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