text: //
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  //
  // cpp.c
  //
  
  #define _CRT_SECURE_NO_WARNINGS
  
  #include <sstream>
  #include <cstdlib>
  #include <cstring>
  #include <cctype>
  
  #include "PpContext.h"
  #include "PpTokens.h"
  
  namespace glslang {
  
  int TPpContext::InitCPP()
  {
      pool = mem_CreatePool(0, 0);
  
      return 1;
  }
  
  // Handle #define
  int TPpContext::CPPdefine(TPpToken* ppToken)
  {
      MacroSymbol mac;
      Symbol *symb;
  
      // get macro name
      int token = scanToken(ppToken);
      if (token != PpAtomIdentifier) {
          parseContext.ppError(ppToken->loc, "must be followed by macro name", "#define", "");
          return token;
      }
      if (ppToken->loc.string >= 0) {
          // We are in user code; check for reserved name use:
          parseContext.reservedPpErrorCheck(ppToken->loc, ppToken->name, "#define");
      }
  
      // save the original atom
      const int defAtom = ppToken->atom;
  
      // gather parameters to the macro, between (...)
      token = scanToken(ppToken);
      if (token == '(' && ! ppToken->space) {
          int argc = 0;
          int args[maxMacroArgs];
          do {
              token = scanToken(ppToken);
              if (argc == 0 && token == ')') 
                  break;
              if (token != PpAtomIdentifier) {
                  parseContext.ppError(ppToken->loc, "bad argument", "#define", "");
  
                  return token;
              }
              // check for duplication of parameter name
              bool duplicate = false;
              for (int a = 0; a < argc; ++a) {
                  if (args[a] == ppToken->atom) {
                      parseContext.ppError(ppToken->loc, "duplicate macro parameter", "#define", "");
                      duplicate = true;
                      break;
                  }
              }
              if (! duplicate) {
                  if (argc < maxMacroArgs)
                      args[argc++] = ppToken->atom;
                  else
                      parseContext.ppError(ppToken->loc, "too many macro parameters", "#define", "");
              }
              token = scanToken(ppToken);
          } while (token == ',');
          if (token != ')') {
              parseContext.ppError(ppToken->loc, "missing parenthesis", "#define", "");
  
              return token;
          }
          mac.argc = argc;
          mac.args = (int*)mem_Alloc(pool, argc * sizeof(int));
          memcpy(mac.args, args, argc * sizeof(int));
          token = scanToken(ppToken);
      }
  
      // record the definition of the macro
      TSourceLoc defineLoc = ppToken->loc; // because ppToken is going to go to the next line before we report errors
      mac.body = new TokenStream;
      while (token != '\n' && token != EndOfInput) {
          RecordToken(mac.body, token, ppToken);
          token = scanToken(ppToken);
          if (token != '\n' && ppToken->space)
              RecordToken(mac.body, ' ', ppToken);
      }
  
      // check for duplicate definition
      symb = LookUpSymbol(defAtom);
      if (symb) {
          if (! symb->mac.undef) {
              // Already defined -- need to make sure they are identical:
              // "Two replacement lists are identical if and only if the preprocessing tokens in both have the same number,
              // ordering, spelling, and white-space separation, where all white-space separations are considered identical."
              if (symb->mac.argc != mac.argc)
                  parseContext.ppError(defineLoc, "Macro redefined; different number of arguments:", "#define", GetAtomString(defAtom));
              else {
                  for (int argc = 0; argc < mac.argc; argc++) {
                      if (symb->mac.args[argc] != mac.args[argc])
                          parseContext.ppError(defineLoc, "Macro redefined; different argument names:", "#define", GetAtomString(defAtom));
                  }
                  RewindTokenStream(symb->mac.body);
                  RewindTokenStream(mac.body);
                  int newToken;
                  do {
                      int oldToken;
                      TPpToken oldPpToken;
                      TPpToken newPpToken;
                      oldToken = ReadToken(symb->mac.body, &oldPpToken);
                      newToken = ReadToken(mac.body, &newPpToken);
                      if (oldToken != newToken || oldPpToken != newPpToken) {
                          parseContext.ppError(defineLoc, "Macro redefined; different substitutions:", "#define", GetAtomString(defAtom));
                          break; 
                      }
                  } while (newToken > 0);
              }
          }
      } else
          symb = AddSymbol(defAtom);
  
      delete symb->mac.body;
      symb->mac = mac;
  
      return '\n';
  }
  
  // Handle #undef
  int TPpContext::CPPundef(TPpToken* ppToken)
  {
      int token = scanToken(ppToken);
      Symbol *symb;
      if (token != PpAtomIdentifier) {
          parseContext.ppError(ppToken->loc, "must be followed by macro name", "#undef", "");
  
          return token;
      }
  
      parseContext.reservedPpErrorCheck(ppToken->loc, ppToken->name, "#undef");
  
      symb = LookUpSymbol(ppToken->atom);
      if (symb) {
          symb->mac.undef = 1;
      }
      token = scanToken(ppToken);
      if (token != '\n')
          parseContext.ppError(ppToken->loc, "can only be followed by a single macro name", "#undef", "");
  
      return token;
  }
  
  // Handle #else
  /* Skip forward to appropriate spot.  This is used both
  ** to skip to a #endif after seeing an #else, AND to skip to a #else,
  ** #elif, or #endif after a #if/#ifdef/#ifndef/#elif test was false.
  */
  int TPpContext::CPPelse(int matchelse, TPpToken* ppToken)
  {
      int atom;
      int depth = 0;
      int token = scanToken(ppToken);
  
      while (token != EndOfInput) {
          if (token != '#') {
              while (token != '\n' && token != EndOfInput)
                  token = scanToken(ppToken);
  
              if (token == EndOfInput)
                  return token;
  
              token = scanToken(ppToken);
              continue;
          }
  
          if ((token = scanToken(ppToken)) != PpAtomIdentifier)
              continue;
  
          atom = ppToken->atom;
          if (atom == PpAtomIf || atom == PpAtomIfdef || atom == PpAtomIfndef) {
              depth++; 
              ifdepth++; 
              elsetracker++;
          } else if (atom == PpAtomEndif) {
              token = extraTokenCheck(atom, ppToken, scanToken(ppToken));
              elseSeen[elsetracker] = false;
              --elsetracker;
              if (depth == 0) {
                  // found the #endif we are looking for
                  if (ifdepth) 
                      --ifdepth;
                  break;
              }
              --depth;
              --ifdepth;
          } else if (matchelse && depth == 0) {
              if (atom == PpAtomElse) {
                  elseSeen[elsetracker] = true;
                  token = extraTokenCheck(atom, ppToken, scanToken(ppToken));
                  // found the #else we are looking for
                  break;
              } else if (atom == PpAtomElif) {
                  if (elseSeen[elsetracker])
                      parseContext.ppError(ppToken->loc, "#elif after #else", "#elif", "");
                  /* we decrement ifdepth here, because CPPif will increment
                  * it and we really want to leave it alone */
                  if (ifdepth) {
                      --ifdepth;
                      elseSeen[elsetracker] = false;
                      --elsetracker;
                  }
  
                  return CPPif(ppToken);
              }
          } else if (atom == PpAtomElse) {
              if (elseSeen[elsetracker])
                  parseContext.ppError(ppToken->loc, "#else after #else", "#else", "");
              else
                  elseSeen[elsetracker] = true;
              token = extraTokenCheck(atom, ppToken, scanToken(ppToken));
          } else if (atom == PpAtomElif) {
              if (elseSeen[elsetracker])
                  parseContext.ppError(ppToken->loc, "#elif after #else", "#elif", "");
          }
      }
  
      return token;
  }
  
  // Call when there should be no more tokens left on a line.
  int TPpContext::extraTokenCheck(int atom, TPpToken* ppToken, int token)
  {
      if (token != '\n' && token != EndOfInput) {
          static const char* message = "unexpected tokens following directive";
  
          const char* label;
          if (atom == PpAtomElse)
              label = "#else";
          else if (atom == PpAtomElif)
              label = "#elif";
          else if (atom == PpAtomEndif)
              label = "#endif";
          else if (atom == PpAtomIf)
              label = "#if";
          else if (atom == PpAtomLine)
              label = "#line";
          else
              label = "";
  
          if (parseContext.relaxedErrors())
              parseContext.ppWarn(ppToken->loc, message, label, "");
          else
              parseContext.ppError(ppToken->loc, message, label, "");
  
          while (token != '\n' && token != EndOfInput)
              token = scanToken(ppToken);
      }
  
      return token;
  }
  
  enum eval_prec {
      MIN_PRECEDENCE,
      COND, LOGOR, LOGAND, OR, XOR, AND, EQUAL, RELATION, SHIFT, ADD, MUL, UNARY,
      MAX_PRECEDENCE
  };
  
  namespace {
  
      int op_logor(int a, int b) { return a || b; }
      int op_logand(int a, int b) { return a && b; }
      int op_or(int a, int b) { return a | b; }
      int op_xor(int a, int b) { return a ^ b; }
      int op_and(int a, int b) { return a & b; }
      int op_eq(int a, int b) { return a == b; }
      int op_ne(int a, int b) { return a != b; }
      int op_ge(int a, int b) { return a >= b; }
      int op_le(int a, int b) { return a <= b; }
      int op_gt(int a, int b) { return a > b; }
      int op_lt(int a, int b) { return a < b; }
      int op_shl(int a, int b) { return a << b; }
      int op_shr(int a, int b) { return a >> b; }
      int op_add(int a, int b) { return a + b; }
      int op_sub(int a, int b) { return a - b; }
      int op_mul(int a, int b) { return a * b; }
      int op_div(int a, int b) { return a / b; }
      int op_mod(int a, int b) { return a % b; }
      int op_pos(int a) { return a; }
      int op_neg(int a) { return -a; }
      int op_cmpl(int a) { return ~a; }
      int op_not(int a) { return !a; }
  
  };
  
  struct TBinop {
      int token, precedence, (*op)(int, int);
  } binop[] = {
      { PpAtomOr, LOGOR, op_logor },
      { PpAtomAnd, LOGAND, op_logand },
      { '|', OR, op_or },
      { '^', XOR, op_xor },
      { '&', AND, op_and },
      { PpAtomEQ, EQUAL, op_eq },
      { PpAtomNE, EQUAL, op_ne },
      { '>', RELATION, op_gt },
      { PpAtomGE, RELATION, op_ge },
      { '<', RELATION, op_lt },
      { PpAtomLE, RELATION, op_le },
      { PpAtomLeft, SHIFT, op_shl },
      { PpAtomRight, SHIFT, op_shr },
      { '+', ADD, op_add },
      { '-', ADD, op_sub },
      { '*', MUL, op_mul },
      { '/', MUL, op_div },
      { '%', MUL, op_mod },
  };
  
  struct TUnop {
      int token, (*op)(int);
  } unop[] = {
      { '+', op_pos },
      { '-', op_neg },
      { '~', op_cmpl },
      { '!', op_not },
  };
  
  #define NUM_ELEMENTS(A) (sizeof(A) / sizeof(A[0]))
  
  int TPpContext::eval(int token, int precedence, bool shortCircuit, int& res, bool& err, TPpToken* ppToken)
  {
      TSourceLoc loc = ppToken->loc;  // because we sometimes read the newline before reporting the error
      if (token == PpAtomIdentifier) {
          if (ppToken->atom == PpAtomDefined) {
              bool needclose = 0;
              token = scanToken(ppToken);
              if (token == '(') {
                  needclose = true;
                  token = scanToken(ppToken);
              }
              if (token != PpAtomIdentifier) {
                  parseContext.ppError(loc, "incorrect directive, expected identifier", "preprocessor evaluation", "");
                  err = true;
                  res = 0;
  
                  return token;
              }
              Symbol* s = LookUpSymbol(ppToken->atom);
              res = s ? ! s->mac.undef : 0;
              token = scanToken(ppToken);
              if (needclose) {
                  if (token != ')') {
                      parseContext.ppError(loc, "expected ')'", "preprocessor evaluation", "");
                      err = true;
                      res = 0;
  
                      return token;
                  }
                  token = scanToken(ppToken);
              }
          } else {
              token = evalToToken(token, shortCircuit, res, err, ppToken);
              return eval(token, precedence, shortCircuit, res, err, ppToken);
          }
      } else if (token == PpAtomConstInt) {
          res = ppToken->ival;
          token = scanToken(ppToken);
      } else if (token == '(') {
          token = scanToken(ppToken);
          token = eval(token, MIN_PRECEDENCE, shortCircuit, res, err, ppToken);
          if (! err) {
              if (token != ')') {
                  parseContext.ppError(loc, "expected ')'", "preprocessor evaluation", "");
                  err = true;
                  res = 0;
  
                  return token;
              }
              token = scanToken(ppToken);
          }
      } else {
          int op = NUM_ELEMENTS(unop) - 1;
          for (; op >= 0; op--) {
              if (unop[op].token == token)
                  break;
          }
          if (op >= 0) {
              token = scanToken(ppToken);
              token = eval(token, UNARY, shortCircuit, res, err, ppToken);
              res = unop[op].op(res);
          } else {
              parseContext.ppError(loc, "bad expression", "preprocessor evaluation", "");
              err = true;
              res = 0;
  
              return token;
          }
      }
  
      token = evalToToken(token, shortCircuit, res, err, ppToken);
  
      // Perform evaluation of binary operation, if there is one, otherwise we are done.
      while (! err) {
          if (token == ')' || token == '\n') 
              break;
          int op;
          for (op = NUM_ELEMENTS(binop) - 1; op >= 0; op--) {
              if (binop[op].token == token)
                  break;
          }
          if (op < 0 || binop[op].precedence <= precedence)
              break;
          int leftSide = res;
  
          // Setup short-circuiting, needed for ES, unless already in a short circuit.
          // (Once in a short-circuit, can't turn off again, until that whole subexpression is done.
          if (! shortCircuit) {
              if ((token == PpAtomOr  && leftSide == 1) ||
                  (token == PpAtomAnd && leftSide == 0))
                  shortCircuit = true;
          }
  
          token = scanToken(ppToken);
          token = eval(token, binop[op].precedence, shortCircuit, res, err, ppToken);
  
          if (binop[op].op == op_div || binop[op].op == op_mod) {
              if (res == 0) {
                  parseContext.ppError(loc, "division by 0", "preprocessor evaluation", "");
                  res = 1;
              }
          }
          res = binop[op].op(leftSide, res);
      }
  
      return token;
  }
  
  // Expand macros, skipping empty expansions, to get to the first real token in those expansions.
  int TPpContext::evalToToken(int token, bool shortCircuit, int& res, bool& err, TPpToken* ppToken)
  {
      while (token == PpAtomIdentifier && ppToken->atom != PpAtomDefined) {
          int macroReturn = MacroExpand(ppToken->atom, ppToken, true, false);
          if (macroReturn == 0) {
              parseContext.ppError(ppToken->loc, "can't evaluate expression", "preprocessor evaluation", "");
              err = true;
              res = 0;
              token = scanToken(ppToken);
              break;
          }
          if (macroReturn == -1) {
              if (! shortCircuit && parseContext.profile == EEsProfile) {
                  const char* message = "undefined macro in expression not allowed in es profile";
                  if (parseContext.relaxedErrors())
                      parseContext.ppWarn(ppToken->loc, message, "preprocessor evaluation", ppToken->name);
                  else
                      parseContext.ppError(ppToken->loc, message, "preprocessor evaluation", ppToken->name);
              }
          }
          token = scanToken(ppToken);
      }
  
      return token;
  }
  
  // Handle #if
  int TPpContext::CPPif(TPpToken* ppToken) 
  {
      int token = scanToken(ppToken);
      elsetracker++;
      ifdepth++;
      if (ifdepth > maxIfNesting) {
          parseContext.ppError(ppToken->loc, "maximum nesting depth exceeded", "#if", "");
          return 0;
      }
      int res = 0;
      bool err = false;
      token = eval(token, MIN_PRECEDENCE, false, res, err, ppToken);
      token = extraTokenCheck(PpAtomIf, ppToken, token);
      if (!res && !err)
          token = CPPelse(1, ppToken);
  
      return token;
  }
  
  // Handle #ifdef
  int TPpContext::CPPifdef(int defined, TPpToken* ppToken)
  {
      int token = scanToken(ppToken);
      int name = ppToken->atom;
      if (++ifdepth > maxIfNesting) {
          parseContext.ppError(ppToken->loc, "maximum nesting depth exceeded", "#ifdef", "");
          return 0;
      }
      elsetracker++;
      if (token != PpAtomIdentifier) {
          if (defined)
              parseContext.ppError(ppToken->loc, "must be followed by macro name", "#ifdef", "");
          else 
              parseContext.ppError(ppToken->loc, "must be followed by macro name", "#ifndef", "");
      } else {
          Symbol *s = LookUpSymbol(name);
          token = scanToken(ppToken);
          if (token != '\n') {
              parseContext.ppError(ppToken->loc, "unexpected tokens following #ifdef directive - expected a newline", "#ifdef", "");
              while (token != '\n' && token != EndOfInput)
                  token = scanToken(ppToken);
          }
          if (((s && !s->mac.undef) ? 1 : 0) != defined)
              token = CPPelse(1, ppToken);
      }
  
      return token;
  }
  
  // Handle #include
  int TPpContext::CPPinclude(TPpToken* ppToken)
  {
      const TSourceLoc directiveLoc = ppToken->loc;
      int token = scanToken(ppToken);
      if (token != PpAtomConstString) {
          // TODO: handle angle brackets.
          parseContext.ppError(directiveLoc, "must be followed by a file designation", "#include", "");
      } else {
          // Make a copy of the name because it will be overwritten by the next token scan.
          const std::string filename = ppToken->name;
          token = scanToken(ppToken);
          if (token != '\n' && token != EndOfInput) {
              parseContext.ppError(ppToken->loc, "extra content after file designation", "#include", "");
          } else {
              TShader::Includer::IncludeResult* res = includer.include(filename.c_str(), TShader::Includer::EIncludeRelative, currentSourceFile.c_str(), includeStack.size() + 1);
              if (res && !res->file_name.empty()) {
                  if (res->file_data && res->file_length) {
                      const bool forNextLine = parseContext.lineDirectiveShouldSetNextLine();
                      std::ostringstream prologue;
                      std::ostringstream epilogue;
                      prologue << "#line " << forNextLine << " " << "\"" << res->file_name << "\"\n";
                      epilogue << (res->file_data[res->file_length - 1] == '\n'? "" : "\n") << "#line " << directiveLoc.line + forNextLine << " " << directiveLoc.getStringNameOrNum() << "\n";
                      pushInput(new TokenizableIncludeFile(directiveLoc, prologue.str(), res, epilogue.str(), this));
                  }
                  // At EOF, there's no "current" location anymore.
                  if (token != EndOfInput) parseContext.setCurrentColumn(0);
                  // Don't accidentally return EndOfInput, which will end all preprocessing.
                  return '\n';
              } else {
                  std::string message =
                      res ? std::string(res->file_data, res->file_length)
                          : std::string("Could not process include directive");
                  parseContext.ppError(directiveLoc, message.c_str(), "#include", "");
                  if (res) {
                      includer.releaseInclude(res);
                  }
              }
          }
      }
      return token;
  }
  
  // Handle #line
  int TPpContext::CPPline(TPpToken* ppToken) 
  {
      // "#line must have, after macro substitution, one of the following forms:
      // "#line line
      // "#line line source-string-number"
  
      int token = scanToken(ppToken);
      const TSourceLoc directiveLoc = ppToken->loc;
      if (token == '\n') {
          parseContext.ppError(ppToken->loc, "must by followed by an integral literal", "#line", "");
          return token;
      }
  
      int lineRes = 0; // Line number after macro expansion.
      int lineToken = 0;
      bool hasFile = false;
      int fileRes = 0; // Source file number after macro expansion.
      const char* sourceName = nullptr; // Optional source file name.
      bool lineErr = false;
      bool fileErr = false;
      token = eval(token, MIN_PRECEDENCE, false, lineRes, lineErr, ppToken);
      if (! lineErr) {
          lineToken = lineRes;
          if (token == '\n')
              ++lineRes;
  
          if (parseContext.lineDirectiveShouldSetNextLine())
              --lineRes;
          parseContext.setCurrentLine(lineRes);
  
          if (token != '\n') {
              if (token == PpAtomConstString) {
                  parseContext.ppRequireExtensions(directiveLoc, 1, &E_GL_GOOGLE_cpp_style_line_directive, "filename-based #line");
                  // We need to save a copy of the string instead of pointing
                  // to the name field of the token since the name field
                  // will likely be overwritten by the next token scan.
                  sourceName = GetAtomString(LookUpAddString(ppToken->name));
                  parseContext.setCurrentSourceName(sourceName);
                  hasFile = true;
                  token = scanToken(ppToken);
              } else {
                  token = eval(token, MIN_PRECEDENCE, false, fileRes, fileErr, ppToken);
                  if (! fileErr) {
                      parseContext.setCurrentString(fileRes);
                      hasFile = true;
                  }
              }
          }
      }
      if (!fileErr && !lineErr) {
          parseContext.notifyLineDirective(directiveLoc.line, lineToken, hasFile, fileRes, sourceName);
      }
      token = extraTokenCheck(PpAtomLine, ppToken, token);
  
      return token;
  }
  
  // Handle #error
  int TPpContext::CPPerror(TPpToken* ppToken) 
  {
      int token = scanToken(ppToken);
      std::string message;
      TSourceLoc loc = ppToken->loc;
  
      while (token != '\n' && token != EndOfInput) {
          if (token == PpAtomConstInt   || token == PpAtomConstUint   ||
              token == PpAtomConstInt64 || token == PpAtomConstUint64 ||
              token == PpAtomConstFloat || token == PpAtomConstDouble) {
                  message.append(ppToken->name);
          } else if (token == PpAtomIdentifier || token == PpAtomConstString) {
              message.append(ppToken->name);
          } else {
              message.append(GetAtomString(token));
          }
          message.append(" ");
          token = scanToken(ppToken);
      }
      parseContext.notifyErrorDirective(loc.line, message.c_str());
      //store this msg into the shader's information log..set the Compile Error flag!!!!
      parseContext.ppError(loc, message.c_str(), "#error", "");
  
      return '\n';
  }
  
  // Handle #pragma
  int TPpContext::CPPpragma(TPpToken* ppToken)
  {
      char SrcStrName[2];
      TVector<TString> tokens;
  
      TSourceLoc loc = ppToken->loc;  // because we go to the next line before processing
      int token = scanToken(ppToken);
      while (token != '\n' && token != EndOfInput) {
          switch (token) {
          case PpAtomIdentifier:
          case PpAtomConstInt:
          case PpAtomConstUint:
          case PpAtomConstInt64:
          case PpAtomConstUint64:
          case PpAtomConstFloat:
          case PpAtomConstDouble:
              tokens.push_back(ppToken->name);
              break;
          default:
              SrcStrName[0] = (char)token;
              SrcStrName[1] = '\0';
              tokens.push_back(SrcStrName);
          }
          token = scanToken(ppToken);
      }
  
      if (token == EndOfInput)
          parseContext.ppError(loc, "directive must end with a newline", "#pragma", "");
      else
          parseContext.handlePragma(loc, tokens);
  
      return token;
  }
  
  // #version: This is just for error checking: the version and profile are decided before preprocessing starts
  int TPpContext::CPPversion(TPpToken* ppToken)
  {
      int token = scanToken(ppToken);
  
      if (errorOnVersion || versionSeen)
          parseContext.ppError(ppToken->loc, "must occur first in shader", "#version", "");
      versionSeen = true;
  
      if (token == '\n') {
          parseContext.ppError(ppToken->loc, "must be followed by version number", "#version", "");
  
          return token;
      }
  
      if (token != PpAtomConstInt)
          parseContext.ppError(ppToken->loc, "must be followed by version number", "#version", "");
  
      ppToken->ival = atoi(ppToken->name);
      int versionNumber = ppToken->ival;
      int line = ppToken->loc.line;
      token = scanToken(ppToken);
  
      if (token == '\n') {
          parseContext.notifyVersion(line, versionNumber, nullptr);
          return token;
      } else {
          if (ppToken->atom != PpAtomCore &&
              ppToken->atom != PpAtomCompatibility &&
              ppToken->atom != PpAtomEs)
              parseContext.ppError(ppToken->loc, "bad profile name; use es, core, or compatibility", "#version", "");
          parseContext.notifyVersion(line, versionNumber, ppToken->name);
          token = scanToken(ppToken);
  
          if (token == '\n')
              return token;
          else
              parseContext.ppError(ppToken->loc, "bad tokens following profile -- expected newline", "#version", "");
      }
  
      return token;
  }
  
  // Handle #extension
  int TPpContext::CPPextension(TPpToken* ppToken)
  {
      int line = ppToken->loc.line;
      int token = scanToken(ppToken);
      char extensionName[MaxTokenLength + 1];
  
      if (token=='\n') {
          parseContext.ppError(ppToken->loc, "extension name not specified", "#extension", "");
          return token;
      }
  
      if (token != PpAtomIdentifier)
          parseContext.ppError(ppToken->loc, "extension name expected", "#extension", "");
  
      assert(strlen(ppToken->name) <= MaxTokenLength);
      strcpy(extensionName, ppToken->name);
  
      token = scanToken(ppToken);
      if (token != ':') {
          parseContext.ppError(ppToken->loc, "':' missing after extension name", "#extension", "");
          return token;
      }
  
      token = scanToken(ppToken);
      if (token != PpAtomIdentifier) {
          parseContext.ppError(ppToken->loc, "behavior for extension not specified", "#extension", "");
          return token;
      }
  
      parseContext.updateExtensionBehavior(line, extensionName, ppToken->name);
      parseContext.notifyExtensionDirective(line, extensionName, ppToken->name);
  
      token = scanToken(ppToken);
      if (token == '\n')
          return token;
      else
          parseContext.ppError(ppToken->loc,  "extra tokens -- expected newline", "#extension","");
  
      return token;
  }
  
  int TPpContext::readCPPline(TPpToken* ppToken)
  {
      int token = scanToken(ppToken);
  
      if (token == PpAtomIdentifier) {
          switch (ppToken->atom) {
          case PpAtomDefine:
              token = CPPdefine(ppToken);
              break;
          case PpAtomElse:
              if (elsetracker[elseSeen])
                  parseContext.ppError(ppToken->loc, "#else after #else", "#else", "");
              elsetracker[elseSeen] = true;
              if (! ifdepth)
                  parseContext.ppError(ppToken->loc, "mismatched statements", "#else", "");
              token = extraTokenCheck(PpAtomElse, ppToken, scanToken(ppToken));
              token = CPPelse(0, ppToken);
              break;
          case PpAtomElif:
              if (! ifdepth)
                  parseContext.ppError(ppToken->loc, "mismatched statements", "#elif", "");
              if (elseSeen[elsetracker])
                  parseContext.ppError(ppToken->loc, "#elif after #else", "#elif", "");
              // this token is really a dont care, but we still need to eat the tokens
              token = scanToken(ppToken); 
              while (token != '\n' && token != EndOfInput)
                  token = scanToken(ppToken);
              token = CPPelse(0, ppToken);
              break;
          case PpAtomEndif:
              if (! ifdepth)
                  parseContext.ppError(ppToken->loc, "mismatched statements", "#endif", "");
              else {
                  elseSeen[elsetracker] = false;
                  --elsetracker;
                  --ifdepth;
              }
              token = extraTokenCheck(PpAtomEndif, ppToken, scanToken(ppToken));
              break;
          case PpAtomIf:
              token = CPPif(ppToken);
              break;
          case PpAtomIfdef:
              token = CPPifdef(1, ppToken);
              break;
          case PpAtomIfndef:
              token = CPPifdef(0, ppToken);
              break;
          case PpAtomInclude:
              parseContext.ppRequireExtensions(ppToken->loc, 1, &E_GL_GOOGLE_include_directive, "#include");
              token = CPPinclude(ppToken);
              break;
          case PpAtomLine:
              token = CPPline(ppToken);
              break;
          case PpAtomPragma:
              token = CPPpragma(ppToken);
              break;
          case PpAtomUndef:
              token = CPPundef(ppToken);
              break;
          case PpAtomError:
              token = CPPerror(ppToken);
              break;
          case PpAtomVersion:
              token = CPPversion(ppToken);
              break;
          case PpAtomExtension:
              token = CPPextension(ppToken);
              break;
          default:
              parseContext.ppError(ppToken->loc, "invalid directive:", "#", ppToken->name);
              break;
          }
      } else if (token != '\n' && token != EndOfInput)
          parseContext.ppError(ppToken->loc, "invalid directive", "#", "");
  
      while (token != '\n' && token != EndOfInput)
          token = scanToken(ppToken);
  
      return token;
  }
  
  TPpContext::TokenStream* TPpContext::PrescanMacroArg(TokenStream* a, TPpToken* ppToken, bool newLineOkay)
  {
      int token;
      TokenStream *n;
      RewindTokenStream(a);
      do {
          token = ReadToken(a, ppToken);
          if (token == PpAtomIdentifier && LookUpSymbol(ppToken->atom))
              break;
      } while (token != EndOfInput);
  
      if (token == EndOfInput)
          return a;
  
      n = new TokenStream;
      pushInput(new tMarkerInput(this));
      pushTokenStreamInput(a);
      while ((token = scanToken(ppToken)) != tMarkerInput::marker) {
          if (token == PpAtomIdentifier && MacroExpand(ppToken->atom, ppToken, false, newLineOkay) != 0)
              continue;
          RecordToken(n, token, ppToken);
      }
      popInput();
      delete a;
  
      return n;
  }
  
  // 
  // Return the next token for a macro expansion, handling macro args.
  //
  int TPpContext::tMacroInput::scan(TPpToken* ppToken)
  {
      int token;
      do {
          token = pp->ReadToken(mac->body, ppToken);
      } while (token == ' ');  // handle white space in macro
  
      // TODO: preprocessor:  properly handle whitespace (or lack of it) between tokens when expanding
      if (token == PpAtomIdentifier) {
          int i;
          for (i = mac->argc - 1; i >= 0; i--)
              if (mac->args[i] == ppToken->atom) 
                  break;
          if (i >= 0) {
              pp->pushTokenStreamInput(args[i]);
  
              return pp->scanToken(ppToken);
          }
      }
  
      if (token == EndOfInput)
          mac->busy = 0;
  
      return token;
  }
  
  // return a textual zero, for scanning a macro that was never defined
  int TPpContext::tZeroInput::scan(TPpToken* ppToken)
  {
      if (done)
          return EndOfInput;
  
      strcpy(ppToken->name, "0");
      ppToken->ival = 0;
      ppToken->space = false;
      done = true;
  
      return PpAtomConstInt;
  }
  
  //
  // Check an identifier (atom) to see if it is a macro that should be expanded.
  // If it is, and defined, push a tInput that will produce the appropriate expansion
  // and return 1.
  // If it is, but undefined, and expandUndef is requested, push a tInput that will 
  // expand to 0 and return -1.
  // Otherwise, return 0 to indicate no expansion, which is not necessarily an error.
  //
  int TPpContext::MacroExpand(int atom, TPpToken* ppToken, bool expandUndef, bool newLineOkay)
  {
      ppToken->space = false;
      switch (atom) {
      case PpAtomLineMacro:
          ppToken->ival = parseContext.getCurrentLoc().line;
          snprintf(ppToken->name, sizeof(ppToken->name), "%d", ppToken->ival);
          UngetToken(PpAtomConstInt, ppToken);
          return 1;
  
      case PpAtomFileMacro: {
          if (parseContext.getCurrentLoc().name)
              parseContext.ppRequireExtensions(ppToken->loc, 1, &E_GL_GOOGLE_cpp_style_line_directive, "filename-based __FILE__");
          ppToken->ival = parseContext.getCurrentLoc().string;
          snprintf(ppToken->name, sizeof(ppToken->name), "%s", ppToken->loc.getStringNameOrNum().c_str());
          UngetToken(PpAtomConstInt, ppToken);
          return 1;
      }
  
      case PpAtomVersionMacro:
          ppToken->ival = parseContext.version;
          snprintf(ppToken->name, sizeof(ppToken->name), "%d", ppToken->ival);
          UngetToken(PpAtomConstInt, ppToken);
          return 1;
  
      default:
          break;
      }
  
      Symbol *sym = LookUpSymbol(atom);
      int token;
      int depth = 0;
  
      // no recursive expansions
      if (sym && sym->mac.busy)
          return 0;
  
      // not expanding undefined macros
      if ((! sym || sym->mac.undef) && ! expandUndef)
          return 0;
  
      // 0 is the value of an undefined macro
      if ((! sym || sym->mac.undef) && expandUndef) {
          pushInput(new tZeroInput(this));
          return -1;
      }
  
      tMacroInput *in = new tMacroInput(this);
  
      TSourceLoc loc = ppToken->loc;  // in case we go to the next line before discovering the error
      in->mac = &sym->mac;
      if (sym->mac.args) {
          token = scanToken(ppToken);
          if (newLineOkay) {
              while (token == '\n')
                  token = scanToken(ppToken);
          }
          if (token != '(') {
              parseContext.ppError(loc, "expected '(' following", "macro expansion", GetAtomString(atom));
              UngetToken(token, ppToken);
              ppToken->atom = atom;
  
              delete in;
              return 0;
          }
          in->args.resize(in->mac->argc);
          for (int i = 0; i < in->mac->argc; i++)
              in->args[i] = new TokenStream;
          int arg = 0;
          bool tokenRecorded = false;
          do {
              depth = 0;
              while (1) {
                  token = scanToken(ppToken);
                  if (token == EndOfInput) {
                      parseContext.ppError(loc, "End of input in macro", "macro expansion", GetAtomString(atom));
                      delete in;
                      return 0;
                  }
                  if (token == '\n') {
                      if (! newLineOkay) {
                          parseContext.ppError(loc, "End of line in macro substitution:", "macro expansion", GetAtomString(atom));
                          delete in;
                          return 0;
                      }
                      continue;
                  }
                  if (token == '#') {
                      parseContext.ppError(ppToken->loc, "unexpected '#'", "macro expansion", GetAtomString(atom));
                      delete in;
                      return 0;
                  }
                  if (in->mac->argc == 0 && token != ')')
                      break;
                  if (depth == 0 && (token == ',' || token == ')'))
                      break;
                  if (token == '(')
                      depth++;
                  if (token == ')')
                      depth--;
                  RecordToken(in->args[arg], token, ppToken);
                  tokenRecorded = true;
              }
              if (token == ')') {
                  if (in->mac->argc == 1 && tokenRecorded == 0)
                      break;
                  arg++;
                  break;
              }
              arg++;
          } while (arg < in->mac->argc);
  
          if (arg < in->mac->argc)
              parseContext.ppError(loc, "Too few args in Macro", "macro expansion", GetAtomString(atom));
          else if (token != ')') {
              depth=0;
              while (token != EndOfInput && (depth > 0 || token != ')')) {
                  if (token == ')')
                      depth--;
                  token = scanToken(ppToken);
                  if (token == '(')
                      depth++;
              }
  
              if (token == EndOfInput) {
                  parseContext.ppError(loc, "End of input in macro", "macro expansion", GetAtomString(atom));
                  delete in;
                  return 0;
              }
              parseContext.ppError(loc, "Too many args in macro", "macro expansion", GetAtomString(atom));
          }
          for (int i = 0; i < in->mac->argc; i++)
              in->args[i] = PrescanMacroArg(in->args[i], ppToken, newLineOkay);
      }
  
      pushInput(in);
      sym->mac.busy = 1;
      RewindTokenStream(sym->mac.body);
  
      return 1;
  }
  
  } // end namespace glslang
  