1 //===--- PrecompiledPreamble.cpp - Build precompiled preambles --*- C++ -*-===//
2 //
3 //                     The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 // Helper class to build precompiled preamble.
11 //
12 //===----------------------------------------------------------------------===//
13 
14 #include "clang/Frontend/PrecompiledPreamble.h"
15 #include "clang/AST/DeclObjC.h"
16 #include "clang/Basic/TargetInfo.h"
17 #include "clang/Basic/VirtualFileSystem.h"
18 #include "clang/Frontend/CompilerInstance.h"
19 #include "clang/Frontend/CompilerInvocation.h"
20 #include "clang/Frontend/FrontendActions.h"
21 #include "clang/Frontend/FrontendOptions.h"
22 #include "clang/Lex/Lexer.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/Mutex.h"
31 #include "llvm/Support/MutexGuard.h"
32 #include "llvm/Support/Process.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(LLVM_ON_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<vfs::FileSystem>
52 createVFSOverlayForPreamblePCH(StringRef PCHFilename,
53                                std::unique_ptr<llvm::MemoryBuffer> PCHBuffer,
54                                IntrusiveRefCntPtr<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<vfs::InMemoryFileSystem> PCHFS(
58       new vfs::InMemoryFileSystem());
59   PCHFS->addFile(PCHFilename, 0, std::move(PCHBuffer));
60   IntrusiveRefCntPtr<vfs::OverlayFileSystem> Overlay(
61       new vfs::OverlayFileSystem(VFS));
62   Overlay->pushOverlay(PCHFS);
63   return Overlay;
64 }
65 
66 /// Keeps a track of files to be deleted in destructor.
67 class TemporaryFiles {
68 public:
69   // A static instance to be used by all clients.
70   static TemporaryFiles &getInstance();
71 
72 private:
73   // Disallow constructing the class directly.
74   TemporaryFiles() = default;
75   // Disallow copy.
76   TemporaryFiles(const TemporaryFiles &) = delete;
77 
78 public:
79   ~TemporaryFiles();
80 
81   /// Adds \p File to a set of tracked files.
82   void addFile(StringRef File);
83 
84   /// Remove \p File from disk and from the set of tracked files.
85   void removeFile(StringRef File);
86 
87 private:
88   llvm::sys::SmartMutex<false> Mutex;
89   llvm::StringSet<> Files;
90 };
91 
92 TemporaryFiles &TemporaryFiles::getInstance() {
93   static TemporaryFiles Instance;
94   return Instance;
95 }
96 
97 TemporaryFiles::~TemporaryFiles() {
98   llvm::MutexGuard Guard(Mutex);
99   for (const auto &File : Files)
100     llvm::sys::fs::remove(File.getKey());
101 }
102 
103 void TemporaryFiles::addFile(StringRef File) {
104   llvm::MutexGuard Guard(Mutex);
105   auto IsInserted = Files.insert(File).second;
106   (void)IsInserted;
107   assert(IsInserted && "File has already been added");
108 }
109 
110 void TemporaryFiles::removeFile(StringRef File) {
111   llvm::MutexGuard Guard(Mutex);
112   auto WasPresent = Files.erase(File);
113   (void)WasPresent;
114   assert(WasPresent && "File was not tracked");
115   llvm::sys::fs::remove(File);
116 }
117 
118 class PrecompilePreambleAction : public ASTFrontendAction {
119 public:
120   PrecompilePreambleAction(std::string *InMemStorage,
121                            PreambleCallbacks &Callbacks)
122       : InMemStorage(InMemStorage), Callbacks(Callbacks) {}
123 
124   std::unique_ptr<ASTConsumer> CreateASTConsumer(CompilerInstance &CI,
125                                                  StringRef InFile) override;
126 
127   bool hasEmittedPreamblePCH() const { return HasEmittedPreamblePCH; }
128 
129   void setEmittedPreamblePCH(ASTWriter &Writer) {
130     this->HasEmittedPreamblePCH = true;
131     Callbacks.AfterPCHEmitted(Writer);
132   }
133 
134   bool shouldEraseOutputFiles() override { return !hasEmittedPreamblePCH(); }
135   bool hasCodeCompletionSupport() const override { return false; }
136   bool hasASTFileSupport() const override { return false; }
137   TranslationUnitKind getTranslationUnitKind() override { return TU_Prefix; }
138 
139 private:
140   friend class PrecompilePreambleConsumer;
141 
142   bool HasEmittedPreamblePCH = false;
143   std::string *InMemStorage;
144   PreambleCallbacks &Callbacks;
145 };
146 
147 class PrecompilePreambleConsumer : public PCHGenerator {
148 public:
149   PrecompilePreambleConsumer(PrecompilePreambleAction &Action,
150                              const Preprocessor &PP, StringRef isysroot,
151                              std::unique_ptr<raw_ostream> Out)
152       : PCHGenerator(PP, "", isysroot, std::make_shared<PCHBuffer>(),
153                      ArrayRef<std::shared_ptr<ModuleFileExtension>>(),
154                      /*AllowASTWithErrors=*/true),
155         Action(Action), Out(std::move(Out)) {}
156 
157   bool HandleTopLevelDecl(DeclGroupRef DG) override {
158     Action.Callbacks.HandleTopLevelDecl(DG);
159     return true;
160   }
161 
162   void HandleTranslationUnit(ASTContext &Ctx) override {
163     PCHGenerator::HandleTranslationUnit(Ctx);
164     if (!hasEmittedPCH())
165       return;
166 
167     // Write the generated bitstream to "Out".
168     *Out << getPCH();
169     // Make sure it hits disk now.
170     Out->flush();
171     // Free the buffer.
172     llvm::SmallVector<char, 0> Empty;
173     getPCH() = std::move(Empty);
174 
175     Action.setEmittedPreamblePCH(getWriter());
176   }
177 
178 private:
179   PrecompilePreambleAction &Action;
180   std::unique_ptr<raw_ostream> Out;
181 };
182 
183 std::unique_ptr<ASTConsumer>
184 PrecompilePreambleAction::CreateASTConsumer(CompilerInstance &CI,
185                                             StringRef InFile) {
186   std::string Sysroot;
187   if (!GeneratePCHAction::ComputeASTConsumerArguments(CI, Sysroot))
188     return nullptr;
189 
190   std::unique_ptr<llvm::raw_ostream> OS;
191   if (InMemStorage) {
192     OS = llvm::make_unique<llvm::raw_string_ostream>(*InMemStorage);
193   } else {
194     std::string OutputFile;
195     OS = GeneratePCHAction::CreateOutputFile(CI, InFile, OutputFile);
196   }
197   if (!OS)
198     return nullptr;
199 
200   if (!CI.getFrontendOpts().RelocatablePCH)
201     Sysroot.clear();
202 
203   return llvm::make_unique<PrecompilePreambleConsumer>(
204       *this, CI.getPreprocessor(), Sysroot, std::move(OS));
205 }
206 
207 template <class T> bool moveOnNoError(llvm::ErrorOr<T> Val, T &Output) {
208   if (!Val)
209     return false;
210   Output = std::move(*Val);
211   return true;
212 }
213 
214 } // namespace
215 
216 PreambleBounds clang::ComputePreambleBounds(const LangOptions &LangOpts,
217                                             llvm::MemoryBuffer *Buffer,
218                                             unsigned MaxLines) {
219   return Lexer::ComputePreamble(Buffer->getBuffer(), LangOpts, MaxLines);
220 }
221 
222 llvm::ErrorOr<PrecompiledPreamble> PrecompiledPreamble::Build(
223     const CompilerInvocation &Invocation,
224     const llvm::MemoryBuffer *MainFileBuffer, PreambleBounds Bounds,
225     DiagnosticsEngine &Diagnostics, IntrusiveRefCntPtr<vfs::FileSystem> VFS,
226     std::shared_ptr<PCHContainerOperations> PCHContainerOps, bool StoreInMemory,
227     PreambleCallbacks &Callbacks) {
228   assert(VFS && "VFS is null");
229 
230   if (!Bounds.Size)
231     return BuildPreambleError::PreambleIsEmpty;
232 
233   auto PreambleInvocation = std::make_shared<CompilerInvocation>(Invocation);
234   FrontendOptions &FrontendOpts = PreambleInvocation->getFrontendOpts();
235   PreprocessorOptions &PreprocessorOpts =
236       PreambleInvocation->getPreprocessorOpts();
237 
238   llvm::Optional<TempPCHFile> TempFile;
239   if (!StoreInMemory) {
240     // Create a temporary file for the precompiled preamble. In rare
241     // circumstances, this can fail.
242     llvm::ErrorOr<PrecompiledPreamble::TempPCHFile> PreamblePCHFile =
243         PrecompiledPreamble::TempPCHFile::CreateNewPreamblePCHFile();
244     if (!PreamblePCHFile)
245       return BuildPreambleError::CouldntCreateTempFile;
246     TempFile = std::move(*PreamblePCHFile);
247   }
248 
249   PCHStorage Storage = StoreInMemory ? PCHStorage(InMemoryPreamble())
250                                      : PCHStorage(std::move(*TempFile));
251 
252   // Save the preamble text for later; we'll need to compare against it for
253   // subsequent reparses.
254   std::vector<char> PreambleBytes(MainFileBuffer->getBufferStart(),
255                                   MainFileBuffer->getBufferStart() +
256                                       Bounds.Size);
257   bool PreambleEndsAtStartOfLine = Bounds.PreambleEndsAtStartOfLine;
258 
259   // Tell the compiler invocation to generate a temporary precompiled header.
260   FrontendOpts.ProgramAction = frontend::GeneratePCH;
261   FrontendOpts.OutputFile = StoreInMemory ? getInMemoryPreamblePath()
262                                           : Storage.asFile().getFilePath();
263   PreprocessorOpts.PrecompiledPreambleBytes.first = 0;
264   PreprocessorOpts.PrecompiledPreambleBytes.second = false;
265   // Inform preprocessor to record conditional stack when building the preamble.
266   PreprocessorOpts.GeneratePreamble = true;
267 
268   // Create the compiler instance to use for building the precompiled preamble.
269   std::unique_ptr<CompilerInstance> Clang(
270       new CompilerInstance(std::move(PCHContainerOps)));
271 
272   // Recover resources if we crash before exiting this method.
273   llvm::CrashRecoveryContextCleanupRegistrar<CompilerInstance> CICleanup(
274       Clang.get());
275 
276   Clang->setInvocation(std::move(PreambleInvocation));
277   Clang->setDiagnostics(&Diagnostics);
278 
279   // Create the target instance.
280   Clang->setTarget(TargetInfo::CreateTargetInfo(
281       Clang->getDiagnostics(), Clang->getInvocation().TargetOpts));
282   if (!Clang->hasTarget())
283     return BuildPreambleError::CouldntCreateTargetInfo;
284 
285   // Inform the target of the language options.
286   //
287   // FIXME: We shouldn't need to do this, the target should be immutable once
288   // created. This complexity should be lifted elsewhere.
289   Clang->getTarget().adjust(Clang->getLangOpts());
290 
291   assert(Clang->getFrontendOpts().Inputs.size() == 1 &&
292          "Invocation must have exactly one source file!");
293   assert(Clang->getFrontendOpts().Inputs[0].getKind().getFormat() ==
294              InputKind::Source &&
295          "FIXME: AST inputs not yet supported here!");
296   assert(Clang->getFrontendOpts().Inputs[0].getKind().getLanguage() !=
297              InputKind::LLVM_IR &&
298          "IR inputs not support here!");
299 
300   // Clear out old caches and data.
301   Diagnostics.Reset();
302   ProcessWarningOptions(Diagnostics, Clang->getDiagnosticOpts());
303 
304   VFS =
305       createVFSFromCompilerInvocation(Clang->getInvocation(), Diagnostics, VFS);
306   if (!VFS)
307     return BuildPreambleError::CouldntCreateVFSOverlay;
308 
309   // Create a file manager object to provide access to and cache the filesystem.
310   Clang->setFileManager(new FileManager(Clang->getFileSystemOpts(), VFS));
311 
312   // Create the source manager.
313   Clang->setSourceManager(
314       new SourceManager(Diagnostics, Clang->getFileManager()));
315 
316   auto PreambleDepCollector = std::make_shared<DependencyCollector>();
317   Clang->addDependencyCollector(PreambleDepCollector);
318 
319   // Remap the main source file to the preamble buffer.
320   StringRef MainFilePath = FrontendOpts.Inputs[0].getFile();
321   auto PreambleInputBuffer = llvm::MemoryBuffer::getMemBufferCopy(
322       MainFileBuffer->getBuffer().slice(0, Bounds.Size), MainFilePath);
323   if (PreprocessorOpts.RetainRemappedFileBuffers) {
324     // MainFileBuffer will be deleted by unique_ptr after leaving the method.
325     PreprocessorOpts.addRemappedFile(MainFilePath, PreambleInputBuffer.get());
326   } else {
327     // In that case, remapped buffer will be deleted by CompilerInstance on
328     // BeginSourceFile, so we call release() to avoid double deletion.
329     PreprocessorOpts.addRemappedFile(MainFilePath,
330                                      PreambleInputBuffer.release());
331   }
332 
333   std::unique_ptr<PrecompilePreambleAction> Act;
334   Act.reset(new PrecompilePreambleAction(
335       StoreInMemory ? &Storage.asMemory().Data : nullptr, Callbacks));
336   Callbacks.BeforeExecute(*Clang);
337   if (!Act->BeginSourceFile(*Clang.get(), Clang->getFrontendOpts().Inputs[0]))
338     return BuildPreambleError::BeginSourceFileFailed;
339 
340   std::unique_ptr<PPCallbacks> DelegatedPPCallbacks =
341       Callbacks.createPPCallbacks();
342   if (DelegatedPPCallbacks)
343     Clang->getPreprocessor().addPPCallbacks(std::move(DelegatedPPCallbacks));
344 
345   Act->Execute();
346 
347   // Run the callbacks.
348   Callbacks.AfterExecute(*Clang);
349 
350   Act->EndSourceFile();
351 
352   if (!Act->hasEmittedPreamblePCH())
353     return BuildPreambleError::CouldntEmitPCH;
354 
355   // Keep track of all of the files that the source manager knows about,
356   // so we can verify whether they have changed or not.
357   llvm::StringMap<PrecompiledPreamble::PreambleFileHash> FilesInPreamble;
358 
359   SourceManager &SourceMgr = Clang->getSourceManager();
360   for (auto &Filename : PreambleDepCollector->getDependencies()) {
361     const FileEntry *File = Clang->getFileManager().getFile(Filename);
362     if (!File || File == SourceMgr.getFileEntryForID(SourceMgr.getMainFileID()))
363       continue;
364     if (time_t ModTime = File->getModificationTime()) {
365       FilesInPreamble[File->getName()] =
366           PrecompiledPreamble::PreambleFileHash::createForFile(File->getSize(),
367                                                                ModTime);
368     } else {
369       llvm::MemoryBuffer *Buffer = SourceMgr.getMemoryBufferForFile(File);
370       FilesInPreamble[File->getName()] =
371           PrecompiledPreamble::PreambleFileHash::createForMemoryBuffer(Buffer);
372     }
373   }
374 
375   return PrecompiledPreamble(std::move(Storage), std::move(PreambleBytes),
376                              PreambleEndsAtStartOfLine,
377                              std::move(FilesInPreamble));
378 }
379 
380 PreambleBounds PrecompiledPreamble::getBounds() const {
381   return PreambleBounds(PreambleBytes.size(), PreambleEndsAtStartOfLine);
382 }
383 
384 std::size_t PrecompiledPreamble::getSize() const {
385   switch (Storage.getKind()) {
386   case PCHStorage::Kind::Empty:
387     assert(false && "Calling getSize() on invalid PrecompiledPreamble. "
388                     "Was it std::moved?");
389     return 0;
390   case PCHStorage::Kind::InMemory:
391     return Storage.asMemory().Data.size();
392   case PCHStorage::Kind::TempFile: {
393     uint64_t Result;
394     if (llvm::sys::fs::file_size(Storage.asFile().getFilePath(), Result))
395       return 0;
396 
397     assert(Result <= std::numeric_limits<std::size_t>::max() &&
398            "file size did not fit into size_t");
399     return Result;
400   }
401   }
402   llvm_unreachable("Unhandled storage kind");
403 }
404 
405 bool PrecompiledPreamble::CanReuse(const CompilerInvocation &Invocation,
406                                    const llvm::MemoryBuffer *MainFileBuffer,
407                                    PreambleBounds Bounds,
408                                    vfs::FileSystem *VFS) const {
409 
410   assert(
411       Bounds.Size <= MainFileBuffer->getBufferSize() &&
412       "Buffer is too large. Bounds were calculated from a different buffer?");
413 
414   auto PreambleInvocation = std::make_shared<CompilerInvocation>(Invocation);
415   PreprocessorOptions &PreprocessorOpts =
416       PreambleInvocation->getPreprocessorOpts();
417 
418   if (!Bounds.Size)
419     return false;
420 
421   // We've previously computed a preamble. Check whether we have the same
422   // preamble now that we did before, and that there's enough space in
423   // the main-file buffer within the precompiled preamble to fit the
424   // new main file.
425   if (PreambleBytes.size() != Bounds.Size ||
426       PreambleEndsAtStartOfLine != Bounds.PreambleEndsAtStartOfLine ||
427       memcmp(PreambleBytes.data(), MainFileBuffer->getBufferStart(),
428              Bounds.Size) != 0)
429     return false;
430   // The preamble has not changed. We may be able to re-use the precompiled
431   // preamble.
432 
433   // Check that none of the files used by the preamble have changed.
434   // First, make a record of those files that have been overridden via
435   // remapping or unsaved_files.
436   std::map<llvm::sys::fs::UniqueID, PreambleFileHash> OverriddenFiles;
437   for (const auto &R : PreprocessorOpts.RemappedFiles) {
438     vfs::Status Status;
439     if (!moveOnNoError(VFS->status(R.second), Status)) {
440       // If we can't stat the file we're remapping to, assume that something
441       // horrible happened.
442       return false;
443     }
444 
445     OverriddenFiles[Status.getUniqueID()] = PreambleFileHash::createForFile(
446         Status.getSize(), llvm::sys::toTimeT(Status.getLastModificationTime()));
447   }
448 
449   for (const auto &RB : PreprocessorOpts.RemappedFileBuffers) {
450     vfs::Status Status;
451     if (!moveOnNoError(VFS->status(RB.first), Status))
452       return false;
453 
454     OverriddenFiles[Status.getUniqueID()] =
455         PreambleFileHash::createForMemoryBuffer(RB.second);
456   }
457 
458   // Check whether anything has changed.
459   for (const auto &F : FilesInPreamble) {
460     vfs::Status Status;
461     if (!moveOnNoError(VFS->status(F.first()), Status)) {
462       // If we can't stat the file, assume that something horrible happened.
463       return false;
464     }
465 
466     std::map<llvm::sys::fs::UniqueID, PreambleFileHash>::iterator Overridden =
467         OverriddenFiles.find(Status.getUniqueID());
468     if (Overridden != OverriddenFiles.end()) {
469       // This file was remapped; check whether the newly-mapped file
470       // matches up with the previous mapping.
471       if (Overridden->second != F.second)
472         return false;
473       continue;
474     }
475 
476     // The file was not remapped; check whether it has changed on disk.
477     if (Status.getSize() != uint64_t(F.second.Size) ||
478         llvm::sys::toTimeT(Status.getLastModificationTime()) !=
479             F.second.ModTime)
480       return false;
481   }
482   return true;
483 }
484 
485 void PrecompiledPreamble::AddImplicitPreamble(
486     CompilerInvocation &CI, IntrusiveRefCntPtr<vfs::FileSystem> &VFS,
487     llvm::MemoryBuffer *MainFileBuffer) const {
488   assert(VFS && "VFS must not be null");
489 
490   auto &PreprocessorOpts = CI.getPreprocessorOpts();
491 
492   // Remap main file to point to MainFileBuffer.
493   auto MainFilePath = CI.getFrontendOpts().Inputs[0].getFile();
494   PreprocessorOpts.addRemappedFile(MainFilePath, MainFileBuffer);
495 
496   // Configure ImpicitPCHInclude.
497   PreprocessorOpts.PrecompiledPreambleBytes.first = PreambleBytes.size();
498   PreprocessorOpts.PrecompiledPreambleBytes.second = PreambleEndsAtStartOfLine;
499   PreprocessorOpts.DisablePCHValidation = true;
500 
501   setupPreambleStorage(Storage, PreprocessorOpts, VFS);
502 }
503 
504 PrecompiledPreamble::PrecompiledPreamble(
505     PCHStorage Storage, std::vector<char> PreambleBytes,
506     bool PreambleEndsAtStartOfLine,
507     llvm::StringMap<PreambleFileHash> FilesInPreamble)
508     : Storage(std::move(Storage)), FilesInPreamble(std::move(FilesInPreamble)),
509       PreambleBytes(std::move(PreambleBytes)),
510       PreambleEndsAtStartOfLine(PreambleEndsAtStartOfLine) {
511   assert(this->Storage.getKind() != PCHStorage::Kind::Empty);
512 }
513 
514 llvm::ErrorOr<PrecompiledPreamble::TempPCHFile>
515 PrecompiledPreamble::TempPCHFile::CreateNewPreamblePCHFile() {
516   // FIXME: This is a hack so that we can override the preamble file during
517   // crash-recovery testing, which is the only case where the preamble files
518   // are not necessarily cleaned up.
519   const char *TmpFile = ::getenv("CINDEXTEST_PREAMBLE_FILE");
520   if (TmpFile)
521     return TempPCHFile::createFromCustomPath(TmpFile);
522   return TempPCHFile::createInSystemTempDir("preamble", "pch");
523 }
524 
525 llvm::ErrorOr<PrecompiledPreamble::TempPCHFile>
526 PrecompiledPreamble::TempPCHFile::createInSystemTempDir(const Twine &Prefix,
527                                                         StringRef Suffix) {
528   llvm::SmallString<64> File;
529   // Using a version of createTemporaryFile with a file descriptor guarantees
530   // that we would never get a race condition in a multi-threaded setting
531   // (i.e., multiple threads getting the same temporary path).
532   int FD;
533   auto EC = llvm::sys::fs::createTemporaryFile(Prefix, Suffix, FD, File);
534   if (EC)
535     return EC;
536   // We only needed to make sure the file exists, close the file right away.
537   llvm::sys::Process::SafelyCloseFileDescriptor(FD);
538   return TempPCHFile(std::move(File).str());
539 }
540 
541 llvm::ErrorOr<PrecompiledPreamble::TempPCHFile>
542 PrecompiledPreamble::TempPCHFile::createFromCustomPath(const Twine &Path) {
543   return TempPCHFile(Path.str());
544 }
545 
546 PrecompiledPreamble::TempPCHFile::TempPCHFile(std::string FilePath)
547     : FilePath(std::move(FilePath)) {
548   TemporaryFiles::getInstance().addFile(*this->FilePath);
549 }
550 
551 PrecompiledPreamble::TempPCHFile::TempPCHFile(TempPCHFile &&Other) {
552   FilePath = std::move(Other.FilePath);
553   Other.FilePath = None;
554 }
555 
556 PrecompiledPreamble::TempPCHFile &PrecompiledPreamble::TempPCHFile::
557 operator=(TempPCHFile &&Other) {
558   RemoveFileIfPresent();
559 
560   FilePath = std::move(Other.FilePath);
561   Other.FilePath = None;
562   return *this;
563 }
564 
565 PrecompiledPreamble::TempPCHFile::~TempPCHFile() { RemoveFileIfPresent(); }
566 
567 void PrecompiledPreamble::TempPCHFile::RemoveFileIfPresent() {
568   if (FilePath) {
569     TemporaryFiles::getInstance().removeFile(*FilePath);
570     FilePath = None;
571   }
572 }
573 
574 llvm::StringRef PrecompiledPreamble::TempPCHFile::getFilePath() const {
575   assert(FilePath && "TempPCHFile doesn't have a FilePath. Had it been moved?");
576   return *FilePath;
577 }
578 
579 PrecompiledPreamble::PCHStorage::PCHStorage(TempPCHFile File)
580     : StorageKind(Kind::TempFile) {
581   new (&asFile()) TempPCHFile(std::move(File));
582 }
583 
584 PrecompiledPreamble::PCHStorage::PCHStorage(InMemoryPreamble Memory)
585     : StorageKind(Kind::InMemory) {
586   new (&asMemory()) InMemoryPreamble(std::move(Memory));
587 }
588 
589 PrecompiledPreamble::PCHStorage::PCHStorage(PCHStorage &&Other) : PCHStorage() {
590   *this = std::move(Other);
591 }
592 
593 PrecompiledPreamble::PCHStorage &PrecompiledPreamble::PCHStorage::
594 operator=(PCHStorage &&Other) {
595   destroy();
596 
597   StorageKind = Other.StorageKind;
598   switch (StorageKind) {
599   case Kind::Empty:
600     // do nothing;
601     break;
602   case Kind::TempFile:
603     new (&asFile()) TempPCHFile(std::move(Other.asFile()));
604     break;
605   case Kind::InMemory:
606     new (&asMemory()) InMemoryPreamble(std::move(Other.asMemory()));
607     break;
608   }
609 
610   Other.setEmpty();
611   return *this;
612 }
613 
614 PrecompiledPreamble::PCHStorage::~PCHStorage() { destroy(); }
615 
616 PrecompiledPreamble::PCHStorage::Kind
617 PrecompiledPreamble::PCHStorage::getKind() const {
618   return StorageKind;
619 }
620 
621 PrecompiledPreamble::TempPCHFile &PrecompiledPreamble::PCHStorage::asFile() {
622   assert(getKind() == Kind::TempFile);
623   return *reinterpret_cast<TempPCHFile *>(Storage.buffer);
624 }
625 
626 const PrecompiledPreamble::TempPCHFile &
627 PrecompiledPreamble::PCHStorage::asFile() const {
628   return const_cast<PCHStorage *>(this)->asFile();
629 }
630 
631 PrecompiledPreamble::InMemoryPreamble &
632 PrecompiledPreamble::PCHStorage::asMemory() {
633   assert(getKind() == Kind::InMemory);
634   return *reinterpret_cast<InMemoryPreamble *>(Storage.buffer);
635 }
636 
637 const PrecompiledPreamble::InMemoryPreamble &
638 PrecompiledPreamble::PCHStorage::asMemory() const {
639   return const_cast<PCHStorage *>(this)->asMemory();
640 }
641 
642 void PrecompiledPreamble::PCHStorage::destroy() {
643   switch (StorageKind) {
644   case Kind::Empty:
645     return;
646   case Kind::TempFile:
647     asFile().~TempPCHFile();
648     return;
649   case Kind::InMemory:
650     asMemory().~InMemoryPreamble();
651     return;
652   }
653 }
654 
655 void PrecompiledPreamble::PCHStorage::setEmpty() {
656   destroy();
657   StorageKind = Kind::Empty;
658 }
659 
660 PrecompiledPreamble::PreambleFileHash
661 PrecompiledPreamble::PreambleFileHash::createForFile(off_t Size,
662                                                      time_t ModTime) {
663   PreambleFileHash Result;
664   Result.Size = Size;
665   Result.ModTime = ModTime;
666   Result.MD5 = {};
667   return Result;
668 }
669 
670 PrecompiledPreamble::PreambleFileHash
671 PrecompiledPreamble::PreambleFileHash::createForMemoryBuffer(
672     const llvm::MemoryBuffer *Buffer) {
673   PreambleFileHash Result;
674   Result.Size = Buffer->getBufferSize();
675   Result.ModTime = 0;
676 
677   llvm::MD5 MD5Ctx;
678   MD5Ctx.update(Buffer->getBuffer().data());
679   MD5Ctx.final(Result.MD5);
680 
681   return Result;
682 }
683 
684 void PrecompiledPreamble::setupPreambleStorage(
685     const PCHStorage &Storage, PreprocessorOptions &PreprocessorOpts,
686     IntrusiveRefCntPtr<vfs::FileSystem> &VFS) {
687   if (Storage.getKind() == PCHStorage::Kind::TempFile) {
688     const TempPCHFile &PCHFile = Storage.asFile();
689     PreprocessorOpts.ImplicitPCHInclude = PCHFile.getFilePath();
690 
691     // Make sure we can access the PCH file even if we're using a VFS
692     IntrusiveRefCntPtr<vfs::FileSystem> RealFS = vfs::getRealFileSystem();
693     auto PCHPath = PCHFile.getFilePath();
694     if (VFS == RealFS || VFS->exists(PCHPath))
695       return;
696     auto Buf = RealFS->getBufferForFile(PCHPath);
697     if (!Buf) {
698       // We can't read the file even from RealFS, this is clearly an error,
699       // but we'll just leave the current VFS as is and let clang's code
700       // figure out what to do with missing PCH.
701       return;
702     }
703 
704     // We have a slight inconsistency here -- we're using the VFS to
705     // read files, but the PCH was generated in the real file system.
706     VFS = createVFSOverlayForPreamblePCH(PCHPath, std::move(*Buf), VFS);
707   } else {
708     assert(Storage.getKind() == PCHStorage::Kind::InMemory);
709     // For in-memory preamble, we have to provide a VFS overlay that makes it
710     // accessible.
711     StringRef PCHPath = getInMemoryPreamblePath();
712     PreprocessorOpts.ImplicitPCHInclude = PCHPath;
713 
714     auto Buf = llvm::MemoryBuffer::getMemBuffer(Storage.asMemory().Data);
715     VFS = createVFSOverlayForPreamblePCH(PCHPath, std::move(Buf), VFS);
716   }
717 }
718 
719 void PreambleCallbacks::BeforeExecute(CompilerInstance &CI) {}
720 void PreambleCallbacks::AfterExecute(CompilerInstance &CI) {}
721 void PreambleCallbacks::AfterPCHEmitted(ASTWriter &Writer) {}
722 void PreambleCallbacks::HandleTopLevelDecl(DeclGroupRef DG) {}
723 std::unique_ptr<PPCallbacks> PreambleCallbacks::createPPCallbacks() {
724   return nullptr;
725 }
726 
727 std::error_code clang::make_error_code(BuildPreambleError Error) {
728   return std::error_code(static_cast<int>(Error), BuildPreambleErrorCategory());
729 }
730 
731 const char *BuildPreambleErrorCategory::name() const noexcept {
732   return "build-preamble.error";
733 }
734 
735 std::string BuildPreambleErrorCategory::message(int condition) const {
736   switch (static_cast<BuildPreambleError>(condition)) {
737   case BuildPreambleError::PreambleIsEmpty:
738     return "Preamble is empty";
739   case BuildPreambleError::CouldntCreateTempFile:
740     return "Could not create temporary file for PCH";
741   case BuildPreambleError::CouldntCreateTargetInfo:
742     return "CreateTargetInfo() return null";
743   case BuildPreambleError::CouldntCreateVFSOverlay:
744     return "Could not create VFS Overlay";
745   case BuildPreambleError::BeginSourceFileFailed:
746     return "BeginSourceFile() return an error";
747   case BuildPreambleError::CouldntEmitPCH:
748     return "Could not emit PCH";
749   }
750   llvm_unreachable("unexpected BuildPreambleError");
751 }
752