer(CompilerInstance &CI,
274                                            StringRef InFile) {
275  std::string Sysroot;
276  if (!GeneratePCHAction::ComputeASTConsumerArguments(CI, Sysroot))
277    return nullptr;
278
279  std::unique_ptr<llvm::raw_ostream> OS;
280  if (InMemStorage) {
281    OS = std::make_unique<llvm::raw_string_ostream>(*InMemStorage);
282  } else {
283    std::string OutputFile;
284    OS = GeneratePCHAction::CreateOutputFile(CI, InFile, OutputFile);
285  }
286  if (!OS)
287    return nullptr;
288
289  if (!CI.getFrontendOpts().RelocatablePCH)
290    Sysroot.clear();
291
292  return std::make_unique<PrecompilePreambleConsumer>(
293      *this, CI.getPreprocessor(), CI.getModuleCache(), Sysroot, std::move(OS));
294}
295
296template <class T> bool moveOnNoError(llvm::ErrorOr<T> Val, T &Output) {
297  if (!Val)
298    return false;
299  Output = std::move(*Val);
300  return true;
301}
302
303} // namespace
304
305PreambleBounds clang::ComputePreambleBounds(const LangOptions &LangOpts,
306                                            const llvm::MemoryBufferRef &Buffer,
307                                            unsigned MaxLines) {
308  return Lexer::ComputePreamble(Buffer.getBuffer(), LangOpts, MaxLines);
309}
310
311llvm::ErrorOr<PrecompiledPreamble> PrecompiledPreamble::Build(
312    const CompilerInvocation &Invocation,
313    const llvm::MemoryBuffer *MainFileBuffer, PreambleBounds Bounds,
314    DiagnosticsEngine &Diagnostics,
315    IntrusiveRefCntPtr<llvm::vfs::FileSystem> VFS,
316    std::shared_ptr<PCHContainerOperations> PCHContainerOps, bool StoreInMemory,
317    PreambleCallbacks &Callbacks) {
318  assert(VFS && "VFS is null");
319
320  auto PreambleInvocation = std::make_shared<CompilerInvocation>(Invocation);
321  FrontendOptions &FrontendOpts = PreambleInvocation->getFrontendOpts();
322  PreprocessorOptions &PreprocessorOpts =
323      PreambleInvocation->getPreprocessorOpts();
324
325  llvm::Optional<TempPCHFile> TempFile;
326  if (!StoreInMemory) {
327    // Create a temporary file for the precompiled preamble. In rare
328    // circumstances, this can fail.
329    llvm::ErrorOr<PrecompiledPreamble::TempPCHFile> PreamblePCHFile =
330        PrecompiledPreamble::TempPCHFile::CreateNewPreamblePCHFile();
331    if (!PreamblePCHFile)
332      return BuildPreambleError::CouldntCreateTempFile;
333    TempFile = std::move(*PreamblePCHFile);
334  }
335
336  PCHStorage Storage = StoreInMemory ? PCHStorage(InMemoryPreamble())
337                                     : PCHStorage(std::move(*TempFile));
338
339  // Save the preamble text for later; we'll need to compare against it for
340  // subsequent reparses.
341  std::vector<char> PreambleBytes(MainFileBuffer->getBufferStart(),
342                                  MainFileBuffer->getBufferStart() +
343                                      Bounds.Size);
344  bool PreambleEndsAtStartOfLine = Bounds.PreambleEndsAtStartOfLine;
345
346  // Tell the compiler invocation to generate a temporary precompiled header.
347  FrontendOpts.ProgramAction = frontend::GeneratePCH;
348  FrontendOpts.OutputFile =
349      std::string(StoreInMemory ? getInMemoryPreamblePath()
350                                : Storage.asFile().getFilePath());
351  PreprocessorOpts.PrecompiledPreambleBytes.first = 0;
352  PreprocessorOpts.PrecompiledPreambleBytes.second = false;
353  // Inform preprocessor to record conditional stack when building the preamble.
354  PreprocessorOpts.GeneratePreamble = true;
355
356  // Create the compiler instance to use for building the precompiled preamble.
357  std::unique_ptr<CompilerInstance> Clang(
358      new CompilerInstance(std::move(PCHContainerOps)));
359
360  // Recover resources if we crash before exiting this method.
361  llvm::CrashRecoveryContextCleanupRegistrar<CompilerInstance> CICleanup(
362      Clang.get());
363
364  Clang->setInvocation(std::move(PreambleInvocation));
365  Clang->setDiagnostics(&Diagnostics);
366
367  // Create the target instance.
368  if (!Clang->createTarget())
369    return BuildPreambleError::CouldntCreateTargetInfo;
370
371  if (Clang->getFrontendOpts().Inputs.size() != 1 ||
372      Clang->getFrontendOpts().Inputs[0].getKind().getFormat() !=
373          InputKind::Source ||
374      Clang->getFrontendOpts().Inputs[0].getKind().getLanguage() ==
375          Language::LLVM_IR) {
376    return BuildPreambleError::BadInputs;
377  }
378
379  // Clear out old caches and data.
380  Diagnostics.Reset();
381  ProcessWarningOptions(Diagnostics, Clang->getDiagnosticOpts());
382
383  VFS =
384      createVFSFromCompilerInvocation(Clang->getInvocation(), Diagnostics, VFS);
385
386  // Create a file manager object to provide access to and cache the filesystem.
387  Clang->setFileManager(new FileManager(Clang->getFileSystemOpts(), VFS));
388
389  // Create the source manager.
390  Clang->setSourceManager(
391      new SourceManager(Diagnostics, Clang->getFileManager()));
392
393  auto PreambleDepCollector = std::make_shared<PreambleDependencyCollector>();
394  Clang->addDependencyCollector(PreambleDepCollector);
395
396  Clang->getLangOpts().CompilingPCH = true;
397
398  // Remap the main source file to the preamble buffer.
399  StringRef MainFilePath = FrontendOpts.Inputs[0].getFile();
400  auto PreambleInputBuffer = llvm::MemoryBuffer::getMemBufferCopy(
401      MainFileBuffer->getBuffer().slice(0, Bounds.Size), MainFilePath);
402  if (PreprocessorOpts.RetainRemappedFileBuffers) {
403    // MainFileBuffer will be deleted by unique_ptr after leaving the method.
404    PreprocessorOpts.addRemappedFile(MainFilePath, PreambleInputBuffer.get());
405  } else {
406    // In that case, remapped buffer will be deleted by CompilerInstance on
407    // BeginSourceFile, so we call release() to avoid double deletion.
408    PreprocessorOpts.addRemappedFile(MainFilePath,
409                                     PreambleInputBuffer.release());
410  }
411
412  std::unique_ptr<PrecompilePreambleAction> Act;
413  Act.reset(new PrecompilePreambleAction(
414      StoreInMemory ? &Storage.asMemory().Data : nullptr, Callbacks));
415  Callbacks.BeforeExecute(*Clang);
416  if (!Act->BeginSourceFile(*Clang.get(), Clang->getFrontendOpts().Inputs[0]))
417    return BuildPreambleError::BeginSourceFileFailed;
418
419  std::unique_ptr<PPCallbacks> DelegatedPPCallbacks =
420      Callbacks.createPPCallbacks();
421  if (DelegatedPPCallbacks)
422    Clang->getPreprocessor().addPPCallbacks(std::move(DelegatedPPCallbacks));
423  if (auto CommentHandler = Callbacks.getCommentHandler())
424    Clang->getPreprocessor().addCommentHandler(CommentHandler);
425  llvm::StringSet<> MissingFiles;
426  Clang->getPreprocessor().addPPCallbacks(
427      std::make_unique<MissingFileCollector>(
428          MissingFiles, Clang->getPreprocessor().getHeaderSearchInfo(),
429          Clang->getSourceManager()));
430
431  if (llvm::Error Err = Act->Execute())
432    return errorToErrorCode(std::move(Err));
433
434  // Run the callbacks.
435  Callbacks.AfterExecute(*Clang);
436
437  Act->EndSourceFile();
438
439  if (!Act->hasEmittedPreamblePCH())
440    return BuildPreambleError::CouldntEmitPCH;
441
442  // Keep track of all of the files that the source manager knows about,
443  // so we can verify whether they have changed or not.
444  llvm::StringMap<PrecompiledPreamble::PreambleFileHash> FilesInPreamble;
445
446  SourceManager &SourceMgr = Clang->getSourceManager();
447  for (auto &Filename : PreambleDepCollector->getDependencies()) {
448    auto FileOrErr = Clang->getFileManager().getFile(Filename);
449    if (!FileOrErr ||
450        *FileOrErr == SourceMgr.getFileEntryForID(SourceMgr.getMainFileID()))
451      continue;
452    auto File = *FileOrErr;
453    if (time_t ModTime = File->getModificationTime()) {
454      FilesInPreamble[File->getName()] =
455          PrecompiledPreamble::PreambleFileHash::createForFile(File->getSize(),
456                                                               ModTime);
457    } else {
458      llvm::MemoryBufferRef Buffer =
459          SourceMgr.getMemoryBufferForFileOrFake(File);
460      FilesInPreamble[File->getName()] =
461          PrecompiledPreamble::PreambleFileHash::createForMemoryBuffer(Buffer);
462    }
463  }
464
465  return PrecompiledPreamble(
466      std::move(Storage), std::move(PreambleBytes), PreambleEndsAtStartOfLine,
467      std::move(FilesInPreamble), std::move(MissingFiles));
468}
469
470PreambleBounds PrecompiledPreamble::getBounds() const {
471  return PreambleBounds(PreambleBytes.size(), PreambleEndsAtStartOfLine);
472}
473
474std::size_t PrecompiledPreamble::getSize() const {
475  switch (Storage.getKind()) {
476  case PCHStorage::Kind::Empty:
477    assert(false && "Calling getSize() on invalid PrecompiledPreamble. "
478                    "Was it std::moved?");
479    return 0;
480  case PCHStorage::Kind::InMemory:
481    return Storage.asMemory().Data.size();
482  case PCHStorage::Kind::TempFile: {
483    uint64_t Result;
484    if (llvm::sys::fs::file_size(Storage.asFile().getFilePath(), Result))
485      return 0;
486
487    assert(Result <= std::numeric_limits<std::size_t>::max() &&
488           "file size did not fit into size_t");
489    return Result;
490  }
491  }
492  llvm_unreachable("Unhandled storage kind");
493}
494
495bool PrecompiledPreamble::CanReuse(const CompilerInvocation &Invocation,
496                                   const llvm::MemoryBufferRef &MainFileBuffer,
497                                   PreambleBounds Bounds,
498                                   llvm::vfs::FileSystem &VFS) const {
499
500  assert(
501      Bounds.Size <= MainFileBuffer.getBufferSize() &&
502      "Buffer is too large. Bounds were calculated from a different buffer?");
503
504  auto PreambleInvocation = std::make_shared<CompilerInvocation>(Invocation);
505  PreprocessorOptions &PreprocessorOpts =
506      PreambleInvocation->getPreprocessorOpts();
507
508  // We've previously computed a preamble. Check whether we have the same
509  // preamble now that we did before, and that there's enough space in
510  // the main-file buffer within the precompiled preamble to fit the
511  // new main file.
512  if (PreambleBytes.size() != Bounds.Size ||
513      PreambleEndsAtStartOfLine != Bounds.PreambleEndsAtStartOfLine ||
514      !std::equal(PreambleBytes.begin(), PreambleBytes.end(),
515                  MainFileBuffer.getBuffer().begin()))
516    return false;
517  // The preamble has not changed. We may be able to re-use the precompiled
518  // preamble.
519
520  // Check that none of the files used by the preamble have changed.
521  // First, make a record of those files that have been overridden via
522  // remapping or unsaved_files.
523  std::map<llvm::sys::fs::UniqueID, PreambleFileHash> OverriddenFiles;
524  llvm::StringSet<> OverriddenAbsPaths; // Either by buffers or files.
525  for (const auto &R : PreprocessorOpts.RemappedFiles) {
526    llvm::vfs::Status Status;
527    if (!moveOnNoError(VFS.status(R.second), Status)) {
528      // If we can't stat the file we're remapping to, assume that something
529      // horrible happened.
530      return false;
531    }
532    // If a mapped file was previously missing, then it has changed.
533    llvm::SmallString<128> MappedPath(R.first);
534    if (!VFS.makeAbsolute(MappedPath))
535      OverriddenAbsPaths.insert(MappedPath);
536
537    OverriddenFiles[Status.getUniqueID()] = PreambleFileHash::createForFile(
538        Status.getSize(), llvm::sys::toTimeT(Status.getLastModificationTime()));
539  }
540
541  // OverridenFileBuffers tracks only the files not found in VFS.
542  llvm::StringMap<PreambleFileHash> OverridenFileBuffers;
543  for (const auto &RB : PreprocessorOpts.RemappedFileBuffers) {
544    const PrecompiledPreamble::PreambleFileHash PreambleHash =
545        PreambleFileHash::createForMemoryBuffer(RB.second->getMemBufferRef());
546    llvm::vfs::Status Status;
547    if (moveOnNoError(VFS.status(RB.first), Status))
548      OverriddenFiles[Status.getUniqueID()] = PreambleHash;
549    else
550      OverridenFileBuffers[RB.first] = PreambleHash;
551
552    llvm::SmallString<128> MappedPath(RB.first);
553    if (!VFS.makeAbsolute(MappedPath))
554      OverriddenAbsPaths.insert(MappedPath);
555  }
556
557  // Check whether anything has changed.
558  for (const auto &F : FilesInPreamble) {
559    auto OverridenFileBuffer = OverridenFileBuffers.find(F.first());
560    if (OverridenFileBuffer != OverridenFileBuffers.end()) {
561      // The file's buffer was remapped and the file was not found in VFS.
562      // Check whether it matches up with the previous mapping.
563      if (OverridenFileBuffer->second != F.second)
564        return false;
565      continue;
566    }
567
568    llvm::vfs::Status Status;
569    if (!moveOnNoError(VFS.status(F.first()), Status)) {
570      // If the file's buffer is not remapped and we can't stat it,
571      // assume that something horrible happened.
572      return false;
573    }
574
575    std::map<llvm::sys::fs::UniqueID, PreambleFileHash>::iterator Overridden =
576        OverriddenFiles.find(Status.getUniqueID());
577    if (Overridden != OverriddenFiles.end()) {
578      // This file was remapped; check whether the newly-mapped file
579      // matches up with the previous mapping.
580      if (Overridden->second != F.second)
581        return false;
582      continue;
583    }
584
585    // Neither the file's buffer nor the file itself was remapped;
586    // check whether it has changed on disk.
587    if (Status.getSize() != uint64_t(F.second.Size) ||
588        llvm::sys::toTimeT(Status.getLastModificationTime()) !=
589            F.second.ModTime)
590      return false;
591  }
592  for (const auto &F : MissingFiles) {
593    // A missing file may be "provided" by an override buffer or file.
594    if (OverriddenAbsPaths.count(F.getKey()))
595      return false;
596    // If a file previously recorded as missing exists as a regular file, then
597    // consider the preamble out-of-date.
598    if (auto Status = VFS.status(F.getKey())) {
599      if (Status->isRegularFile())
600        return false;
601    }
602  }
603  return true;
604}
605
606void PrecompiledPreamble::AddImplicitPreamble(
607    CompilerInvocation &CI, IntrusiveRefCntPtr<llvm::vfs::FileSystem> &VFS,
608    llvm::MemoryBuffer *MainFileBuffer) const {
609  PreambleBounds Bounds(PreambleBytes.size(), PreambleEndsAtStartOfLine);
610  configurePreamble(Bounds, CI, VFS, MainFileBuffer);
611}
612
613void PrecompiledPreamble::OverridePreamble(
614    CompilerInvocation &CI, IntrusiveRefCntPtr<llvm::vfs::FileSystem> &VFS,
615    llvm::MemoryBuffer *MainFileBuffer) const {
616  auto Bounds = ComputePreambleBounds(*CI.getLangOpts(), *MainFileBuffer, 0);
617  configurePreamble(Bounds, CI, VFS, MainFileBuffer);
618}
619
620PrecompiledPreamble::PrecompiledPreamble(
621    PCHStorage Storage, std::vector<char> PreambleBytes,
622    bool PreambleEndsAtStartOfLine,
623    llvm::StringMap<PreambleFileHash> FilesInPreamble,
624    llvm::StringSet<> MissingFiles)
625    : Storage(std::move(Storage)), FilesInPreamble(std::move(FilesInPreamble)),
626      MissingFiles(std::move(MissingFiles)),
627      PreambleBytes(std::move(PreambleBytes)),
628      PreambleEndsAtStartOfLine(PreambleEndsAtStartOfLine) {
629  assert(this->Storage.getKind() != PCHStorage::Kind::Empty);
630}
631
632llvm::ErrorOr<PrecompiledPreamble::TempPCHFile>
633PrecompiledPreamble::TempPCHFile::CreateNewPreamblePCHFile() {
634  // FIXME: This is a hack so that we can override the preamble file during
635  // crash-recovery testing, which is the only case where the preamble files
636  // are not necessarily cleaned up.
637  if (const char *TmpFile = ::getenv("CINDEXTEST_PREAMBLE_FILE"))
638    return TempPCHFile(TmpFile);
639
640  llvm::SmallString<64> File;
641  // Using a version of createTemporaryFile with a file descriptor guarantees
642  // that we would never get a race condition in a multi-threaded setting
643  // (i.e., multiple threads getting the same temporary path).
644  int FD;
645  auto EC = llvm::sys::fs::createTemporaryFile("preamble", "pch", FD, File);
646  if (EC)
647    return EC;
648  // We only needed to make sure the file exists, close the file right away.
649  llvm::sys::Process::SafelyCloseFileDescriptor(FD);
650  return TempPCHFile(std::string(std::move(File).str()));
651}
652
653PrecompiledPreamble::TempPCHFile::TempPCHFile(std::string FilePath)
654    : FilePath(std::move(FilePath)) {
655  TemporaryFiles::getInstance().addFile(*this->FilePath);
656}
657
658PrecompiledPreamble::TempPCHFile::TempPCHFile(TempPCHFile &&Other) {
659  FilePath = std::move(Other.FilePath);
660  Other.FilePath = None;
661}
662
663PrecompiledPreamble::TempPCHFile &PrecompiledPreamble::TempPCHFile::
664operator=(TempPCHFile &&Other) {
665  RemoveFileIfPresent();
666
667  FilePath = std::move(Other.FilePath);
668  Other.FilePath = None;
669  return *this;
670}
671
672PrecompiledPreamble::TempPCHFile::~TempPCHFile() { RemoveFileIfPresent(); }
673
674void PrecompiledPreamble::TempPCHFile::RemoveFileIfPresent() {
675  if (FilePath) {
676    TemporaryFiles::getInstance().removeFile(*FilePath);
677    FilePath = None;
678  }
679}
680
681llvm::StringRef PrecompiledPreamble::TempPCHFile::getFilePath() const {
682  assert(FilePath && "TempPCHFile doesn't have a FilePath. Had it been moved?");
683  return *FilePath;
684}
685
686PrecompiledPreamble::PCHStorage::PCHStorage(TempPCHFile File)
687    : StorageKind(Kind::TempFile) {
688  new (&asFile()) TempPCHFile(std::move(File));
689}
690
691PrecompiledPreamble::PCHStorage::PCHStorage(InMemoryPreamble Memory)
692    : StorageKind(Kind::InMemory) {
693  new (&asMemory()) InMemoryPreamble(std::move(Memory));
694}
695
696PrecompiledPreamble::PCHStorage::PCHStorage(PCHStorage &&Other) : PCHStorage() {
697  *this = std::move(Other);
698}
699
700PrecompiledPreamble::PCHStorage &PrecompiledPreamble::PCHStorage::
701operator=(PCHStorage &&Other) {
702  destroy();
703
704  StorageKind = Other.StorageKind;
705  switch (StorageKind) {
706  case Kind::Empty:
707    // do nothing;
708    break;
709  case Kind::TempFile:
710    new (&asFile()) TempPCHFile(std::move(Other.asFile()));
711    break;
712  case Kind::InMemory:
713    new (&asMemory()) InMemoryPreamble(std::move(Other.asMemory()));
714    break;
715  }
716
717  Other.setEmpty();
718  return *this;
719}
720
721PrecompiledPreamble::PCHStorage::~PCHStorage() { destroy(); }
722
723PrecompiledPreamble::PCHStorage::Kind
724PrecompiledPreamble::PCHStorage::getKind() const {
725  return StorageKind;
726}
727
728PrecompiledPreamble::TempPCHFile &PrecompiledPreamble::PCHStorage::asFile() {
729  assert(getKind() == Kind::TempFile);
730  return *reinterpret_cast<TempPCHFile *>(&Storage);
731}
732
733const PrecompiledPreamble::TempPCHFile &
734PrecompiledPreamble::PCHStorage::asFile() const {
735  return const_cast<PCHStorage *>(this)->asFile();
736}
737
738PrecompiledPreamble::InMemoryPreamble &
739PrecompiledPreamble::PCHStorage::asMemory() {
740  assert(getKind() == Kind::InMemory);
741  return *reinterpret_cast<InMemoryPreamble *>(&Storage);
742}
743
744const PrecompiledPreamble::InMemoryPreamble &
745PrecompiledPreamble::PCHStorage::asMemory() const {
746  return const_cast<PCHStorage *>(this)->asMemory();
747}
748
749void PrecompiledPreamble::PCHStorage::destroy() {
750  switch (StorageKind) {
751  case Kind::Empty:
752    return;
753  case Kind::TempFile:
754    asFile().~TempPCHFile();
755    return;
756  case Kind::InMemory:
757    asMemory().~InMemoryPreamble();
758    return;
759  }
760}
761
762void PrecompiledPreamble::PCHStorage::setEmpty() {
763  destroy();
764  StorageKind = Kind::Empty;
765}
766
767PrecompiledPreamble::PreambleFileHash
768PrecompiledPreamble::PreambleFileHash::createForFile(off_t Size,
769                                                     time_t ModTime) {
770  PreambleFileHash Result;
771  Result.Size = Size;
772  Result.ModTime = ModTime;
773  Result.MD5 = {};
774  return Result;
775}
776
777PrecompiledPreamble::PreambleFileHash
778PrecompiledPreamble::PreambleFileHash::createForMemoryBuffer(
779    const llvm::MemoryBufferRef &Buffer) {
780  PreambleFileHash Result;
781  Result.Size = Buffer.getBufferSize();
782  Result.ModTime = 0;
783
784  llvm::MD5 MD5Ctx;
785  MD5Ctx.update(Buffer.getBuffer().data());
786  MD5Ctx.final(Result.MD5);
787
788  return Result;
789}
790
791void PrecompiledPreamble::configurePreamble(
792    PreambleBounds Bounds, CompilerInvocation &CI,
793    IntrusiveRefCntPtr<llvm::vfs::FileSystem> &VFS,
794    llvm::MemoryBuffer *MainFileBuffer) const {
795  assert(VFS);
796
797  auto &PreprocessorOpts = CI.getPreprocessorOpts();
798
799  // Remap main file to point to MainFileBuffer.
800  auto MainFilePath = CI.getFrontendOpts().Inputs[0].getFile();
801  PreprocessorOpts.addRemappedFile(MainFilePath, MainFileBuffer);
802
803  // Configure ImpicitPCHInclude.
804  PreprocessorOpts.PrecompiledPreambleBytes.first = Bounds.Size;
805  PreprocessorOpts.PrecompiledPreambleBytes.second =
806      Bounds.PreambleEndsAtStartOfLine;
807  PreprocessorOpts.DisablePCHOrModuleValidation =
808      DisableValidationForModuleKind::PCH;
809
810  setupPreambleStorage(Storage, PreprocessorOpts, VFS);
811}
812
813void PrecompiledPreamble::setupPreambleStorage(
814    const PCHStorage &Storage, PreprocessorOptions &PreprocessorOpts,
815    IntrusiveRefCntPtr<llvm::vfs::FileSystem> &VFS) {
816  if (Storage.getKind() == PCHStorage::Kind::TempFile) {
817    const TempPCHFile &PCHFile = Storage.asFile();
818    PreprocessorOpts.ImplicitPCHInclude = std::string(PCHFile.getFilePath());
819
820    // Make sure we can access the PCH file even if we're using a VFS
821    IntrusiveRefCntPtr<llvm::vfs::FileSystem> RealFS =
822        llvm::vfs::getRealFileSystem();
823    auto PCHPath = PCHFile.getFilePath();
824    if (VFS == RealFS || VFS->exists(PCHPath))
825      return;
826    auto Buf = RealFS->getBufferForFile(PCHPath);
827    if (!Buf) {
828      // We can't read the file even from RealFS, this is clearly an error,
829      // but we'll just leave the current VFS as is and let clang's code
830      // figure out what to do with missing PCH.
831      return;
832    }
833
834    // We have a slight inconsistency here -- we're using the VFS to
835    // read files, but the PCH was generated in the real file system.
836    VFS = createVFSOverlayForPreamblePCH(PCHPath, std::move(*Buf), VFS);
837  } else {
838    assert(Storage.getKind() == PCHStorage::Kind::InMemory);
839    // For in-memory preamble, we have to provide a VFS overlay that makes it
840    // accessible.
841    StringRef PCHPath = getInMemoryPreamblePath();
842    PreprocessorOpts.ImplicitPCHInclude = std::string(PCHPath);
843
844    auto Buf = llvm::MemoryBuffer::getMemBuffer(Storage.asMemory().Data);
845    VFS = createVFSOverlayForPreamblePCH(PCHPath, std::move(Buf), VFS);
846  }
847}
848
849void PreambleCallbacks::BeforeExecute(CompilerInstance &CI) {}
850void PreambleCallbacks::AfterExecute(CompilerInstance &CI) {}
851void PreambleCallbacks::AfterPCHEmitted(ASTWriter &Writer) {}
852void PreambleCallbacks::HandleTopLevelDecl(DeclGroupRef DG) {}
853std::unique_ptr<PPCallbacks> PreambleCallbacks::createPPCallbacks() {
854  return nullptr;
855}
856CommentHandler *PreambleCallbacks::getCommentHandler() { return nullptr; }
857
858static llvm::ManagedStatic<BuildPreambleErrorCategory> BuildPreambleErrCategory;
859
860std::error_code clang::make_error_code(BuildPreambleError Error) {
861  return std::error_code(static_cast<int>(Error), *BuildPreambleErrCategory);
862}
863
864const char *BuildPreambleErrorCategory::name() const noexcept {
865  return "build-preamble.error";
866}
867
868std::string BuildPreambleErrorCategory::message(int condition) const {
869  switch (static_cast<BuildPreambleError>(condition)) {
870  case BuildPreambleError::CouldntCreateTempFile:
871    return "Could not create temporary file for PCH";
872  case BuildPreambleError::CouldntCreateTargetInfo:
873    return "CreateTargetInfo() return null";
874  case BuildPreambleError::BeginSourceFileFailed:
875    return "BeginSourceFile() return an error";
876  case BuildPreambleError::CouldntEmitPCH:
877    return "Could not emit PCH";
878  case BuildPreambleError::BadInputs:
879    return "Command line arguments must contain exactly one source file";
880  }
881  llvm_unreachable("unexpected BuildPreambleError");
882}
883