lib/Frontend/InitPreprocessor.cpp

//===--- InitPreprocessor.cpp - PP initialization code. ---------*- C++ -*-===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements the clang::InitializePreprocessor function.
//
//===----------------------------------------------------------------------===//

#include "clang/Frontend/Utils.h"
#include "clang/Basic/FileManager.h"
#include "clang/Basic/MacroBuilder.h"
#include "clang/Basic/SourceManager.h"
#include "clang/Basic/TargetInfo.h"
#include "clang/Basic/Version.h"
#include "clang/Frontend/FrontendDiagnostic.h"
#include "clang/Frontend/FrontendOptions.h"
#include "clang/Lex/HeaderSearch.h"
#include "clang/Lex/Preprocessor.h"
#include "clang/Lex/PreprocessorOptions.h"
#include "clang/Serialization/ASTReader.h"
#include "llvm/ADT/APFloat.h"
#include "llvm/Support/FileSystem.h"
#include "llvm/Support/MemoryBuffer.h"
#include "llvm/Support/Path.h"
using namespace clang;

static bool MacroBodyEndsInBackslash(StringRef MacroBody) {
  while (!MacroBody.empty() && isWhitespace(MacroBody.back()))
    MacroBody = MacroBody.drop_back();
  return !MacroBody.empty() && MacroBody.back() == '\\';
}

// Append a #define line to Buf for Macro.  Macro should be of the form XXX,
// in which case we emit "#define XXX 1" or "XXX=Y z W" in which case we emit
// "#define XXX Y z W".  To get a #define with no value, use "XXX=".
static void DefineBuiltinMacro(MacroBuilder &Builder, StringRef Macro,
                               DiagnosticsEngine &Diags) {
  std::pair<StringRef, StringRef> MacroPair = Macro.split('=');
  StringRef MacroName = MacroPair.first;
  StringRef MacroBody = MacroPair.second;
  if (MacroName.size() != Macro.size()) {
    // Per GCC -D semantics, the macro ends at \n if it exists.
    StringRef::size_type End = MacroBody.find_first_of("\n\r");
    if (End != StringRef::npos)
      Diags.Report(diag::warn_fe_macro_contains_embedded_newline)
        << MacroName;
    MacroBody = MacroBody.substr(0, End);
    // We handle macro bodies which end in a backslash by appending an extra
    // backslash+newline.  This makes sure we don't accidentally treat the
    // backslash as a line continuation marker.
    if (MacroBodyEndsInBackslash(MacroBody))
      Builder.defineMacro(MacroName, Twine(MacroBody) + "\\\n");
    else
      Builder.defineMacro(MacroName, MacroBody);
  } else {
    // Push "macroname 1".
    Builder.defineMacro(Macro);
  }
}

/// AddImplicitInclude - Add an implicit \#include of the specified file to the
/// predefines buffer.
static void AddImplicitInclude(MacroBuilder &Builder, StringRef File,
                               FileManager &FileMgr) {
  Builder.append(Twine("#include \"") +
                 HeaderSearch::NormalizeDashIncludePath(File, FileMgr) + "\"");
}

static void AddImplicitIncludeMacros(MacroBuilder &Builder,
                                     StringRef File,
                                     FileManager &FileMgr) {
  Builder.append(Twine("#__include_macros \"") +
                 HeaderSearch::NormalizeDashIncludePath(File, FileMgr) + "\"");
  // Marker token to stop the __include_macros fetch loop.
  Builder.append("##"); // ##?
}

/// AddImplicitIncludePTH - Add an implicit \#include using the original file
/// used to generate a PTH cache.
static void AddImplicitIncludePTH(MacroBuilder &Builder, Preprocessor &PP,
                                  StringRef ImplicitIncludePTH) {
  PTHManager *P = PP.getPTHManager();
  // Null check 'P' in the corner case where it couldn't be created.
  const char *OriginalFile = P ? P->getOriginalSourceFile() : 0;

  if (!OriginalFile) {
    PP.getDiagnostics().Report(diag::err_fe_pth_file_has_no_source_header)
      << ImplicitIncludePTH;
    return;
  }

  AddImplicitInclude(Builder, OriginalFile, PP.getFileManager());
}

/// \brief Add an implicit \#include using the original file used to generate
/// a PCH file.
static void AddImplicitIncludePCH(MacroBuilder &Builder, Preprocessor &PP,
                                  StringRef ImplicitIncludePCH) {
  std::string OriginalFile =
    ASTReader::getOriginalSourceFile(ImplicitIncludePCH, PP.getFileManager(),
                                     PP.getDiagnostics());
  if (OriginalFile.empty())
    return;

  AddImplicitInclude(Builder, OriginalFile, PP.getFileManager());
}

/// PickFP - This is used to pick a value based on the FP semantics of the
/// specified FP model.
template <typename T>
static T PickFP(const llvm::fltSemantics *Sem, T IEEESingleVal,
                T IEEEDoubleVal, T X87DoubleExtendedVal, T PPCDoubleDoubleVal,
                T IEEEQuadVal) {
  if (Sem == (const llvm::fltSemantics*)&llvm::APFloat::IEEEsingle)
    return IEEESingleVal;
  if (Sem == (const llvm::fltSemantics*)&llvm::APFloat::IEEEdouble)
    return IEEEDoubleVal;
  if (Sem == (const llvm::fltSemantics*)&llvm::APFloat::x87DoubleExtended)
    return X87DoubleExtendedVal;
  if (Sem == (const llvm::fltSemantics*)&llvm::APFloat::PPCDoubleDouble)
    return PPCDoubleDoubleVal;
  assert(Sem == (const llvm::fltSemantics*)&llvm::APFloat::IEEEquad);
  return IEEEQuadVal;
}

static void DefineFloatMacros(MacroBuilder &Builder, StringRef Prefix,
                              const llvm::fltSemantics *Sem, StringRef Ext) {
  const char *DenormMin, *Epsilon, *Max, *Min;
  DenormMin = PickFP(Sem, "1.40129846e-45", "4.9406564584124654e-324",
                     "3.64519953188247460253e-4951",
                     "4.94065645841246544176568792868221e-324",
                     "6.47517511943802511092443895822764655e-4966");
  int Digits = PickFP(Sem, 6, 15, 18, 31, 33);
  Epsilon = PickFP(Sem, "1.19209290e-7", "2.2204460492503131e-16",
                   "1.08420217248550443401e-19",
                   "4.94065645841246544176568792868221e-324",
                   "1.92592994438723585305597794258492732e-34");
  int MantissaDigits = PickFP(Sem, 24, 53, 64, 106, 113);
  int Min10Exp = PickFP(Sem, -37, -307, -4931, -291, -4931);
  int Max10Exp = PickFP(Sem, 38, 308, 4932, 308, 4932);
  int MinExp = PickFP(Sem, -125, -1021, -16381, -968, -16381);
  int MaxExp = PickFP(Sem, 128, 1024, 16384, 1024, 16384);
  Min = PickFP(Sem, "1.17549435e-38", "2.2250738585072014e-308",
               "3.36210314311209350626e-4932",
               "2.00416836000897277799610805135016e-292",
               "3.36210314311209350626267781732175260e-4932");
  Max = PickFP(Sem, "3.40282347e+38", "1.7976931348623157e+308",
               "1.18973149535723176502e+4932",
               "1.79769313486231580793728971405301e+308",
               "1.18973149535723176508575932662800702e+4932");

  SmallString<32> DefPrefix;
  DefPrefix = "__";
  DefPrefix += Prefix;
  DefPrefix += "_";

  Builder.defineMacro(DefPrefix + "DENORM_MIN__", Twine(DenormMin)+Ext);
  Builder.defineMacro(DefPrefix + "HAS_DENORM__");
  Builder.defineMacro(DefPrefix + "DIG__", Twine(Digits));
  Builder.defineMacro(DefPrefix + "EPSILON__", Twine(Epsilon)+Ext);
  Builder.defineMacro(DefPrefix + "HAS_INFINITY__");
  Builder.defineMacro(DefPrefix + "HAS_QUIET_NAN__");
  Builder.defineMacro(DefPrefix + "MANT_DIG__", Twine(MantissaDigits));

  Builder.defineMacro(DefPrefix + "MAX_10_EXP__", Twine(Max10Exp));
  Builder.defineMacro(DefPrefix + "MAX_EXP__", Twine(MaxExp));
  Builder.defineMacro(DefPrefix + "MAX__", Twine(Max)+Ext);

  Builder.defineMacro(DefPrefix + "MIN_10_EXP__","("+Twine(Min10Exp)+")");
  Builder.defineMacro(DefPrefix + "MIN_EXP__", "("+Twine(MinExp)+")");
  Builder.defineMacro(DefPrefix + "MIN__", Twine(Min)+Ext);
}


/// DefineTypeSize - Emit a macro to the predefines buffer that declares a macro
/// named MacroName with the max value for a type with width 'TypeWidth' a
/// signedness of 'isSigned' and with a value suffix of 'ValSuffix' (e.g. LL).
static void DefineTypeSize(StringRef MacroName, unsigned TypeWidth,
                           StringRef ValSuffix, bool isSigned,
                           MacroBuilder &Builder) {
  llvm::APInt MaxVal = isSigned ? llvm::APInt::getSignedMaxValue(TypeWidth)
                                : llvm::APInt::getMaxValue(TypeWidth);
  Builder.defineMacro(MacroName, MaxVal.toString(10, isSigned) + ValSuffix);
}

/// DefineTypeSize - An overloaded helper that uses TargetInfo to determine
/// the width, suffix, and signedness of the given type
static void DefineTypeSize(StringRef MacroName, TargetInfo::IntType Ty,
                           const TargetInfo &TI, MacroBuilder &Builder) {
  DefineTypeSize(MacroName, TI.getTypeWidth(Ty), TI.getTypeConstantSuffix(Ty), 
                 TI.isTypeSigned(Ty), Builder);
}

static void DefineType(const Twine &MacroName, TargetInfo::IntType Ty,
                       MacroBuilder &Builder) {
  Builder.defineMacro(MacroName, TargetInfo::getTypeName(Ty));
}

static void DefineTypeWidth(StringRef MacroName, TargetInfo::IntType Ty,
                            const TargetInfo &TI, MacroBuilder &Builder) {
  Builder.defineMacro(MacroName, Twine(TI.getTypeWidth(Ty)));
}

static void DefineTypeSizeof(StringRef MacroName, unsigned BitWidth,
                             const TargetInfo &TI, MacroBuilder &Builder) {
  Builder.defineMacro(MacroName,
                      Twine(BitWidth / TI.getCharWidth()));
}

static void DefineExactWidthIntType(TargetInfo::IntType Ty, 
                               const TargetInfo &TI, MacroBuilder &Builder) {
  int TypeWidth = TI.getTypeWidth(Ty);

  // Use the target specified int64 type, when appropriate, so that [u]int64_t
  // ends up being defined in terms of the correct type.
  if (TypeWidth == 64)
    Ty = TI.getInt64Type();

  DefineType("__INT" + Twine(TypeWidth) + "_TYPE__", Ty, Builder);

  StringRef ConstSuffix(TargetInfo::getTypeConstantSuffix(Ty));
  if (!ConstSuffix.empty())
    Builder.defineMacro("__INT" + Twine(TypeWidth) + "_C_SUFFIX__",
                        ConstSuffix);
}

/// Get the value the ATOMIC_*_LOCK_FREE macro should have for a type with
/// the specified properties.
static const char *getLockFreeValue(unsigned TypeWidth, unsigned TypeAlign,
                                    unsigned InlineWidth) {
  // Fully-aligned, power-of-2 sizes no larger than the inline
  // width will be inlined as lock-free operations.
  if (TypeWidth == TypeAlign && (TypeWidth & (TypeWidth - 1)) == 0 &&
      TypeWidth <= InlineWidth)
    return "2"; // "always lock free"
  // We cannot be certain what operations the lib calls might be
  // able to implement as lock-free on future processors.
  return "1"; // "sometimes lock free"
}

/// \brief Add definitions required for a smooth interaction between
/// Objective-C++ automated reference counting and libstdc++ (4.2).
static void AddObjCXXARCLibstdcxxDefines(const LangOptions &LangOpts, 
                                         MacroBuilder &Builder) {
  Builder.defineMacro("_GLIBCXX_PREDEFINED_OBJC_ARC_IS_SCALAR");
  
  std::string Result;
  {
    // Provide specializations for the __is_scalar type trait so that 
    // lifetime-qualified objects are not considered "scalar" types, which
    // libstdc++ uses as an indicator of the presence of trivial copy, assign,
    // default-construct, and destruct semantics (none of which hold for
    // lifetime-qualified objects in ARC).
    llvm::raw_string_ostream Out(Result);
    
    Out << "namespace std {\n"
        << "\n"
        << "struct __true_type;\n"
        << "struct __false_type;\n"
        << "\n";
    
    Out << "template<typename _Tp> struct __is_scalar;\n"
        << "\n";
      
    Out << "template<typename _Tp>\n"
        << "struct __is_scalar<__attribute__((objc_ownership(strong))) _Tp> {\n"
        << "  enum { __value = 0 };\n"
        << "  typedef __false_type __type;\n"
        << "};\n"
        << "\n";
      
    if (LangOpts.ObjCARCWeak) {
      Out << "template<typename _Tp>\n"
          << "struct __is_scalar<__attribute__((objc_ownership(weak))) _Tp> {\n"
          << "  enum { __value = 0 };\n"
          << "  typedef __false_type __type;\n"
          << "};\n"
          << "\n";
    }
    
    Out << "template<typename _Tp>\n"
        << "struct __is_scalar<__attribute__((objc_ownership(autoreleasing)))"
        << " _Tp> {\n"
        << "  enum { __value = 0 };\n"
        << "  typedef __false_type __type;\n"
        << "};\n"
        << "\n";
      
    Out << "}\n";
  }
  Builder.append(Result);
}

static void InitializeStandardPredefinedMacros(const TargetInfo &TI,
                                               const LangOptions &LangOpts,
                                               const FrontendOptions &FEOpts,
                                               MacroBuilder &Builder) {
  if (!LangOpts.MicrosoftMode && !LangOpts.TraditionalCPP)
    Builder.defineMacro("__STDC__");
  if (LangOpts.Freestanding)
    Builder.defineMacro("__STDC_HOSTED__", "0");
  else
    Builder.defineMacro("__STDC_HOSTED__");

  if (!LangOpts.CPlusPlus) {
    if (LangOpts.C11)
      Builder.defineMacro("__STDC_VERSION__", "201112L");
    else if (LangOpts.C99)
      Builder.defineMacro("__STDC_VERSION__", "199901L");
    else if (!LangOpts.GNUMode && LangOpts.Digraphs)
      Builder.defineMacro("__STDC_VERSION__", "199409L");
  } else {
    // FIXME: Use the right value for __cplusplus for C++1y once one is chosen.
    if (LangOpts.CPlusPlus1y)
      Builder.defineMacro("__cplusplus", "201305L");
    // C++11 [cpp.predefined]p1:
    //   The name __cplusplus is defined to the value 201103L when compiling a
    //   C++ translation unit.
    else if (LangOpts.CPlusPlus11)
      Builder.defineMacro("__cplusplus", "201103L");
    // C++03 [cpp.predefined]p1:
    //   The name __cplusplus is defined to the value 199711L when compiling a
    //   C++ translation unit.
    else
      Builder.defineMacro("__cplusplus", "199711L");
  }

  // In C11 these are environment macros. In C++11 they are only defined
  // as part of <cuchar>. To prevent breakage when mixing C and C++
  // code, define these macros unconditionally. We can define them
  // unconditionally, as Clang always uses UTF-16 and UTF-32 for 16-bit
  // and 32-bit character literals.
  Builder.defineMacro("__STDC_UTF_16__", "1");
  Builder.defineMacro("__STDC_UTF_32__", "1");

  if (LangOpts.ObjC1)
    Builder.defineMacro("__OBJC__");

  // Not "standard" per se, but available even with the -undef flag.
  if (LangOpts.AsmPreprocessor)
    Builder.defineMacro("__ASSEMBLER__");
}

/// Initialize the predefined C++ language feature test macros defined in
/// ISO/IEC JTC1/SC22/WG21 (C++) SD-6: "SG10 Feature Test Recommendations".
static void InitializeCPlusPlusFeatureTestMacros(const LangOptions &LangOpts,
                                                 MacroBuilder &Builder) {
  // C++11 features.
  if (LangOpts.CPlusPlus11) {
    Builder.defineMacro("__cpp_unicode_characters", "200704");
    Builder.defineMacro("__cpp_raw_strings", "200710");
    Builder.defineMacro("__cpp_unicode_literals", "200710");
    Builder.defineMacro("__cpp_user_defined_literals", "200809");
    Builder.defineMacro("__cpp_lambdas", "200907");
    Builder.defineMacro("__cpp_constexpr",
                        LangOpts.CPlusPlus1y ? "201304" : "200704");
    Builder.defineMacro("__cpp_static_assert", "200410");
    Builder.defineMacro("__cpp_decltype", "200707");
    Builder.defineMacro("__cpp_attributes", "200809");
    Builder.defineMacro("__cpp_rvalue_references", "200610");
    Builder.defineMacro("__cpp_variadic_templates", "200704");
  }

  // C++14 features.
  if (LangOpts.CPlusPlus1y) {
    Builder.defineMacro("__cpp_binary_literals", "201304");
    Builder.defineMacro("__cpp_init_captures", "201304");
    Builder.defineMacro("__cpp_generic_lambdas", "201304");
    Builder.defineMacro("__cpp_decltype_auto", "201304");
    Builder.defineMacro("__cpp_return_type_deduction", "201304");
    Builder.defineMacro("__cpp_aggregate_nsdmi", "201304");
    Builder.defineMacro("__cpp_variable_templates", "201304");
  }
}

static void InitializePredefinedMacros(const TargetInfo &TI,
                                       const LangOptions &LangOpts,
                                       const FrontendOptions &FEOpts,
                                       MacroBuilder &Builder) {
  // Compiler version introspection macros.
  Builder.defineMacro("__llvm__");  // LLVM Backend
  Builder.defineMacro("__clang__"); // Clang Frontend
#define TOSTR2(X) #X
#define TOSTR(X) TOSTR2(X)
  Builder.defineMacro("__clang_major__", TOSTR(CLANG_VERSION_MAJOR));
  Builder.defineMacro("__clang_minor__", TOSTR(CLANG_VERSION_MINOR));
#ifdef CLANG_VERSION_PATCHLEVEL
  Builder.defineMacro("__clang_patchlevel__", TOSTR(CLANG_VERSION_PATCHLEVEL));
#else
  Builder.defineMacro("__clang_patchlevel__", "0");
#endif
  Builder.defineMacro("__clang_version__", 
                      "\"" CLANG_VERSION_STRING " "
                      + getClangFullRepositoryVersion() + "\"");
#undef TOSTR
#undef TOSTR2
  if (!LangOpts.MicrosoftMode) {
    // Currently claim to be compatible with GCC 4.2.1-5621, but only if we're
    // not compiling for MSVC compatibility
    Builder.defineMacro("__GNUC_MINOR__", "2");
    Builder.defineMacro("__GNUC_PATCHLEVEL__", "1");
    Builder.defineMacro("__GNUC__", "4");
    Builder.defineMacro("__GXX_ABI_VERSION", "1002");
  }

  // Define macros for the C11 / C++11 memory orderings
  Builder.defineMacro("__ATOMIC_RELAXED", "0");
  Builder.defineMacro("__ATOMIC_CONSUME", "1");
  Builder.defineMacro("__ATOMIC_ACQUIRE", "2");
  Builder.defineMacro("__ATOMIC_RELEASE", "3");
  Builder.defineMacro("__ATOMIC_ACQ_REL", "4");
  Builder.defineMacro("__ATOMIC_SEQ_CST", "5");

  // Support for #pragma redefine_extname (Sun compatibility)
  Builder.defineMacro("__PRAGMA_REDEFINE_EXTNAME", "1");

  // As sad as it is, enough software depends on the __VERSION__ for version
  // checks that it is necessary to report 4.2.1 (the base GCC version we claim
  // compatibility with) first.
  Builder.defineMacro("__VERSION__", "\"4.2.1 Compatible " + 
                      Twine(getClangFullCPPVersion()) + "\"");

  // Initialize language-specific preprocessor defines.

  // Standard conforming mode?
  if (!LangOpts.GNUMode)
    Builder.defineMacro("__STRICT_ANSI__");

  if (LangOpts.CPlusPlus11)
    Builder.defineMacro("__GXX_EXPERIMENTAL_CXX0X__");

  if (LangOpts.ObjC1) {
    if (LangOpts.ObjCRuntime.isNonFragile()) {
      Builder.defineMacro("__OBJC2__");
      
      if (LangOpts.ObjCExceptions)
        Builder.defineMacro("OBJC_ZEROCOST_EXCEPTIONS");
    }

    if (LangOpts.getGC() != LangOptions::NonGC)
      Builder.defineMacro("__OBJC_GC__");

    if (LangOpts.ObjCRuntime.isNeXTFamily())
      Builder.defineMacro("__NEXT_RUNTIME__");

    if (LangOpts.ObjCRuntime.getKind() == ObjCRuntime::ObjFW) {
      VersionTuple tuple = LangOpts.ObjCRuntime.getVersion();

      unsigned minor = 0;
      if (tuple.getMinor().hasValue())
        minor = tuple.getMinor().getValue();

      unsigned subminor = 0;
      if (tuple.getSubminor().hasValue())
        subminor = tuple.getSubminor().getValue();

      Builder.defineMacro("__OBJFW_RUNTIME_ABI__",
                          Twine(tuple.getMajor() * 10000 + minor * 100 +
                                subminor));
    }

    Builder.defineMacro("IBOutlet", "__attribute__((iboutlet))");
    Builder.defineMacro("IBOutletCollection(ClassName)",
                        "__attribute__((iboutletcollection(ClassName)))");
    Builder.defineMacro("IBAction", "void)__attribute__((ibaction)");
  }

  if (LangOpts.CPlusPlus)
    InitializeCPlusPlusFeatureTestMacros(LangOpts, Builder);

  // darwin_constant_cfstrings controls this. This is also dependent
  // on other things like the runtime I believe.  This is set even for C code.
  if (!LangOpts.NoConstantCFStrings)
      Builder.defineMacro("__CONSTANT_CFSTRINGS__");

  if (LangOpts.ObjC2)
    Builder.defineMacro("OBJC_NEW_PROPERTIES");

  if (LangOpts.PascalStrings)
    Builder.defineMacro("__PASCAL_STRINGS__");

  if (LangOpts.Blocks) {
    Builder.defineMacro("__block", "__attribute__((__blocks__(byref)))");
    Builder.defineMacro("__BLOCKS__");
  }

  if (LangOpts.CXXExceptions)
    Builder.defineMacro("__EXCEPTIONS");
  if (LangOpts.RTTI)
    Builder.defineMacro("__GXX_RTTI");
  if (LangOpts.SjLjExceptions)
    Builder.defineMacro("__USING_SJLJ_EXCEPTIONS__");

  if (LangOpts.Deprecated)
    Builder.defineMacro("__DEPRECATED");

  if (LangOpts.CPlusPlus) {
    Builder.defineMacro("__GNUG__", "4");
    Builder.defineMacro("__GXX_WEAK__");
    Builder.defineMacro("__private_extern__", "extern");
  }

  if (LangOpts.MicrosoftExt) {
    // Both __PRETTY_FUNCTION__ and __FUNCTION__ are GCC extensions, however
    // VC++ appears to only like __FUNCTION__.
    Builder.defineMacro("__PRETTY_FUNCTION__", "__FUNCTION__");
    // Work around some issues with Visual C++ headers.
    if (LangOpts.WChar) {
      // wchar_t supported as a keyword.
      Builder.defineMacro("_WCHAR_T_DEFINED");
      Builder.defineMacro("_NATIVE_WCHAR_T_DEFINED");
    }
    if (LangOpts.CPlusPlus) {
      // FIXME: Support Microsoft's __identifier extension in the lexer.
      Builder.append("#define __identifier(x) x");
      Builder.append("class type_info;");
    }
  }

  if (LangOpts.Optimize)
    Builder.defineMacro("__OPTIMIZE__");
  if (LangOpts.OptimizeSize)
    Builder.defineMacro("__OPTIMIZE_SIZE__");

  if (LangOpts.FastMath)
    Builder.defineMacro("__FAST_MATH__");

  // Initialize target-specific preprocessor defines.

  // __BYTE_ORDER__ was added in GCC 4.6. It's analogous
  // to the macro __BYTE_ORDER (no trailing underscores)
  // from glibc's <endian.h> header.
  // We don't support the PDP-11 as a target, but include
  // the define so it can still be compared against.
  Builder.defineMacro("__ORDER_LITTLE_ENDIAN__", "1234");
  Builder.defineMacro("__ORDER_BIG_ENDIAN__",    "4321");
  Builder.defineMacro("__ORDER_PDP_ENDIAN__",    "3412");
  if (TI.isBigEndian())
    Builder.defineMacro("__BYTE_ORDER__", "__ORDER_BIG_ENDIAN__");
  else
    Builder.defineMacro("__BYTE_ORDER__", "__ORDER_LITTLE_ENDIAN__");


  if (TI.getPointerWidth(0) == 64 && TI.getLongWidth() == 64
      && TI.getIntWidth() == 32) {
    Builder.defineMacro("_LP64");
    Builder.defineMacro("__LP64__");
  }

  // Define type sizing macros based on the target properties.
  assert(TI.getCharWidth() == 8 && "Only support 8-bit char so far");
  Builder.defineMacro("__CHAR_BIT__", "8");

  DefineTypeSize("__SCHAR_MAX__", TargetInfo::SignedChar, TI, Builder);
  DefineTypeSize("__SHRT_MAX__", TargetInfo::SignedShort, TI, Builder);
  DefineTypeSize("__INT_MAX__", TargetInfo::SignedInt, TI, Builder);
  DefineTypeSize("__LONG_MAX__", TargetInfo::SignedLong, TI, Builder);
  DefineTypeSize("__LONG_LONG_MAX__", TargetInfo::SignedLongLong, TI, Builder);
  DefineTypeSize("__WCHAR_MAX__", TI.getWCharType(), TI, Builder);
  DefineTypeSize("__INTMAX_MAX__", TI.getIntMaxType(), TI, Builder);
  DefineTypeSize("__SIZE_MAX__", TI.getSizeType(), TI, Builder);

  DefineTypeSizeof("__SIZEOF_DOUBLE__", TI.getDoubleWidth(), TI, Builder);
  DefineTypeSizeof("__SIZEOF_FLOAT__", TI.getFloatWidth(), TI, Builder);
  DefineTypeSizeof("__SIZEOF_INT__", TI.getIntWidth(), TI, Builder);
  DefineTypeSizeof("__SIZEOF_LONG__", TI.getLongWidth(), TI, Builder);
  DefineTypeSizeof("__SIZEOF_LONG_DOUBLE__",TI.getLongDoubleWidth(),TI,Builder);
  DefineTypeSizeof("__SIZEOF_LONG_LONG__", TI.getLongLongWidth(), TI, Builder);
  DefineTypeSizeof("__SIZEOF_POINTER__", TI.getPointerWidth(0), TI, Builder);
  DefineTypeSizeof("__SIZEOF_SHORT__", TI.getShortWidth(), TI, Builder);
  DefineTypeSizeof("__SIZEOF_PTRDIFF_T__",
                   TI.getTypeWidth(TI.getPtrDiffType(0)), TI, Builder);
  DefineTypeSizeof("__SIZEOF_SIZE_T__",
                   TI.getTypeWidth(TI.getSizeType()), TI, Builder);
  DefineTypeSizeof("__SIZEOF_WCHAR_T__",
                   TI.getTypeWidth(TI.getWCharType()), TI, Builder);
  DefineTypeSizeof("__SIZEOF_WINT_T__",
                   TI.getTypeWidth(TI.getWIntType()), TI, Builder);
  if (TI.hasInt128Type())
    DefineTypeSizeof("__SIZEOF_INT128__", 128, TI, Builder);

  DefineType("__INTMAX_TYPE__", TI.getIntMaxType(), Builder);
  DefineType("__UINTMAX_TYPE__", TI.getUIntMaxType(), Builder);
  DefineTypeWidth("__INTMAX_WIDTH__",  TI.getIntMaxType(), TI, Builder);
  DefineType("__PTRDIFF_TYPE__", TI.getPtrDiffType(0), Builder);
  DefineTypeWidth("__PTRDIFF_WIDTH__", TI.getPtrDiffType(0), TI, Builder);
  DefineType("__INTPTR_TYPE__", TI.getIntPtrType(), Builder);
  DefineTypeWidth("__INTPTR_WIDTH__", TI.getIntPtrType(), TI, Builder);
  DefineType("__SIZE_TYPE__", TI.getSizeType(), Builder);
  DefineTypeWidth("__SIZE_WIDTH__", TI.getSizeType(), TI, Builder);
  DefineType("__WCHAR_TYPE__", TI.getWCharType(), Builder);
  DefineTypeWidth("__WCHAR_WIDTH__", TI.getWCharType(), TI, Builder);
  DefineType("__WINT_TYPE__", TI.getWIntType(), Builder);
  DefineTypeWidth("__WINT_WIDTH__", TI.getWIntType(), TI, Builder);
  DefineTypeWidth("__SIG_ATOMIC_WIDTH__", TI.getSigAtomicType(), TI, Builder);
  DefineType("__CHAR16_TYPE__", TI.getChar16Type(), Builder);
  DefineType("__CHAR32_TYPE__", TI.getChar32Type(), Builder);

  DefineFloatMacros(Builder, "FLT", &TI.getFloatFormat(), "F");
  DefineFloatMacros(Builder, "DBL", &TI.getDoubleFormat(), "");
  DefineFloatMacros(Builder, "LDBL", &TI.getLongDoubleFormat(), "L");

  // Define a __POINTER_WIDTH__ macro for stdint.h.
  Builder.defineMacro("__POINTER_WIDTH__",
                      Twine((int)TI.getPointerWidth(0)));

  if (!LangOpts.CharIsSigned)
    Builder.defineMacro("__CHAR_UNSIGNED__");

  if (!TargetInfo::isTypeSigned(TI.getWCharType()))
    Builder.defineMacro("__WCHAR_UNSIGNED__");

  if (!TargetInfo::isTypeSigned(TI.getWIntType()))
    Builder.defineMacro("__WINT_UNSIGNED__");

  // Define exact-width integer types for stdint.h
  Builder.defineMacro("__INT" + Twine(TI.getCharWidth()) + "_TYPE__",
                      "char");

  if (TI.getShortWidth() > TI.getCharWidth())
    DefineExactWidthIntType(TargetInfo::SignedShort, TI, Builder);

  if (TI.getIntWidth() > TI.getShortWidth())
    DefineExactWidthIntType(TargetInfo::SignedInt, TI, Builder);

  if (TI.getLongWidth() > TI.getIntWidth())
    DefineExactWidthIntType(TargetInfo::SignedLong, TI, Builder);

  if (TI.getLongLongWidth() > TI.getLongWidth())
    DefineExactWidthIntType(TargetInfo::SignedLongLong, TI, Builder);

  if (const char *Prefix = TI.getUserLabelPrefix())
    Builder.defineMacro("__USER_LABEL_PREFIX__", Prefix);

  if (LangOpts.FastMath || LangOpts.FiniteMathOnly)
    Builder.defineMacro("__FINITE_MATH_ONLY__", "1");
  else
    Builder.defineMacro("__FINITE_MATH_ONLY__", "0");

  if (LangOpts.GNUInline)
    Builder.defineMacro("__GNUC_GNU_INLINE__");
  else
    Builder.defineMacro("__GNUC_STDC_INLINE__");

  // The value written by __atomic_test_and_set.
  // FIXME: This is target-dependent.
  Builder.defineMacro("__GCC_ATOMIC_TEST_AND_SET_TRUEVAL", "1");

  // Used by libstdc++ to implement ATOMIC_<foo>_LOCK_FREE.
  unsigned InlineWidthBits = TI.getMaxAtomicInlineWidth();
#define DEFINE_LOCK_FREE_MACRO(TYPE, Type) \
  Builder.defineMacro("__GCC_ATOMIC_" #TYPE "_LOCK_FREE", \
                      getLockFreeValue(TI.get##Type##Width(), \
                                       TI.get##Type##Align(), \
                                       InlineWidthBits));
  DEFINE_LOCK_FREE_MACRO(BOOL, Bool);
  DEFINE_LOCK_FREE_MACRO(CHAR, Char);
  DEFINE_LOCK_FREE_MACRO(CHAR16_T, Char16);
  DEFINE_LOCK_FREE_MACRO(CHAR32_T, Char32);
  DEFINE_LOCK_FREE_MACRO(WCHAR_T, WChar);
  DEFINE_LOCK_FREE_MACRO(SHORT, Short);
  DEFINE_LOCK_FREE_MACRO(INT, Int);
  DEFINE_LOCK_FREE_MACRO(LONG, Long);
  DEFINE_LOCK_FREE_MACRO(LLONG, LongLong);
  Builder.defineMacro("__GCC_ATOMIC_POINTER_LOCK_FREE",
                      getLockFreeValue(TI.getPointerWidth(0),
                                       TI.getPointerAlign(0),
                                       InlineWidthBits));
#undef DEFINE_LOCK_FREE_MACRO

  if (LangOpts.NoInlineDefine)
    Builder.defineMacro("__NO_INLINE__");

  if (unsigned PICLevel = LangOpts.PICLevel) {
    Builder.defineMacro("__PIC__", Twine(PICLevel));
    Builder.defineMacro("__pic__", Twine(PICLevel));
  }
  if (unsigned PIELevel = LangOpts.PIELevel) {
    Builder.defineMacro("__PIE__", Twine(PIELevel));
    Builder.defineMacro("__pie__", Twine(PIELevel));
  }

  // Macros to control C99 numerics and <float.h>
  Builder.defineMacro("__FLT_EVAL_METHOD__", Twine(TI.getFloatEvalMethod()));
  Builder.defineMacro("__FLT_RADIX__", "2");
  int Dig = PickFP(&TI.getLongDoubleFormat(), -1/*FIXME*/, 17, 21, 33, 36);
  Builder.defineMacro("__DECIMAL_DIG__", Twine(Dig));

  if (LangOpts.getStackProtector() == LangOptions::SSPOn)
    Builder.defineMacro("__SSP__");
  else if (LangOpts.getStackProtector() == LangOptions::SSPReq)
    Builder.defineMacro("__SSP_ALL__", "2");

  if (FEOpts.ProgramAction == frontend::RewriteObjC)
    Builder.defineMacro("__weak", "__attribute__((objc_gc(weak)))");

  // Define a macro that exists only when using the static analyzer.
  if (FEOpts.ProgramAction == frontend::RunAnalysis)
    Builder.defineMacro("__clang_analyzer__");

  if (LangOpts.FastRelaxedMath)
    Builder.defineMacro("__FAST_RELAXED_MATH__");

  if (LangOpts.ObjCAutoRefCount) {
    Builder.defineMacro("__weak", "__attribute__((objc_ownership(weak)))");
    Builder.defineMacro("__strong", "__attribute__((objc_ownership(strong)))");
    Builder.defineMacro("__autoreleasing",
                        "__attribute__((objc_ownership(autoreleasing)))");
    Builder.defineMacro("__unsafe_unretained",
                        "__attribute__((objc_ownership(none)))");
  }

  // OpenMP definition
  if (LangOpts.OpenMP) {
    // OpenMP 2.2: 
    //   In implementations that support a preprocessor, the _OPENMP
    //   macro name is defined to have the decimal value yyyymm where
    //   yyyy and mm are the year and the month designations of the
    //   version of the OpenMP API that the implementation support.
    Builder.defineMacro("_OPENMP", "201107");
  }

  // Get other target #defines.
  TI.getTargetDefines(LangOpts, Builder);
}

// Initialize the remapping of files to alternative contents, e.g.,
// those specified through other files.
static void InitializeFileRemapping(DiagnosticsEngine &Diags,
                                    SourceManager &SourceMgr,
                                    FileManager &FileMgr,
                                    const PreprocessorOptions &InitOpts) {
  // Remap files in the source manager (with buffers).
  for (PreprocessorOptions::const_remapped_file_buffer_iterator
         Remap = InitOpts.remapped_file_buffer_begin(),
         RemapEnd = InitOpts.remapped_file_buffer_end();
       Remap != RemapEnd;
       ++Remap) {
    // Create the file entry for the file that we're mapping from.
    const FileEntry *FromFile = FileMgr.getVirtualFile(Remap->first,
                                                Remap->second->getBufferSize(),
                                                       0);
    if (!FromFile) {
      Diags.Report(diag::err_fe_remap_missing_from_file)
        << Remap->first;
      if (!InitOpts.RetainRemappedFileBuffers)
        delete Remap->second;
      continue;
    }

    // Override the contents of the "from" file with the contents of
    // the "to" file.
    SourceMgr.overrideFileContents(FromFile, Remap->second,
                                   InitOpts.RetainRemappedFileBuffers);
  }

  // Remap files in the source manager (with other files).
  for (PreprocessorOptions::const_remapped_file_iterator
         Remap = InitOpts.remapped_file_begin(),
         RemapEnd = InitOpts.remapped_file_end();
       Remap != RemapEnd;
       ++Remap) {
    // Find the file that we're mapping to.
    const FileEntry *ToFile = FileMgr.getFile(Remap->second);
    if (!ToFile) {
      Diags.Report(diag::err_fe_remap_missing_to_file)
      << Remap->first << Remap->second;
      continue;
    }
    
    // Create the file entry for the file that we're mapping from.
    const FileEntry *FromFile = FileMgr.getVirtualFile(Remap->first,
                                                       ToFile->getSize(), 0);
    if (!FromFile) {
      Diags.Report(diag::err_fe_remap_missing_from_file)
      << Remap->first;
      continue;
    }
    
    // Override the contents of the "from" file with the contents of
    // the "to" file.
    SourceMgr.overrideFileContents(FromFile, ToFile);
  }

  SourceMgr.setOverridenFilesKeepOriginalName(
                                        InitOpts.RemappedFilesKeepOriginalName);
}

/// InitializePreprocessor - Initialize the preprocessor getting it and the
/// environment ready to process a single file. This returns true on error.
///
void clang::InitializePreprocessor(Preprocessor &PP,
                                   const PreprocessorOptions &InitOpts,
                                   const HeaderSearchOptions &HSOpts,
                                   const FrontendOptions &FEOpts) {
  const LangOptions &LangOpts = PP.getLangOpts();
  std::string PredefineBuffer;
  PredefineBuffer.reserve(4080);
  llvm::raw_string_ostream Predefines(PredefineBuffer);
  MacroBuilder Builder(Predefines);

  InitializeFileRemapping(PP.getDiagnostics(), PP.getSourceManager(),
                          PP.getFileManager(), InitOpts);

  // Emit line markers for various builtin sections of the file.  We don't do
  // this in asm preprocessor mode, because "# 4" is not a line marker directive
  // in this mode.
  if (!PP.getLangOpts().AsmPreprocessor)
    Builder.append("# 1 \"<built-in>\" 3");

  // Install things like __POWERPC__, __GNUC__, etc into the macro table.
  if (InitOpts.UsePredefines) {
    InitializePredefinedMacros(PP.getTargetInfo(), LangOpts, FEOpts, Builder);

    // Install definitions to make Objective-C++ ARC work well with various
    // C++ Standard Library implementations.
    if (LangOpts.ObjC1 && LangOpts.CPlusPlus && LangOpts.ObjCAutoRefCount) {
      switch (InitOpts.ObjCXXARCStandardLibrary) {
      case ARCXX_nolib:
        case ARCXX_libcxx:
        break;

      case ARCXX_libstdcxx:
        AddObjCXXARCLibstdcxxDefines(LangOpts, Builder);
        break;
      }
    }
  }
  
  // Even with predefines off, some macros are still predefined.
  // These should all be defined in the preprocessor according to the
  // current language configuration.
  InitializeStandardPredefinedMacros(PP.getTargetInfo(), PP.getLangOpts(),
                                     FEOpts, Builder);

  // Add on the predefines from the driver.  Wrap in a #line directive to report
  // that they come from the command line.
  if (!PP.getLangOpts().AsmPreprocessor)
    Builder.append("# 1 \"<command line>\" 1");

  // Process #define's and #undef's in the order they are given.
  for (unsigned i = 0, e = InitOpts.Macros.size(); i != e; ++i) {
    if (InitOpts.Macros[i].second)  // isUndef
      Builder.undefineMacro(InitOpts.Macros[i].first);
    else
      DefineBuiltinMacro(Builder, InitOpts.Macros[i].first,
                         PP.getDiagnostics());
  }

  // If -imacros are specified, include them now.  These are processed before
  // any -include directives.
  for (unsigned i = 0, e = InitOpts.MacroIncludes.size(); i != e; ++i)
    AddImplicitIncludeMacros(Builder, InitOpts.MacroIncludes[i],
                             PP.getFileManager());

  // Process -include-pch/-include-pth directives.
  if (!InitOpts.ImplicitPCHInclude.empty())
    AddImplicitIncludePCH(Builder, PP, InitOpts.ImplicitPCHInclude);
  if (!InitOpts.ImplicitPTHInclude.empty())
    AddImplicitIncludePTH(Builder, PP, InitOpts.ImplicitPTHInclude);

  // Process -include directives.
  for (unsigned i = 0, e = InitOpts.Includes.size(); i != e; ++i) {
    const std::string &Path = InitOpts.Includes[i];
    AddImplicitInclude(Builder, Path, PP.getFileManager());
  }

  // Exit the command line and go back to <built-in> (2 is LC_LEAVE).
  if (!PP.getLangOpts().AsmPreprocessor)
    Builder.append("# 1 \"<built-in>\" 2");

  // Instruct the preprocessor to skip the preamble.
  PP.setSkipMainFilePreamble(InitOpts.PrecompiledPreambleBytes.first,
                             InitOpts.PrecompiledPreambleBytes.second);
                          
  // Copy PredefinedBuffer into the Preprocessor.
  PP.setPredefines(Predefines.str());
  
  // Initialize the header search object.
  ApplyHeaderSearchOptions(PP.getHeaderSearchInfo(), HSOpts,
                           PP.getLangOpts(),
                           PP.getTargetInfo().getTriple());
}