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"
17using namespace clang;
18
19
20/// IsStringPrefix - Return true if Str is a string prefix.
21/// 'L', 'u', 'U', or 'u8'. Including raw versions.
22static 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.
47bool 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
69TokenConcatenation::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.
128static 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 "...".
160bool 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}
298