clang/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/TargetInfo.h"
#include "clang/Frontend/FrontendDiagnostic.h"
#include "clang/Frontend/PreprocessorOptions.h"
#include "clang/Lex/Preprocessor.h"
#include "clang/Basic/FileManager.h"
#include "clang/Basic/SourceManager.h"
#include "llvm/ADT/StringExtras.h"
#include "llvm/ADT/StringMap.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/Support/MemoryBuffer.h"
#include "llvm/System/Path.h"
using namespace clang;

// 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(std::vector<char> &Buf, llvm::StringRef Macro,
                               Diagnostic *Diags = 0) {
  const char Command[] = "#define ";
  Buf.insert(Buf.end(), Command, Command+strlen(Command));
  std::pair<llvm::StringRef, llvm::StringRef> MacroPair = Macro.split('=');
  llvm::StringRef MacroName = MacroPair.first;
  llvm::StringRef MacroBody = MacroPair.second;
  if (!MacroBody.empty()) {
    // Turn the = into ' '.
    Buf.insert(Buf.end(), MacroName.begin(), MacroName.end());
    Buf.push_back(' ');

    // Per GCC -D semantics, the macro ends at \n if it exists.
    const char *End = strpbrk(MacroBody.data(), "\n\r");
    if (End) {
      assert(Diags && "Unexpected macro with embedded newline!");
      Diags->Report(diag::warn_fe_macro_contains_embedded_newline)
        << MacroName;
    } else {
      End = MacroBody.end();
    }

    Buf.insert(Buf.end(), MacroBody.begin(), End);
  } else {
    // Push "macroname 1".
    Buf.insert(Buf.end(), Macro.begin(), Macro.end());
    Buf.push_back(' ');
    Buf.push_back('1');
  }
  Buf.push_back('\n');
}

// Append a #undef line to Buf for Macro.  Macro should be of the form XXX
// and we emit "#undef XXX".
static void UndefineBuiltinMacro(std::vector<char> &Buf, const char *Macro) {
  // Push "macroname".
  const char Command[] = "#undef ";
  Buf.insert(Buf.end(), Command, Command+strlen(Command));
  Buf.insert(Buf.end(), Macro, Macro+strlen(Macro));
  Buf.push_back('\n');
}

std::string clang::NormalizeDashIncludePath(llvm::StringRef File) {
  // Implicit include paths should be resolved relative to the current
  // working directory first, and then use the regular header search
  // mechanism. The proper way to handle this is to have the
  // predefines buffer located at the current working directory, but
  // it has not file entry. For now, workaround this by using an
  // absolute path if we find the file here, and otherwise letting
  // header search handle it.
  llvm::sys::Path Path(File);
  Path.makeAbsolute();
  if (!Path.exists())
    Path = File;

  return Lexer::Stringify(Path.str());
}

/// Add the quoted name of an implicit include file.
static void AddQuotedIncludePath(std::vector<char> &Buf,
                                 const std::string &File) {

  // Escape double quotes etc.
  Buf.push_back('"');
  std::string EscapedFile = NormalizeDashIncludePath(File);
  Buf.insert(Buf.end(), EscapedFile.begin(), EscapedFile.end());
  Buf.push_back('"');
}

/// AddImplicitInclude - Add an implicit #include of the specified file to the
/// predefines buffer.
static void AddImplicitInclude(std::vector<char> &Buf,
                               const std::string &File) {
  const char Command[] = "#include ";
  Buf.insert(Buf.end(), Command, Command+strlen(Command));
  AddQuotedIncludePath(Buf, File);
  Buf.push_back('\n');
}

static void AddImplicitIncludeMacros(std::vector<char> &Buf,
                                     const std::string &File) {
  const char Command[] = "#__include_macros ";
  Buf.insert(Buf.end(), Command, Command+strlen(Command));
  AddQuotedIncludePath(Buf, File);
  Buf.push_back('\n');
  // Marker token to stop the __include_macros fetch loop.
  const char *Marker = "##\n"; // ##?
  Buf.insert(Buf.end(), Marker, Marker+strlen(Marker));
}

/// AddImplicitIncludePTH - Add an implicit #include using the original file
///  used to generate a PTH cache.
static void AddImplicitIncludePTH(std::vector<char> &Buf, Preprocessor &PP,
  const std::string& ImplicitIncludePTH) {
  PTHManager *P = PP.getPTHManager();
  assert(P && "No PTHManager.");
  const char *OriginalFile = P->getOriginalSourceFile();

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

  AddImplicitInclude(Buf, OriginalFile);
}

/// 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(std::vector<char> &Buf, const char *Prefix,
                              const llvm::fltSemantics *Sem) {
  const char *DenormMin, *Epsilon, *Max, *Min;
  DenormMin = PickFP(Sem, "1.40129846e-45F", "4.9406564584124654e-324",
                     "3.64519953188247460253e-4951L",
                     "4.94065645841246544176568792868221e-324L",
                     "6.47517511943802511092443895822764655e-4966L");
  int Digits = PickFP(Sem, 6, 15, 18, 31, 33);
  Epsilon = PickFP(Sem, "1.19209290e-7F", "2.2204460492503131e-16",
                   "1.08420217248550443401e-19L",
                   "4.94065645841246544176568792868221e-324L",
                   "1.92592994438723585305597794258492732e-34L");
  int HasInifinity = 1, HasQuietNaN = 1;
  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-38F", "2.2250738585072014e-308",
               "3.36210314311209350626e-4932L",
               "2.00416836000897277799610805135016e-292L",
               "3.36210314311209350626267781732175260e-4932L");
  Max = PickFP(Sem, "3.40282347e+38F", "1.7976931348623157e+308",
               "1.18973149535723176502e+4932L",
               "1.79769313486231580793728971405301e+308L",
               "1.18973149535723176508575932662800702e+4932L");

  char MacroBuf[100];
  sprintf(MacroBuf, "__%s_DENORM_MIN__=%s", Prefix, DenormMin);
  DefineBuiltinMacro(Buf, MacroBuf);
  sprintf(MacroBuf, "__%s_DIG__=%d", Prefix, Digits);
  DefineBuiltinMacro(Buf, MacroBuf);
  sprintf(MacroBuf, "__%s_EPSILON__=%s", Prefix, Epsilon);
  DefineBuiltinMacro(Buf, MacroBuf);
  sprintf(MacroBuf, "__%s_HAS_INFINITY__=%d", Prefix, HasInifinity);
  DefineBuiltinMacro(Buf, MacroBuf);
  sprintf(MacroBuf, "__%s_HAS_QUIET_NAN__=%d", Prefix, HasQuietNaN);
  DefineBuiltinMacro(Buf, MacroBuf);
  sprintf(MacroBuf, "__%s_MANT_DIG__=%d", Prefix, MantissaDigits);
  DefineBuiltinMacro(Buf, MacroBuf);
  sprintf(MacroBuf, "__%s_MAX_10_EXP__=%d", Prefix, Max10Exp);
  DefineBuiltinMacro(Buf, MacroBuf);
  sprintf(MacroBuf, "__%s_MAX_EXP__=%d", Prefix, MaxExp);
  DefineBuiltinMacro(Buf, MacroBuf);
  sprintf(MacroBuf, "__%s_MAX__=%s", Prefix, Max);
  DefineBuiltinMacro(Buf, MacroBuf);
  sprintf(MacroBuf, "__%s_MIN_10_EXP__=(%d)", Prefix, Min10Exp);
  DefineBuiltinMacro(Buf, MacroBuf);
  sprintf(MacroBuf, "__%s_MIN_EXP__=(%d)", Prefix, MinExp);
  DefineBuiltinMacro(Buf, MacroBuf);
  sprintf(MacroBuf, "__%s_MIN__=%s", Prefix, Min);
  DefineBuiltinMacro(Buf, MacroBuf);
  sprintf(MacroBuf, "__%s_HAS_DENORM__=1", Prefix);
  DefineBuiltinMacro(Buf, MacroBuf);
}


/// 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(const char *MacroName, unsigned TypeWidth,
                           const char *ValSuffix, bool isSigned,
                           std::vector<char> &Buf) {
  char MacroBuf[60];
  long long MaxVal;
  if (isSigned)
    MaxVal = (1LL << (TypeWidth - 1)) - 1;
  else
    MaxVal = ~0LL >> (64-TypeWidth);

  // FIXME: Switch to using raw_ostream and avoid utostr().
  sprintf(MacroBuf, "%s=%s%s", MacroName, llvm::utostr(MaxVal).c_str(),
          ValSuffix);
  DefineBuiltinMacro(Buf, MacroBuf);
}

/// DefineTypeSize - An overloaded helper that uses TargetInfo to determine
/// the width, suffix, and signedness of the given type
static void DefineTypeSize(const char *MacroName, TargetInfo::IntType Ty,
                           const TargetInfo &TI, std::vector<char> &Buf) {
  DefineTypeSize(MacroName, TI.getTypeWidth(Ty), TI.getTypeConstantSuffix(Ty), 
                 TI.isTypeSigned(Ty), Buf);
}

static void DefineType(const char *MacroName, TargetInfo::IntType Ty,
                       std::vector<char> &Buf) {
  char MacroBuf[60];
  sprintf(MacroBuf, "%s=%s", MacroName, TargetInfo::getTypeName(Ty));
  DefineBuiltinMacro(Buf, MacroBuf);
}

static void DefineTypeWidth(const char *MacroName, TargetInfo::IntType Ty,
                            const TargetInfo &TI, std::vector<char> &Buf) {
  char MacroBuf[60];
  sprintf(MacroBuf, "%s=%d", MacroName, TI.getTypeWidth(Ty));
  DefineBuiltinMacro(Buf, MacroBuf);
}

static void DefineExactWidthIntType(TargetInfo::IntType Ty, 
                               const TargetInfo &TI, std::vector<char> &Buf) {
  char MacroBuf[60];
  int TypeWidth = TI.getTypeWidth(Ty);
  sprintf(MacroBuf, "__INT%d_TYPE__", TypeWidth);
  DefineType(MacroBuf, Ty, Buf);


  const char *ConstSuffix = TargetInfo::getTypeConstantSuffix(Ty);
  if (strlen(ConstSuffix) > 0) {
    sprintf(MacroBuf, "__INT%d_C_SUFFIX__=%s", TypeWidth, ConstSuffix);
    DefineBuiltinMacro(Buf, MacroBuf);
  }
}

static void InitializePredefinedMacros(const TargetInfo &TI,
                                       const LangOptions &LangOpts,
                                       std::vector<char> &Buf) {
  // Compiler version introspection macros.
  DefineBuiltinMacro(Buf, "__llvm__=1");   // LLVM Backend
  DefineBuiltinMacro(Buf, "__clang__=1");  // Clang Frontend

  // Currently claim to be compatible with GCC 4.2.1-5621.
  DefineBuiltinMacro(Buf, "__GNUC_MINOR__=2");
  DefineBuiltinMacro(Buf, "__GNUC_PATCHLEVEL__=1");
  DefineBuiltinMacro(Buf, "__GNUC__=4");
  DefineBuiltinMacro(Buf, "__GXX_ABI_VERSION=1002");
  DefineBuiltinMacro(Buf, "__VERSION__=\"4.2.1 Compatible Clang Compiler\"");


  // Initialize language-specific preprocessor defines.

  // These should all be defined in the preprocessor according to the
  // current language configuration.
  if (!LangOpts.Microsoft)
    DefineBuiltinMacro(Buf, "__STDC__=1");
  if (LangOpts.AsmPreprocessor)
    DefineBuiltinMacro(Buf, "__ASSEMBLER__=1");

  if (!LangOpts.CPlusPlus) {
    if (LangOpts.C99)
      DefineBuiltinMacro(Buf, "__STDC_VERSION__=199901L");
    else if (!LangOpts.GNUMode && LangOpts.Digraphs)
      DefineBuiltinMacro(Buf, "__STDC_VERSION__=199409L");
  }

  // Standard conforming mode?
  if (!LangOpts.GNUMode)
    DefineBuiltinMacro(Buf, "__STRICT_ANSI__=1");

  if (LangOpts.CPlusPlus0x)
    DefineBuiltinMacro(Buf, "__GXX_EXPERIMENTAL_CXX0X__");

  if (LangOpts.Freestanding)
    DefineBuiltinMacro(Buf, "__STDC_HOSTED__=0");
  else
    DefineBuiltinMacro(Buf, "__STDC_HOSTED__=1");

  if (LangOpts.ObjC1) {
    DefineBuiltinMacro(Buf, "__OBJC__=1");
    if (LangOpts.ObjCNonFragileABI) {
      DefineBuiltinMacro(Buf, "__OBJC2__=1");
      DefineBuiltinMacro(Buf, "OBJC_ZEROCOST_EXCEPTIONS=1");
    }

    if (LangOpts.getGCMode() != LangOptions::NonGC)
      DefineBuiltinMacro(Buf, "__OBJC_GC__=1");

    if (LangOpts.NeXTRuntime)
      DefineBuiltinMacro(Buf, "__NEXT_RUNTIME__=1");
  }

  // darwin_constant_cfstrings controls this. This is also dependent
  // on other things like the runtime I believe.  This is set even for C code.
  DefineBuiltinMacro(Buf, "__CONSTANT_CFSTRINGS__=1");

  if (LangOpts.ObjC2)
    DefineBuiltinMacro(Buf, "OBJC_NEW_PROPERTIES");

  if (LangOpts.PascalStrings)
    DefineBuiltinMacro(Buf, "__PASCAL_STRINGS__");

  if (LangOpts.Blocks) {
    DefineBuiltinMacro(Buf, "__block=__attribute__((__blocks__(byref)))");
    DefineBuiltinMacro(Buf, "__BLOCKS__=1");
  }

  if (LangOpts.Exceptions)
    DefineBuiltinMacro(Buf, "__EXCEPTIONS=1");

  if (LangOpts.CPlusPlus) {
    DefineBuiltinMacro(Buf, "__DEPRECATED=1");
    DefineBuiltinMacro(Buf, "__GNUG__=4");
    DefineBuiltinMacro(Buf, "__GXX_WEAK__=1");
    if (LangOpts.GNUMode)
      DefineBuiltinMacro(Buf, "__cplusplus=1");
    else
      // C++ [cpp.predefined]p1:
      //   The name_ _cplusplusis defined to the value199711Lwhen compiling a
      //   C++ translation unit.
      DefineBuiltinMacro(Buf, "__cplusplus=199711L");
    DefineBuiltinMacro(Buf, "__private_extern__=extern");
    // Ugly hack to work with GNU libstdc++.
    DefineBuiltinMacro(Buf, "_GNU_SOURCE=1");
  }

  if (LangOpts.Microsoft) {
    // Filter out some microsoft extensions when trying to parse in ms-compat
    // mode.
    DefineBuiltinMacro(Buf, "__int8=__INT8_TYPE__");
    DefineBuiltinMacro(Buf, "__int16=__INT16_TYPE__");
    DefineBuiltinMacro(Buf, "__int32=__INT32_TYPE__");
    DefineBuiltinMacro(Buf, "__int64=__INT64_TYPE__");
    // Both __PRETTY_FUNCTION__ and __FUNCTION__ are GCC extensions, however
    // VC++ appears to only like __FUNCTION__.
    DefineBuiltinMacro(Buf, "__PRETTY_FUNCTION__=__FUNCTION__");
    // Work around some issues with Visual C++ headerws.
    if (LangOpts.CPlusPlus) {
      // Since we define wchar_t in C++ mode.
      DefineBuiltinMacro(Buf, "_WCHAR_T_DEFINED=1");
      DefineBuiltinMacro(Buf, "_NATIVE_WCHAR_T_DEFINED=1");
      // FIXME:  This should be temporary until we have a __pragma
      // solution, to avoid some errors flagged in VC++ headers.
      DefineBuiltinMacro(Buf, "_CRT_SECURE_CPP_OVERLOAD_SECURE_NAMES=0");
    }
  }

  if (LangOpts.Optimize)
    DefineBuiltinMacro(Buf, "__OPTIMIZE__=1");
  if (LangOpts.OptimizeSize)
    DefineBuiltinMacro(Buf, "__OPTIMIZE_SIZE__=1");

  // Initialize target-specific preprocessor defines.

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

  DefineTypeSize("__SCHAR_MAX__", TI.getCharWidth(), "", true, Buf);
  DefineTypeSize("__SHRT_MAX__", TargetInfo::SignedShort, TI, Buf);
  DefineTypeSize("__INT_MAX__", TargetInfo::SignedInt, TI, Buf);
  DefineTypeSize("__LONG_MAX__", TargetInfo::SignedLong, TI, Buf);
  DefineTypeSize("__LONG_LONG_MAX__", TargetInfo::SignedLongLong, TI, Buf);
  DefineTypeSize("__WCHAR_MAX__", TI.getWCharType(), TI, Buf);
  DefineTypeSize("__INTMAX_MAX__", TI.getIntMaxType(), TI, Buf);

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

  DefineFloatMacros(Buf, "FLT", &TI.getFloatFormat());
  DefineFloatMacros(Buf, "DBL", &TI.getDoubleFormat());
  DefineFloatMacros(Buf, "LDBL", &TI.getLongDoubleFormat());

  // Define a __POINTER_WIDTH__ macro for stdint.h.
  char MacroBuf[60];
  sprintf(MacroBuf, "__POINTER_WIDTH__=%d", (int)TI.getPointerWidth(0));
  DefineBuiltinMacro(Buf, MacroBuf);

  if (!LangOpts.CharIsSigned)
    DefineBuiltinMacro(Buf, "__CHAR_UNSIGNED__");

  // Define exact-width integer types for stdint.h
  sprintf(MacroBuf, "__INT%d_TYPE__=char", TI.getCharWidth());
  DefineBuiltinMacro(Buf, MacroBuf);

  if (TI.getShortWidth() > TI.getCharWidth())
    DefineExactWidthIntType(TargetInfo::SignedShort, TI, Buf);
                      
  if (TI.getIntWidth() > TI.getShortWidth())
    DefineExactWidthIntType(TargetInfo::SignedInt, TI, Buf);
                              
  if (TI.getLongWidth() > TI.getIntWidth())
    DefineExactWidthIntType(TargetInfo::SignedLong, TI, Buf);
                                      
  if (TI.getLongLongWidth() > TI.getLongWidth())
    DefineExactWidthIntType(TargetInfo::SignedLongLong, TI, Buf);
  
  // Add __builtin_va_list typedef.
  {
    const char *VAList = TI.getVAListDeclaration();
    Buf.insert(Buf.end(), VAList, VAList+strlen(VAList));
    Buf.push_back('\n');
  }

  if (const char *Prefix = TI.getUserLabelPrefix()) {
    sprintf(MacroBuf, "__USER_LABEL_PREFIX__=%s", Prefix);
    DefineBuiltinMacro(Buf, MacroBuf);
  }

  // Build configuration options.  FIXME: these should be controlled by
  // command line options or something.
  DefineBuiltinMacro(Buf, "__FINITE_MATH_ONLY__=0");

  if (LangOpts.GNUInline)
    DefineBuiltinMacro(Buf, "__GNUC_GNU_INLINE__=1");
  else
    DefineBuiltinMacro(Buf, "__GNUC_STDC_INLINE__=1");

  if (LangOpts.NoInline)
    DefineBuiltinMacro(Buf, "__NO_INLINE__=1");

  if (unsigned PICLevel = LangOpts.PICLevel) {
    sprintf(MacroBuf, "__PIC__=%d", PICLevel);
    DefineBuiltinMacro(Buf, MacroBuf);

    sprintf(MacroBuf, "__pic__=%d", PICLevel);
    DefineBuiltinMacro(Buf, MacroBuf);
  }

  // Macros to control C99 numerics and <float.h>
  DefineBuiltinMacro(Buf, "__FLT_EVAL_METHOD__=0");
  DefineBuiltinMacro(Buf, "__FLT_RADIX__=2");
  sprintf(MacroBuf, "__DECIMAL_DIG__=%d",
          PickFP(&TI.getLongDoubleFormat(), -1/*FIXME*/, 17, 21, 33, 36));
  DefineBuiltinMacro(Buf, MacroBuf);

  if (LangOpts.getStackProtectorMode() == LangOptions::SSPOn)
    DefineBuiltinMacro(Buf, "__SSP__=1");
  else if (LangOpts.getStackProtectorMode() == LangOptions::SSPReq)
    DefineBuiltinMacro(Buf, "__SSP_ALL__=2");

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

// Initialize the remapping of files to alternative contents, e.g.,
// those specified through other files.
static void InitializeFileRemapping(Diagnostic &Diags,
                                    SourceManager &SourceMgr,
                                    FileManager &FileMgr,
                                    const PreprocessorOptions &InitOpts) {
  // Remap files in the source manager.
  for (PreprocessorOptions::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;
    }

    // Load the contents of the file we're mapping to.
    std::string ErrorStr;
    const llvm::MemoryBuffer *Buffer
      = llvm::MemoryBuffer::getFile(ToFile->getName(), &ErrorStr);
    if (!Buffer) {
      Diags.Report(diag::err_fe_error_opening)
        << Remap->second << ErrorStr;
      continue;
    }

    // Override the contents of the "from" file with the contents of
    // the "to" file.
    SourceMgr.overrideFileContents(FromFile, Buffer);
  }
}

/// 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) {
  std::vector<char> PredefineBuffer;

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

  const char *LineDirective = "# 1 \"<built-in>\" 3\n";
  PredefineBuffer.insert(PredefineBuffer.end(),
                         LineDirective, LineDirective+strlen(LineDirective));

  // Install things like __POWERPC__, __GNUC__, etc into the macro table.
  if (InitOpts.UsePredefines)
    InitializePredefinedMacros(PP.getTargetInfo(), PP.getLangOptions(),
                               PredefineBuffer);

  // Add on the predefines from the driver.  Wrap in a #line directive to report
  // that they come from the command line.
  LineDirective = "# 1 \"<command line>\" 1\n";
  PredefineBuffer.insert(PredefineBuffer.end(),
                         LineDirective, LineDirective+strlen(LineDirective));

  // 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
      UndefineBuiltinMacro(PredefineBuffer, InitOpts.Macros[i].first.c_str());
    else
      DefineBuiltinMacro(PredefineBuffer, InitOpts.Macros[i].first.c_str(),
                         &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(PredefineBuffer, InitOpts.MacroIncludes[i]);

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

  // Exit the command line and go back to <built-in> (2 is LC_LEAVE).
  LineDirective = "# 1 \"<built-in>\" 2\n";
  PredefineBuffer.insert(PredefineBuffer.end(),
                         LineDirective, LineDirective+strlen(LineDirective));

  // Null terminate PredefinedBuffer and add it.
  PredefineBuffer.push_back(0);
  PP.setPredefines(&PredefineBuffer[0]);

  // Initialize the header search object.
  ApplyHeaderSearchOptions(PP.getHeaderSearchInfo(), HSOpts,
                           PP.getLangOptions(),
                           PP.getTargetInfo().getTriple());
}