text: //===--- TokenConcatenation.cpp - Token Concatenation Avoidance -----------===//
  //
  // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
  // See https://llvm.org/LICENSE.txt for license information.
  // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
  //
  //===----------------------------------------------------------------------===//
  //
  // This file implements the TokenConcatenation class.
  //
  //===----------------------------------------------------------------------===//
  
  #include "clang/Lex/TokenConcatenation.h"
  #include "clang/Basic/CharInfo.h"
  #include "clang/Lex/Preprocessor.h"
  #include "llvm/Support/ErrorHandling.h"
  using namespace clang;
  
  
  /// IsStringPrefix - Return true if Str is a string prefix.
  /// 'L', 'u', 'U', or 'u8'. Including raw versions.
  static bool IsStringPrefix(StringRef Str, bool CPlusPlus11) {
  
    if (Str[0] == 'L' ||
        (CPlusPlus11 && (Str[0] == 'u' || Str[0] == 'U' || Str[0] == 'R'))) {
  
      if (Str.size() == 1)
        return true; // "L", "u", "U", and "R"
  
      // Check for raw flavors. Need to make sure the first character wasn't
      // already R. Need CPlusPlus11 check for "LR".
      if (Str[1] == 'R' && Str[0] != 'R' && Str.size() == 2 && CPlusPlus11)
        return true; // "LR", "uR", "UR"
  
      // Check for "u8" and "u8R"
      if (Str[0] == 'u' && Str[1] == '8') {
        if (Str.size() == 2) return true; // "u8"
        if (Str.size() == 3 && Str[2] == 'R') return true; // "u8R"
      }
    }
  
    return false;
  }
  
  /// IsIdentifierStringPrefix - Return true if the spelling of the token
  /// is literally 'L', 'u', 'U', or 'u8'. Including raw versions.
  bool TokenConcatenation::IsIdentifierStringPrefix(const Token &Tok) const {
    const LangOptions &LangOpts = PP.getLangOpts();
  
    if (!Tok.needsCleaning()) {
      if (Tok.getLength() < 1 || Tok.getLength() > 3)
        return false;
      SourceManager &SM = PP.getSourceManager();
      const char *Ptr = SM.getCharacterData(SM.getSpellingLoc(Tok.getLocation()));
      return IsStringPrefix(StringRef(Ptr, Tok.getLength()),
                            LangOpts.CPlusPlus11);
    }
  
    if (Tok.getLength() < 256) {
      char Buffer[256];
      const char *TokPtr = Buffer;
      unsigned length = PP.getSpelling(Tok, TokPtr);
      return IsStringPrefix(StringRef(TokPtr, length), LangOpts.CPlusPlus11);
    }
  
    return IsStringPrefix(StringRef(PP.getSpelling(Tok)), LangOpts.CPlusPlus11);
  }
  
  TokenConcatenation::TokenConcatenation(const Preprocessor &pp) : PP(pp) {
    memset(TokenInfo, 0, sizeof(TokenInfo));
  
    // These tokens have custom code in AvoidConcat.
    TokenInfo[tok::identifier      ] |= aci_custom;
    TokenInfo[tok::numeric_constant] |= aci_custom_firstchar;
    TokenInfo[tok::period          ] |= aci_custom_firstchar;
    TokenInfo[tok::amp             ] |= aci_custom_firstchar;
    TokenInfo[tok::plus            ] |= aci_custom_firstchar;
    TokenInfo[tok::minus           ] |= aci_custom_firstchar;
    TokenInfo[tok::slash           ] |= aci_custom_firstchar;
    TokenInfo[tok::less            ] |= aci_custom_firstchar;
    TokenInfo[tok::greater         ] |= aci_custom_firstchar;
    TokenInfo[tok::pipe            ] |= aci_custom_firstchar;
    TokenInfo[tok::percent         ] |= aci_custom_firstchar;
    TokenInfo[tok::colon           ] |= aci_custom_firstchar;
    TokenInfo[tok::hash            ] |= aci_custom_firstchar;
    TokenInfo[tok::arrow           ] |= aci_custom_firstchar;
  
    // These tokens have custom code in C++11 mode.
    if (PP.getLangOpts().CPlusPlus11) {
      TokenInfo[tok::string_literal      ] |= aci_custom;
      TokenInfo[tok::wide_string_literal ] |= aci_custom;
      TokenInfo[tok::utf8_string_literal ] |= aci_custom;
      TokenInfo[tok::utf16_string_literal] |= aci_custom;
      TokenInfo[tok::utf32_string_literal] |= aci_custom;
      TokenInfo[tok::char_constant       ] |= aci_custom;
      TokenInfo[tok::wide_char_constant  ] |= aci_custom;
      TokenInfo[tok::utf16_char_constant ] |= aci_custom;
      TokenInfo[tok::utf32_char_constant ] |= aci_custom;
    }
  
    // These tokens have custom code in C++17 mode.
    if (PP.getLangOpts().CPlusPlus17)
      TokenInfo[tok::utf8_char_constant] |= aci_custom;
  
    // These tokens have custom code in C++2a mode.
    if (PP.getLangOpts().CPlusPlus2a)
      TokenInfo[tok::lessequal ] |= aci_custom_firstchar;
  
    // These tokens change behavior if followed by an '='.
    TokenInfo[tok::amp         ] |= aci_avoid_equal;           // &=
    TokenInfo[tok::plus        ] |= aci_avoid_equal;           // +=
    TokenInfo[tok::minus       ] |= aci_avoid_equal;           // -=
    TokenInfo[tok::slash       ] |= aci_avoid_equal;           // /=
    TokenInfo[tok::less        ] |= aci_avoid_equal;           // <=
    TokenInfo[tok::greater     ] |= aci_avoid_equal;           // >=
    TokenInfo[tok::pipe        ] |= aci_avoid_equal;           // |=
    TokenInfo[tok::percent     ] |= aci_avoid_equal;           // %=
    TokenInfo[tok::star        ] |= aci_avoid_equal;           // *=
    TokenInfo[tok::exclaim     ] |= aci_avoid_equal;           // !=
    TokenInfo[tok::lessless    ] |= aci_avoid_equal;           // <<=
    TokenInfo[tok::greatergreater] |= aci_avoid_equal;         // >>=
    TokenInfo[tok::caret       ] |= aci_avoid_equal;           // ^=
    TokenInfo[tok::equal       ] |= aci_avoid_equal;           // ==
  }
  
  /// GetFirstChar - Get the first character of the token \arg Tok,
  /// avoiding calls to getSpelling where possible.
  static char GetFirstChar(const Preprocessor &PP, const Token &Tok) {
    if (IdentifierInfo *II = Tok.getIdentifierInfo()) {
      // Avoid spelling identifiers, the most common form of token.
      return II->getNameStart()[0];
    } else if (!Tok.needsCleaning()) {
      if (Tok.isLiteral() && Tok.getLiteralData()) {
        return *Tok.getLiteralData();
      } else {
        SourceManager &SM = PP.getSourceManager();
        return *SM.getCharacterData(SM.getSpellingLoc(Tok.getLocation()));
      }
    } else if (Tok.getLength() < 256) {
      char Buffer[256];
      const char *TokPtr = Buffer;
      PP.getSpelling(Tok, TokPtr);
      return TokPtr[0];
    } else {
      return PP.getSpelling(Tok)[0];
    }
  }
  
  /// AvoidConcat - If printing PrevTok immediately followed by Tok would cause
  /// the two individual tokens to be lexed as a single token, return true
  /// (which causes a space to be printed between them).  This allows the output
  /// of -E mode to be lexed to the same token stream as lexing the input
  /// directly would.
  ///
  /// This code must conservatively return true if it doesn't want to be 100%
  /// accurate.  This will cause the output to include extra space characters,
  /// but the resulting output won't have incorrect concatenations going on.
  /// Examples include "..", which we print with a space between, because we
  /// don't want to track enough to tell "x.." from "...".
  bool TokenConcatenation::AvoidConcat(const Token &PrevPrevTok,
                                       const Token &PrevTok,
                                       const Token &Tok) const {
    // First, check to see if the tokens were directly adjacent in the original
    // source.  If they were, it must be okay to stick them together: if there
    // were an issue, the tokens would have been lexed differently.
    SourceManager &SM = PP.getSourceManager();
    SourceLocation PrevSpellLoc = SM.getSpellingLoc(PrevTok.getLocation());
    SourceLocation SpellLoc = SM.getSpellingLoc(Tok.getLocation());
    if (PrevSpellLoc.getLocWithOffset(PrevTok.getLength()) == SpellLoc)
      return false;
  
    tok::TokenKind PrevKind = PrevTok.getKind();
    if (!PrevTok.isAnnotation() && PrevTok.getIdentifierInfo())
      PrevKind = tok::identifier; // Language keyword or named operator.
  
    // Look up information on when we should avoid concatenation with prevtok.
    unsigned ConcatInfo = TokenInfo[PrevKind];
  
    // If prevtok never causes a problem for anything after it, return quickly.
    if (ConcatInfo == 0) return false;
  
    if (ConcatInfo & aci_avoid_equal) {
      // If the next token is '=' or '==', avoid concatenation.
      if (Tok.isOneOf(tok::equal, tok::equalequal))
        return true;
      ConcatInfo &= ~aci_avoid_equal;
    }
    if (Tok.isAnnotation()) {
      // Modules annotation can show up when generated automatically for includes.
      assert(Tok.isOneOf(tok::annot_module_include, tok::annot_module_begin,
                         tok::annot_module_end) &&
             "unexpected annotation in AvoidConcat");
      ConcatInfo = 0;
    }
  
    if (ConcatInfo == 0)
      return false;
  
    // Basic algorithm: we look at the first character of the second token, and
    // determine whether it, if appended to the first token, would form (or
    // would contribute) to a larger token if concatenated.
    char FirstChar = 0;
    if (ConcatInfo & aci_custom) {
      // If the token does not need to know the first character, don't get it.
    } else {
      FirstChar = GetFirstChar(PP, Tok);
    }
  
    switch (PrevKind) {
    default:
      llvm_unreachable("InitAvoidConcatTokenInfo built wrong");
  
    case tok::raw_identifier:
      llvm_unreachable("tok::raw_identifier in non-raw lexing mode!");
  
    case tok::string_literal:
    case tok::wide_string_literal:
    case tok::utf8_string_literal:
    case tok::utf16_string_literal:
    case tok::utf32_string_literal:
    case tok::char_constant:
    case tok::wide_char_constant:
    case tok::utf8_char_constant:
    case tok::utf16_char_constant:
    case tok::utf32_char_constant:
      if (!PP.getLangOpts().CPlusPlus11)
        return false;
  
      // In C++11, a string or character literal followed by an identifier is a
      // single token.
      if (Tok.getIdentifierInfo())
        return true;
  
      // A ud-suffix is an identifier. If the previous token ends with one, treat
      // it as an identifier.
      if (!PrevTok.hasUDSuffix())
        return false;
      LLVM_FALLTHROUGH;
    case tok::identifier:   // id+id or id+number or id+L"foo".
      // id+'.'... will not append.
      if (Tok.is(tok::numeric_constant))
        return GetFirstChar(PP, Tok) != '.';
  
      if (Tok.getIdentifierInfo() ||
          Tok.isOneOf(tok::wide_string_literal, tok::utf8_string_literal,
                      tok::utf16_string_literal, tok::utf32_string_literal,
                      tok::wide_char_constant, tok::utf8_char_constant,
                      tok::utf16_char_constant, tok::utf32_char_constant))
        return true;
  
      // If this isn't identifier + string, we're done.
      if (Tok.isNot(tok::char_constant) && Tok.isNot(tok::string_literal))
        return false;
  
      // Otherwise, this is a narrow character or string.  If the *identifier*
      // is a literal 'L', 'u8', 'u' or 'U', avoid pasting L "foo" -> L"foo".
      return IsIdentifierStringPrefix(PrevTok);
  
    case tok::numeric_constant:
      return isPreprocessingNumberBody(FirstChar) ||
             FirstChar == '+' || FirstChar == '-';
    case tok::period:          // ..., .*, .1234
      return (FirstChar == '.' && PrevPrevTok.is(tok::period)) ||
             isDigit(FirstChar) ||
             (PP.getLangOpts().CPlusPlus && FirstChar == '*');
    case tok::amp:             // &&
      return FirstChar == '&';
    case tok::plus:            // ++
      return FirstChar == '+';
    case tok::minus:           // --, ->, ->*
      return FirstChar == '-' || FirstChar == '>';
    case tok::slash:           //, /*, //
      return FirstChar == '*' || FirstChar == '/';
    case tok::less:            // <<, <<=, <:, <%
      return FirstChar == '<' || FirstChar == ':' || FirstChar == '%';
    case tok::greater:         // >>, >>=
      return FirstChar == '>';
    case tok::pipe:            // ||
      return FirstChar == '|';
    case tok::percent:         // %>, %:
      return FirstChar == '>' || FirstChar == ':';
    case tok::colon:           // ::, :>
      return FirstChar == '>' ||
      (PP.getLangOpts().CPlusPlus && FirstChar == ':');
    case tok::hash:            // ##, #@, %:%:
      return FirstChar == '#' || FirstChar == '@' || FirstChar == '%';
    case tok::arrow:           // ->*
      return PP.getLangOpts().CPlusPlus && FirstChar == '*';
    case tok::lessequal:       // <=> (C++2a)
      return PP.getLangOpts().CPlusPlus2a && FirstChar == '>';
    }
  }
  