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(SL: SM.getSpellingLoc(Loc: Tok.getLocation()));
55 return IsStringPrefix(Str: StringRef(Ptr, Tok.getLength()),
56 CPlusPlus11: LangOpts.CPlusPlus11);
57 }
58
59 if (Tok.getLength() < 256) {
60 char Buffer[256];
61 const char *TokPtr = Buffer;
62 unsigned length = PP.getSpelling(Tok, Buffer&: TokPtr);
63 return IsStringPrefix(Str: StringRef(TokPtr, length), CPlusPlus11: LangOpts.CPlusPlus11);
64 }
65
66 return IsStringPrefix(Str: StringRef(PP.getSpelling(Tok)), CPlusPlus11: LangOpts.CPlusPlus11);
67}
68
69TokenConcatenation::TokenConcatenation(const Preprocessor &pp) : PP(pp) {
70 memset(s: TokenInfo, c: 0, n: 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(SL: SM.getSpellingLoc(Loc: Tok.getLocation()));
138 }
139 } else if (Tok.getLength() < 256) {
140 char Buffer[256];
141 const char *TokPtr = Buffer;
142 PP.getSpelling(Tok, Buffer&: 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(Loc: PrevTok.getLocation());
173 SourceLocation SpellLoc = SM.getSpellingLoc(Loc: Tok.getLocation());
174 if (PrevSpellLoc.getLocWithOffset(Offset: 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(K1: tok::equal, K2: 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(K: tok::numeric_constant))
247 return GetFirstChar(PP, Tok) != '.';
248
249 if (Tok.getIdentifierInfo() ||
250 Tok.isOneOf(K1: tok::wide_string_literal, Ks: tok::utf8_string_literal,
251 Ks: tok::utf16_string_literal, Ks: tok::utf32_string_literal,
252 Ks: tok::wide_char_constant, Ks: tok::utf8_char_constant,
253 Ks: tok::utf16_char_constant, Ks: tok::utf32_char_constant))
254 return true;
255
256 // If this isn't identifier + string, we're done.
257 if (Tok.isNot(K: tok::char_constant) && Tok.isNot(K: 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(Tok: PrevTok);
263
264 case tok::numeric_constant:
265 return isPreprocessingNumberBody(c: FirstChar) ||
266 FirstChar == '+' || FirstChar == '-';
267 case tok::period: // ..., .*, .1234
268 return (FirstChar == '.' && PrevPrevTok.is(K: tok::period)) ||
269 isDigit(c: 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

source code of clang/lib/Lex/TokenConcatenation.cpp