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