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      1 //===--- Tooling.cpp - Running clang standalone tools ---------------------===//
      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 //  This file implements functions to run clang tools standalone instead
     11 //  of running them as a plugin.
     12 //
     13 //===----------------------------------------------------------------------===//
     14 
     15 #include "clang/Tooling/Tooling.h"
     16 #include "clang/AST/ASTConsumer.h"
     17 #include "clang/Driver/Compilation.h"
     18 #include "clang/Driver/Driver.h"
     19 #include "clang/Driver/Tool.h"
     20 #include "clang/Driver/ToolChain.h"
     21 #include "clang/Frontend/ASTUnit.h"
     22 #include "clang/Frontend/CompilerInstance.h"
     23 #include "clang/Frontend/FrontendDiagnostic.h"
     24 #include "clang/Frontend/TextDiagnosticPrinter.h"
     25 #include "clang/Tooling/ArgumentsAdjusters.h"
     26 #include "clang/Tooling/CompilationDatabase.h"
     27 #include "llvm/ADT/STLExtras.h"
     28 #include "llvm/Config/llvm-config.h"
     29 #include "llvm/Option/Option.h"
     30 #include "llvm/Support/Debug.h"
     31 #include "llvm/Support/FileSystem.h"
     32 #include "llvm/Support/Host.h"
     33 #include "llvm/Support/raw_ostream.h"
     34 #include <utility>
     35 
     36 #define DEBUG_TYPE "clang-tooling"
     37 
     38 namespace clang {
     39 namespace tooling {
     40 
     41 ToolAction::~ToolAction() {}
     42 
     43 FrontendActionFactory::~FrontendActionFactory() {}
     44 
     45 // FIXME: This file contains structural duplication with other parts of the
     46 // code that sets up a compiler to run tools on it, and we should refactor
     47 // it to be based on the same framework.
     48 
     49 /// \brief Builds a clang driver initialized for running clang tools.
     50 static clang::driver::Driver *newDriver(
     51     clang::DiagnosticsEngine *Diagnostics, const char *BinaryName,
     52     IntrusiveRefCntPtr<vfs::FileSystem> VFS) {
     53   clang::driver::Driver *CompilerDriver =
     54       new clang::driver::Driver(BinaryName, llvm::sys::getDefaultTargetTriple(),
     55                                 *Diagnostics, std::move(VFS));
     56   CompilerDriver->setTitle("clang_based_tool");
     57   return CompilerDriver;
     58 }
     59 
     60 /// \brief Retrieves the clang CC1 specific flags out of the compilation's jobs.
     61 ///
     62 /// Returns NULL on error.
     63 static const llvm::opt::ArgStringList *getCC1Arguments(
     64     clang::DiagnosticsEngine *Diagnostics,
     65     clang::driver::Compilation *Compilation) {
     66   // We expect to get back exactly one Command job, if we didn't something
     67   // failed. Extract that job from the Compilation.
     68   const clang::driver::JobList &Jobs = Compilation->getJobs();
     69   if (Jobs.size() != 1 || !isa<clang::driver::Command>(*Jobs.begin())) {
     70     SmallString<256> error_msg;
     71     llvm::raw_svector_ostream error_stream(error_msg);
     72     Jobs.Print(error_stream, "; ", true);
     73     Diagnostics->Report(clang::diag::err_fe_expected_compiler_job)
     74         << error_stream.str();
     75     return nullptr;
     76   }
     77 
     78   // The one job we find should be to invoke clang again.
     79   const clang::driver::Command &Cmd =
     80       cast<clang::driver::Command>(*Jobs.begin());
     81   if (StringRef(Cmd.getCreator().getName()) != "clang") {
     82     Diagnostics->Report(clang::diag::err_fe_expected_clang_command);
     83     return nullptr;
     84   }
     85 
     86   return &Cmd.getArguments();
     87 }
     88 
     89 /// \brief Returns a clang build invocation initialized from the CC1 flags.
     90 clang::CompilerInvocation *newInvocation(
     91     clang::DiagnosticsEngine *Diagnostics,
     92     const llvm::opt::ArgStringList &CC1Args) {
     93   assert(!CC1Args.empty() && "Must at least contain the program name!");
     94   clang::CompilerInvocation *Invocation = new clang::CompilerInvocation;
     95   clang::CompilerInvocation::CreateFromArgs(
     96       *Invocation, CC1Args.data() + 1, CC1Args.data() + CC1Args.size(),
     97       *Diagnostics);
     98   Invocation->getFrontendOpts().DisableFree = false;
     99   Invocation->getCodeGenOpts().DisableFree = false;
    100   Invocation->getDependencyOutputOpts() = DependencyOutputOptions();
    101   return Invocation;
    102 }
    103 
    104 bool runToolOnCode(clang::FrontendAction *ToolAction, const Twine &Code,
    105                    const Twine &FileName,
    106                    std::shared_ptr<PCHContainerOperations> PCHContainerOps) {
    107   return runToolOnCodeWithArgs(ToolAction, Code, std::vector<std::string>(),
    108                                FileName, "clang-tool",
    109                                std::move(PCHContainerOps));
    110 }
    111 
    112 static std::vector<std::string>
    113 getSyntaxOnlyToolArgs(const Twine &ToolName,
    114                       const std::vector<std::string> &ExtraArgs,
    115                       StringRef FileName) {
    116   std::vector<std::string> Args;
    117   Args.push_back(ToolName.str());
    118   Args.push_back("-fsyntax-only");
    119   Args.insert(Args.end(), ExtraArgs.begin(), ExtraArgs.end());
    120   Args.push_back(FileName.str());
    121   return Args;
    122 }
    123 
    124 bool runToolOnCodeWithArgs(
    125     clang::FrontendAction *ToolAction, const Twine &Code,
    126     const std::vector<std::string> &Args, const Twine &FileName,
    127     const Twine &ToolName,
    128     std::shared_ptr<PCHContainerOperations> PCHContainerOps,
    129     const FileContentMappings &VirtualMappedFiles) {
    130 
    131   SmallString<16> FileNameStorage;
    132   StringRef FileNameRef = FileName.toNullTerminatedStringRef(FileNameStorage);
    133   llvm::IntrusiveRefCntPtr<vfs::OverlayFileSystem> OverlayFileSystem(
    134       new vfs::OverlayFileSystem(vfs::getRealFileSystem()));
    135   llvm::IntrusiveRefCntPtr<vfs::InMemoryFileSystem> InMemoryFileSystem(
    136       new vfs::InMemoryFileSystem);
    137   OverlayFileSystem->pushOverlay(InMemoryFileSystem);
    138   llvm::IntrusiveRefCntPtr<FileManager> Files(
    139       new FileManager(FileSystemOptions(), OverlayFileSystem));
    140   ToolInvocation Invocation(getSyntaxOnlyToolArgs(ToolName, Args, FileNameRef),
    141                             ToolAction, Files.get(),
    142                             std::move(PCHContainerOps));
    143 
    144   SmallString<1024> CodeStorage;
    145   InMemoryFileSystem->addFile(FileNameRef, 0,
    146                               llvm::MemoryBuffer::getMemBuffer(
    147                                   Code.toNullTerminatedStringRef(CodeStorage)));
    148 
    149   for (auto &FilenameWithContent : VirtualMappedFiles) {
    150     InMemoryFileSystem->addFile(
    151         FilenameWithContent.first, 0,
    152         llvm::MemoryBuffer::getMemBuffer(FilenameWithContent.second));
    153   }
    154 
    155   return Invocation.run();
    156 }
    157 
    158 std::string getAbsolutePath(StringRef File) {
    159   StringRef RelativePath(File);
    160   // FIXME: Should '.\\' be accepted on Win32?
    161   if (RelativePath.startswith("./")) {
    162     RelativePath = RelativePath.substr(strlen("./"));
    163   }
    164 
    165   SmallString<1024> AbsolutePath = RelativePath;
    166   std::error_code EC = llvm::sys::fs::make_absolute(AbsolutePath);
    167   assert(!EC);
    168   (void)EC;
    169   llvm::sys::path::native(AbsolutePath);
    170   return AbsolutePath.str();
    171 }
    172 
    173 void addTargetAndModeForProgramName(std::vector<std::string> &CommandLine,
    174                                     StringRef InvokedAs) {
    175   if (!CommandLine.empty() && !InvokedAs.empty()) {
    176     bool AlreadyHasTarget = false;
    177     bool AlreadyHasMode = false;
    178     // Skip CommandLine[0].
    179     for (auto Token = ++CommandLine.begin(); Token != CommandLine.end();
    180          ++Token) {
    181       StringRef TokenRef(*Token);
    182       AlreadyHasTarget |=
    183           (TokenRef == "-target" || TokenRef.startswith("-target="));
    184       AlreadyHasMode |= (TokenRef == "--driver-mode" ||
    185                          TokenRef.startswith("--driver-mode="));
    186     }
    187     auto TargetMode =
    188         clang::driver::ToolChain::getTargetAndModeFromProgramName(InvokedAs);
    189     if (!AlreadyHasMode && !TargetMode.second.empty()) {
    190       CommandLine.insert(++CommandLine.begin(), TargetMode.second);
    191     }
    192     if (!AlreadyHasTarget && !TargetMode.first.empty()) {
    193       CommandLine.insert(++CommandLine.begin(), {"-target", TargetMode.first});
    194     }
    195   }
    196 }
    197 
    198 namespace {
    199 
    200 class SingleFrontendActionFactory : public FrontendActionFactory {
    201   FrontendAction *Action;
    202 
    203 public:
    204   SingleFrontendActionFactory(FrontendAction *Action) : Action(Action) {}
    205 
    206   FrontendAction *create() override { return Action; }
    207 };
    208 
    209 }
    210 
    211 ToolInvocation::ToolInvocation(
    212     std::vector<std::string> CommandLine, ToolAction *Action,
    213     FileManager *Files, std::shared_ptr<PCHContainerOperations> PCHContainerOps)
    214     : CommandLine(std::move(CommandLine)), Action(Action), OwnsAction(false),
    215       Files(Files), PCHContainerOps(std::move(PCHContainerOps)),
    216       DiagConsumer(nullptr) {}
    217 
    218 ToolInvocation::ToolInvocation(
    219     std::vector<std::string> CommandLine, FrontendAction *FAction,
    220     FileManager *Files, std::shared_ptr<PCHContainerOperations> PCHContainerOps)
    221     : CommandLine(std::move(CommandLine)),
    222       Action(new SingleFrontendActionFactory(FAction)), OwnsAction(true),
    223       Files(Files), PCHContainerOps(std::move(PCHContainerOps)),
    224       DiagConsumer(nullptr) {}
    225 
    226 ToolInvocation::~ToolInvocation() {
    227   if (OwnsAction)
    228     delete Action;
    229 }
    230 
    231 void ToolInvocation::mapVirtualFile(StringRef FilePath, StringRef Content) {
    232   SmallString<1024> PathStorage;
    233   llvm::sys::path::native(FilePath, PathStorage);
    234   MappedFileContents[PathStorage] = Content;
    235 }
    236 
    237 bool ToolInvocation::run() {
    238   std::vector<const char*> Argv;
    239   for (const std::string &Str : CommandLine)
    240     Argv.push_back(Str.c_str());
    241   const char *const BinaryName = Argv[0];
    242   IntrusiveRefCntPtr<DiagnosticOptions> DiagOpts = new DiagnosticOptions();
    243   TextDiagnosticPrinter DiagnosticPrinter(
    244       llvm::errs(), &*DiagOpts);
    245   DiagnosticsEngine Diagnostics(
    246       IntrusiveRefCntPtr<clang::DiagnosticIDs>(new DiagnosticIDs()), &*DiagOpts,
    247       DiagConsumer ? DiagConsumer : &DiagnosticPrinter, false);
    248 
    249   const std::unique_ptr<clang::driver::Driver> Driver(
    250       newDriver(&Diagnostics, BinaryName, Files->getVirtualFileSystem()));
    251   // Since the input might only be virtual, don't check whether it exists.
    252   Driver->setCheckInputsExist(false);
    253   const std::unique_ptr<clang::driver::Compilation> Compilation(
    254       Driver->BuildCompilation(llvm::makeArrayRef(Argv)));
    255   const llvm::opt::ArgStringList *const CC1Args = getCC1Arguments(
    256       &Diagnostics, Compilation.get());
    257   if (!CC1Args) {
    258     return false;
    259   }
    260   std::unique_ptr<clang::CompilerInvocation> Invocation(
    261       newInvocation(&Diagnostics, *CC1Args));
    262   // FIXME: remove this when all users have migrated!
    263   for (const auto &It : MappedFileContents) {
    264     // Inject the code as the given file name into the preprocessor options.
    265     std::unique_ptr<llvm::MemoryBuffer> Input =
    266         llvm::MemoryBuffer::getMemBuffer(It.getValue());
    267     Invocation->getPreprocessorOpts().addRemappedFile(It.getKey(),
    268                                                       Input.release());
    269   }
    270   return runInvocation(BinaryName, Compilation.get(), Invocation.release(),
    271                        std::move(PCHContainerOps));
    272 }
    273 
    274 bool ToolInvocation::runInvocation(
    275     const char *BinaryName, clang::driver::Compilation *Compilation,
    276     clang::CompilerInvocation *Invocation,
    277     std::shared_ptr<PCHContainerOperations> PCHContainerOps) {
    278   // Show the invocation, with -v.
    279   if (Invocation->getHeaderSearchOpts().Verbose) {
    280     llvm::errs() << "clang Invocation:\n";
    281     Compilation->getJobs().Print(llvm::errs(), "\n", true);
    282     llvm::errs() << "\n";
    283   }
    284 
    285   return Action->runInvocation(Invocation, Files, std::move(PCHContainerOps),
    286                                DiagConsumer);
    287 }
    288 
    289 bool FrontendActionFactory::runInvocation(
    290     CompilerInvocation *Invocation, FileManager *Files,
    291     std::shared_ptr<PCHContainerOperations> PCHContainerOps,
    292     DiagnosticConsumer *DiagConsumer) {
    293   // Create a compiler instance to handle the actual work.
    294   clang::CompilerInstance Compiler(std::move(PCHContainerOps));
    295   Compiler.setInvocation(Invocation);
    296   Compiler.setFileManager(Files);
    297 
    298   // The FrontendAction can have lifetime requirements for Compiler or its
    299   // members, and we need to ensure it's deleted earlier than Compiler. So we
    300   // pass it to an std::unique_ptr declared after the Compiler variable.
    301   std::unique_ptr<FrontendAction> ScopedToolAction(create());
    302 
    303   // Create the compiler's actual diagnostics engine.
    304   Compiler.createDiagnostics(DiagConsumer, /*ShouldOwnClient=*/false);
    305   if (!Compiler.hasDiagnostics())
    306     return false;
    307 
    308   Compiler.createSourceManager(*Files);
    309 
    310   const bool Success = Compiler.ExecuteAction(*ScopedToolAction);
    311 
    312   Files->clearStatCaches();
    313   return Success;
    314 }
    315 
    316 ClangTool::ClangTool(const CompilationDatabase &Compilations,
    317                      ArrayRef<std::string> SourcePaths,
    318                      std::shared_ptr<PCHContainerOperations> PCHContainerOps)
    319     : Compilations(Compilations), SourcePaths(SourcePaths),
    320       PCHContainerOps(std::move(PCHContainerOps)),
    321       OverlayFileSystem(new vfs::OverlayFileSystem(vfs::getRealFileSystem())),
    322       InMemoryFileSystem(new vfs::InMemoryFileSystem),
    323       Files(new FileManager(FileSystemOptions(), OverlayFileSystem)),
    324       DiagConsumer(nullptr) {
    325   OverlayFileSystem->pushOverlay(InMemoryFileSystem);
    326   appendArgumentsAdjuster(getClangStripOutputAdjuster());
    327   appendArgumentsAdjuster(getClangSyntaxOnlyAdjuster());
    328 }
    329 
    330 ClangTool::~ClangTool() {}
    331 
    332 void ClangTool::mapVirtualFile(StringRef FilePath, StringRef Content) {
    333   MappedFileContents.push_back(std::make_pair(FilePath, Content));
    334 }
    335 
    336 void ClangTool::appendArgumentsAdjuster(ArgumentsAdjuster Adjuster) {
    337   if (ArgsAdjuster)
    338     ArgsAdjuster =
    339         combineAdjusters(std::move(ArgsAdjuster), std::move(Adjuster));
    340   else
    341     ArgsAdjuster = std::move(Adjuster);
    342 }
    343 
    344 void ClangTool::clearArgumentsAdjusters() {
    345   ArgsAdjuster = nullptr;
    346 }
    347 
    348 static void injectResourceDir(CommandLineArguments &Args, const char *Argv0,
    349                               void *MainAddr) {
    350   // Allow users to override the resource dir.
    351   for (StringRef Arg : Args)
    352     if (Arg.startswith("-resource-dir"))
    353       return;
    354 
    355   // If there's no override in place add our resource dir.
    356   Args.push_back("-resource-dir=" +
    357                  CompilerInvocation::GetResourcesPath(Argv0, MainAddr));
    358 }
    359 
    360 int ClangTool::run(ToolAction *Action) {
    361   // Exists solely for the purpose of lookup of the resource path.
    362   // This just needs to be some symbol in the binary.
    363   static int StaticSymbol;
    364 
    365   llvm::SmallString<128> InitialDirectory;
    366   if (std::error_code EC = llvm::sys::fs::current_path(InitialDirectory))
    367     llvm::report_fatal_error("Cannot detect current path: " +
    368                              Twine(EC.message()));
    369 
    370   // First insert all absolute paths into the in-memory VFS. These are global
    371   // for all compile commands.
    372   if (SeenWorkingDirectories.insert("/").second)
    373     for (const auto &MappedFile : MappedFileContents)
    374       if (llvm::sys::path::is_absolute(MappedFile.first))
    375         InMemoryFileSystem->addFile(
    376             MappedFile.first, 0,
    377             llvm::MemoryBuffer::getMemBuffer(MappedFile.second));
    378 
    379   bool ProcessingFailed = false;
    380   for (const auto &SourcePath : SourcePaths) {
    381     std::string File(getAbsolutePath(SourcePath));
    382 
    383     // Currently implementations of CompilationDatabase::getCompileCommands can
    384     // change the state of the file system (e.g.  prepare generated headers), so
    385     // this method needs to run right before we invoke the tool, as the next
    386     // file may require a different (incompatible) state of the file system.
    387     //
    388     // FIXME: Make the compilation database interface more explicit about the
    389     // requirements to the order of invocation of its members.
    390     std::vector<CompileCommand> CompileCommandsForFile =
    391         Compilations.getCompileCommands(File);
    392     if (CompileCommandsForFile.empty()) {
    393       // FIXME: There are two use cases here: doing a fuzzy
    394       // "find . -name '*.cc' |xargs tool" match, where as a user I don't care
    395       // about the .cc files that were not found, and the use case where I
    396       // specify all files I want to run over explicitly, where this should
    397       // be an error. We'll want to add an option for this.
    398       llvm::errs() << "Skipping " << File << ". Compile command not found.\n";
    399       continue;
    400     }
    401     for (CompileCommand &CompileCommand : CompileCommandsForFile) {
    402       // FIXME: chdir is thread hostile; on the other hand, creating the same
    403       // behavior as chdir is complex: chdir resolves the path once, thus
    404       // guaranteeing that all subsequent relative path operations work
    405       // on the same path the original chdir resulted in. This makes a
    406       // difference for example on network filesystems, where symlinks might be
    407       // switched during runtime of the tool. Fixing this depends on having a
    408       // file system abstraction that allows openat() style interactions.
    409       if (OverlayFileSystem->setCurrentWorkingDirectory(
    410               CompileCommand.Directory))
    411         llvm::report_fatal_error("Cannot chdir into \"" +
    412                                  Twine(CompileCommand.Directory) + "\n!");
    413 
    414       // Now fill the in-memory VFS with the relative file mappings so it will
    415       // have the correct relative paths. We never remove mappings but that
    416       // should be fine.
    417       if (SeenWorkingDirectories.insert(CompileCommand.Directory).second)
    418         for (const auto &MappedFile : MappedFileContents)
    419           if (!llvm::sys::path::is_absolute(MappedFile.first))
    420             InMemoryFileSystem->addFile(
    421                 MappedFile.first, 0,
    422                 llvm::MemoryBuffer::getMemBuffer(MappedFile.second));
    423 
    424       std::vector<std::string> CommandLine = CompileCommand.CommandLine;
    425       if (ArgsAdjuster)
    426         CommandLine = ArgsAdjuster(CommandLine, CompileCommand.Filename);
    427       assert(!CommandLine.empty());
    428 
    429       // Add the resource dir based on the binary of this tool. argv[0] in the
    430       // compilation database may refer to a different compiler and we want to
    431       // pick up the very same standard library that compiler is using. The
    432       // builtin headers in the resource dir need to match the exact clang
    433       // version the tool is using.
    434       // FIXME: On linux, GetMainExecutable is independent of the value of the
    435       // first argument, thus allowing ClangTool and runToolOnCode to just
    436       // pass in made-up names here. Make sure this works on other platforms.
    437       injectResourceDir(CommandLine, "clang_tool", &StaticSymbol);
    438 
    439       // FIXME: We need a callback mechanism for the tool writer to output a
    440       // customized message for each file.
    441       DEBUG({ llvm::dbgs() << "Processing: " << File << ".\n"; });
    442       ToolInvocation Invocation(std::move(CommandLine), Action, Files.get(),
    443                                 PCHContainerOps);
    444       Invocation.setDiagnosticConsumer(DiagConsumer);
    445 
    446       if (!Invocation.run()) {
    447         // FIXME: Diagnostics should be used instead.
    448         llvm::errs() << "Error while processing " << File << ".\n";
    449         ProcessingFailed = true;
    450       }
    451       // Return to the initial directory to correctly resolve next file by
    452       // relative path.
    453       if (OverlayFileSystem->setCurrentWorkingDirectory(InitialDirectory.c_str()))
    454         llvm::report_fatal_error("Cannot chdir into \"" +
    455                                  Twine(InitialDirectory) + "\n!");
    456     }
    457   }
    458   return ProcessingFailed ? 1 : 0;
    459 }
    460 
    461 namespace {
    462 
    463 class ASTBuilderAction : public ToolAction {
    464   std::vector<std::unique_ptr<ASTUnit>> &ASTs;
    465 
    466 public:
    467   ASTBuilderAction(std::vector<std::unique_ptr<ASTUnit>> &ASTs) : ASTs(ASTs) {}
    468 
    469   bool runInvocation(CompilerInvocation *Invocation, FileManager *Files,
    470                      std::shared_ptr<PCHContainerOperations> PCHContainerOps,
    471                      DiagnosticConsumer *DiagConsumer) override {
    472     std::unique_ptr<ASTUnit> AST = ASTUnit::LoadFromCompilerInvocation(
    473         Invocation, std::move(PCHContainerOps),
    474         CompilerInstance::createDiagnostics(&Invocation->getDiagnosticOpts(),
    475                                             DiagConsumer,
    476                                             /*ShouldOwnClient=*/false),
    477         Files);
    478     if (!AST)
    479       return false;
    480 
    481     ASTs.push_back(std::move(AST));
    482     return true;
    483   }
    484 };
    485 }
    486 
    487 int ClangTool::buildASTs(std::vector<std::unique_ptr<ASTUnit>> &ASTs) {
    488   ASTBuilderAction Action(ASTs);
    489   return run(&Action);
    490 }
    491 
    492 std::unique_ptr<ASTUnit>
    493 buildASTFromCode(const Twine &Code, const Twine &FileName,
    494                  std::shared_ptr<PCHContainerOperations> PCHContainerOps) {
    495   return buildASTFromCodeWithArgs(Code, std::vector<std::string>(), FileName,
    496                                   "clang-tool", std::move(PCHContainerOps));
    497 }
    498 
    499 std::unique_ptr<ASTUnit> buildASTFromCodeWithArgs(
    500     const Twine &Code, const std::vector<std::string> &Args,
    501     const Twine &FileName, const Twine &ToolName,
    502     std::shared_ptr<PCHContainerOperations> PCHContainerOps) {
    503   SmallString<16> FileNameStorage;
    504   StringRef FileNameRef = FileName.toNullTerminatedStringRef(FileNameStorage);
    505 
    506   std::vector<std::unique_ptr<ASTUnit>> ASTs;
    507   ASTBuilderAction Action(ASTs);
    508   llvm::IntrusiveRefCntPtr<vfs::OverlayFileSystem> OverlayFileSystem(
    509       new vfs::OverlayFileSystem(vfs::getRealFileSystem()));
    510   llvm::IntrusiveRefCntPtr<vfs::InMemoryFileSystem> InMemoryFileSystem(
    511       new vfs::InMemoryFileSystem);
    512   OverlayFileSystem->pushOverlay(InMemoryFileSystem);
    513   llvm::IntrusiveRefCntPtr<FileManager> Files(
    514       new FileManager(FileSystemOptions(), OverlayFileSystem));
    515   ToolInvocation Invocation(getSyntaxOnlyToolArgs(ToolName, Args, FileNameRef),
    516                             &Action, Files.get(), std::move(PCHContainerOps));
    517 
    518   SmallString<1024> CodeStorage;
    519   InMemoryFileSystem->addFile(FileNameRef, 0,
    520                               llvm::MemoryBuffer::getMemBuffer(
    521                                   Code.toNullTerminatedStringRef(CodeStorage)));
    522   if (!Invocation.run())
    523     return nullptr;
    524 
    525   assert(ASTs.size() == 1);
    526   return std::move(ASTs[0]);
    527 }
    528 
    529 } // end namespace tooling
    530 } // end namespace clang
    531