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/LangStandard.h"
16 #include "clang/Basic/TargetInfo.h"
17 #include "clang/Frontend/CompilerInstance.h"
18 #include "clang/Frontend/CompilerInvocation.h"
19 #include "clang/Frontend/FrontendActions.h"
20 #include "clang/Frontend/FrontendOptions.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/StringExtras.h"
26 #include "llvm/ADT/StringSet.h"
27 #include "llvm/Config/llvm-config.h"
28 #include "llvm/Support/CrashRecoveryContext.h"
29 #include "llvm/Support/FileSystem.h"
30 #include "llvm/Support/Process.h"
31 #include "llvm/Support/VirtualFileSystem.h"
32 #include <limits>
33 #include <mutex>
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   std::mutex Mutex;
99   llvm::StringSet<> Files;
100 };
101 
102 TemporaryFiles &TemporaryFiles::getInstance() {
103   static TemporaryFiles Instance;
104   return Instance;
105 }
106 
107 TemporaryFiles::~TemporaryFiles() {
108   std::lock_guard<std::mutex> Guard(Mutex);
109   for (const auto &File : Files)
110     llvm::sys::fs::remove(File.getKey());
111 }
112 
113 void TemporaryFiles::addFile(StringRef File) {
114   std::lock_guard<std::mutex> 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   std::lock_guard<std::mutex> 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 = std::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 std::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   if (Clang->getFrontendOpts().Inputs.size() != 1 ||
303       Clang->getFrontendOpts().Inputs[0].getKind().getFormat() !=
304           InputKind::Source ||
305       Clang->getFrontendOpts().Inputs[0].getKind().getLanguage() ==
306           Language::LLVM_IR) {
307     return BuildPreambleError::BadInputs;
308   }
309 
310   // Clear out old caches and data.
311   Diagnostics.Reset();
312   ProcessWarningOptions(Diagnostics, Clang->getDiagnosticOpts());
313 
314   VFS =
315       createVFSFromCompilerInvocation(Clang->getInvocation(), Diagnostics, VFS);
316 
317   // Create a file manager object to provide access to and cache the filesystem.
318   Clang->setFileManager(new FileManager(Clang->getFileSystemOpts(), VFS));
319 
320   // Create the source manager.
321   Clang->setSourceManager(
322       new SourceManager(Diagnostics, Clang->getFileManager()));
323 
324   auto PreambleDepCollector = std::make_shared<PreambleDependencyCollector>();
325   Clang->addDependencyCollector(PreambleDepCollector);
326 
327   // Remap the main source file to the preamble buffer.
328   StringRef MainFilePath = FrontendOpts.Inputs[0].getFile();
329   auto PreambleInputBuffer = llvm::MemoryBuffer::getMemBufferCopy(
330       MainFileBuffer->getBuffer().slice(0, Bounds.Size), MainFilePath);
331   if (PreprocessorOpts.RetainRemappedFileBuffers) {
332     // MainFileBuffer will be deleted by unique_ptr after leaving the method.
333     PreprocessorOpts.addRemappedFile(MainFilePath, PreambleInputBuffer.get());
334   } else {
335     // In that case, remapped buffer will be deleted by CompilerInstance on
336     // BeginSourceFile, so we call release() to avoid double deletion.
337     PreprocessorOpts.addRemappedFile(MainFilePath,
338                                      PreambleInputBuffer.release());
339   }
340 
341   std::unique_ptr<PrecompilePreambleAction> Act;
342   Act.reset(new PrecompilePreambleAction(
343       StoreInMemory ? &Storage.asMemory().Data : nullptr, Callbacks));
344   Callbacks.BeforeExecute(*Clang);
345   if (!Act->BeginSourceFile(*Clang.get(), Clang->getFrontendOpts().Inputs[0]))
346     return BuildPreambleError::BeginSourceFileFailed;
347 
348   std::unique_ptr<PPCallbacks> DelegatedPPCallbacks =
349       Callbacks.createPPCallbacks();
350   if (DelegatedPPCallbacks)
351     Clang->getPreprocessor().addPPCallbacks(std::move(DelegatedPPCallbacks));
352   if (auto CommentHandler = Callbacks.getCommentHandler())
353     Clang->getPreprocessor().addCommentHandler(CommentHandler);
354 
355   if (llvm::Error Err = Act->Execute())
356     return errorToErrorCode(std::move(Err));
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     auto FileOrErr = Clang->getFileManager().getFile(Filename);
373     if (!FileOrErr ||
374         *FileOrErr == SourceMgr.getFileEntryForID(SourceMgr.getMainFileID()))
375       continue;
376     auto File = *FileOrErr;
377     if (time_t ModTime = File->getModificationTime()) {
378       FilesInPreamble[File->getName()] =
379           PrecompiledPreamble::PreambleFileHash::createForFile(File->getSize(),
380                                                                ModTime);
381     } else {
382       const llvm::MemoryBuffer *Buffer = SourceMgr.getMemoryBufferForFile(File);
383       FilesInPreamble[File->getName()] =
384           PrecompiledPreamble::PreambleFileHash::createForMemoryBuffer(Buffer);
385     }
386   }
387 
388   return PrecompiledPreamble(std::move(Storage), std::move(PreambleBytes),
389                              PreambleEndsAtStartOfLine,
390                              std::move(FilesInPreamble));
391 }
392 
393 PreambleBounds PrecompiledPreamble::getBounds() const {
394   return PreambleBounds(PreambleBytes.size(), PreambleEndsAtStartOfLine);
395 }
396 
397 std::size_t PrecompiledPreamble::getSize() const {
398   switch (Storage.getKind()) {
399   case PCHStorage::Kind::Empty:
400     assert(false && "Calling getSize() on invalid PrecompiledPreamble. "
401                     "Was it std::moved?");
402     return 0;
403   case PCHStorage::Kind::InMemory:
404     return Storage.asMemory().Data.size();
405   case PCHStorage::Kind::TempFile: {
406     uint64_t Result;
407     if (llvm::sys::fs::file_size(Storage.asFile().getFilePath(), Result))
408       return 0;
409 
410     assert(Result <= std::numeric_limits<std::size_t>::max() &&
411            "file size did not fit into size_t");
412     return Result;
413   }
414   }
415   llvm_unreachable("Unhandled storage kind");
416 }
417 
418 bool PrecompiledPreamble::CanReuse(const CompilerInvocation &Invocation,
419                                    const llvm::MemoryBuffer *MainFileBuffer,
420                                    PreambleBounds Bounds,
421                                    llvm::vfs::FileSystem *VFS) const {
422 
423   assert(
424       Bounds.Size <= MainFileBuffer->getBufferSize() &&
425       "Buffer is too large. Bounds were calculated from a different buffer?");
426 
427   auto PreambleInvocation = std::make_shared<CompilerInvocation>(Invocation);
428   PreprocessorOptions &PreprocessorOpts =
429       PreambleInvocation->getPreprocessorOpts();
430 
431   // We've previously computed a preamble. Check whether we have the same
432   // preamble now that we did before, and that there's enough space in
433   // the main-file buffer within the precompiled preamble to fit the
434   // new main file.
435   if (PreambleBytes.size() != Bounds.Size ||
436       PreambleEndsAtStartOfLine != Bounds.PreambleEndsAtStartOfLine ||
437       !std::equal(PreambleBytes.begin(), PreambleBytes.end(),
438                   MainFileBuffer->getBuffer().begin()))
439     return false;
440   // The preamble has not changed. We may be able to re-use the precompiled
441   // preamble.
442 
443   // Check that none of the files used by the preamble have changed.
444   // First, make a record of those files that have been overridden via
445   // remapping or unsaved_files.
446   std::map<llvm::sys::fs::UniqueID, PreambleFileHash> OverriddenFiles;
447   for (const auto &R : PreprocessorOpts.RemappedFiles) {
448     llvm::vfs::Status Status;
449     if (!moveOnNoError(VFS->status(R.second), Status)) {
450       // If we can't stat the file we're remapping to, assume that something
451       // horrible happened.
452       return false;
453     }
454 
455     OverriddenFiles[Status.getUniqueID()] = PreambleFileHash::createForFile(
456         Status.getSize(), llvm::sys::toTimeT(Status.getLastModificationTime()));
457   }
458 
459   // OverridenFileBuffers tracks only the files not found in VFS.
460   llvm::StringMap<PreambleFileHash> OverridenFileBuffers;
461   for (const auto &RB : PreprocessorOpts.RemappedFileBuffers) {
462     const PrecompiledPreamble::PreambleFileHash PreambleHash =
463         PreambleFileHash::createForMemoryBuffer(RB.second);
464     llvm::vfs::Status Status;
465     if (moveOnNoError(VFS->status(RB.first), Status))
466       OverriddenFiles[Status.getUniqueID()] = PreambleHash;
467     else
468       OverridenFileBuffers[RB.first] = PreambleHash;
469   }
470 
471   // Check whether anything has changed.
472   for (const auto &F : FilesInPreamble) {
473     auto OverridenFileBuffer = OverridenFileBuffers.find(F.first());
474     if (OverridenFileBuffer != OverridenFileBuffers.end()) {
475       // The file's buffer was remapped and the file was not found in VFS.
476       // Check whether it matches up with the previous mapping.
477       if (OverridenFileBuffer->second != F.second)
478         return false;
479       continue;
480     }
481 
482     llvm::vfs::Status Status;
483     if (!moveOnNoError(VFS->status(F.first()), Status)) {
484       // If the file's buffer is not remapped and we can't stat it,
485       // assume that something horrible happened.
486       return false;
487     }
488 
489     std::map<llvm::sys::fs::UniqueID, PreambleFileHash>::iterator Overridden =
490         OverriddenFiles.find(Status.getUniqueID());
491     if (Overridden != OverriddenFiles.end()) {
492       // This file was remapped; check whether the newly-mapped file
493       // matches up with the previous mapping.
494       if (Overridden->second != F.second)
495         return false;
496       continue;
497     }
498 
499     // Neither the file's buffer nor the file itself was remapped;
500     // check whether it has changed on disk.
501     if (Status.getSize() != uint64_t(F.second.Size) ||
502         llvm::sys::toTimeT(Status.getLastModificationTime()) !=
503             F.second.ModTime)
504       return false;
505   }
506   return true;
507 }
508 
509 void PrecompiledPreamble::AddImplicitPreamble(
510     CompilerInvocation &CI, IntrusiveRefCntPtr<llvm::vfs::FileSystem> &VFS,
511     llvm::MemoryBuffer *MainFileBuffer) const {
512   PreambleBounds Bounds(PreambleBytes.size(), PreambleEndsAtStartOfLine);
513   configurePreamble(Bounds, CI, VFS, MainFileBuffer);
514 }
515 
516 void PrecompiledPreamble::OverridePreamble(
517     CompilerInvocation &CI, IntrusiveRefCntPtr<llvm::vfs::FileSystem> &VFS,
518     llvm::MemoryBuffer *MainFileBuffer) const {
519   auto Bounds = ComputePreambleBounds(*CI.getLangOpts(), MainFileBuffer, 0);
520   configurePreamble(Bounds, CI, VFS, MainFileBuffer);
521 }
522 
523 PrecompiledPreamble::PrecompiledPreamble(
524     PCHStorage Storage, std::vector<char> PreambleBytes,
525     bool PreambleEndsAtStartOfLine,
526     llvm::StringMap<PreambleFileHash> FilesInPreamble)
527     : Storage(std::move(Storage)), FilesInPreamble(std::move(FilesInPreamble)),
528       PreambleBytes(std::move(PreambleBytes)),
529       PreambleEndsAtStartOfLine(PreambleEndsAtStartOfLine) {
530   assert(this->Storage.getKind() != PCHStorage::Kind::Empty);
531 }
532 
533 llvm::ErrorOr<PrecompiledPreamble::TempPCHFile>
534 PrecompiledPreamble::TempPCHFile::CreateNewPreamblePCHFile() {
535   // FIXME: This is a hack so that we can override the preamble file during
536   // crash-recovery testing, which is the only case where the preamble files
537   // are not necessarily cleaned up.
538   if (const char *TmpFile = ::getenv("CINDEXTEST_PREAMBLE_FILE"))
539     return TempPCHFile(TmpFile);
540 
541   llvm::SmallString<64> File;
542   // Using a version of createTemporaryFile with a file descriptor guarantees
543   // that we would never get a race condition in a multi-threaded setting
544   // (i.e., multiple threads getting the same temporary path).
545   int FD;
546   auto EC = llvm::sys::fs::createTemporaryFile("preamble", "pch", FD, File);
547   if (EC)
548     return EC;
549   // We only needed to make sure the file exists, close the file right away.
550   llvm::sys::Process::SafelyCloseFileDescriptor(FD);
551   return TempPCHFile(std::move(File).str());
552 }
553 
554 PrecompiledPreamble::TempPCHFile::TempPCHFile(std::string FilePath)
555     : FilePath(std::move(FilePath)) {
556   TemporaryFiles::getInstance().addFile(*this->FilePath);
557 }
558 
559 PrecompiledPreamble::TempPCHFile::TempPCHFile(TempPCHFile &&Other) {
560   FilePath = std::move(Other.FilePath);
561   Other.FilePath = None;
562 }
563 
564 PrecompiledPreamble::TempPCHFile &PrecompiledPreamble::TempPCHFile::
565 operator=(TempPCHFile &&Other) {
566   RemoveFileIfPresent();
567 
568   FilePath = std::move(Other.FilePath);
569   Other.FilePath = None;
570   return *this;
571 }
572 
573 PrecompiledPreamble::TempPCHFile::~TempPCHFile() { RemoveFileIfPresent(); }
574 
575 void PrecompiledPreamble::TempPCHFile::RemoveFileIfPresent() {
576   if (FilePath) {
577     TemporaryFiles::getInstance().removeFile(*FilePath);
578     FilePath = None;
579   }
580 }
581 
582 llvm::StringRef PrecompiledPreamble::TempPCHFile::getFilePath() const {
583   assert(FilePath && "TempPCHFile doesn't have a FilePath. Had it been moved?");
584   return *FilePath;
585 }
586 
587 PrecompiledPreamble::PCHStorage::PCHStorage(TempPCHFile File)
588     : StorageKind(Kind::TempFile) {
589   new (&asFile()) TempPCHFile(std::move(File));
590 }
591 
592 PrecompiledPreamble::PCHStorage::PCHStorage(InMemoryPreamble Memory)
593     : StorageKind(Kind::InMemory) {
594   new (&asMemory()) InMemoryPreamble(std::move(Memory));
595 }
596 
597 PrecompiledPreamble::PCHStorage::PCHStorage(PCHStorage &&Other) : PCHStorage() {
598   *this = std::move(Other);
599 }
600 
601 PrecompiledPreamble::PCHStorage &PrecompiledPreamble::PCHStorage::
602 operator=(PCHStorage &&Other) {
603   destroy();
604 
605   StorageKind = Other.StorageKind;
606   switch (StorageKind) {
607   case Kind::Empty:
608     // do nothing;
609     break;
610   case Kind::TempFile:
611     new (&asFile()) TempPCHFile(std::move(Other.asFile()));
612     break;
613   case Kind::InMemory:
614     new (&asMemory()) InMemoryPreamble(std::move(Other.asMemory()));
615     break;
616   }
617 
618   Other.setEmpty();
619   return *this;
620 }
621 
622 PrecompiledPreamble::PCHStorage::~PCHStorage() { destroy(); }
623 
624 PrecompiledPreamble::PCHStorage::Kind
625 PrecompiledPreamble::PCHStorage::getKind() const {
626   return StorageKind;
627 }
628 
629 PrecompiledPreamble::TempPCHFile &PrecompiledPreamble::PCHStorage::asFile() {
630   assert(getKind() == Kind::TempFile);
631   return *reinterpret_cast<TempPCHFile *>(Storage.buffer);
632 }
633 
634 const PrecompiledPreamble::TempPCHFile &
635 PrecompiledPreamble::PCHStorage::asFile() const {
636   return const_cast<PCHStorage *>(this)->asFile();
637 }
638 
639 PrecompiledPreamble::InMemoryPreamble &
640 PrecompiledPreamble::PCHStorage::asMemory() {
641   assert(getKind() == Kind::InMemory);
642   return *reinterpret_cast<InMemoryPreamble *>(Storage.buffer);
643 }
644 
645 const PrecompiledPreamble::InMemoryPreamble &
646 PrecompiledPreamble::PCHStorage::asMemory() const {
647   return const_cast<PCHStorage *>(this)->asMemory();
648 }
649 
650 void PrecompiledPreamble::PCHStorage::destroy() {
651   switch (StorageKind) {
652   case Kind::Empty:
653     return;
654   case Kind::TempFile:
655     asFile().~TempPCHFile();
656     return;
657   case Kind::InMemory:
658     asMemory().~InMemoryPreamble();
659     return;
660   }
661 }
662 
663 void PrecompiledPreamble::PCHStorage::setEmpty() {
664   destroy();
665   StorageKind = Kind::Empty;
666 }
667 
668 PrecompiledPreamble::PreambleFileHash
669 PrecompiledPreamble::PreambleFileHash::createForFile(off_t Size,
670                                                      time_t ModTime) {
671   PreambleFileHash Result;
672   Result.Size = Size;
673   Result.ModTime = ModTime;
674   Result.MD5 = {};
675   return Result;
676 }
677 
678 PrecompiledPreamble::PreambleFileHash
679 PrecompiledPreamble::PreambleFileHash::createForMemoryBuffer(
680     const llvm::MemoryBuffer *Buffer) {
681   PreambleFileHash Result;
682   Result.Size = Buffer->getBufferSize();
683   Result.ModTime = 0;
684 
685   llvm::MD5 MD5Ctx;
686   MD5Ctx.update(Buffer->getBuffer().data());
687   MD5Ctx.final(Result.MD5);
688 
689   return Result;
690 }
691 
692 void PrecompiledPreamble::configurePreamble(
693     PreambleBounds Bounds, CompilerInvocation &CI,
694     IntrusiveRefCntPtr<llvm::vfs::FileSystem> &VFS,
695     llvm::MemoryBuffer *MainFileBuffer) const {
696   assert(VFS);
697 
698   auto &PreprocessorOpts = CI.getPreprocessorOpts();
699 
700   // Remap main file to point to MainFileBuffer.
701   auto MainFilePath = CI.getFrontendOpts().Inputs[0].getFile();
702   PreprocessorOpts.addRemappedFile(MainFilePath, MainFileBuffer);
703 
704   // Configure ImpicitPCHInclude.
705   PreprocessorOpts.PrecompiledPreambleBytes.first = Bounds.Size;
706   PreprocessorOpts.PrecompiledPreambleBytes.second =
707       Bounds.PreambleEndsAtStartOfLine;
708   PreprocessorOpts.DisablePCHValidation = true;
709 
710   setupPreambleStorage(Storage, PreprocessorOpts, VFS);
711 }
712 
713 void PrecompiledPreamble::setupPreambleStorage(
714     const PCHStorage &Storage, PreprocessorOptions &PreprocessorOpts,
715     IntrusiveRefCntPtr<llvm::vfs::FileSystem> &VFS) {
716   if (Storage.getKind() == PCHStorage::Kind::TempFile) {
717     const TempPCHFile &PCHFile = Storage.asFile();
718     PreprocessorOpts.ImplicitPCHInclude = PCHFile.getFilePath();
719 
720     // Make sure we can access the PCH file even if we're using a VFS
721     IntrusiveRefCntPtr<llvm::vfs::FileSystem> RealFS =
722         llvm::vfs::getRealFileSystem();
723     auto PCHPath = PCHFile.getFilePath();
724     if (VFS == RealFS || VFS->exists(PCHPath))
725       return;
726     auto Buf = RealFS->getBufferForFile(PCHPath);
727     if (!Buf) {
728       // We can't read the file even from RealFS, this is clearly an error,
729       // but we'll just leave the current VFS as is and let clang's code
730       // figure out what to do with missing PCH.
731       return;
732     }
733 
734     // We have a slight inconsistency here -- we're using the VFS to
735     // read files, but the PCH was generated in the real file system.
736     VFS = createVFSOverlayForPreamblePCH(PCHPath, std::move(*Buf), VFS);
737   } else {
738     assert(Storage.getKind() == PCHStorage::Kind::InMemory);
739     // For in-memory preamble, we have to provide a VFS overlay that makes it
740     // accessible.
741     StringRef PCHPath = getInMemoryPreamblePath();
742     PreprocessorOpts.ImplicitPCHInclude = PCHPath;
743 
744     auto Buf = llvm::MemoryBuffer::getMemBuffer(Storage.asMemory().Data);
745     VFS = createVFSOverlayForPreamblePCH(PCHPath, std::move(Buf), VFS);
746   }
747 }
748 
749 void PreambleCallbacks::BeforeExecute(CompilerInstance &CI) {}
750 void PreambleCallbacks::AfterExecute(CompilerInstance &CI) {}
751 void PreambleCallbacks::AfterPCHEmitted(ASTWriter &Writer) {}
752 void PreambleCallbacks::HandleTopLevelDecl(DeclGroupRef DG) {}
753 std::unique_ptr<PPCallbacks> PreambleCallbacks::createPPCallbacks() {
754   return nullptr;
755 }
756 CommentHandler *PreambleCallbacks::getCommentHandler() { return nullptr; }
757 
758 static llvm::ManagedStatic<BuildPreambleErrorCategory> BuildPreambleErrCategory;
759 
760 std::error_code clang::make_error_code(BuildPreambleError Error) {
761   return std::error_code(static_cast<int>(Error), *BuildPreambleErrCategory);
762 }
763 
764 const char *BuildPreambleErrorCategory::name() const noexcept {
765   return "build-preamble.error";
766 }
767 
768 std::string BuildPreambleErrorCategory::message(int condition) const {
769   switch (static_cast<BuildPreambleError>(condition)) {
770   case BuildPreambleError::CouldntCreateTempFile:
771     return "Could not create temporary file for PCH";
772   case BuildPreambleError::CouldntCreateTargetInfo:
773     return "CreateTargetInfo() return null";
774   case BuildPreambleError::BeginSourceFileFailed:
775     return "BeginSourceFile() return an error";
776   case BuildPreambleError::CouldntEmitPCH:
777     return "Could not emit PCH";
778   case BuildPreambleError::BadInputs:
779     return "Command line arguments must contain exactly one source file";
780   }
781   llvm_unreachable("unexpected BuildPreambleError");
782 }
783