clang/lib/Lex/TokenConcatenation.cpp

   1 //===--- TokenConcatenation.cpp - Token Concatenation Avoidance -----------===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8 //
   9 // This file implements the TokenConcatenation class.
  10 //
  11 //===----------------------------------------------------------------------===//
  12
  13 #include "clang/Lex/TokenConcatenation.h"
  14 #include "clang/Basic/CharInfo.h"
  15 #include "clang/Lex/Preprocessor.h"
  16 #include "llvm/Support/ErrorHandling.h"
  17 using namespace clang;
  18
  19
  20 /// IsStringPrefix - Return true if Str is a string prefix.
  21 /// 'L', 'u', 'U', or 'u8'. Including raw versions.
  22 static bool IsStringPrefix(StringRef Str, bool CPlusPlus11) {
  23
  24   if (Str[0] == 'L' ||
  25       (CPlusPlus11 && (Str[0] == 'u' || Str[0] == 'U' || Str[0] == 'R'))) {
  26
  27     if (Str.size() == 1)
  28       return true; // "L", "u", "U", and "R"
  29
  30     // Check for raw flavors. Need to make sure the first character wasn't
  31     // already R. Need CPlusPlus11 check for "LR".
  32     if (Str[1] == 'R' && Str[0] != 'R' && Str.size() == 2 && CPlusPlus11)
  33       return true; // "LR", "uR", "UR"
  34
  35     // Check for "u8" and "u8R"
  36     if (Str[0] == 'u' && Str[1] == '8') {
  37       if (Str.size() == 2) return true; // "u8"
  38       if (Str.size() == 3 && Str[2] == 'R') return true; // "u8R"
  39     }
  40   }
  41
  42   return false;
  43 }
  44
  45 /// IsIdentifierStringPrefix - Return true if the spelling of the token
  46 /// is literally 'L', 'u', 'U', or 'u8'. Including raw versions.
  47 bool TokenConcatenation::IsIdentifierStringPrefix(const Token &Tok) const {
  48   const LangOptions &LangOpts = PP.getLangOpts();
  49
  50   if (!Tok.needsCleaning()) {
  51     if (Tok.getLength() < 1 || Tok.getLength() > 3)
  52       return false;
  53     SourceManager &SM = PP.getSourceManager();
  54     const char *Ptr = SM.getCharacterData(SM.getSpellingLoc(Tok.getLocation()));
  55     return IsStringPrefix(StringRef(Ptr, Tok.getLength()),
  56                           LangOpts.CPlusPlus11);
  57   }
  58
  59   if (Tok.getLength() < 256) {
  60     char Buffer[256];
  61     const char *TokPtr = Buffer;
  62     unsigned length = PP.getSpelling(Tok, TokPtr);
  63     return IsStringPrefix(StringRef(TokPtr, length), LangOpts.CPlusPlus11);
  64   }
  65
  66   return IsStringPrefix(StringRef(PP.getSpelling(Tok)), LangOpts.CPlusPlus11);
  67 }
  68
  69 TokenConcatenation::TokenConcatenation(const Preprocessor &pp) : PP(pp) {
  70   memset(TokenInfo, 0, sizeof(TokenInfo));
  71
  72   // These tokens have custom code in AvoidConcat.
  73   TokenInfo[tok::identifier      ] |= aci_custom;
  74   TokenInfo[tok::numeric_constant] |= aci_custom_firstchar;
  75   TokenInfo[tok::period          ] |= aci_custom_firstchar;
  76   TokenInfo[tok::amp             ] |= aci_custom_firstchar;
  77   TokenInfo[tok::plus            ] |= aci_custom_firstchar;
  78   TokenInfo[tok::minus           ] |= aci_custom_firstchar;
  79   TokenInfo[tok::slash           ] |= aci_custom_firstchar;
  80   TokenInfo[tok::less            ] |= aci_custom_firstchar;
  81   TokenInfo[tok::greater         ] |= aci_custom_firstchar;
  82   TokenInfo[tok::pipe            ] |= aci_custom_firstchar;
  83   TokenInfo[tok::percent         ] |= aci_custom_firstchar;
  84   TokenInfo[tok::colon           ] |= aci_custom_firstchar;
  85   TokenInfo[tok::hash            ] |= aci_custom_firstchar;
  86   TokenInfo[tok::arrow           ] |= aci_custom_firstchar;
  87
  88   // These tokens have custom code in C++11 mode.
  89   if (PP.getLangOpts().CPlusPlus11) {
  90     TokenInfo[tok::string_literal      ] |= aci_custom;
  91     TokenInfo[tok::wide_string_literal ] |= aci_custom;
  92     TokenInfo[tok::utf8_string_literal ] |= aci_custom;
  93     TokenInfo[tok::utf16_string_literal] |= aci_custom;
  94     TokenInfo[tok::utf32_string_literal] |= aci_custom;
  95     TokenInfo[tok::char_constant       ] |= aci_custom;
  96     TokenInfo[tok::wide_char_constant  ] |= aci_custom;
  97     TokenInfo[tok::utf16_char_constant ] |= aci_custom;
  98     TokenInfo[tok::utf32_char_constant ] |= aci_custom;
  99   }
 100
 101   // These tokens have custom code in C++17 mode.
 102   if (PP.getLangOpts().CPlusPlus17)
 103     TokenInfo[tok::utf8_char_constant] |= aci_custom;
 104
 105   // These tokens have custom code in C++2a mode.
 106   if (PP.getLangOpts().CPlusPlus20)
 107     TokenInfo[tok::lessequal ] |= aci_custom_firstchar;
 108
 109   // These tokens change behavior if followed by an '='.
 110   TokenInfo[tok::amp         ] |= aci_avoid_equal;           // &=
 111   TokenInfo[tok::plus        ] |= aci_avoid_equal;           // +=
 112   TokenInfo[tok::minus       ] |= aci_avoid_equal;           // -=
 113   TokenInfo[tok::slash       ] |= aci_avoid_equal;           // /=
 114   TokenInfo[tok::less        ] |= aci_avoid_equal;           // <=
 115   TokenInfo[tok::greater     ] |= aci_avoid_equal;           // >=
 116   TokenInfo[tok::pipe        ] |= aci_avoid_equal;           // |=
 117   TokenInfo[tok::percent     ] |= aci_avoid_equal;           // %=
 118   TokenInfo[tok::star        ] |= aci_avoid_equal;           // *=
 119   TokenInfo[tok::exclaim     ] |= aci_avoid_equal;           // !=
 120   TokenInfo[tok::lessless    ] |= aci_avoid_equal;           // <<=
 121   TokenInfo[tok::greatergreater] |= aci_avoid_equal;         // >>=
 122   TokenInfo[tok::caret       ] |= aci_avoid_equal;           // ^=
 123   TokenInfo[tok::equal       ] |= aci_avoid_equal;           // ==
 124 }
 125
 126 /// GetFirstChar - Get the first character of the token \arg Tok,
 127 /// avoiding calls to getSpelling where possible.
 128 static char GetFirstChar(const Preprocessor &PP, const Token &Tok) {
 129   if (IdentifierInfo *II = Tok.getIdentifierInfo()) {
 130     // Avoid spelling identifiers, the most common form of token.
 131     return II->getNameStart()[0];
 132   } else if (!Tok.needsCleaning()) {
 133     if (Tok.isLiteral() && Tok.getLiteralData()) {
 134       return *Tok.getLiteralData();
 135     } else {
 136       SourceManager &SM = PP.getSourceManager();
 137       return *SM.getCharacterData(SM.getSpellingLoc(Tok.getLocation()));
 138     }
 139   } else if (Tok.getLength() < 256) {
 140     char Buffer[256];
 141     const char *TokPtr = Buffer;
 142     PP.getSpelling(Tok, TokPtr);
 143     return TokPtr[0];
 144   } else {
 145     return PP.getSpelling(Tok)[0];
 146   }
 147 }
 148
 149 /// AvoidConcat - If printing PrevTok immediately followed by Tok would cause
 150 /// the two individual tokens to be lexed as a single token, return true
 151 /// (which causes a space to be printed between them).  This allows the output
 152 /// of -E mode to be lexed to the same token stream as lexing the input
 153 /// directly would.
 154 ///
 155 /// This code must conservatively return true if it doesn't want to be 100%
 156 /// accurate.  This will cause the output to include extra space characters,
 157 /// but the resulting output won't have incorrect concatenations going on.
 158 /// Examples include "..", which we print with a space between, because we
 159 /// don't want to track enough to tell "x.." from "...".
 160 bool TokenConcatenation::AvoidConcat(const Token &PrevPrevTok,
 161                                      const Token &PrevTok,
 162                                      const Token &Tok) const {
 163   // Conservatively assume that every annotation token that has a printable
 164   // form requires whitespace.
 165   if (PrevTok.isAnnotation())
 166     return true;
 167
 168   // First, check to see if the tokens were directly adjacent in the original
 169   // source.  If they were, it must be okay to stick them together: if there
 170   // were an issue, the tokens would have been lexed differently.
 171   SourceManager &SM = PP.getSourceManager();
 172   SourceLocation PrevSpellLoc = SM.getSpellingLoc(PrevTok.getLocation());
 173   SourceLocation SpellLoc = SM.getSpellingLoc(Tok.getLocation());
 174   if (PrevSpellLoc.getLocWithOffset(PrevTok.getLength()) == SpellLoc)
 175     return false;
 176
 177   tok::TokenKind PrevKind = PrevTok.getKind();
 178   if (!PrevTok.isAnnotation() && PrevTok.getIdentifierInfo())
 179     PrevKind = tok::identifier; // Language keyword or named operator.
 180
 181   // Look up information on when we should avoid concatenation with prevtok.
 182   unsigned ConcatInfo = TokenInfo[PrevKind];
 183
 184   // If prevtok never causes a problem for anything after it, return quickly.
 185   if (ConcatInfo == 0) return false;
 186
 187   if (ConcatInfo & aci_avoid_equal) {
 188     // If the next token is '=' or '==', avoid concatenation.
 189     if (Tok.isOneOf(tok::equal, tok::equalequal))
 190       return true;
 191     ConcatInfo &= ~aci_avoid_equal;
 192   }
 193   if (Tok.isAnnotation()) {
 194     // Modules annotation can show up when generated automatically for includes.
 195     assert(Tok.isOneOf(tok::annot_module_include, tok::annot_module_begin,
 196                        tok::annot_module_end) &&
 197            "unexpected annotation in AvoidConcat");
 198     ConcatInfo = 0;
 199   }
 200
 201   if (ConcatInfo == 0)
 202     return false;
 203
 204   // Basic algorithm: we look at the first character of the second token, and
 205   // determine whether it, if appended to the first token, would form (or
 206   // would contribute) to a larger token if concatenated.
 207   char FirstChar = 0;
 208   if (ConcatInfo & aci_custom) {
 209     // If the token does not need to know the first character, don't get it.
 210   } else {
 211     FirstChar = GetFirstChar(PP, Tok);
 212   }
 213
 214   switch (PrevKind) {
 215   default:
 216     llvm_unreachable("InitAvoidConcatTokenInfo built wrong");
 217
 218   case tok::raw_identifier:
 219     llvm_unreachable("tok::raw_identifier in non-raw lexing mode!");
 220
 221   case tok::string_literal:
 222   case tok::wide_string_literal:
 223   case tok::utf8_string_literal:
 224   case tok::utf16_string_literal:
 225   case tok::utf32_string_literal:
 226   case tok::char_constant:
 227   case tok::wide_char_constant:
 228   case tok::utf8_char_constant:
 229   case tok::utf16_char_constant:
 230   case tok::utf32_char_constant:
 231     if (!PP.getLangOpts().CPlusPlus11)
 232       return false;
 233
 234     // In C++11, a string or character literal followed by an identifier is a
 235     // single token.
 236     if (Tok.getIdentifierInfo())
 237       return true;
 238
 239     // A ud-suffix is an identifier. If the previous token ends with one, treat
 240     // it as an identifier.
 241     if (!PrevTok.hasUDSuffix())
 242       return false;
 243     [[fallthrough]];
 244   case tok::identifier:   // id+id or id+number or id+L"foo".
 245     // id+'.'... will not append.
 246     if (Tok.is(tok::numeric_constant))
 247       return GetFirstChar(PP, Tok) != '.';
 248
 249     if (Tok.getIdentifierInfo() ||
 250         Tok.isOneOf(tok::wide_string_literal, tok::utf8_string_literal,
 251                     tok::utf16_string_literal, tok::utf32_string_literal,
 252                     tok::wide_char_constant, tok::utf8_char_constant,
 253                     tok::utf16_char_constant, tok::utf32_char_constant))
 254       return true;
 255
 256     // If this isn't identifier + string, we're done.
 257     if (Tok.isNot(tok::char_constant) && Tok.isNot(tok::string_literal))
 258       return false;
 259
 260     // Otherwise, this is a narrow character or string.  If the *identifier*
 261     // is a literal 'L', 'u8', 'u' or 'U', avoid pasting L "foo" -> L"foo".
 262     return IsIdentifierStringPrefix(PrevTok);
 263
 264   case tok::numeric_constant:
 265     return isPreprocessingNumberBody(FirstChar) ||
 266            FirstChar == '+' || FirstChar == '-';
 267   case tok::period:          // ..., .*, .1234
 268     return (FirstChar == '.' && PrevPrevTok.is(tok::period)) ||
 269            isDigit(FirstChar) ||
 270            (PP.getLangOpts().CPlusPlus && FirstChar == '*');
 271   case tok::amp:             // &&
 272     return FirstChar == '&';
 273   case tok::plus:            // ++
 274     return FirstChar == '+';
 275   case tok::minus:           // --, ->, ->*
 276     return FirstChar == '-' || FirstChar == '>';
 277   case tok::slash:           //, /*, //
 278     return FirstChar == '*' || FirstChar == '/';
 279   case tok::less:            // <<, <<=, <:, <%
 280     return FirstChar == '<' || FirstChar == ':' || FirstChar == '%';
 281   case tok::greater:         // >>, >>=
 282     return FirstChar == '>';
 283   case tok::pipe:            // ||
 284     return FirstChar == '|';
 285   case tok::percent:         // %>, %:
 286     return FirstChar == '>' || FirstChar == ':';
 287   case tok::colon:           // ::, :>
 288     return FirstChar == '>' ||
 289     (PP.getLangOpts().CPlusPlus && FirstChar == ':');
 290   case tok::hash:            // ##, #@, %:%:
 291     return FirstChar == '#' || FirstChar == '@' || FirstChar == '%';
 292   case tok::arrow:           // ->*
 293     return PP.getLangOpts().CPlusPlus && FirstChar == '*';
 294   case tok::lessequal:       // <=> (C++2a)
 295     return PP.getLangOpts().CPlusPlus20 && FirstChar == '>';
 296   }
 297 }