Export clang-format16 via ydblib project

6e6be3a95868fde888d801b7590af4044049563f

1 files changed, 696 insertions, 0 deletions

diff --git a/contrib/libs/clang16/lib/Tooling/Tooling.cpp b/contrib/libs/clang16/lib/Tooling/Tooling.cpp
new file mode 100644
index 0000000000..89835aac07
--- /dev/null
+++ b/contrib/libs/clang16/lib/Tooling/Tooling.cpp
@@ -0,0 +1,696 @@
+//===- Tooling.cpp - Running clang standalone tools -----------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+//  This file implements functions to run clang tools standalone instead
+//  of running them as a plugin.
+//
+//===----------------------------------------------------------------------===//
+
+#include "clang/Tooling/Tooling.h"
+#include "clang/Basic/Diagnostic.h"
+#include "clang/Basic/DiagnosticIDs.h"
+#include "clang/Basic/DiagnosticOptions.h"
+#include "clang/Basic/FileManager.h"
+#include "clang/Basic/FileSystemOptions.h"
+#include "clang/Basic/LLVM.h"
+#include "clang/Driver/Compilation.h"
+#include "clang/Driver/Driver.h"
+#include "clang/Driver/Job.h"
+#include "clang/Driver/Options.h"
+#include "clang/Driver/Tool.h"
+#include "clang/Driver/ToolChain.h"
+#include "clang/Frontend/ASTUnit.h"
+#include "clang/Frontend/CompilerInstance.h"
+#include "clang/Frontend/CompilerInvocation.h"
+#include "clang/Frontend/FrontendDiagnostic.h"
+#include "clang/Frontend/FrontendOptions.h"
+#include "clang/Frontend/TextDiagnosticPrinter.h"
+#include "clang/Lex/HeaderSearchOptions.h"
+#include "clang/Lex/PreprocessorOptions.h"
+#include "clang/Tooling/ArgumentsAdjusters.h"
+#include "clang/Tooling/CompilationDatabase.h"
+#include "llvm/ADT/ArrayRef.h"
+#include "llvm/ADT/IntrusiveRefCntPtr.h"
+#include "llvm/ADT/SmallString.h"
+#include "llvm/ADT/StringRef.h"
+#include "llvm/ADT/Twine.h"
+#include "llvm/Option/ArgList.h"
+#include "llvm/Option/OptTable.h"
+#include "llvm/Option/Option.h"
+#include "llvm/Support/Casting.h"
+#include "llvm/Support/Debug.h"
+#include "llvm/Support/ErrorHandling.h"
+#include "llvm/Support/FileSystem.h"
+#include "llvm/Support/Host.h"
+#include "llvm/Support/MemoryBuffer.h"
+#include "llvm/Support/Path.h"
+#include "llvm/Support/VirtualFileSystem.h"
+#include "llvm/Support/raw_ostream.h"
+#include <cassert>
+#include <cstring>
+#include <memory>
+#include <string>
+#include <system_error>
+#include <utility>
+#include <vector>
+
+#define DEBUG_TYPE "clang-tooling"
+
+using namespace clang;
+using namespace tooling;
+
+ToolAction::~ToolAction() = default;
+
+FrontendActionFactory::~FrontendActionFactory() = default;
+
+// FIXME: This file contains structural duplication with other parts of the
+// code that sets up a compiler to run tools on it, and we should refactor
+// it to be based on the same framework.
+
+/// Builds a clang driver initialized for running clang tools.
+static driver::Driver *
+newDriver(DiagnosticsEngine *Diagnostics, const char *BinaryName,
+          IntrusiveRefCntPtr<llvm::vfs::FileSystem> VFS) {
+  driver::Driver *CompilerDriver =
+      new driver::Driver(BinaryName, llvm::sys::getDefaultTargetTriple(),
+                         *Diagnostics, "clang LLVM compiler", std::move(VFS));
+  CompilerDriver->setTitle("clang_based_tool");
+  return CompilerDriver;
+}
+
+/// Decide whether extra compiler frontend commands can be ignored.
+static bool ignoreExtraCC1Commands(const driver::Compilation *Compilation) {
+  const driver::JobList &Jobs = Compilation->getJobs();
+  const driver::ActionList &Actions = Compilation->getActions();
+
+  bool OffloadCompilation = false;
+
+  // Jobs and Actions look very different depending on whether the Clang tool
+  // injected -fsyntax-only or not. Try to handle both cases here.
+
+  for (const auto &Job : Jobs)
+    if (StringRef(Job.getExecutable()) == "clang-offload-bundler")
+      OffloadCompilation = true;
+
+  if (Jobs.size() > 1) {
+    for (auto *A : Actions){
+      // On MacOSX real actions may end up being wrapped in BindArchAction
+      if (isa<driver::BindArchAction>(A))
+        A = *A->input_begin();
+      if (isa<driver::OffloadAction>(A)) {
+        // Offload compilation has 2 top-level actions, one (at the front) is
+        // the original host compilation and the other is offload action
+        // composed of at least one device compilation. For such case, general
+        // tooling will consider host-compilation only. For tooling on device
+        // compilation, device compilation only option, such as
+        // `--cuda-device-only`, needs specifying.
+        assert(Actions.size() > 1);
+        assert(
+            isa<driver::CompileJobAction>(Actions.front()) ||
+            // On MacOSX real actions may end up being wrapped in
+            // BindArchAction.
+            (isa<driver::BindArchAction>(Actions.front()) &&
+             isa<driver::CompileJobAction>(*Actions.front()->input_begin())));
+        OffloadCompilation = true;
+        break;
+      }
+    }
+  }
+
+  return OffloadCompilation;
+}
+
+namespace clang {
+namespace tooling {
+
+const llvm::opt::ArgStringList *
+getCC1Arguments(DiagnosticsEngine *Diagnostics,
+                driver::Compilation *Compilation) {
+  const driver::JobList &Jobs = Compilation->getJobs();
+
+  auto IsCC1Command = [](const driver::Command &Cmd) {
+    return StringRef(Cmd.getCreator().getName()) == "clang";
+  };
+
+  auto IsSrcFile = [](const driver::InputInfo &II) {
+    return isSrcFile(II.getType());
+  };
+
+  llvm::SmallVector<const driver::Command *, 1> CC1Jobs;
+  for (const driver::Command &Job : Jobs)
+    if (IsCC1Command(Job) && llvm::all_of(Job.getInputInfos(), IsSrcFile))
+      CC1Jobs.push_back(&Job);
+
+  if (CC1Jobs.empty() ||
+      (CC1Jobs.size() > 1 && !ignoreExtraCC1Commands(Compilation))) {
+    SmallString<256> error_msg;
+    llvm::raw_svector_ostream error_stream(error_msg);
+    Jobs.Print(error_stream, "; ", true);
+    Diagnostics->Report(diag::err_fe_expected_compiler_job)
+        << error_stream.str();
+    return nullptr;
+  }
+
+  return &CC1Jobs[0]->getArguments();
+}
+
+/// Returns a clang build invocation initialized from the CC1 flags.
+CompilerInvocation *newInvocation(DiagnosticsEngine *Diagnostics,
+                                  ArrayRef<const char *> CC1Args,
+                                  const char *const BinaryName) {
+  assert(!CC1Args.empty() && "Must at least contain the program name!");
+  CompilerInvocation *Invocation = new CompilerInvocation;
+  CompilerInvocation::CreateFromArgs(*Invocation, CC1Args, *Diagnostics,
+                                     BinaryName);
+  Invocation->getFrontendOpts().DisableFree = false;
+  Invocation->getCodeGenOpts().DisableFree = false;
+  return Invocation;
+}
+
+bool runToolOnCode(std::unique_ptr<FrontendAction> ToolAction,
+                   const Twine &Code, const Twine &FileName,
+                   std::shared_ptr<PCHContainerOperations> PCHContainerOps) {
+  return runToolOnCodeWithArgs(std::move(ToolAction), Code,
+                               std::vector<std::string>(), FileName,
+                               "clang-tool", std::move(PCHContainerOps));
+}
+
+} // namespace tooling
+} // namespace clang
+
+static std::vector<std::string>
+getSyntaxOnlyToolArgs(const Twine &ToolName,
+                      const std::vector<std::string> &ExtraArgs,
+                      StringRef FileName) {
+  std::vector<std::string> Args;
+  Args.push_back(ToolName.str());
+  Args.push_back("-fsyntax-only");
+  Args.insert(Args.end(), ExtraArgs.begin(), ExtraArgs.end());
+  Args.push_back(FileName.str());
+  return Args;
+}
+
+namespace clang {
+namespace tooling {
+
+bool runToolOnCodeWithArgs(
+    std::unique_ptr<FrontendAction> ToolAction, const Twine &Code,
+    llvm::IntrusiveRefCntPtr<llvm::vfs::FileSystem> VFS,
+    const std::vector<std::string> &Args, const Twine &FileName,
+    const Twine &ToolName,
+    std::shared_ptr<PCHContainerOperations> PCHContainerOps) {
+  SmallString<16> FileNameStorage;
+  StringRef FileNameRef = FileName.toNullTerminatedStringRef(FileNameStorage);
+
+  llvm::IntrusiveRefCntPtr<FileManager> Files(
+      new FileManager(FileSystemOptions(), VFS));
+  ArgumentsAdjuster Adjuster = getClangStripDependencyFileAdjuster();
+  ToolInvocation Invocation(
+      getSyntaxOnlyToolArgs(ToolName, Adjuster(Args, FileNameRef), FileNameRef),
+      std::move(ToolAction), Files.get(), std::move(PCHContainerOps));
+  return Invocation.run();
+}
+
+bool runToolOnCodeWithArgs(
+    std::unique_ptr<FrontendAction> ToolAction, const Twine &Code,
+    const std::vector<std::string> &Args, const Twine &FileName,
+    const Twine &ToolName,
+    std::shared_ptr<PCHContainerOperations> PCHContainerOps,
+    const FileContentMappings &VirtualMappedFiles) {
+  llvm::IntrusiveRefCntPtr<llvm::vfs::OverlayFileSystem> OverlayFileSystem(
+      new llvm::vfs::OverlayFileSystem(llvm::vfs::getRealFileSystem()));
+  llvm::IntrusiveRefCntPtr<llvm::vfs::InMemoryFileSystem> InMemoryFileSystem(
+      new llvm::vfs::InMemoryFileSystem);
+  OverlayFileSystem->pushOverlay(InMemoryFileSystem);
+
+  SmallString<1024> CodeStorage;
+  InMemoryFileSystem->addFile(FileName, 0,
+                              llvm::MemoryBuffer::getMemBuffer(
+                                  Code.toNullTerminatedStringRef(CodeStorage)));
+
+  for (auto &FilenameWithContent : VirtualMappedFiles) {
+    InMemoryFileSystem->addFile(
+        FilenameWithContent.first, 0,
+        llvm::MemoryBuffer::getMemBuffer(FilenameWithContent.second));
+  }
+
+  return runToolOnCodeWithArgs(std::move(ToolAction), Code, OverlayFileSystem,
+                               Args, FileName, ToolName);
+}
+
+llvm::Expected<std::string> getAbsolutePath(llvm::vfs::FileSystem &FS,
+                                            StringRef File) {
+  StringRef RelativePath(File);
+  // FIXME: Should '.\\' be accepted on Win32?
+  if (RelativePath.startswith("./")) {
+    RelativePath = RelativePath.substr(strlen("./"));
+  }
+
+  SmallString<1024> AbsolutePath = RelativePath;
+  if (auto EC = FS.makeAbsolute(AbsolutePath))
+    return llvm::errorCodeToError(EC);
+  llvm::sys::path::native(AbsolutePath);
+  return std::string(AbsolutePath.str());
+}
+
+std::string getAbsolutePath(StringRef File) {
+  return llvm::cantFail(getAbsolutePath(*llvm::vfs::getRealFileSystem(), File));
+}
+
+void addTargetAndModeForProgramName(std::vector<std::string> &CommandLine,
+                                    StringRef InvokedAs) {
+  if (CommandLine.empty() || InvokedAs.empty())
+    return;
+  const auto &Table = driver::getDriverOptTable();
+  // --target=X
+  const std::string TargetOPT =
+      Table.getOption(driver::options::OPT_target).getPrefixedName();
+  // -target X
+  const std::string TargetOPTLegacy =
+      Table.getOption(driver::options::OPT_target_legacy_spelling)
+          .getPrefixedName();
+  // --driver-mode=X
+  const std::string DriverModeOPT =
+      Table.getOption(driver::options::OPT_driver_mode).getPrefixedName();
+  auto TargetMode =
+      driver::ToolChain::getTargetAndModeFromProgramName(InvokedAs);
+  // No need to search for target args if we don't have a target/mode to insert.
+  bool ShouldAddTarget = TargetMode.TargetIsValid;
+  bool ShouldAddMode = TargetMode.DriverMode != nullptr;
+  // Skip CommandLine[0].
+  auto CommandLine1 = CommandLine.begin();
+  ++CommandLine1;
+  for (auto Token = CommandLine1; Token != CommandLine.end();
+       ++Token) {
+    StringRef TokenRef(*Token);
+    ShouldAddTarget = ShouldAddTarget && !TokenRef.startswith(TargetOPT) &&
+                      !TokenRef.equals(TargetOPTLegacy);
+    ShouldAddMode = ShouldAddMode && !TokenRef.startswith(DriverModeOPT);
+  }
+  if (ShouldAddMode) {
+    CommandLine.insert(CommandLine1, TargetMode.DriverMode);
+
+  }
+  if (ShouldAddTarget) {
+    CommandLine.insert(CommandLine1,
+                       TargetOPT + TargetMode.TargetPrefix);
+  }
+}
+
+} // namespace tooling
+} // namespace clang
+
+namespace {
+
+class SingleFrontendActionFactory : public FrontendActionFactory {
+  std::unique_ptr<FrontendAction> Action;
+
+public:
+  SingleFrontendActionFactory(std::unique_ptr<FrontendAction> Action)
+      : Action(std::move(Action)) {}
+
+  std::unique_ptr<FrontendAction> create() override {
+    return std::move(Action);
+  }
+};
+
+} // namespace
+
+ToolInvocation::ToolInvocation(
+    std::vector<std::string> CommandLine, ToolAction *Action,
+    FileManager *Files, std::shared_ptr<PCHContainerOperations> PCHContainerOps)
+    : CommandLine(std::move(CommandLine)), Action(Action), OwnsAction(false),
+      Files(Files), PCHContainerOps(std::move(PCHContainerOps)) {}
+
+ToolInvocation::ToolInvocation(
+    std::vector<std::string> CommandLine,
+    std::unique_ptr<FrontendAction> FAction, FileManager *Files,
+    std::shared_ptr<PCHContainerOperations> PCHContainerOps)
+    : CommandLine(std::move(CommandLine)),
+      Action(new SingleFrontendActionFactory(std::move(FAction))),
+      OwnsAction(true), Files(Files),
+      PCHContainerOps(std::move(PCHContainerOps)) {}
+
+ToolInvocation::~ToolInvocation() {
+  if (OwnsAction)
+    delete Action;
+}
+
+bool ToolInvocation::run() {
+  llvm::opt::ArgStringList Argv;
+  for (const std::string &Str : CommandLine)
+    Argv.push_back(Str.c_str());
+  const char *const BinaryName = Argv[0];
+
+  // Parse diagnostic options from the driver command-line only if none were
+  // explicitly set.
+  IntrusiveRefCntPtr<DiagnosticOptions> ParsedDiagOpts;
+  DiagnosticOptions *DiagOpts = this->DiagOpts;
+  if (!DiagOpts) {
+    ParsedDiagOpts = CreateAndPopulateDiagOpts(Argv);
+    DiagOpts = &*ParsedDiagOpts;
+  }
+
+  TextDiagnosticPrinter DiagnosticPrinter(llvm::errs(), DiagOpts);
+  IntrusiveRefCntPtr<DiagnosticsEngine> Diagnostics =
+      CompilerInstance::createDiagnostics(
+          &*DiagOpts, DiagConsumer ? DiagConsumer : &DiagnosticPrinter, false);
+  // Although `Diagnostics` are used only for command-line parsing, the custom
+  // `DiagConsumer` might expect a `SourceManager` to be present.
+  SourceManager SrcMgr(*Diagnostics, *Files);
+  Diagnostics->setSourceManager(&SrcMgr);
+
+  // We already have a cc1, just create an invocation.
+  if (CommandLine.size() >= 2 && CommandLine[1] == "-cc1") {
+    ArrayRef<const char *> CC1Args = ArrayRef(Argv).drop_front();
+    std::unique_ptr<CompilerInvocation> Invocation(
+        newInvocation(&*Diagnostics, CC1Args, BinaryName));
+    if (Diagnostics->hasErrorOccurred())
+      return false;
+    return Action->runInvocation(std::move(Invocation), Files,
+                                 std::move(PCHContainerOps), DiagConsumer);
+  }
+
+  const std::unique_ptr<driver::Driver> Driver(
+      newDriver(&*Diagnostics, BinaryName, &Files->getVirtualFileSystem()));
+  // The "input file not found" diagnostics from the driver are useful.
+  // The driver is only aware of the VFS working directory, but some clients
+  // change this at the FileManager level instead.
+  // In this case the checks have false positives, so skip them.
+  if (!Files->getFileSystemOpts().WorkingDir.empty())
+    Driver->setCheckInputsExist(false);
+  const std::unique_ptr<driver::Compilation> Compilation(
+      Driver->BuildCompilation(llvm::ArrayRef(Argv)));
+  if (!Compilation)
+    return false;
+  const llvm::opt::ArgStringList *const CC1Args = getCC1Arguments(
+      &*Diagnostics, Compilation.get());
+  if (!CC1Args)
+    return false;
+  std::unique_ptr<CompilerInvocation> Invocation(
+      newInvocation(&*Diagnostics, *CC1Args, BinaryName));
+  return runInvocation(BinaryName, Compilation.get(), std::move(Invocation),
+                       std::move(PCHContainerOps));
+}
+
+bool ToolInvocation::runInvocation(
+    const char *BinaryName, driver::Compilation *Compilation,
+    std::shared_ptr<CompilerInvocation> Invocation,
+    std::shared_ptr<PCHContainerOperations> PCHContainerOps) {
+  // Show the invocation, with -v.
+  if (Invocation->getHeaderSearchOpts().Verbose) {
+    llvm::errs() << "clang Invocation:\n";
+    Compilation->getJobs().Print(llvm::errs(), "\n", true);
+    llvm::errs() << "\n";
+  }
+
+  return Action->runInvocation(std::move(Invocation), Files,
+                               std::move(PCHContainerOps), DiagConsumer);
+}
+
+bool FrontendActionFactory::runInvocation(
+    std::shared_ptr<CompilerInvocation> Invocation, FileManager *Files,
+    std::shared_ptr<PCHContainerOperations> PCHContainerOps,
+    DiagnosticConsumer *DiagConsumer) {
+  // Create a compiler instance to handle the actual work.
+  CompilerInstance Compiler(std::move(PCHContainerOps));
+  Compiler.setInvocation(std::move(Invocation));
+  Compiler.setFileManager(Files);
+
+  // The FrontendAction can have lifetime requirements for Compiler or its
+  // members, and we need to ensure it's deleted earlier than Compiler. So we
+  // pass it to an std::unique_ptr declared after the Compiler variable.
+  std::unique_ptr<FrontendAction> ScopedToolAction(create());
+
+  // Create the compiler's actual diagnostics engine.
+  Compiler.createDiagnostics(DiagConsumer, /*ShouldOwnClient=*/false);
+  if (!Compiler.hasDiagnostics())
+    return false;
+
+  Compiler.createSourceManager(*Files);
+
+  const bool Success = Compiler.ExecuteAction(*ScopedToolAction);
+
+  Files->clearStatCache();
+  return Success;
+}
+
+ClangTool::ClangTool(const CompilationDatabase &Compilations,
+                     ArrayRef<std::string> SourcePaths,
+                     std::shared_ptr<PCHContainerOperations> PCHContainerOps,
+                     IntrusiveRefCntPtr<llvm::vfs::FileSystem> BaseFS,
+                     IntrusiveRefCntPtr<FileManager> Files)
+    : Compilations(Compilations), SourcePaths(SourcePaths),
+      PCHContainerOps(std::move(PCHContainerOps)),
+      OverlayFileSystem(new llvm::vfs::OverlayFileSystem(std::move(BaseFS))),
+      InMemoryFileSystem(new llvm::vfs::InMemoryFileSystem),
+      Files(Files ? Files
+                  : new FileManager(FileSystemOptions(), OverlayFileSystem)) {
+  OverlayFileSystem->pushOverlay(InMemoryFileSystem);
+  appendArgumentsAdjuster(getClangStripOutputAdjuster());
+  appendArgumentsAdjuster(getClangSyntaxOnlyAdjuster());
+  appendArgumentsAdjuster(getClangStripDependencyFileAdjuster());
+  if (Files)
+    Files->setVirtualFileSystem(OverlayFileSystem);
+}
+
+ClangTool::~ClangTool() = default;
+
+void ClangTool::mapVirtualFile(StringRef FilePath, StringRef Content) {
+  MappedFileContents.push_back(std::make_pair(FilePath, Content));
+}
+
+void ClangTool::appendArgumentsAdjuster(ArgumentsAdjuster Adjuster) {
+  ArgsAdjuster = combineAdjusters(std::move(ArgsAdjuster), std::move(Adjuster));
+}
+
+void ClangTool::clearArgumentsAdjusters() {
+  ArgsAdjuster = nullptr;
+}
+
+static void injectResourceDir(CommandLineArguments &Args, const char *Argv0,
+                              void *MainAddr) {
+  // Allow users to override the resource dir.
+  for (StringRef Arg : Args)
+    if (Arg.startswith("-resource-dir"))
+      return;
+
+  // If there's no override in place add our resource dir.
+  Args = getInsertArgumentAdjuster(
+      ("-resource-dir=" + CompilerInvocation::GetResourcesPath(Argv0, MainAddr))
+          .c_str())(Args, "");
+}
+
+int ClangTool::run(ToolAction *Action) {
+  // Exists solely for the purpose of lookup of the resource path.
+  // This just needs to be some symbol in the binary.
+  static int StaticSymbol;
+
+  // First insert all absolute paths into the in-memory VFS. These are global
+  // for all compile commands.
+  if (SeenWorkingDirectories.insert("/").second)
+    for (const auto &MappedFile : MappedFileContents)
+      if (llvm::sys::path::is_absolute(MappedFile.first))
+        InMemoryFileSystem->addFile(
+            MappedFile.first, 0,
+            llvm::MemoryBuffer::getMemBuffer(MappedFile.second));
+
+  bool ProcessingFailed = false;
+  bool FileSkipped = false;
+  // Compute all absolute paths before we run any actions, as those will change
+  // the working directory.
+  std::vector<std::string> AbsolutePaths;
+  AbsolutePaths.reserve(SourcePaths.size());
+  for (const auto &SourcePath : SourcePaths) {
+    auto AbsPath = getAbsolutePath(*OverlayFileSystem, SourcePath);
+    if (!AbsPath) {
+      llvm::errs() << "Skipping " << SourcePath
+                   << ". Error while getting an absolute path: "
+                   << llvm::toString(AbsPath.takeError()) << "\n";
+      continue;
+    }
+    AbsolutePaths.push_back(std::move(*AbsPath));
+  }
+
+  // Remember the working directory in case we need to restore it.
+  std::string InitialWorkingDir;
+  if (RestoreCWD) {
+    if (auto CWD = OverlayFileSystem->getCurrentWorkingDirectory()) {
+      InitialWorkingDir = std::move(*CWD);
+    } else {
+      llvm::errs() << "Could not get working directory: "
+                   << CWD.getError().message() << "\n";
+    }
+  }
+
+  for (llvm::StringRef File : AbsolutePaths) {
+    // Currently implementations of CompilationDatabase::getCompileCommands can
+    // change the state of the file system (e.g.  prepare generated headers), so
+    // this method needs to run right before we invoke the tool, as the next
+    // file may require a different (incompatible) state of the file system.
+    //
+    // FIXME: Make the compilation database interface more explicit about the
+    // requirements to the order of invocation of its members.
+    std::vector<CompileCommand> CompileCommandsForFile =
+        Compilations.getCompileCommands(File);
+    if (CompileCommandsForFile.empty()) {
+      llvm::errs() << "Skipping " << File << ". Compile command not found.\n";
+      FileSkipped = true;
+      continue;
+    }
+    for (CompileCommand &CompileCommand : CompileCommandsForFile) {
+      // FIXME: chdir is thread hostile; on the other hand, creating the same
+      // behavior as chdir is complex: chdir resolves the path once, thus
+      // guaranteeing that all subsequent relative path operations work
+      // on the same path the original chdir resulted in. This makes a
+      // difference for example on network filesystems, where symlinks might be
+      // switched during runtime of the tool. Fixing this depends on having a
+      // file system abstraction that allows openat() style interactions.
+      if (OverlayFileSystem->setCurrentWorkingDirectory(
+              CompileCommand.Directory))
+        llvm::report_fatal_error("Cannot chdir into \"" +
+                                 Twine(CompileCommand.Directory) + "\"!");
+
+      // Now fill the in-memory VFS with the relative file mappings so it will
+      // have the correct relative paths. We never remove mappings but that
+      // should be fine.
+      if (SeenWorkingDirectories.insert(CompileCommand.Directory).second)
+        for (const auto &MappedFile : MappedFileContents)
+          if (!llvm::sys::path::is_absolute(MappedFile.first))
+            InMemoryFileSystem->addFile(
+                MappedFile.first, 0,
+                llvm::MemoryBuffer::getMemBuffer(MappedFile.second));
+
+      std::vector<std::string> CommandLine = CompileCommand.CommandLine;
+      if (ArgsAdjuster)
+        CommandLine = ArgsAdjuster(CommandLine, CompileCommand.Filename);
+      assert(!CommandLine.empty());
+
+      // Add the resource dir based on the binary of this tool. argv[0] in the
+      // compilation database may refer to a different compiler and we want to
+      // pick up the very same standard library that compiler is using. The
+      // builtin headers in the resource dir need to match the exact clang
+      // version the tool is using.
+      // FIXME: On linux, GetMainExecutable is independent of the value of the
+      // first argument, thus allowing ClangTool and runToolOnCode to just
+      // pass in made-up names here. Make sure this works on other platforms.
+      injectResourceDir(CommandLine, "clang_tool", &StaticSymbol);
+
+      // FIXME: We need a callback mechanism for the tool writer to output a
+      // customized message for each file.
+      LLVM_DEBUG({ llvm::dbgs() << "Processing: " << File << ".\n"; });
+      ToolInvocation Invocation(std::move(CommandLine), Action, Files.get(),
+                                PCHContainerOps);
+      Invocation.setDiagnosticConsumer(DiagConsumer);
+
+      if (!Invocation.run()) {
+        // FIXME: Diagnostics should be used instead.
+        if (PrintErrorMessage)
+          llvm::errs() << "Error while processing " << File << ".\n";
+        ProcessingFailed = true;
+      }
+    }
+  }
+
+  if (!InitialWorkingDir.empty()) {
+    if (auto EC =
+            OverlayFileSystem->setCurrentWorkingDirectory(InitialWorkingDir))
+      llvm::errs() << "Error when trying to restore working dir: "
+                   << EC.message() << "\n";
+  }
+  return ProcessingFailed ? 1 : (FileSkipped ? 2 : 0);
+}
+
+namespace {
+
+class ASTBuilderAction : public ToolAction {
+  std::vector<std::unique_ptr<ASTUnit>> &ASTs;
+
+public:
+  ASTBuilderAction(std::vector<std::unique_ptr<ASTUnit>> &ASTs) : ASTs(ASTs) {}
+
+  bool runInvocation(std::shared_ptr<CompilerInvocation> Invocation,
+                     FileManager *Files,
+                     std::shared_ptr<PCHContainerOperations> PCHContainerOps,
+                     DiagnosticConsumer *DiagConsumer) override {
+    std::unique_ptr<ASTUnit> AST = ASTUnit::LoadFromCompilerInvocation(
+        Invocation, std::move(PCHContainerOps),
+        CompilerInstance::createDiagnostics(&Invocation->getDiagnosticOpts(),
+                                            DiagConsumer,
+                                            /*ShouldOwnClient=*/false),
+        Files);
+    if (!AST)
+      return false;
+
+    ASTs.push_back(std::move(AST));
+    return true;
+  }
+};
+
+} // namespace
+
+int ClangTool::buildASTs(std::vector<std::unique_ptr<ASTUnit>> &ASTs) {
+  ASTBuilderAction Action(ASTs);
+  return run(&Action);
+}
+
+void ClangTool::setRestoreWorkingDir(bool RestoreCWD) {
+  this->RestoreCWD = RestoreCWD;
+}
+
+void ClangTool::setPrintErrorMessage(bool PrintErrorMessage) {
+  this->PrintErrorMessage = PrintErrorMessage;
+}
+
+namespace clang {
+namespace tooling {
+
+std::unique_ptr<ASTUnit>
+buildASTFromCode(StringRef Code, StringRef FileName,
+                 std::shared_ptr<PCHContainerOperations> PCHContainerOps) {
+  return buildASTFromCodeWithArgs(Code, std::vector<std::string>(), FileName,
+                                  "clang-tool", std::move(PCHContainerOps));
+}
+
+std::unique_ptr<ASTUnit> buildASTFromCodeWithArgs(
+    StringRef Code, const std::vector<std::string> &Args, StringRef FileName,
+    StringRef ToolName, std::shared_ptr<PCHContainerOperations> PCHContainerOps,
+    ArgumentsAdjuster Adjuster, const FileContentMappings &VirtualMappedFiles,
+    DiagnosticConsumer *DiagConsumer) {
+  std::vector<std::unique_ptr<ASTUnit>> ASTs;
+  ASTBuilderAction Action(ASTs);
+  llvm::IntrusiveRefCntPtr<llvm::vfs::OverlayFileSystem> OverlayFileSystem(
+      new llvm::vfs::OverlayFileSystem(llvm::vfs::getRealFileSystem()));
+  llvm::IntrusiveRefCntPtr<llvm::vfs::InMemoryFileSystem> InMemoryFileSystem(
+      new llvm::vfs::InMemoryFileSystem);
+  OverlayFileSystem->pushOverlay(InMemoryFileSystem);
+  llvm::IntrusiveRefCntPtr<FileManager> Files(
+      new FileManager(FileSystemOptions(), OverlayFileSystem));
+
+  ToolInvocation Invocation(
+      getSyntaxOnlyToolArgs(ToolName, Adjuster(Args, FileName), FileName),
+      &Action, Files.get(), std::move(PCHContainerOps));
+  Invocation.setDiagnosticConsumer(DiagConsumer);
+
+  InMemoryFileSystem->addFile(FileName, 0,
+                              llvm::MemoryBuffer::getMemBufferCopy(Code));
+  for (auto &FilenameWithContent : VirtualMappedFiles) {
+    InMemoryFileSystem->addFile(
+        FilenameWithContent.first, 0,
+        llvm::MemoryBuffer::getMemBuffer(FilenameWithContent.second));
+  }
+
+  if (!Invocation.run())
+    return nullptr;
+ 
+  assert(ASTs.size() == 1);
+  return std::move(ASTs[0]);
+}
+
+} // namespace tooling
+} // namespace clang