Index: CMakeLists.txt
===================================================================
--- CMakeLists.txt
+++ CMakeLists.txt
@@ -2,6 +2,7 @@
 add_subdirectory(clang-modernize)
 add_subdirectory(clang-tidy)
 add_subdirectory(modularize)
+add_subdirectory(pp-trace)
 add_subdirectory(remove-cstr-calls)
 add_subdirectory(tool-template)
 
Index: Makefile
===================================================================
--- Makefile
+++ Makefile
@@ -11,7 +11,7 @@
 
 include $(CLANG_LEVEL)/../../Makefile.config
 
-PARALLEL_DIRS := remove-cstr-calls tool-template modularize
+PARALLEL_DIRS := remove-cstr-calls tool-template modularize pp-trace
 DIRS := clang-apply-replacements clang-modernize clang-tidy unittests
 
 include $(CLANG_LEVEL)/Makefile
Index: pp-trace/CMakeLists.txt
===================================================================
--- pp-trace/CMakeLists.txt
+++ pp-trace/CMakeLists.txt
@@ -0,0 +1,18 @@
+set(LLVM_LINK_COMPONENTS
+  ${LLVM_TARGETS_TO_BUILD}
+  asmparser
+  support
+  mc
+  )
+
+add_clang_executable(pp-trace
+  PPTrace.cpp
+  PPCallbacksTracker.cpp
+  )
+
+target_link_libraries(pp-trace
+  clangLex
+  clangParse
+  clangSema
+  clangTooling
+  )
Index: pp-trace/Makefile
===================================================================
--- pp-trace/Makefile
+++ pp-trace/Makefile
@@ -0,0 +1,22 @@
+##===- extra/pp-trace/Makefile --------------------------*- Makefile -*---===##
+#
+#                     The LLVM Compiler Infrastructure
+#
+# This file is distributed under the University of Illinois Open Source
+# License. See LICENSE.TXT for details.
+#
+##===---------------------------------------------------------------------===##
+
+CLANG_LEVEL := ../../..
+
+TOOLNAME = pp-trace
+
+# No plugins, optimize startup time.
+TOOL_NO_EXPORTS = 1
+
+LINK_COMPONENTS := mcparser bitreader support mc option TransformUtils
+USEDLIBS = clangFrontend.a clangSerialization.a clangDriver.a \
+           clangTooling.a clangParse.a clangSema.a clangAnalysis.a \
+           clangEdit.a clangAST.a clangLex.a clangBasic.a
+
+include $(CLANG_LEVEL)/Makefile
Index: pp-trace/PPCallbacksTracker.h
===================================================================
--- pp-trace/PPCallbacksTracker.h
+++ pp-trace/PPCallbacksTracker.h
@@ -0,0 +1,240 @@
+//===--- PPCallbacksTracker.h - Preprocessor tracking -*- C++ -*---------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===--------------------------------------------------------------------===//
+///
+/// \file
+/// \brief Classes and definitions for preprocessor tracking.
+///
+/// The core definition is the PPCallbacksTracker class, derived from Clang's
+/// PPCallbacks class from the Lex library, which overrides all the callbacks
+/// and collects information about each callback call, saving it in a
+/// data structure built up of CallbackCall and Argument objects, which
+/// record the preprocessor callback name and arguments in high-level string
+/// form for later inspection.
+///
+//===--------------------------------------------------------------------===//
+
+#ifndef PPTRACE_PPCALLBACKSTRACKER_H
+#define PPTRACE_PPCALLBACKSTRACKER_H
+
+#include "clang/Lex/PPCallbacks.h"
+#include "clang/Lex/Preprocessor.h"
+
+/// \brief This class represents one callback function argument by name
+///   and value.
+class Argument {
+public:
+  Argument(llvm::StringRef Name, llvm::StringRef Value)
+      : Name(Name), Value(Value) {}
+  Argument() {}
+
+  std::string Name;
+  std::string Value;
+};
+
+/// \brief This class represents one callback call by name and an array
+///   of arguments.
+class CallbackCall {
+public:
+  CallbackCall(llvm::StringRef Name) : Name(Name) {}
+  CallbackCall() {}
+
+  std::string Name;
+  std::vector<Argument> Arguments;
+};
+
+/// \brief This class overrides the PPCallbacks class for tracking preprocessor
+///   activity by means of its callback functions.
+///
+/// This object is given a vector for storing the trace information, built up
+/// of CallbackCall and subordinate Argument objects for representing the
+/// callback calls and their arguments.  It's a reference so the vector can
+/// exist beyond the lifetime of this object, because it's deleted by the
+/// preprocessor automatically in its destructor.
+///
+/// This class supports a mechanism for inhibiting trace output for
+/// specific callbacks by name, for the purpose of eliminating output for
+/// callbacks of no interest that might clutter the output.
+///
+/// Following the constructor and destructor function declarations, the
+/// overidden callback functions are defined.  The remaining functions are
+/// helpers for recording the trace data, to reduce the coupling between it
+/// and the recorded data structure.
+class PPCallbacksTracker : public clang::PPCallbacks {
+public:
+  /// \brief Note that all of the arguments are references, and owned
+  /// by the caller.
+  /// \param Ignore - Set of names of callbacks to ignore.
+  /// \param CallbackCalls - Trace buffer.
+  /// \param PP - The preprocessor.  Needed for getting some argument strings.
+  PPCallbacksTracker(llvm::SmallSet<std::string, 4> &Ignore,
+                     std::vector<CallbackCall> &CallbackCalls,
+                     clang::Preprocessor &PP);
+
+  virtual ~PPCallbacksTracker();
+
+  // Overidden callback functions.
+
+  void FileChanged(clang::SourceLocation Loc,
+                   clang::PPCallbacks::FileChangeReason Reason,
+                   clang::SrcMgr::CharacteristicKind FileType,
+                   clang::FileID PrevFID = clang::FileID()) LLVM_OVERRIDE;
+  void FileSkipped(const clang::FileEntry &ParentFile,
+                   const clang::Token &FilenameTok,
+                   clang::SrcMgr::CharacteristicKind FileType) LLVM_OVERRIDE;
+  bool FileNotFound(llvm::StringRef FileName,
+                    llvm::SmallVectorImpl<char> &RecoveryPath) LLVM_OVERRIDE;
+  void InclusionDirective(clang::SourceLocation HashLoc,
+                          const clang::Token &IncludeTok,
+                          llvm::StringRef FileName, bool IsAngled,
+                          clang::CharSourceRange FilenameRange,
+                          const clang::FileEntry *File,
+                          llvm::StringRef SearchPath,
+                          llvm::StringRef RelativePath,
+                          const clang::Module *Imported) LLVM_OVERRIDE;
+  void moduleImport(clang::SourceLocation ImportLoc, clang::ModuleIdPath Path,
+                    const clang::Module *Imported) LLVM_OVERRIDE;
+  void EndOfMainFile() LLVM_OVERRIDE;
+  void Ident(clang::SourceLocation Loc, const std::string &str) LLVM_OVERRIDE;
+  void PragmaDirective(clang::SourceLocation Loc,
+                       clang::PragmaIntroducerKind Introducer) LLVM_OVERRIDE;
+  void PragmaComment(clang::SourceLocation Loc,
+                     const clang::IdentifierInfo *Kind,
+                     const std::string &Str) LLVM_OVERRIDE;
+  void PragmaDetectMismatch(clang::SourceLocation Loc, const std::string &Name,
+                            const std::string &Value) LLVM_OVERRIDE;
+  void PragmaDebug(clang::SourceLocation Loc,
+                   llvm::StringRef DebugType) LLVM_OVERRIDE;
+  void PragmaMessage(clang::SourceLocation Loc, llvm::StringRef Namespace,
+                     clang::PPCallbacks::PragmaMessageKind Kind,
+                     llvm::StringRef Str) LLVM_OVERRIDE;
+  void PragmaDiagnosticPush(clang::SourceLocation Loc,
+                            llvm::StringRef Namespace) LLVM_OVERRIDE;
+  void PragmaDiagnosticPop(clang::SourceLocation Loc,
+                           llvm::StringRef Namespace) LLVM_OVERRIDE;
+  void PragmaDiagnostic(clang::SourceLocation Loc, llvm::StringRef Namespace,
+                        clang::diag::Mapping mapping,
+                        llvm::StringRef Str) LLVM_OVERRIDE;
+  void PragmaOpenCLExtension(clang::SourceLocation NameLoc,
+                             const clang::IdentifierInfo *Name,
+                             clang::SourceLocation StateLoc,
+                             unsigned State) LLVM_OVERRIDE;
+  void PragmaWarning(clang::SourceLocation Loc, llvm::StringRef WarningSpec,
+                     llvm::ArrayRef<int> Ids) LLVM_OVERRIDE;
+  void PragmaWarningPush(clang::SourceLocation Loc, int Level) LLVM_OVERRIDE;
+  void PragmaWarningPop(clang::SourceLocation Loc) LLVM_OVERRIDE;
+  void MacroExpands(const clang::Token &MacroNameTok,
+                    const clang::MacroDirective *MD, clang::SourceRange Range,
+                    const clang::MacroArgs *Args) LLVM_OVERRIDE;
+  void MacroDefined(const clang::Token &MacroNameTok,
+                    const clang::MacroDirective *MD) LLVM_OVERRIDE;
+  void MacroUndefined(const clang::Token &MacroNameTok,
+                      const clang::MacroDirective *MD) LLVM_OVERRIDE;
+  void Defined(const clang::Token &MacroNameTok,
+               const clang::MacroDirective *MD,
+               clang::SourceRange Range) LLVM_OVERRIDE;
+  void SourceRangeSkipped(clang::SourceRange Range) LLVM_OVERRIDE;
+  void If(clang::SourceLocation Loc, clang::SourceRange ConditionRange,
+          bool ConditionValue) LLVM_OVERRIDE;
+  void Elif(clang::SourceLocation Loc, clang::SourceRange ConditionRange,
+            bool ConditionValue, clang::SourceLocation IfLoc) LLVM_OVERRIDE;
+  void Ifdef(clang::SourceLocation Loc, const clang::Token &MacroNameTok,
+             const clang::MacroDirective *MD) LLVM_OVERRIDE;
+  void Ifndef(clang::SourceLocation Loc, const clang::Token &MacroNameTok,
+              const clang::MacroDirective *MD) LLVM_OVERRIDE;
+  void Else(clang::SourceLocation Loc,
+            clang::SourceLocation IfLoc) LLVM_OVERRIDE;
+  void Endif(clang::SourceLocation Loc,
+             clang::SourceLocation IfLoc) LLVM_OVERRIDE;
+
+  // Helper functions.
+
+  /// \brief Start a new callback.
+  void beginCallback(const char *Name);
+
+  /// \brief Append a string to the top trace item.
+  void append(const char *Str);
+
+  /// \brief Format and append a string to the top trace item.
+  void appendFormatted(const char *Format, ...);
+
+  /// \brief Append a bool argument to the top trace item.
+  void appendArgument(const char *Name, bool Value);
+
+  /// \brief Append an int argument to the top trace item.
+  void appendArgument(const char *Name, int Value);
+
+  /// \brief Append a string argument to the top trace item.
+  void appendArgument(const char *Name, const char *Value);
+
+  /// \brief Append a string reference object argument to the top trace item.
+  void appendArgument(const char *Name, llvm::StringRef Value);
+
+  /// \brief Append a string object argument to the top trace item.
+  void appendArgument(const char *Name, const std::string &Value);
+
+  /// \brief Append a token argument to the top trace item.
+  void appendArgument(const char *Name, const clang::Token &Value);
+
+  /// \brief Append an enum argument to the top trace item.
+  void appendArgument(const char *Name, int Value, const char *Strings[]);
+
+  /// \brief Append a FileID argument to the top trace item.
+  void appendArgument(const char *Name, clang::FileID Value);
+
+  /// \brief Append a FileEntry argument to the top trace item.
+  void appendArgument(const char *Name, const clang::FileEntry *Value);
+
+  /// \brief Append a SourceLocation argument to the top trace item.
+  void appendArgument(const char *Name, clang::SourceLocation Value);
+
+  /// \brief Append a SourceRange argument to the top trace item.
+  void appendArgument(const char *Name, clang::SourceRange Value);
+
+  /// \brief Append a CharSourceRange argument to the top trace item.
+  void appendArgument(const char *Name, clang::CharSourceRange Value);
+
+  /// \brief Append a ModuleIdPath argument to the top trace item.
+  void appendArgument(const char *Name, clang::ModuleIdPath Value);
+
+  /// \brief Append an IdentifierInfo argument to the top trace item.
+  void appendArgument(const char *Name, const clang::IdentifierInfo *Value);
+
+  /// \brief Append a MacroDirective argument to the top trace item.
+  void appendArgument(const char *Name, const clang::MacroDirective *Value);
+
+  /// \brief Append a MacroArgs argument to the top trace item.
+  void appendArgument(const char *Name, const clang::MacroArgs *Value);
+
+  /// \brief Append a Module argument to the top trace item.
+  void appendArgument(const char *Name, const clang::Module *Value);
+
+  /// \brief Append a double-quoted argument to the top trace item.
+  void appendQuotedArgument(const char *Name, std::string &Value);
+
+  /// \brief Append a double-quoted file path argument to the top trace item.
+  void appendFilePathArgument(const char *Name, llvm::StringRef Value);
+
+  /// \brief Get the raw source string of the range.
+  llvm::StringRef getSourceString(clang::CharSourceRange Range);
+
+  /// \brief Callback trace information.
+  /// We use a reference so the trace will be preserved for the caller
+  /// after this object is destructed.
+  std::vector<CallbackCall> &CallbackCalls;
+
+  /// \brief Names of callbacks to ignore.
+  llvm::SmallSet<std::string, 4> &Ignore;
+
+  /// \brief Inhibit trace while this is set.
+  bool DisableTrace;
+
+  clang::Preprocessor &PP;
+};
+
+#endif // PPTRACE_PPCALLBACKSTRACKER_H
Index: pp-trace/PPCallbacksTracker.cpp
===================================================================
--- pp-trace/PPCallbacksTracker.cpp
+++ pp-trace/PPCallbacksTracker.cpp
@@ -0,0 +1,629 @@
+//===--- PPCallbacksTracker.cpp - Preprocessor tracker -*--*-------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===--------------------------------------------------------------------===//
+///
+/// \file
+/// \brief Implementations for preprocessor tracking.
+///
+/// See the header for details.
+///
+//===--------------------------------------------------------------------===//
+
+#include "PPCallbacksTracker.h"
+#include "clang/Lex/MacroArgs.h"
+#include "llvm/Support/raw_ostream.h"
+#include <stdarg.h>
+#include <stdio.h>
+
+// Utility functions.
+
+// Get a "file:line:column" source location string.
+static std::string getSourceLocationString(clang::Preprocessor &PP,
+                                           clang::SourceLocation Loc) {
+  if (Loc.isInvalid())
+    return std::string("(none)");
+
+  if (Loc.isFileID()) {
+    clang::PresumedLoc PLoc = PP.getSourceManager().getPresumedLoc(Loc);
+
+    if (PLoc.isInvalid()) {
+      return std::string("(invalid)");
+    }
+
+    std::string Str;
+    llvm::raw_string_ostream SS(Str);
+
+    // The macro expansion and spelling pos is identical for file locs.
+    SS << "\"" << PLoc.getFilename() << ':' << PLoc.getLine() << ':'
+       << PLoc.getColumn() << "\"";
+
+    std::string Result = SS.str();
+
+    // YAML treats backslash as escape, so use forward slashes.
+    std::replace(Result.begin(), Result.end(), '\\', '/');
+
+    return Result;
+  }
+
+  return std::string("(nonfile)");
+}
+
+// Enum string tables.
+
+// FileChangeReason strings.
+static const char *FileChangeReasonStrings[] = {
+  "EnterFile", "ExitFile", "SystemHeaderPragma", "RenameFile"
+};
+
+// CharacteristicKind strings.
+static const char *CharacteristicKindStrings[] = { "C_User", "C_System",
+                                                   "C_ExternCSystem" };
+
+// MacroDirective::Kind strings.
+static const char *MacroDirectiveKindStrings[] = { "MD_Define", "MD_Undefine",
+                                                   "MD_Visibility" };
+
+// PragmaIntroducerKind strings.
+static const char *PragmaIntroducerKindStrings[] = { "PIK_HashPragma",
+                                                     "PIK__Pragma",
+                                                     "PIK___pragma" };
+
+// PragmaMessageKind strings.
+static const char *PragmaMessageKindStrings[] = { "PMK_Message", "PMK_Warning",
+                                                  "PMK_Error" };
+
+// Mapping strings.
+static const char *MappingStrings[] = { "0",           "MAP_IGNORE",
+                                        "MAP_WARNING", "MAP_ERROR",
+                                        "MAP_FATAL" };
+
+// PPCallbacksTracker functions.
+
+PPCallbacksTracker::PPCallbacksTracker(llvm::SmallSet<std::string, 4> &Ignore,
+                                       std::vector<CallbackCall> &CallbackCalls,
+                                       clang::Preprocessor &PP)
+    : CallbackCalls(CallbackCalls), Ignore(Ignore), PP(PP) {}
+
+PPCallbacksTracker::~PPCallbacksTracker() {}
+
+// Callback functions.
+
+// Callback invoked whenever a source file is entered or exited.
+void PPCallbacksTracker::FileChanged(
+    clang::SourceLocation Loc, clang::PPCallbacks::FileChangeReason Reason,
+    clang::SrcMgr::CharacteristicKind FileType, clang::FileID PrevFID) {
+  beginCallback("FileChanged");
+  appendArgument("Loc", Loc);
+  appendArgument("Reason", Reason, FileChangeReasonStrings);
+  appendArgument("FileType", FileType, CharacteristicKindStrings);
+  appendArgument("PrevFID", PrevFID);
+}
+
+// Callback invoked whenever a source file is skipped as the result
+// of header guard optimization.
+void
+PPCallbacksTracker::FileSkipped(const clang::FileEntry &ParentFile,
+                                const clang::Token &FilenameTok,
+                                clang::SrcMgr::CharacteristicKind FileType) {
+  beginCallback("FileSkipped");
+  appendArgument("ParentFile", &ParentFile);
+  appendArgument("FilenameTok", FilenameTok);
+  appendArgument("FileType", FileType, CharacteristicKindStrings);
+}
+
+// Callback invoked whenever an inclusion directive results in a
+// file-not-found error.
+bool
+PPCallbacksTracker::FileNotFound(llvm::StringRef FileName,
+                                 llvm::SmallVectorImpl<char> &RecoveryPath) {
+  beginCallback("FileNotFound");
+  appendFilePathArgument("FileName", FileName);
+  return false;
+}
+
+// Callback invoked whenever an inclusion directive of
+// any kind (#include, #import, etc.) has been processed, regardless
+// of whether the inclusion will actually result in an inclusion.
+void PPCallbacksTracker::InclusionDirective(
+    clang::SourceLocation HashLoc, const clang::Token &IncludeTok,
+    llvm::StringRef FileName, bool IsAngled,
+    clang::CharSourceRange FilenameRange, const clang::FileEntry *File,
+    llvm::StringRef SearchPath, llvm::StringRef RelativePath,
+    const clang::Module *Imported) {
+  beginCallback("InclusionDirective");
+  appendArgument("IncludeTok", IncludeTok);
+  appendFilePathArgument("FileName", FileName);
+  appendArgument("IsAngled", IsAngled);
+  appendArgument("FilenameRange", FilenameRange);
+  appendArgument("File", File);
+  appendFilePathArgument("SearchPath", SearchPath);
+  appendFilePathArgument("RelativePath", RelativePath);
+  appendArgument("Imported", Imported);
+}
+
+// Callback invoked whenever there was an explicit module-import
+// syntax.
+void PPCallbacksTracker::moduleImport(clang::SourceLocation ImportLoc,
+                                      clang::ModuleIdPath Path,
+                                      const clang::Module *Imported) {
+  beginCallback("moduleImport");
+  appendArgument("ImportLoc", ImportLoc);
+  appendArgument("Path", Path);
+  appendArgument("Imported", Imported);
+}
+
+// Callback invoked when the end of the main file is reached.
+// No subsequent callbacks will be made.
+void PPCallbacksTracker::EndOfMainFile() { beginCallback("EndOfMainFile"); }
+
+// Callback invoked when a #ident or #sccs directive is read.
+void PPCallbacksTracker::Ident(clang::SourceLocation Loc,
+                               const std::string &Str) {
+  beginCallback("Ident");
+  appendArgument("Loc", Loc);
+  appendArgument("Path", Str);
+}
+
+// Callback invoked when start reading any pragma directive.
+void
+PPCallbacksTracker::PragmaDirective(clang::SourceLocation Loc,
+                                    clang::PragmaIntroducerKind Introducer) {
+  beginCallback("PragmaDirective");
+  appendArgument("Loc", Loc);
+  appendArgument("Path", Introducer, PragmaIntroducerKindStrings);
+}
+
+// Callback invoked when a #pragma comment directive is read.
+void PPCallbacksTracker::PragmaComment(clang::SourceLocation Loc,
+                                       const clang::IdentifierInfo *Kind,
+                                       const std::string &Str) {
+  beginCallback("PragmaComment");
+  appendArgument("Loc", Loc);
+  appendArgument("Kind", Kind);
+  appendArgument("Str", Str);
+}
+
+// Callback invoked when a #pragma detect_mismatch directive is
+// read.
+void PPCallbacksTracker::PragmaDetectMismatch(clang::SourceLocation Loc,
+                                              const std::string &Name,
+                                              const std::string &Value) {
+  beginCallback("PragmaDetectMismatch");
+  appendArgument("Loc", Loc);
+  appendArgument("Name", Name);
+  appendArgument("Value", Value);
+}
+
+// Callback invoked when a #pragma clang __debug directive is read.
+void PPCallbacksTracker::PragmaDebug(clang::SourceLocation Loc,
+                                     llvm::StringRef DebugType) {
+  beginCallback("PragmaDebug");
+  appendArgument("Loc", Loc);
+  appendArgument("DebugType", DebugType);
+}
+
+// Callback invoked when a #pragma message directive is read.
+void PPCallbacksTracker::PragmaMessage(
+    clang::SourceLocation Loc, llvm::StringRef Namespace,
+    clang::PPCallbacks::PragmaMessageKind Kind, llvm::StringRef Str) {
+  beginCallback("PragmaMessage");
+  appendArgument("Loc", Loc);
+  appendArgument("Namespace", Namespace);
+  appendArgument("Kind", Kind, PragmaMessageKindStrings);
+  appendArgument("Str", Str);
+}
+
+// Callback invoked when a #pragma gcc dianostic push directive
+// is read.
+void PPCallbacksTracker::PragmaDiagnosticPush(clang::SourceLocation Loc,
+                                              llvm::StringRef Namespace) {
+  beginCallback("PragmaDiagnosticPush");
+  appendArgument("Loc", Loc);
+  appendArgument("Namespace", Namespace);
+}
+
+// Callback invoked when a #pragma gcc dianostic pop directive
+// is read.
+void PPCallbacksTracker::PragmaDiagnosticPop(clang::SourceLocation Loc,
+                                             llvm::StringRef Namespace) {
+  beginCallback("PragmaDiagnosticPop");
+  appendArgument("Loc", Loc);
+  appendArgument("Namespace", Namespace);
+}
+
+// Callback invoked when a #pragma gcc dianostic directive is read.
+void PPCallbacksTracker::PragmaDiagnostic(clang::SourceLocation Loc,
+                                          llvm::StringRef Namespace,
+                                          clang::diag::Mapping Mapping,
+                                          llvm::StringRef Str) {
+  beginCallback("PragmaDiagnostic");
+  appendArgument("Loc", Loc);
+  appendArgument("Namespace", Namespace);
+  appendArgument("Mapping", Mapping, MappingStrings);
+  appendArgument("Str", Str);
+}
+
+// Called when an OpenCL extension is either disabled or
+// enabled with a pragma.
+void PPCallbacksTracker::PragmaOpenCLExtension(
+    clang::SourceLocation NameLoc, const clang::IdentifierInfo *Name,
+    clang::SourceLocation StateLoc, unsigned State) {
+  beginCallback("PragmaOpenCLExtension");
+  appendArgument("NameLoc", NameLoc);
+  appendArgument("Name", Name);
+  appendArgument("StateLoc", StateLoc);
+  appendArgument("State", (int)State);
+}
+
+// Callback invoked when a #pragma warning directive is read.
+void PPCallbacksTracker::PragmaWarning(clang::SourceLocation Loc,
+                                       llvm::StringRef WarningSpec,
+                                       llvm::ArrayRef<int> Ids) {
+  beginCallback("PragmaWarning");
+  appendArgument("Loc", Loc);
+  appendArgument("WarningSpec", WarningSpec);
+
+  std::string Str;
+  llvm::raw_string_ostream SS(Str);
+  SS << "[";
+  for (int i = 0, e = Ids.size(); i != e; ++i) {
+    if (i)
+      SS << ", ";
+    SS << Ids[i];
+  }
+  appendArgument("Ids", SS.str());
+}
+
+// Callback invoked when a #pragma warning(push) directive is read.
+void PPCallbacksTracker::PragmaWarningPush(clang::SourceLocation Loc,
+                                           int Level) {
+  beginCallback("PragmaWarningPush");
+  appendArgument("Loc", Loc);
+  appendArgument("Level", Level);
+}
+
+// Callback invoked when a #pragma warning(pop) directive is read.
+void PPCallbacksTracker::PragmaWarningPop(clang::SourceLocation Loc) {
+  beginCallback("PragmaWarningPop");
+  appendArgument("Loc", Loc);
+}
+
+// Called by Preprocessor::HandleMacroExpandedIdentifier when a
+// macro invocation is found.
+void
+PPCallbacksTracker::MacroExpands(const clang::Token &MacroNameTok,
+                                 const clang::MacroDirective *MacroDirective,
+                                 clang::SourceRange Range,
+                                 const clang::MacroArgs *Args) {
+  beginCallback("MacroExpands");
+  appendArgument("MacroNameTok", MacroNameTok);
+  appendArgument("MacroDirective", MacroDirective);
+  appendArgument("Range", Range);
+  appendArgument("Args", Args);
+}
+
+// Hook called whenever a macro definition is seen.
+void
+PPCallbacksTracker::MacroDefined(const clang::Token &MacroNameTok,
+                                 const clang::MacroDirective *MacroDirective) {
+  beginCallback("MacroDefined");
+  appendArgument("MacroNameTok", MacroNameTok);
+  appendArgument("MacroDirective", MacroDirective);
+}
+
+// Hook called whenever a macro #undef is seen.
+void PPCallbacksTracker::MacroUndefined(
+    const clang::Token &MacroNameTok,
+    const clang::MacroDirective *MacroDirective) {
+  beginCallback("MacroUndefined");
+  appendArgument("MacroNameTok", MacroNameTok);
+  appendArgument("MacroDirective", MacroDirective);
+}
+
+// Hook called whenever the 'defined' operator is seen.
+void PPCallbacksTracker::Defined(const clang::Token &MacroNameTok,
+                                 const clang::MacroDirective *MacroDirective,
+                                 clang::SourceRange Range) {
+  beginCallback("Defined");
+  appendArgument("MacroNameTok", MacroNameTok);
+  appendArgument("MacroDirective", MacroDirective);
+  appendArgument("Range", Range);
+}
+
+// Hook called when a source range is skipped.
+void PPCallbacksTracker::SourceRangeSkipped(clang::SourceRange Range) {
+  beginCallback("SourceRangeSkipped");
+  appendArgument("Range", Range);
+}
+
+// Hook called whenever an #if is seen.
+void PPCallbacksTracker::If(clang::SourceLocation Loc,
+                            clang::SourceRange ConditionRange,
+                            bool ConditionValue) {
+  beginCallback("If");
+  appendArgument("Loc", Loc);
+  appendArgument("ConditionRange", ConditionRange);
+  appendArgument("ConditionValue", ConditionValue);
+}
+
+// Hook called whenever an #elif is seen.
+void PPCallbacksTracker::Elif(clang::SourceLocation Loc,
+                              clang::SourceRange ConditionRange,
+                              bool ConditionValue,
+                              clang::SourceLocation IfLoc) {
+  beginCallback("Elif");
+  appendArgument("Loc", Loc);
+  appendArgument("ConditionRange", ConditionRange);
+  appendArgument("ConditionValue", ConditionValue);
+  appendArgument("IfLoc", IfLoc);
+}
+
+// Hook called whenever an #ifdef is seen.
+void PPCallbacksTracker::Ifdef(clang::SourceLocation Loc,
+                               const clang::Token &MacroNameTok,
+                               const clang::MacroDirective *MacroDirective) {
+  beginCallback("Ifdef");
+  appendArgument("Loc", Loc);
+  appendArgument("MacroNameTok", MacroNameTok);
+  appendArgument("MacroDirective", MacroDirective);
+}
+
+// Hook called whenever an #ifndef is seen.
+void PPCallbacksTracker::Ifndef(clang::SourceLocation Loc,
+                                const clang::Token &MacroNameTok,
+                                const clang::MacroDirective *MacroDirective) {
+  beginCallback("Ifndef");
+  appendArgument("Loc", Loc);
+  appendArgument("MacroNameTok", MacroNameTok);
+  appendArgument("MacroDirective", MacroDirective);
+}
+
+// Hook called whenever an #else is seen.
+void PPCallbacksTracker::Else(clang::SourceLocation Loc,
+                              clang::SourceLocation IfLoc) {
+  beginCallback("Else");
+  appendArgument("Loc", Loc);
+  appendArgument("IfLoc", IfLoc);
+}
+
+// Hook called whenever an #endif is seen.
+void PPCallbacksTracker::Endif(clang::SourceLocation Loc,
+                               clang::SourceLocation IfLoc) {
+  beginCallback("Endif");
+  appendArgument("Loc", Loc);
+  appendArgument("IfLoc", IfLoc);
+}
+
+// Helper functions.
+
+// Start a new callback.
+void PPCallbacksTracker::beginCallback(const char *Name) {
+  DisableTrace = Ignore.count(std::string(Name));
+  if (DisableTrace)
+    return;
+  CallbackCalls.push_back(CallbackCall(Name));
+}
+
+// Append a bool argument to the top trace item.
+void PPCallbacksTracker::appendArgument(const char *Name, bool Value) {
+  appendArgument(Name, (Value ? "true" : "false"));
+}
+
+// Append an int argument to the top trace item.
+void PPCallbacksTracker::appendArgument(const char *Name, int Value) {
+  std::string Str;
+  llvm::raw_string_ostream SS(Str);
+  SS << Value;
+  appendArgument(Name, SS.str());
+}
+
+// Append a string argument to the top trace item.
+void PPCallbacksTracker::appendArgument(const char *Name, const char *Value) {
+  if (DisableTrace)
+    return;
+  CallbackCalls.back().Arguments.push_back(Argument(Name, Value));
+}
+
+// Append a string object argument to the top trace item.
+void PPCallbacksTracker::appendArgument(const char *Name,
+                                        llvm::StringRef Value) {
+  appendArgument(Name, Value.str());
+}
+
+// Append a string object argument to the top trace item.
+void PPCallbacksTracker::appendArgument(const char *Name,
+                                        const std::string &Value) {
+  appendArgument(Name, Value.c_str());
+}
+
+// Append a token argument to the top trace item.
+void PPCallbacksTracker::appendArgument(const char *Name,
+                                        const clang::Token &Value) {
+  appendArgument(Name, PP.getSpelling(Value));
+}
+
+// Append an enum argument to the top trace item.
+void PPCallbacksTracker::appendArgument(const char *Name, int Value,
+                                        const char *Strings[]) {
+  appendArgument(Name, Strings[Value]);
+}
+
+// Append a FileID argument to the top trace item.
+void PPCallbacksTracker::appendArgument(const char *Name, clang::FileID Value) {
+  if (Value.isInvalid()) {
+    appendArgument(Name, "(invalid)");
+    return;
+  }
+  const clang::FileEntry *FileEntry =
+      PP.getSourceManager().getFileEntryForID(Value);
+  if (FileEntry == 0) {
+    appendArgument(Name, "(getFileEntryForID failed)");
+    return;
+  }
+  appendFilePathArgument(Name, FileEntry->getName());
+}
+
+// Append a FileEntry argument to the top trace item.
+void PPCallbacksTracker::appendArgument(const char *Name,
+                                        const clang::FileEntry *Value) {
+  if (Value == 0) {
+    appendArgument(Name, "(null)");
+    return;
+  }
+  appendFilePathArgument(Name, Value->getName());
+}
+
+// Append a SourceLocation argument to the top trace item.
+void PPCallbacksTracker::appendArgument(const char *Name,
+                                        clang::SourceLocation Value) {
+  if (Value.isInvalid()) {
+    appendArgument(Name, "(invalid)");
+    return;
+  }
+  appendArgument(Name, getSourceLocationString(PP, Value).c_str());
+}
+
+// Append a SourceRange argument to the top trace item.
+void PPCallbacksTracker::appendArgument(const char *Name,
+                                        clang::SourceRange Value) {
+  if (DisableTrace)
+    return;
+  if (Value.isInvalid()) {
+    appendArgument(Name, "(invalid)");
+    return;
+  }
+  std::string Str;
+  llvm::raw_string_ostream SS(Str);
+  SS << "[" << getSourceLocationString(PP, Value.getBegin()) << ", "
+     << getSourceLocationString(PP, Value.getEnd()) << "]";
+  appendArgument(Name, SS.str());
+}
+
+// Append a CharSourceRange argument to the top trace item.
+void PPCallbacksTracker::appendArgument(const char *Name,
+                                        clang::CharSourceRange Value) {
+  if (Value.isInvalid()) {
+    appendArgument(Name, "(invalid)");
+    return;
+  }
+  appendArgument(Name, getSourceString(Value).str().c_str());
+}
+
+// Append a SourceLocation argument to the top trace item.
+void PPCallbacksTracker::appendArgument(const char *Name,
+                                        clang::ModuleIdPath Value) {
+  if (DisableTrace)
+    return;
+  std::string Str;
+  llvm::raw_string_ostream SS(Str);
+  SS << "[";
+  for (int I = 0, E = Value.size(); I != E; ++I) {
+    if (I)
+      SS << ", ";
+    SS << "{"
+       << "Name: " << Value[I].first->getName() << ", "
+       << "Loc:" << getSourceLocationString(PP, Value[I].second) << "}";
+  }
+  SS << "]";
+  appendArgument(Name, SS.str());
+}
+
+// Append an IdentifierInfo argument to the top trace item.
+void PPCallbacksTracker::appendArgument(const char *Name,
+                                        const clang::IdentifierInfo *Value) {
+  if (!Value) {
+    appendArgument(Name, "(null)");
+    return;
+  }
+  appendArgument(Name, Value->getName().str().c_str());
+}
+
+// Append a MacroDirective argument to the top trace item.
+void PPCallbacksTracker::appendArgument(const char *Name,
+                                        const clang::MacroDirective *Value) {
+  if (!Value) {
+    appendArgument(Name, "(null)");
+    return;
+  }
+  appendArgument(Name, MacroDirectiveKindStrings[Value->getKind()]);
+}
+
+// Append a MacroArgs argument to the top trace item.
+void PPCallbacksTracker::appendArgument(const char *Name,
+                                        const clang::MacroArgs *Value) {
+  if (!Value) {
+    appendArgument(Name, "(null)");
+    return;
+  }
+  std::string Str;
+  llvm::raw_string_ostream SS(Str);
+  SS << "[";
+  // The argument tokens might include end tokens, so we reflect how
+  // how getUnexpArgument provides the arguments.
+  for (int I = 0, E = Value->getNumArguments(); I < E; ++I) {
+    const clang::Token *Current = Value->getUnexpArgument(I);
+    int TokenCount = Value->getArgLength(Current) + 1; // include EOF
+    E -= TokenCount;
+    if (I)
+      SS << ", ";
+    // We're assuming tokens are contiguous, as otherwise we have no
+    // other way to get at them.
+    --TokenCount;
+    for (int TokenIndex = 0; TokenIndex < TokenCount; ++TokenIndex, ++Current) {
+      if (TokenIndex)
+        SS << " ";
+      // We need to be careful here because the arguments might not be legal in
+      // YAML, so we use the token name for anything but identifiers and
+      // numeric literals.
+      if (Current->isAnyIdentifier() ||
+          Current->is(clang::tok::numeric_constant)) {
+        SS << PP.getSpelling(*Current);
+      } else {
+        SS << "<" << Current->getName() << ">";
+      }
+    }
+  }
+  SS << "]";
+  appendArgument(Name, SS.str());
+}
+
+// Append a Module argument to the top trace item.
+void PPCallbacksTracker::appendArgument(const char *Name,
+                                        const clang::Module *Value) {
+  if (!Value) {
+    appendArgument(Name, "(null)");
+    return;
+  }
+  appendArgument(Name, Value->Name.c_str());
+}
+
+// Append a double-quoted argument to the top trace item.
+void PPCallbacksTracker::appendQuotedArgument(const char *Name,
+                                              std::string &Value) {
+  std::string Str;
+  llvm::raw_string_ostream SS(Str);
+  SS << "\"" << Value << "\"";
+  appendArgument(Name, SS.str());
+}
+
+// Append a double-quoted file path argument to the top trace item.
+void PPCallbacksTracker::appendFilePathArgument(const char *Name,
+                                                llvm::StringRef Value) {
+  std::string Path(Value);
+  // YAML treats backslash as escape, so use forward slashes.
+  std::replace(Path.begin(), Path.end(), '\\', '/');
+  appendQuotedArgument(Name, Path);
+}
+
+// Get the raw source string of the range.
+llvm::StringRef
+PPCallbacksTracker::getSourceString(clang::CharSourceRange Range) {
+  const char *B = PP.getSourceManager().getCharacterData(Range.getBegin());
+  const char *E = PP.getSourceManager().getCharacterData(Range.getEnd());
+  return llvm::StringRef(B, E - B);
+}
Index: pp-trace/PPTrace.cpp
===================================================================
--- pp-trace/PPTrace.cpp
+++ pp-trace/PPTrace.cpp
@@ -0,0 +1,231 @@
+//===--- tools/pp-trace/PPTrace.cpp - Clang preprocessor tracer -----------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements pp-trace, a tool for displaying a textual trace
+// of the Clang preprocessor activity.  It's based on a derivation of the
+// PPCallbacks class, that once registerd with Clang, receives callback calls
+// to its virtual members, and outputs the information passed to the callbacks
+// in a high-level YAML format.
+//
+// The pp-trace tool also serves as the basis for a test of the PPCallbacks
+// mechanism.
+//
+// The pp-trace tool supports the following general command line format:
+//
+//    pp-trace [pp-trace options] (source file(s)) [compiler options]
+//
+// Basically you put the pp-trace options first, then the source file or files,
+// and then any options you want to pass to the compiler.
+//
+// These are the pp-trace options:
+//
+//    -ignore (callback list)     Don't display output for a comma-separated
+//                                list of callbacks, i.e.:
+//                                  -ignore "FileChanged,InclusionDirective"
+//
+//    -output (file|-)            Output trace to the given file (or stdout
+//                                for "-") in a YAML format, e.g.:
+//
+//                                  ---
+//                                  - Callback: Name
+//                                    Argument1: Value1
+//                                    Argument2: Value2
+//                                  (etc.)
+//                                  ...
+//
+//===----------------------------------------------------------------------===//
+
+#include "PPCallbacksTracker.h"
+#include "clang/AST/ASTConsumer.h"
+#include "clang/AST/ASTContext.h"
+#include "clang/AST/RecursiveASTVisitor.h"
+#include "clang/Basic/SourceManager.h"
+#include "clang/Driver/Options.h"
+#include "clang/Frontend/CompilerInstance.h"
+#include "clang/Frontend/FrontendActions.h"
+#include "clang/Lex/Preprocessor.h"
+#include "clang/Tooling/CompilationDatabase.h"
+#include "clang/Tooling/Tooling.h"
+#include "llvm/ADT/OwningPtr.h"
+#include "llvm/Config/config.h"
+#include "llvm/Option/Arg.h"
+#include "llvm/Option/ArgList.h"
+#include "llvm/Option/OptTable.h"
+#include "llvm/Option/Option.h"
+#include "llvm/Support/CommandLine.h"
+#include "llvm/Support/FileSystem.h"
+#include "llvm/Support/MemoryBuffer.h"
+#include "llvm/Support/Path.h"
+#include "llvm/Support/ToolOutputFile.h"
+#include <algorithm>
+#include <fstream>
+#include <iterator>
+#include <string>
+#include <vector>
+
+using namespace clang;
+using namespace clang::driver;
+using namespace clang::driver::options;
+using namespace clang::tooling;
+using namespace llvm;
+using namespace llvm::opt;
+
+// Options:
+
+// Collect the source files.
+cl::list<std::string> SourcePaths(cl::Positional,
+                                  cl::desc("<source0> [... <sourceN>]"),
+                                  cl::OneOrMore);
+
+// Option to specify a list or one or more callback names to ignore.
+cl::opt<std::string> IgnoreCallbacks(
+    "ignore", cl::init(""),
+    cl::desc("Ignore callbacks, i.e. \"Callback1, Callback2...\"."));
+
+// Option to specify the trace output file name.
+cl::opt<std::string> OutputFileName(
+    "output", cl::init(""),
+    cl::desc("Output trace to the given file name or '-' for stdout."));
+
+// Collect all other arguments, which will be passed to the front end.
+cl::list<std::string>
+CC1Arguments(cl::ConsumeAfter,
+             cl::desc("<arguments to be passed to front end>..."));
+
+// Frontend action stuff:
+
+// Consumer is responsible for setting up the callbacks.
+class PPTraceConsumer : public ASTConsumer {
+public:
+  PPTraceConsumer(SmallSet<std::string, 4> &Ignore,
+                  std::vector<CallbackCall> &CallbackCalls, Preprocessor &PP)
+      : CallbacksTracker(new PPCallbacksTracker(Ignore, CallbackCalls, PP)) {
+    PP.addPPCallbacks(CallbacksTracker); // Takes ownership.
+  }
+
+private:
+  PPCallbacksTracker *CallbacksTracker; // Not owned here.
+};
+
+class PPTraceAction : public SyntaxOnlyAction {
+public:
+  PPTraceAction(SmallSet<std::string, 4> &Ignore,
+                std::vector<CallbackCall> &CallbackCalls)
+      : Ignore(Ignore), CallbackCalls(CallbackCalls) {}
+
+protected:
+  virtual clang::ASTConsumer *CreateASTConsumer(CompilerInstance &CI,
+                                                StringRef InFile) {
+    return new PPTraceConsumer(Ignore, CallbackCalls, CI.getPreprocessor());
+  }
+
+private:
+  SmallSet<std::string, 4> &Ignore;
+  std::vector<CallbackCall> &CallbackCalls;
+};
+
+class PPTraceFrontendActionFactory : public FrontendActionFactory {
+public:
+  PPTraceFrontendActionFactory(SmallSet<std::string, 4> &Ignore,
+                               std::vector<CallbackCall> &CallbackCalls)
+      : Ignore(Ignore), CallbackCalls(CallbackCalls) {}
+
+  virtual PPTraceAction *create() {
+    return new PPTraceAction(Ignore, CallbackCalls);
+  }
+
+private:
+  SmallSet<std::string, 4> &Ignore;
+  std::vector<CallbackCall> &CallbackCalls;
+};
+
+// Output the trace given its data structure and a stream.
+int outputPPTrace(std::vector<CallbackCall> &CallbackCalls,
+                  llvm::raw_ostream &OS) {
+  // Mark start of document.
+  OS << "---\n";
+
+  for (std::vector<CallbackCall>::const_iterator I = CallbackCalls.begin(),
+                                                 E = CallbackCalls.end();
+       I != E; ++I) {
+    const CallbackCall &Callback = *I;
+    OS << "- Callback: " << Callback.Name << "\n";
+
+    for (std::vector<Argument>::const_iterator AI = Callback.Arguments.begin(),
+                                               AE = Callback.Arguments.end();
+         AI != AE; ++AI) {
+      const Argument &Arg = *AI;
+      OS << "  " << Arg.Name << ": " << Arg.Value << "\n";
+    }
+  }
+
+  // Mark end of document.
+  OS << "...\n";
+
+  return 0;
+}
+
+// Program entry point.
+int main(int Argc, const char **Argv) {
+
+  // Parse command line.
+  cl::ParseCommandLineOptions(Argc, Argv, "pp-trace.\n");
+
+  // Parse the IgnoreCallbacks list into strings.
+  SmallVector<StringRef, 32> IgnoreCallbacksStrings;
+  StringRef(IgnoreCallbacks).split(IgnoreCallbacksStrings, ",",
+                                   /*MaxSplit=*/ -1, /*KeepEmpty=*/false);
+  SmallSet<std::string, 4> Ignore;
+  for (SmallVector<StringRef, 32>::iterator I = IgnoreCallbacksStrings.begin(),
+                                            E = IgnoreCallbacksStrings.end();
+       I != E; ++I)
+    Ignore.insert(*I);
+
+  // Create the compilation database.
+  SmallString<256> PathBuf;
+  sys::fs::current_path(PathBuf);
+  OwningPtr<CompilationDatabase> Compilations;
+  Compilations.reset(
+      new FixedCompilationDatabase(Twine(PathBuf), CC1Arguments));
+
+  // Store the callback trace information here.
+  std::vector<CallbackCall> CallbackCalls;
+
+  // Create the tool and run the compilation.
+  ClangTool Tool(*Compilations, SourcePaths);
+  int HadErrors =
+      Tool.run(new PPTraceFrontendActionFactory(Ignore, CallbackCalls));
+
+  // If we had errors, exit early.
+  if (HadErrors)
+    return HadErrors;
+
+  // Do the output.
+  // If file name is "-", output to stdout.
+  if (!OutputFileName.size() || (OutputFileName == "-")) {
+    HadErrors = outputPPTrace(CallbackCalls, llvm::outs());
+  } else {
+    // Set up output file.
+    std::string Error;
+    llvm::tool_output_file Out(OutputFileName.c_str(), Error);
+    if (!Error.empty()) {
+      llvm::errs() << "pp-trace: error creating " << OutputFileName << ":"
+                   << Error << "\n";
+      return 1;
+    }
+
+    HadErrors = outputPPTrace(CallbackCalls, Out.os());
+
+    // Tell tool_output_file that we want to keep the file.
+    if (HadErrors == 0)
+      Out.keep();
+  }
+
+  return HadErrors;
+}
Index: test/pp-trace/Input/Level1A.h
===================================================================
--- test/pp-trace/Input/Level1A.h
+++ test/pp-trace/Input/Level1A.h
@@ -0,0 +1,2 @@
+#include "Level2A.h"
+#define MACRO_1A 1
Index: test/pp-trace/Input/Level1B.h
===================================================================
--- test/pp-trace/Input/Level1B.h
+++ test/pp-trace/Input/Level1B.h
@@ -0,0 +1 @@
+#define MACRO_1B 1
Index: test/pp-trace/Input/Level2A.h
===================================================================
--- test/pp-trace/Input/Level2A.h
+++ test/pp-trace/Input/Level2A.h
@@ -0,0 +1 @@
+#define MACRO_2A 1
Index: test/pp-trace/pp-trace-include.cpp
===================================================================
--- test/pp-trace/pp-trace-include.cpp
+++ test/pp-trace/pp-trace-include.cpp
@@ -0,0 +1,119 @@
+// RUN: pp-trace %s -undef -target x86_64 -std=c++11 | FileCheck --strict-whitespace %s
+
+#include "Input/Level1A.h"
+#include "Input/Level1B.h"
+
+// CHECK: ---
+// CHECK-NEXT: - Callback: FileChanged
+// CHECK-NEXT:   Loc: "{{.*}}{{[/\\]}}pp-trace-include.cpp:1:1"
+// CHECK-NEXT:   Reason: EnterFile
+// CHECK-NEXT:   FileType: C_User
+// CHECK-NEXT:   PrevFID: (invalid)
+// CHECK-NEXT: - Callback: FileChanged
+// CHECK-NEXT:   Loc: "<built-in>:1:1"
+// CHECK-NEXT:   Reason: EnterFile
+// CHECK-NEXT:   FileType: C_User
+// CHECK-NEXT:   PrevFID: (invalid)
+// CHECK-NEXT: - Callback: FileChanged
+// CHECK-NEXT:   Loc: "<built-in>:1:1"
+// CHECK-NEXT:   Reason: RenameFile
+// CHECK-NEXT:   FileType: C_System
+// CHECK-NEXT:   PrevFID: (invalid)
+// CHECK-NEXT: - Callback: MacroDefined
+// CHECK-NEXT:   MacroNameTok: __STDC__
+// CHECK-NEXT:   MacroDirective: MD_Define
+// CHECK-NEXT: - Callback: MacroDefined
+// CHECK-NEXT:   MacroNameTok: __STDC_HOSTED__
+// CHECK-NEXT:   MacroDirective: MD_Define
+// CHECK-NEXT: - Callback: MacroDefined
+// CHECK-NEXT:   MacroNameTok: __cplusplus
+// CHECK-NEXT:   MacroDirective: MD_Define
+// CHECK-NEXT: - Callback: MacroDefined
+// CHECK-NEXT:   MacroNameTok: __STDC_UTF_16__
+// CHECK-NEXT:   MacroDirective: MD_Define
+// CHECK-NEXT: - Callback: MacroDefined
+// CHECK-NEXT:   MacroNameTok: __STDC_UTF_32__
+// CHECK-NEXT:   MacroDirective: MD_Define
+// CHECK-NEXT: - Callback: FileChanged
+// CHECK-NEXT:   Loc: "<command line>:1:1"
+// CHECK-NEXT:   Reason: EnterFile
+// CHECK-NEXT:   FileType: C_User
+// CHECK-NEXT:   PrevFID: (invalid)
+// CHECK-NEXT: - Callback: FileChanged
+// CHECK-NEXT:   Loc: "<built-in>:1:1"
+// CHECK-NEXT:   Reason: ExitFile
+// CHECK-NEXT:   FileType: C_User
+// CHECK-NEXT:   PrevFID: (invalid)
+// CHECK-NEXT: - Callback: FileChanged
+// CHECK-NEXT:   Loc: "{{.*}}{{[/\\]}}pp-trace-include.cpp:1:1"
+// CHECK-NEXT:   Reason: ExitFile
+// CHECK-NEXT:   FileType: C_User
+// CHECK-NEXT:   PrevFID: (getFileEntryForID failed)
+// CHECK-NEXT: - Callback: InclusionDirective
+// CHECK-NEXT:   IncludeTok: include
+// CHECK-NEXT:   FileName: "Input/Level1A.h"
+// CHECK-NEXT:   IsAngled: false
+// CHECK-NEXT:   FilenameRange: "Input/Level1A.h"
+// CHECK-NEXT:   File: "{{.*}}{{[/\\]}}Input/Level1A.h"
+// CHECK-NEXT:   SearchPath: "{{.*}}{{[/\\]}}pp-trace"
+// CHECK-NEXT:   RelativePath: "Input/Level1A.h"
+// CHECK-NEXT:   Imported: (null)
+// CHECK-NEXT: - Callback: FileChanged
+// CHECK-NEXT:   Loc: "{{.*}}{{[/\\]}}Input/Level1A.h:1:1"
+// CHECK-NEXT:   Reason: EnterFile
+// CHECK-NEXT:   FileType: C_User
+// CHECK-NEXT:   PrevFID: (invalid)
+// CHECK-NEXT: - Callback: InclusionDirective
+// CHECK-NEXT:   IncludeTok: include
+// CHECK-NEXT:   FileName: "Level2A.h"
+// CHECK-NEXT:   IsAngled: false
+// CHECK-NEXT:   FilenameRange: "Level2A.h"
+// CHECK-NEXT:   File: "{{.*}}{{[/\\]}}Input/Level2A.h"
+// CHECK-NEXT:   SearchPath: "{{.*}}{{[/\\]}}Input"
+// CHECK-NEXT:   RelativePath: "Level2A.h"
+// CHECK-NEXT:   Imported: (null)
+// CHECK-NEXT: - Callback: FileChanged
+// CHECK-NEXT:   Loc: "{{.*}}{{[/\\]}}Input/Level2A.h:1:1"
+// CHECK-NEXT:   Reason: EnterFile
+// CHECK-NEXT:   FileType: C_User
+// CHECK-NEXT:   PrevFID: (invalid)
+// CHECK-NEXT: - Callback: MacroDefined
+// CHECK-NEXT:   MacroNameTok: MACRO_2A
+// CHECK-NEXT:   MacroDirective: MD_Define
+// CHECK-NEXT: - Callback: FileChanged
+// CHECK-NEXT:   Loc: "{{.*}}{{[/\\]}}Input/Level1A.h:2:1"
+// CHECK-NEXT:   Reason: ExitFile
+// CHECK-NEXT:   FileType: C_User
+// CHECK-NEXT:   PrevFID: "{{.*}}{{[/\\]}}Input/Level2A.h"
+// CHECK-NEXT: - Callback: MacroDefined
+// CHECK-NEXT:   MacroNameTok: MACRO_1A
+// CHECK-NEXT:   MacroDirective: MD_Define
+// CHECK-NEXT: - Callback: FileChanged
+// CHECK-NEXT:   Loc: "{{.*}}{{[/\\]}}pp-trace-include.cpp:4:1"
+// CHECK-NEXT:   Reason: ExitFile
+// CHECK-NEXT:   FileType: C_User
+// CHECK-NEXT:   PrevFID: "{{.*}}{{[/\\]}}Input/Level1A.h"
+// CHECK-NEXT: - Callback: InclusionDirective
+// CHECK-NEXT:   IncludeTok: include
+// CHECK-NEXT:   FileName: "Input/Level1B.h"
+// CHECK-NEXT:   IsAngled: false
+// CHECK-NEXT:   FilenameRange: "Input/Level1B.h"
+// CHECK-NEXT:   File: "{{.*}}{{[/\\]}}Input/Level1B.h"
+// CHECK-NEXT:   SearchPath: "{{.*}}{{[/\\]}}pp-trace"
+// CHECK-NEXT:   RelativePath: "Input/Level1B.h"
+// CHECK-NEXT:   Imported: (null)
+// CHECK-NEXT: - Callback: FileChanged
+// CHECK-NEXT:   Loc: "{{.*}}{{[/\\]}}Input/Level1B.h:1:1"
+// CHECK-NEXT:   Reason: EnterFile
+// CHECK-NEXT:   FileType: C_User
+// CHECK-NEXT:   PrevFID: (invalid)
+// CHECK-NEXT: - Callback: MacroDefined
+// CHECK-NEXT:   MacroNameTok: MACRO_1B
+// CHECK-NEXT:   MacroDirective: MD_Define
+// CHECK-NEXT: - Callback: FileChanged
+// CHECK-NEXT:   Loc: "{{.*}}{{[/\\]}}pp-trace-include.cpp:5:1"
+// CHECK-NEXT:   Reason: ExitFile
+// CHECK-NEXT:   FileType: C_User
+// CHECK-NEXT:   PrevFID: "{{.*}}{{[/\\]}}Input/Level1B.h"
+// CHECK-NEXT: - Callback: EndOfMainFile
+// CHECK-NEXT: ...
Index: test/pp-trace/pp-trace-macro.cpp
===================================================================
--- test/pp-trace/pp-trace-macro.cpp
+++ test/pp-trace/pp-trace-macro.cpp
@@ -0,0 +1,101 @@
+// RUN: pp-trace -ignore FileChanged %s -undef -target x86_64 -std=c++11 | FileCheck --strict-whitespace %s
+
+#define MACRO 1
+int i = MACRO;
+#if defined(MACRO)
+#endif
+#undef MACRO
+#if defined(MACRO)
+#endif
+#define FUNCMACRO(ARG1) ARG1
+int j = FUNCMACRO(1);
+#define X X_IMPL(a+y,b) X_IMPL2(c)
+#define X_IMPL(p1,p2)
+#define X_IMPL2(p1)
+X
+
+// CHECK: ---
+// CHECK-NEXT: - Callback: MacroDefined
+// CHECK-NEXT:   MacroNameTok: __STDC__
+// CHECK-NEXT:   MacroDirective: MD_Define
+// CHECK-NEXT: - Callback: MacroDefined
+// CHECK-NEXT:   MacroNameTok: __STDC_HOSTED__
+// CHECK-NEXT:   MacroDirective: MD_Define
+// CHECK-NEXT: - Callback: MacroDefined
+// CHECK-NEXT:   MacroNameTok: __cplusplus
+// CHECK-NEXT:   MacroDirective: MD_Define
+// CHECK-NEXT: - Callback: MacroDefined
+// CHECK-NEXT:   MacroNameTok: __STDC_UTF_16__
+// CHECK-NEXT:   MacroDirective: MD_Define

+// CHECK-NEXT: - Callback: MacroDefined
+// CHECK-NEXT:   MacroNameTok: __STDC_UTF_32__
+// CHECK-NEXT:   MacroDirective: MD_Define
+// CHECK-NEXT: - Callback: MacroDefined
+// CHECK-NEXT:   MacroNameTok: MACRO
+// CHECK-NEXT:   MacroDirective: MD_Define
+// CHECK-NEXT: - Callback: MacroExpands
+// CHECK-NEXT:   MacroNameTok: MACRO
+// CHECK-NEXT:   MacroDirective: MD_Define
+// CHECK-NEXT:   Range: ["{{.*}}{{[/\\]}}pp-trace-macro.cpp:4:9", "{{.*}}{{[/\\]}}pp-trace-macro.cpp:4:9"]
+// CHECK-NEXT:   Args: (null)
+// CHECK-NEXT: - Callback: Defined
+// CHECK-NEXT:   MacroNameTok: MACRO
+// CHECK-NEXT:   MacroDirective: MD_Define
+// CHECK-NEXT:   Range: ["{{.*}}{{[/\\]}}pp-trace-macro.cpp:5:5", "{{.*}}{{[/\\]}}pp-trace-macro.cpp:5:19"]
+// CHECK-NEXT: - Callback: If
+// CHECK-NEXT:   Loc: "{{.*}}{{[/\\]}}pp-trace-macro.cpp:5:2"
+// CHECK-NEXT:   ConditionRange: ["{{.*}}{{[/\\]}}pp-trace-macro.cpp:5:4", "{{.*}}{{[/\\]}}pp-trace-macro.cpp:6:1"]
+// CHECK-NEXT:   ConditionValue: true
+// CHECK-NEXT: - Callback: Endif
+// CHECK-NEXT:   Loc: "{{.*}}{{[/\\]}}pp-trace-macro.cpp:6:2"
+// CHECK-NEXT:   IfLoc: "{{.*}}{{[/\\]}}pp-trace-macro.cpp:5:2"
+// CHECK-NEXT: - Callback: MacroUndefined
+// CHECK-NEXT:   MacroNameTok: MACRO
+// CHECK-NEXT:   MacroDirective: MD_Define
+// CHECK-NEXT: - Callback: Defined
+// CHECK-NEXT:   MacroNameTok: MACRO
+// CHECK-NEXT:   MacroDirective: (null)
+// CHECK-NEXT:   Range: ["{{.*}}{{[/\\]}}pp-trace-macro.cpp:8:5", "{{.*}}{{[/\\]}}pp-trace-macro.cpp:8:19"]
+// CHECK-NEXT: - Callback: If
+// CHECK-NEXT:   Loc: "{{.*}}{{[/\\]}}pp-trace-macro.cpp:8:2"
+// CHECK-NEXT:   ConditionRange: ["{{.*}}{{[/\\]}}pp-trace-macro.cpp:8:4", "{{.*}}{{[/\\]}}pp-trace-macro.cpp:9:1"]
+// CHECK-NEXT:   ConditionValue: false
+// CHECK-NEXT: - Callback: Endif
+// CHECK-NEXT:   Loc: "{{.*}}{{[/\\]}}pp-trace-macro.cpp:9:2"
+// CHECK-NEXT:   IfLoc: "{{.*}}{{[/\\]}}pp-trace-macro.cpp:8:2"
+// CHECK-NEXT: - Callback: SourceRangeSkipped
+// CHECK-NEXT:   Range: ["{{.*}}{{[/\\]}}pp-trace-macro.cpp:8:2", "{{.*}}{{[/\\]}}pp-trace-macro.cpp:9:2"]
+// CHECK-NEXT: - Callback: MacroDefined
+// CHECK-NEXT:   MacroNameTok: FUNCMACRO
+// CHECK-NEXT:   MacroDirective: MD_Define
+// CHECK-NEXT: - Callback: MacroExpands
+// CHECK-NEXT:   MacroNameTok: FUNCMACRO
+// CHECK-NEXT:   MacroDirective: MD_Define
+// CHECK-NEXT:   Range: ["{{.*}}{{[/\\]}}pp-trace-macro.cpp:11:9", "{{.*}}{{[/\\]}}pp-trace-macro.cpp:11:20"]
+// CHECK-NEXT:   Args: [1]
+// CHECK-NEXT: - Callback: MacroDefined
+// CHECK-NEXT:   MacroNameTok: X
+// CHECK-NEXT:   MacroDirective: MD_Define
+// CHECK-NEXT: - Callback: MacroDefined
+// CHECK-NEXT:   MacroNameTok: X_IMPL
+// CHECK-NEXT:   MacroDirective: MD_Define
+// CHECK-NEXT: - Callback: MacroDefined
+// CHECK-NEXT:   MacroNameTok: X_IMPL2
+// CHECK-NEXT:   MacroDirective: MD_Define
+// CHECK-NEXT: - Callback: MacroExpands
+// CHECK-NEXT:   MacroNameTok: X
+// CHECK-NEXT:   MacroDirective: MD_Define
+// CHECK-NEXT:   Range: ["{{.*}}{{[/\\]}}pp-trace-macro.cpp:15:1", "{{.*}}{{[/\\]}}pp-trace-macro.cpp:15:1"]
+// CHECK-NEXT:   Args: (null)
+// CHECK-NEXT: - Callback: MacroExpands
+// CHECK-NEXT:   MacroNameTok: X_IMPL
+// CHECK-NEXT:   MacroDirective: MD_Define
+// CHECK-NEXT:   Range: [(nonfile), (nonfile)]
+// CHECK-NEXT:   Args: [a plus y, b]
+// CHECK-NEXT: - Callback: MacroExpands
+// CHECK-NEXT:   MacroNameTok: X_IMPL2
+// CHECK-NEXT:   MacroDirective: MD_Define
+// CHECK-NEXT:   Range: [(nonfile), (nonfile)]
+// CHECK-NEXT:   Args: [c]
+// CHECK-NEXT: - Callback: EndOfMainFile
+// CHECK-NEXT: ...