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/Basic/Diagnostic.h"
17 #include "clang/Basic/DiagnosticIDs.h"
18 #include "clang/Basic/DiagnosticOptions.h"
19 #include "clang/Basic/FileManager.h"
20 #include "clang/Basic/FileSystemOptions.h"
21 #include "clang/Basic/LLVM.h"
22 #include "clang/Basic/VirtualFileSystem.h"
23 #include "clang/Driver/Compilation.h"
24 #include "clang/Driver/Driver.h"
25 #include "clang/Driver/Job.h"
26 #include "clang/Driver/Options.h"
27 #include "clang/Driver/Tool.h"
28 #include "clang/Driver/ToolChain.h"
29 #include "clang/Frontend/ASTUnit.h"
30 #include "clang/Frontend/CompilerInstance.h"
31 #include "clang/Frontend/CompilerInvocation.h"
32 #include "clang/Frontend/FrontendDiagnostic.h"
33 #include "clang/Frontend/FrontendOptions.h"
34 #include "clang/Frontend/TextDiagnosticPrinter.h"
35 #include "clang/Lex/HeaderSearchOptions.h"
36 #include "clang/Lex/PreprocessorOptions.h"
37 #include "clang/Tooling/ArgumentsAdjusters.h"
38 #include "clang/Tooling/CompilationDatabase.h"
39 #include "llvm/ADT/ArrayRef.h"
40 #include "llvm/ADT/IntrusiveRefCntPtr.h"
41 #include "llvm/ADT/SmallString.h"
42 #include "llvm/ADT/StringRef.h"
43 #include "llvm/ADT/Twine.h"
44 #include "llvm/Config/llvm-config.h"
45 #include "llvm/Option/ArgList.h"
46 #include "llvm/Option/OptTable.h"
47 #include "llvm/Option/Option.h"
48 #include "llvm/Support/Casting.h"
49 #include "llvm/Support/Debug.h"
50 #include "llvm/Support/ErrorHandling.h"
51 #include "llvm/Support/FileSystem.h"
52 #include "llvm/Support/Host.h"
53 #include "llvm/Support/MemoryBuffer.h"
54 #include "llvm/Support/Path.h"
55 #include "llvm/Support/raw_ostream.h"
56 #include <cassert>
57 #include <cstring>
58 #include <memory>
59 #include <string>
60 #include <system_error>
61 #include <utility>
62 #include <vector>
63 
64 #define DEBUG_TYPE "clang-tooling"
65 
66 using namespace clang;
67 using namespace tooling;
68 
69 ToolAction::~ToolAction() = default;
70 
71 FrontendActionFactory::~FrontendActionFactory() = default;
72 
73 // FIXME: This file contains structural duplication with other parts of the
74 // code that sets up a compiler to run tools on it, and we should refactor
75 // it to be based on the same framework.
76 
77 /// \brief Builds a clang driver initialized for running clang tools.
78 static driver::Driver *newDriver(
79     DiagnosticsEngine *Diagnostics, const char *BinaryName,
80     IntrusiveRefCntPtr<vfs::FileSystem> VFS) {
81   driver::Driver *CompilerDriver =
82       new driver::Driver(BinaryName, llvm::sys::getDefaultTargetTriple(),
83                          *Diagnostics, std::move(VFS));
84   CompilerDriver->setTitle("clang_based_tool");
85   return CompilerDriver;
86 }
87 
88 /// \brief Retrieves the clang CC1 specific flags out of the compilation's jobs.
89 ///
90 /// Returns nullptr on error.
91 static const llvm::opt::ArgStringList *getCC1Arguments(
92     DiagnosticsEngine *Diagnostics, driver::Compilation *Compilation) {
93   // We expect to get back exactly one Command job, if we didn't something
94   // failed. Extract that job from the Compilation.
95   const driver::JobList &Jobs = Compilation->getJobs();
96   if (Jobs.size() != 1 || !isa<driver::Command>(*Jobs.begin())) {
97     SmallString<256> error_msg;
98     llvm::raw_svector_ostream error_stream(error_msg);
99     Jobs.Print(error_stream, "; ", true);
100     Diagnostics->Report(diag::err_fe_expected_compiler_job)
101         << error_stream.str();
102     return nullptr;
103   }
104 
105   // The one job we find should be to invoke clang again.
106   const auto &Cmd = cast<driver::Command>(*Jobs.begin());
107   if (StringRef(Cmd.getCreator().getName()) != "clang") {
108     Diagnostics->Report(diag::err_fe_expected_clang_command);
109     return nullptr;
110   }
111 
112   return &Cmd.getArguments();
113 }
114 
115 namespace clang {
116 namespace tooling {
117 
118 /// \brief Returns a clang build invocation initialized from the CC1 flags.
119 CompilerInvocation *newInvocation(
120     DiagnosticsEngine *Diagnostics, const llvm::opt::ArgStringList &CC1Args) {
121   assert(!CC1Args.empty() && "Must at least contain the program name!");
122   CompilerInvocation *Invocation = new CompilerInvocation;
123   CompilerInvocation::CreateFromArgs(
124       *Invocation, CC1Args.data() + 1, CC1Args.data() + CC1Args.size(),
125       *Diagnostics);
126   Invocation->getFrontendOpts().DisableFree = false;
127   Invocation->getCodeGenOpts().DisableFree = false;
128   return Invocation;
129 }
130 
131 bool runToolOnCode(FrontendAction *ToolAction, const Twine &Code,
132                    const Twine &FileName,
133                    std::shared_ptr<PCHContainerOperations> PCHContainerOps) {
134   return runToolOnCodeWithArgs(ToolAction, Code, std::vector<std::string>(),
135                                FileName, "clang-tool",
136                                std::move(PCHContainerOps));
137 }
138 
139 } // namespace tooling
140 } // namespace clang
141 
142 static std::vector<std::string>
143 getSyntaxOnlyToolArgs(const Twine &ToolName,
144                       const std::vector<std::string> &ExtraArgs,
145                       StringRef FileName) {
146   std::vector<std::string> Args;
147   Args.push_back(ToolName.str());
148   Args.push_back("-fsyntax-only");
149   Args.insert(Args.end(), ExtraArgs.begin(), ExtraArgs.end());
150   Args.push_back(FileName.str());
151   return Args;
152 }
153 
154 namespace clang {
155 namespace tooling {
156 
157 bool runToolOnCodeWithArgs(
158     FrontendAction *ToolAction, const Twine &Code,
159     const std::vector<std::string> &Args, const Twine &FileName,
160     const Twine &ToolName,
161     std::shared_ptr<PCHContainerOperations> PCHContainerOps,
162     const FileContentMappings &VirtualMappedFiles) {
163   SmallString<16> FileNameStorage;
164   StringRef FileNameRef = FileName.toNullTerminatedStringRef(FileNameStorage);
165   llvm::IntrusiveRefCntPtr<vfs::OverlayFileSystem> OverlayFileSystem(
166       new vfs::OverlayFileSystem(vfs::getRealFileSystem()));
167   llvm::IntrusiveRefCntPtr<vfs::InMemoryFileSystem> InMemoryFileSystem(
168       new vfs::InMemoryFileSystem);
169   OverlayFileSystem->pushOverlay(InMemoryFileSystem);
170   llvm::IntrusiveRefCntPtr<FileManager> Files(
171       new FileManager(FileSystemOptions(), OverlayFileSystem));
172   ArgumentsAdjuster Adjuster = getClangStripDependencyFileAdjuster();
173   ToolInvocation Invocation(
174       getSyntaxOnlyToolArgs(ToolName, Adjuster(Args, FileNameRef), FileNameRef),
175       ToolAction, Files.get(),
176       std::move(PCHContainerOps));
177 
178   SmallString<1024> CodeStorage;
179   InMemoryFileSystem->addFile(FileNameRef, 0,
180                               llvm::MemoryBuffer::getMemBuffer(
181                                   Code.toNullTerminatedStringRef(CodeStorage)));
182 
183   for (auto &FilenameWithContent : VirtualMappedFiles) {
184     InMemoryFileSystem->addFile(
185         FilenameWithContent.first, 0,
186         llvm::MemoryBuffer::getMemBuffer(FilenameWithContent.second));
187   }
188 
189   return Invocation.run();
190 }
191 
192 std::string getAbsolutePath(StringRef File) {
193   StringRef RelativePath(File);
194   // FIXME: Should '.\\' be accepted on Win32?
195   if (RelativePath.startswith("./")) {
196     RelativePath = RelativePath.substr(strlen("./"));
197   }
198 
199   SmallString<1024> AbsolutePath = RelativePath;
200   std::error_code EC = llvm::sys::fs::make_absolute(AbsolutePath);
201   assert(!EC);
202   (void)EC;
203   llvm::sys::path::native(AbsolutePath);
204   return AbsolutePath.str();
205 }
206 
207 void addTargetAndModeForProgramName(std::vector<std::string> &CommandLine,
208                                     StringRef InvokedAs) {
209   if (!CommandLine.empty() && !InvokedAs.empty()) {
210     bool AlreadyHasTarget = false;
211     bool AlreadyHasMode = false;
212     // Skip CommandLine[0].
213     for (auto Token = ++CommandLine.begin(); Token != CommandLine.end();
214          ++Token) {
215       StringRef TokenRef(*Token);
216       AlreadyHasTarget |=
217           (TokenRef == "-target" || TokenRef.startswith("-target="));
218       AlreadyHasMode |= (TokenRef == "--driver-mode" ||
219                          TokenRef.startswith("--driver-mode="));
220     }
221     auto TargetMode =
222         driver::ToolChain::getTargetAndModeFromProgramName(InvokedAs);
223     if (!AlreadyHasMode && TargetMode.DriverMode) {
224       CommandLine.insert(++CommandLine.begin(), TargetMode.DriverMode);
225     }
226     if (!AlreadyHasTarget && TargetMode.TargetIsValid) {
227       CommandLine.insert(++CommandLine.begin(), {"-target",
228                                                  TargetMode.TargetPrefix});
229     }
230   }
231 }
232 
233 } // namespace tooling
234 } // namespace clang
235 
236 namespace {
237 
238 class SingleFrontendActionFactory : public FrontendActionFactory {
239   FrontendAction *Action;
240 
241 public:
242   SingleFrontendActionFactory(FrontendAction *Action) : Action(Action) {}
243 
244   FrontendAction *create() override { return Action; }
245 };
246 
247 } // namespace
248 
249 ToolInvocation::ToolInvocation(
250     std::vector<std::string> CommandLine, ToolAction *Action,
251     FileManager *Files, std::shared_ptr<PCHContainerOperations> PCHContainerOps)
252     : CommandLine(std::move(CommandLine)), Action(Action), OwnsAction(false),
253       Files(Files), PCHContainerOps(std::move(PCHContainerOps)) {}
254 
255 ToolInvocation::ToolInvocation(
256     std::vector<std::string> CommandLine, FrontendAction *FAction,
257     FileManager *Files, std::shared_ptr<PCHContainerOperations> PCHContainerOps)
258     : CommandLine(std::move(CommandLine)),
259       Action(new SingleFrontendActionFactory(FAction)), OwnsAction(true),
260       Files(Files), PCHContainerOps(std::move(PCHContainerOps)) {}
261 
262 ToolInvocation::~ToolInvocation() {
263   if (OwnsAction)
264     delete Action;
265 }
266 
267 void ToolInvocation::mapVirtualFile(StringRef FilePath, StringRef Content) {
268   SmallString<1024> PathStorage;
269   llvm::sys::path::native(FilePath, PathStorage);
270   MappedFileContents[PathStorage] = Content;
271 }
272 
273 bool ToolInvocation::run() {
274   std::vector<const char*> Argv;
275   for (const std::string &Str : CommandLine)
276     Argv.push_back(Str.c_str());
277   const char *const BinaryName = Argv[0];
278   IntrusiveRefCntPtr<DiagnosticOptions> DiagOpts = new DiagnosticOptions();
279   unsigned MissingArgIndex, MissingArgCount;
280   std::unique_ptr<llvm::opt::OptTable> Opts = driver::createDriverOptTable();
281   llvm::opt::InputArgList ParsedArgs = Opts->ParseArgs(
282       ArrayRef<const char *>(Argv).slice(1), MissingArgIndex, MissingArgCount);
283   ParseDiagnosticArgs(*DiagOpts, ParsedArgs);
284   TextDiagnosticPrinter DiagnosticPrinter(
285       llvm::errs(), &*DiagOpts);
286   DiagnosticsEngine Diagnostics(
287       IntrusiveRefCntPtr<DiagnosticIDs>(new DiagnosticIDs()), &*DiagOpts,
288       DiagConsumer ? DiagConsumer : &DiagnosticPrinter, false);
289 
290   const std::unique_ptr<driver::Driver> Driver(
291       newDriver(&Diagnostics, BinaryName, Files->getVirtualFileSystem()));
292   // Since the input might only be virtual, don't check whether it exists.
293   Driver->setCheckInputsExist(false);
294   const std::unique_ptr<driver::Compilation> Compilation(
295       Driver->BuildCompilation(llvm::makeArrayRef(Argv)));
296   if (!Compilation)
297     return false;
298   const llvm::opt::ArgStringList *const CC1Args = getCC1Arguments(
299       &Diagnostics, Compilation.get());
300   if (!CC1Args)
301     return false;
302   std::unique_ptr<CompilerInvocation> Invocation(
303       newInvocation(&Diagnostics, *CC1Args));
304   // FIXME: remove this when all users have migrated!
305   for (const auto &It : MappedFileContents) {
306     // Inject the code as the given file name into the preprocessor options.
307     std::unique_ptr<llvm::MemoryBuffer> Input =
308         llvm::MemoryBuffer::getMemBuffer(It.getValue());
309     Invocation->getPreprocessorOpts().addRemappedFile(It.getKey(),
310                                                       Input.release());
311   }
312   return runInvocation(BinaryName, Compilation.get(), std::move(Invocation),
313                        std::move(PCHContainerOps));
314 }
315 
316 bool ToolInvocation::runInvocation(
317     const char *BinaryName, driver::Compilation *Compilation,
318     std::shared_ptr<CompilerInvocation> Invocation,
319     std::shared_ptr<PCHContainerOperations> PCHContainerOps) {
320   // Show the invocation, with -v.
321   if (Invocation->getHeaderSearchOpts().Verbose) {
322     llvm::errs() << "clang Invocation:\n";
323     Compilation->getJobs().Print(llvm::errs(), "\n", true);
324     llvm::errs() << "\n";
325   }
326 
327   return Action->runInvocation(std::move(Invocation), Files,
328                                std::move(PCHContainerOps), DiagConsumer);
329 }
330 
331 bool FrontendActionFactory::runInvocation(
332     std::shared_ptr<CompilerInvocation> Invocation, FileManager *Files,
333     std::shared_ptr<PCHContainerOperations> PCHContainerOps,
334     DiagnosticConsumer *DiagConsumer) {
335   // Create a compiler instance to handle the actual work.
336   CompilerInstance Compiler(std::move(PCHContainerOps));
337   Compiler.setInvocation(std::move(Invocation));
338   Compiler.setFileManager(Files);
339 
340   // The FrontendAction can have lifetime requirements for Compiler or its
341   // members, and we need to ensure it's deleted earlier than Compiler. So we
342   // pass it to an std::unique_ptr declared after the Compiler variable.
343   std::unique_ptr<FrontendAction> ScopedToolAction(create());
344 
345   // Create the compiler's actual diagnostics engine.
346   Compiler.createDiagnostics(DiagConsumer, /*ShouldOwnClient=*/false);
347   if (!Compiler.hasDiagnostics())
348     return false;
349 
350   Compiler.createSourceManager(*Files);
351 
352   const bool Success = Compiler.ExecuteAction(*ScopedToolAction);
353 
354   Files->clearStatCaches();
355   return Success;
356 }
357 
358 ClangTool::ClangTool(const CompilationDatabase &Compilations,
359                      ArrayRef<std::string> SourcePaths,
360                      std::shared_ptr<PCHContainerOperations> PCHContainerOps,
361                      IntrusiveRefCntPtr<vfs::FileSystem> BaseFS)
362     : Compilations(Compilations), SourcePaths(SourcePaths),
363       PCHContainerOps(std::move(PCHContainerOps)),
364       OverlayFileSystem(new vfs::OverlayFileSystem(std::move(BaseFS))),
365       InMemoryFileSystem(new vfs::InMemoryFileSystem),
366       Files(new FileManager(FileSystemOptions(), OverlayFileSystem)) {
367   OverlayFileSystem->pushOverlay(InMemoryFileSystem);
368   appendArgumentsAdjuster(getClangStripOutputAdjuster());
369   appendArgumentsAdjuster(getClangSyntaxOnlyAdjuster());
370   appendArgumentsAdjuster(getClangStripDependencyFileAdjuster());
371 }
372 
373 ClangTool::~ClangTool() = default;
374 
375 void ClangTool::mapVirtualFile(StringRef FilePath, StringRef Content) {
376   MappedFileContents.push_back(std::make_pair(FilePath, Content));
377 }
378 
379 void ClangTool::appendArgumentsAdjuster(ArgumentsAdjuster Adjuster) {
380   ArgsAdjuster = combineAdjusters(std::move(ArgsAdjuster), std::move(Adjuster));
381 }
382 
383 void ClangTool::clearArgumentsAdjusters() {
384   ArgsAdjuster = nullptr;
385 }
386 
387 static void injectResourceDir(CommandLineArguments &Args, const char *Argv0,
388                               void *MainAddr) {
389   // Allow users to override the resource dir.
390   for (StringRef Arg : Args)
391     if (Arg.startswith("-resource-dir"))
392       return;
393 
394   // If there's no override in place add our resource dir.
395   Args.push_back("-resource-dir=" +
396                  CompilerInvocation::GetResourcesPath(Argv0, MainAddr));
397 }
398 
399 int ClangTool::run(ToolAction *Action) {
400   // Exists solely for the purpose of lookup of the resource path.
401   // This just needs to be some symbol in the binary.
402   static int StaticSymbol;
403 
404   llvm::SmallString<128> InitialDirectory;
405   if (std::error_code EC = llvm::sys::fs::current_path(InitialDirectory))
406     llvm::report_fatal_error("Cannot detect current path: " +
407                              Twine(EC.message()));
408 
409   // First insert all absolute paths into the in-memory VFS. These are global
410   // for all compile commands.
411   if (SeenWorkingDirectories.insert("/").second)
412     for (const auto &MappedFile : MappedFileContents)
413       if (llvm::sys::path::is_absolute(MappedFile.first))
414         InMemoryFileSystem->addFile(
415             MappedFile.first, 0,
416             llvm::MemoryBuffer::getMemBuffer(MappedFile.second));
417 
418   bool ProcessingFailed = false;
419   bool FileSkipped = false;
420   for (const auto &SourcePath : SourcePaths) {
421     std::string File(getAbsolutePath(SourcePath));
422 
423     // Currently implementations of CompilationDatabase::getCompileCommands can
424     // change the state of the file system (e.g.  prepare generated headers), so
425     // this method needs to run right before we invoke the tool, as the next
426     // file may require a different (incompatible) state of the file system.
427     //
428     // FIXME: Make the compilation database interface more explicit about the
429     // requirements to the order of invocation of its members.
430     std::vector<CompileCommand> CompileCommandsForFile =
431         Compilations.getCompileCommands(File);
432     if (CompileCommandsForFile.empty()) {
433       llvm::errs() << "Skipping " << File << ". Compile command not found.\n";
434       FileSkipped = true;
435       continue;
436     }
437     for (CompileCommand &CompileCommand : CompileCommandsForFile) {
438       // FIXME: chdir is thread hostile; on the other hand, creating the same
439       // behavior as chdir is complex: chdir resolves the path once, thus
440       // guaranteeing that all subsequent relative path operations work
441       // on the same path the original chdir resulted in. This makes a
442       // difference for example on network filesystems, where symlinks might be
443       // switched during runtime of the tool. Fixing this depends on having a
444       // file system abstraction that allows openat() style interactions.
445       if (OverlayFileSystem->setCurrentWorkingDirectory(
446               CompileCommand.Directory))
447         llvm::report_fatal_error("Cannot chdir into \"" +
448                                  Twine(CompileCommand.Directory) + "\n!");
449 
450       // Now fill the in-memory VFS with the relative file mappings so it will
451       // have the correct relative paths. We never remove mappings but that
452       // should be fine.
453       if (SeenWorkingDirectories.insert(CompileCommand.Directory).second)
454         for (const auto &MappedFile : MappedFileContents)
455           if (!llvm::sys::path::is_absolute(MappedFile.first))
456             InMemoryFileSystem->addFile(
457                 MappedFile.first, 0,
458                 llvm::MemoryBuffer::getMemBuffer(MappedFile.second));
459 
460       std::vector<std::string> CommandLine = CompileCommand.CommandLine;
461       if (ArgsAdjuster)
462         CommandLine = ArgsAdjuster(CommandLine, CompileCommand.Filename);
463       assert(!CommandLine.empty());
464 
465       // Add the resource dir based on the binary of this tool. argv[0] in the
466       // compilation database may refer to a different compiler and we want to
467       // pick up the very same standard library that compiler is using. The
468       // builtin headers in the resource dir need to match the exact clang
469       // version the tool is using.
470       // FIXME: On linux, GetMainExecutable is independent of the value of the
471       // first argument, thus allowing ClangTool and runToolOnCode to just
472       // pass in made-up names here. Make sure this works on other platforms.
473       injectResourceDir(CommandLine, "clang_tool", &StaticSymbol);
474 
475       // FIXME: We need a callback mechanism for the tool writer to output a
476       // customized message for each file.
477       DEBUG({ llvm::dbgs() << "Processing: " << File << ".\n"; });
478       ToolInvocation Invocation(std::move(CommandLine), Action, Files.get(),
479                                 PCHContainerOps);
480       Invocation.setDiagnosticConsumer(DiagConsumer);
481 
482       if (!Invocation.run()) {
483         // FIXME: Diagnostics should be used instead.
484         llvm::errs() << "Error while processing " << File << ".\n";
485         ProcessingFailed = true;
486       }
487       // Return to the initial directory to correctly resolve next file by
488       // relative path.
489       if (OverlayFileSystem->setCurrentWorkingDirectory(InitialDirectory.c_str()))
490         llvm::report_fatal_error("Cannot chdir into \"" +
491                                  Twine(InitialDirectory) + "\n!");
492     }
493   }
494   return ProcessingFailed ? 1 : (FileSkipped ? 2 : 0);
495 }
496 
497 namespace {
498 
499 class ASTBuilderAction : public ToolAction {
500   std::vector<std::unique_ptr<ASTUnit>> &ASTs;
501 
502 public:
503   ASTBuilderAction(std::vector<std::unique_ptr<ASTUnit>> &ASTs) : ASTs(ASTs) {}
504 
505   bool runInvocation(std::shared_ptr<CompilerInvocation> Invocation,
506                      FileManager *Files,
507                      std::shared_ptr<PCHContainerOperations> PCHContainerOps,
508                      DiagnosticConsumer *DiagConsumer) override {
509     std::unique_ptr<ASTUnit> AST = ASTUnit::LoadFromCompilerInvocation(
510         Invocation, std::move(PCHContainerOps),
511         CompilerInstance::createDiagnostics(&Invocation->getDiagnosticOpts(),
512                                             DiagConsumer,
513                                             /*ShouldOwnClient=*/false),
514         Files);
515     if (!AST)
516       return false;
517 
518     ASTs.push_back(std::move(AST));
519     return true;
520   }
521 };
522 
523 } // namespace
524 
525 int ClangTool::buildASTs(std::vector<std::unique_ptr<ASTUnit>> &ASTs) {
526   ASTBuilderAction Action(ASTs);
527   return run(&Action);
528 }
529 
530 namespace clang {
531 namespace tooling {
532 
533 std::unique_ptr<ASTUnit>
534 buildASTFromCode(const Twine &Code, const Twine &FileName,
535                  std::shared_ptr<PCHContainerOperations> PCHContainerOps) {
536   return buildASTFromCodeWithArgs(Code, std::vector<std::string>(), FileName,
537                                   "clang-tool", std::move(PCHContainerOps));
538 }
539 
540 std::unique_ptr<ASTUnit> buildASTFromCodeWithArgs(
541     const Twine &Code, const std::vector<std::string> &Args,
542     const Twine &FileName, const Twine &ToolName,
543     std::shared_ptr<PCHContainerOperations> PCHContainerOps,
544     ArgumentsAdjuster Adjuster) {
545   SmallString<16> FileNameStorage;
546   StringRef FileNameRef = FileName.toNullTerminatedStringRef(FileNameStorage);
547 
548   std::vector<std::unique_ptr<ASTUnit>> ASTs;
549   ASTBuilderAction Action(ASTs);
550   llvm::IntrusiveRefCntPtr<vfs::OverlayFileSystem> OverlayFileSystem(
551       new vfs::OverlayFileSystem(vfs::getRealFileSystem()));
552   llvm::IntrusiveRefCntPtr<vfs::InMemoryFileSystem> InMemoryFileSystem(
553       new vfs::InMemoryFileSystem);
554   OverlayFileSystem->pushOverlay(InMemoryFileSystem);
555   llvm::IntrusiveRefCntPtr<FileManager> Files(
556       new FileManager(FileSystemOptions(), OverlayFileSystem));
557 
558   ToolInvocation Invocation(
559       getSyntaxOnlyToolArgs(ToolName, Adjuster(Args, FileNameRef), FileNameRef),
560       &Action, Files.get(), std::move(PCHContainerOps));
561 
562   SmallString<1024> CodeStorage;
563   InMemoryFileSystem->addFile(FileNameRef, 0,
564                               llvm::MemoryBuffer::getMemBuffer(
565                                   Code.toNullTerminatedStringRef(CodeStorage)));
566   if (!Invocation.run())
567     return nullptr;
568 
569   assert(ASTs.size() == 1);
570   return std::move(ASTs[0]);
571 }
572 
573 } // namespace tooling
574 } // namespace clang
575