1 //===--- ParseInit.cpp - Initializer Parsing ------------------------------===//
2 //
3 // The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 // This file implements initializer parsing as specified by C99 6.7.8.
11 //
12 //===----------------------------------------------------------------------===//
13
14 #include "clang/Parse/ParseDiagnostic.h"
15 #include "clang/Parse/Parser.h"
16 #include "clang/Parse/RAIIObjectsForParser.h"
17 #include "clang/Sema/Designator.h"
18 #include "clang/Sema/Scope.h"
19 #include "llvm/ADT/SmallString.h"
20 using namespace clang;
21
22
23 /// MayBeDesignationStart - Return true if the current token might be the start
24 /// of a designator. If we can tell it is impossible that it is a designator,
25 /// return false.
MayBeDesignationStart()26 bool Parser::MayBeDesignationStart() {
27 switch (Tok.getKind()) {
28 default:
29 return false;
30
31 case tok::period: // designator: '.' identifier
32 return true;
33
34 case tok::l_square: { // designator: array-designator
35 if (!PP.getLangOpts().CPlusPlus11)
36 return true;
37
38 // C++11 lambda expressions and C99 designators can be ambiguous all the
39 // way through the closing ']' and to the next character. Handle the easy
40 // cases here, and fall back to tentative parsing if those fail.
41 switch (PP.LookAhead(0).getKind()) {
42 case tok::equal:
43 case tok::r_square:
44 // Definitely starts a lambda expression.
45 return false;
46
47 case tok::amp:
48 case tok::kw_this:
49 case tok::identifier:
50 // We have to do additional analysis, because these could be the
51 // start of a constant expression or a lambda capture list.
52 break;
53
54 default:
55 // Anything not mentioned above cannot occur following a '[' in a
56 // lambda expression.
57 return true;
58 }
59
60 // Handle the complicated case below.
61 break;
62 }
63 case tok::identifier: // designation: identifier ':'
64 return PP.LookAhead(0).is(tok::colon);
65 }
66
67 // Parse up to (at most) the token after the closing ']' to determine
68 // whether this is a C99 designator or a lambda.
69 TentativeParsingAction Tentative(*this);
70
71 LambdaIntroducer Intro;
72 bool SkippedInits = false;
73 Optional<unsigned> DiagID(ParseLambdaIntroducer(Intro, &SkippedInits));
74
75 if (DiagID) {
76 // If this can't be a lambda capture list, it's a designator.
77 Tentative.Revert();
78 return true;
79 }
80
81 // Once we hit the closing square bracket, we look at the next
82 // token. If it's an '=', this is a designator. Otherwise, it's a
83 // lambda expression. This decision favors lambdas over the older
84 // GNU designator syntax, which allows one to omit the '=', but is
85 // consistent with GCC.
86 tok::TokenKind Kind = Tok.getKind();
87 // FIXME: If we didn't skip any inits, parse the lambda from here
88 // rather than throwing away then reparsing the LambdaIntroducer.
89 Tentative.Revert();
90 return Kind == tok::equal;
91 }
92
CheckArrayDesignatorSyntax(Parser & P,SourceLocation Loc,Designation & Desig)93 static void CheckArrayDesignatorSyntax(Parser &P, SourceLocation Loc,
94 Designation &Desig) {
95 // If we have exactly one array designator, this used the GNU
96 // 'designation: array-designator' extension, otherwise there should be no
97 // designators at all!
98 if (Desig.getNumDesignators() == 1 &&
99 (Desig.getDesignator(0).isArrayDesignator() ||
100 Desig.getDesignator(0).isArrayRangeDesignator()))
101 P.Diag(Loc, diag::ext_gnu_missing_equal_designator);
102 else if (Desig.getNumDesignators() > 0)
103 P.Diag(Loc, diag::err_expected_equal_designator);
104 }
105
106 /// ParseInitializerWithPotentialDesignator - Parse the 'initializer' production
107 /// checking to see if the token stream starts with a designator.
108 ///
109 /// designation:
110 /// designator-list '='
111 /// [GNU] array-designator
112 /// [GNU] identifier ':'
113 ///
114 /// designator-list:
115 /// designator
116 /// designator-list designator
117 ///
118 /// designator:
119 /// array-designator
120 /// '.' identifier
121 ///
122 /// array-designator:
123 /// '[' constant-expression ']'
124 /// [GNU] '[' constant-expression '...' constant-expression ']'
125 ///
126 /// NOTE: [OBC] allows '[ objc-receiver objc-message-args ]' as an
127 /// initializer (because it is an expression). We need to consider this case
128 /// when parsing array designators.
129 ///
ParseInitializerWithPotentialDesignator()130 ExprResult Parser::ParseInitializerWithPotentialDesignator() {
131
132 // If this is the old-style GNU extension:
133 // designation ::= identifier ':'
134 // Handle it as a field designator. Otherwise, this must be the start of a
135 // normal expression.
136 if (Tok.is(tok::identifier)) {
137 const IdentifierInfo *FieldName = Tok.getIdentifierInfo();
138
139 SmallString<256> NewSyntax;
140 llvm::raw_svector_ostream(NewSyntax) << '.' << FieldName->getName()
141 << " = ";
142
143 SourceLocation NameLoc = ConsumeToken(); // Eat the identifier.
144
145 assert(Tok.is(tok::colon) && "MayBeDesignationStart not working properly!");
146 SourceLocation ColonLoc = ConsumeToken();
147
148 Diag(NameLoc, diag::ext_gnu_old_style_field_designator)
149 << FixItHint::CreateReplacement(SourceRange(NameLoc, ColonLoc),
150 NewSyntax);
151
152 Designation D;
153 D.AddDesignator(Designator::getField(FieldName, SourceLocation(), NameLoc));
154 return Actions.ActOnDesignatedInitializer(D, ColonLoc, true,
155 ParseInitializer());
156 }
157
158 // Desig - This is initialized when we see our first designator. We may have
159 // an objc message send with no designator, so we don't want to create this
160 // eagerly.
161 Designation Desig;
162
163 // Parse each designator in the designator list until we find an initializer.
164 while (Tok.is(tok::period) || Tok.is(tok::l_square)) {
165 if (Tok.is(tok::period)) {
166 // designator: '.' identifier
167 SourceLocation DotLoc = ConsumeToken();
168
169 if (Tok.isNot(tok::identifier)) {
170 Diag(Tok.getLocation(), diag::err_expected_field_designator);
171 return ExprError();
172 }
173
174 Desig.AddDesignator(Designator::getField(Tok.getIdentifierInfo(), DotLoc,
175 Tok.getLocation()));
176 ConsumeToken(); // Eat the identifier.
177 continue;
178 }
179
180 // We must have either an array designator now or an objc message send.
181 assert(Tok.is(tok::l_square) && "Unexpected token!");
182
183 // Handle the two forms of array designator:
184 // array-designator: '[' constant-expression ']'
185 // array-designator: '[' constant-expression '...' constant-expression ']'
186 //
187 // Also, we have to handle the case where the expression after the
188 // designator an an objc message send: '[' objc-message-expr ']'.
189 // Interesting cases are:
190 // [foo bar] -> objc message send
191 // [foo] -> array designator
192 // [foo ... bar] -> array designator
193 // [4][foo bar] -> obsolete GNU designation with objc message send.
194 //
195 // We do not need to check for an expression starting with [[ here. If it
196 // contains an Objective-C message send, then it is not an ill-formed
197 // attribute. If it is a lambda-expression within an array-designator, then
198 // it will be rejected because a constant-expression cannot begin with a
199 // lambda-expression.
200 InMessageExpressionRAIIObject InMessage(*this, true);
201
202 BalancedDelimiterTracker T(*this, tok::l_square);
203 T.consumeOpen();
204 SourceLocation StartLoc = T.getOpenLocation();
205
206 ExprResult Idx;
207
208 // If Objective-C is enabled and this is a typename (class message
209 // send) or send to 'super', parse this as a message send
210 // expression. We handle C++ and C separately, since C++ requires
211 // much more complicated parsing.
212 if (getLangOpts().ObjC && getLangOpts().CPlusPlus) {
213 // Send to 'super'.
214 if (Tok.is(tok::identifier) && Tok.getIdentifierInfo() == Ident_super &&
215 NextToken().isNot(tok::period) &&
216 getCurScope()->isInObjcMethodScope()) {
217 CheckArrayDesignatorSyntax(*this, StartLoc, Desig);
218 return ParseAssignmentExprWithObjCMessageExprStart(
219 StartLoc, ConsumeToken(), nullptr, nullptr);
220 }
221
222 // Parse the receiver, which is either a type or an expression.
223 bool IsExpr;
224 void *TypeOrExpr;
225 if (ParseObjCXXMessageReceiver(IsExpr, TypeOrExpr)) {
226 SkipUntil(tok::r_square, StopAtSemi);
227 return ExprError();
228 }
229
230 // If the receiver was a type, we have a class message; parse
231 // the rest of it.
232 if (!IsExpr) {
233 CheckArrayDesignatorSyntax(*this, StartLoc, Desig);
234 return ParseAssignmentExprWithObjCMessageExprStart(StartLoc,
235 SourceLocation(),
236 ParsedType::getFromOpaquePtr(TypeOrExpr),
237 nullptr);
238 }
239
240 // If the receiver was an expression, we still don't know
241 // whether we have a message send or an array designator; just
242 // adopt the expression for further analysis below.
243 // FIXME: potentially-potentially evaluated expression above?
244 Idx = ExprResult(static_cast<Expr*>(TypeOrExpr));
245 } else if (getLangOpts().ObjC && Tok.is(tok::identifier)) {
246 IdentifierInfo *II = Tok.getIdentifierInfo();
247 SourceLocation IILoc = Tok.getLocation();
248 ParsedType ReceiverType;
249 // Three cases. This is a message send to a type: [type foo]
250 // This is a message send to super: [super foo]
251 // This is a message sent to an expr: [super.bar foo]
252 switch (Actions.getObjCMessageKind(
253 getCurScope(), II, IILoc, II == Ident_super,
254 NextToken().is(tok::period), ReceiverType)) {
255 case Sema::ObjCSuperMessage:
256 CheckArrayDesignatorSyntax(*this, StartLoc, Desig);
257 return ParseAssignmentExprWithObjCMessageExprStart(
258 StartLoc, ConsumeToken(), nullptr, nullptr);
259
260 case Sema::ObjCClassMessage:
261 CheckArrayDesignatorSyntax(*this, StartLoc, Desig);
262 ConsumeToken(); // the identifier
263 if (!ReceiverType) {
264 SkipUntil(tok::r_square, StopAtSemi);
265 return ExprError();
266 }
267
268 // Parse type arguments and protocol qualifiers.
269 if (Tok.is(tok::less)) {
270 SourceLocation NewEndLoc;
271 TypeResult NewReceiverType
272 = parseObjCTypeArgsAndProtocolQualifiers(IILoc, ReceiverType,
273 /*consumeLastToken=*/true,
274 NewEndLoc);
275 if (!NewReceiverType.isUsable()) {
276 SkipUntil(tok::r_square, StopAtSemi);
277 return ExprError();
278 }
279
280 ReceiverType = NewReceiverType.get();
281 }
282
283 return ParseAssignmentExprWithObjCMessageExprStart(StartLoc,
284 SourceLocation(),
285 ReceiverType,
286 nullptr);
287
288 case Sema::ObjCInstanceMessage:
289 // Fall through; we'll just parse the expression and
290 // (possibly) treat this like an Objective-C message send
291 // later.
292 break;
293 }
294 }
295
296 // Parse the index expression, if we haven't already gotten one
297 // above (which can only happen in Objective-C++).
298 // Note that we parse this as an assignment expression, not a constant
299 // expression (allowing *=, =, etc) to handle the objc case. Sema needs
300 // to validate that the expression is a constant.
301 // FIXME: We also need to tell Sema that we're in a
302 // potentially-potentially evaluated context.
303 if (!Idx.get()) {
304 Idx = ParseAssignmentExpression();
305 if (Idx.isInvalid()) {
306 SkipUntil(tok::r_square, StopAtSemi);
307 return Idx;
308 }
309 }
310
311 // Given an expression, we could either have a designator (if the next
312 // tokens are '...' or ']' or an objc message send. If this is an objc
313 // message send, handle it now. An objc-message send is the start of
314 // an assignment-expression production.
315 if (getLangOpts().ObjC && Tok.isNot(tok::ellipsis) &&
316 Tok.isNot(tok::r_square)) {
317 CheckArrayDesignatorSyntax(*this, Tok.getLocation(), Desig);
318 return ParseAssignmentExprWithObjCMessageExprStart(
319 StartLoc, SourceLocation(), nullptr, Idx.get());
320 }
321
322 // If this is a normal array designator, remember it.
323 if (Tok.isNot(tok::ellipsis)) {
324 Desig.AddDesignator(Designator::getArray(Idx.get(), StartLoc));
325 } else {
326 // Handle the gnu array range extension.
327 Diag(Tok, diag::ext_gnu_array_range);
328 SourceLocation EllipsisLoc = ConsumeToken();
329
330 ExprResult RHS(ParseConstantExpression());
331 if (RHS.isInvalid()) {
332 SkipUntil(tok::r_square, StopAtSemi);
333 return RHS;
334 }
335 Desig.AddDesignator(Designator::getArrayRange(Idx.get(),
336 RHS.get(),
337 StartLoc, EllipsisLoc));
338 }
339
340 T.consumeClose();
341 Desig.getDesignator(Desig.getNumDesignators() - 1).setRBracketLoc(
342 T.getCloseLocation());
343 }
344
345 // Okay, we're done with the designator sequence. We know that there must be
346 // at least one designator, because the only case we can get into this method
347 // without a designator is when we have an objc message send. That case is
348 // handled and returned from above.
349 assert(!Desig.empty() && "Designator is empty?");
350
351 // Handle a normal designator sequence end, which is an equal.
352 if (Tok.is(tok::equal)) {
353 SourceLocation EqualLoc = ConsumeToken();
354 return Actions.ActOnDesignatedInitializer(Desig, EqualLoc, false,
355 ParseInitializer());
356 }
357
358 // We read some number of designators and found something that isn't an = or
359 // an initializer. If we have exactly one array designator, this
360 // is the GNU 'designation: array-designator' extension. Otherwise, it is a
361 // parse error.
362 if (Desig.getNumDesignators() == 1 &&
363 (Desig.getDesignator(0).isArrayDesignator() ||
364 Desig.getDesignator(0).isArrayRangeDesignator())) {
365 Diag(Tok, diag::ext_gnu_missing_equal_designator)
366 << FixItHint::CreateInsertion(Tok.getLocation(), "= ");
367 return Actions.ActOnDesignatedInitializer(Desig, Tok.getLocation(),
368 true, ParseInitializer());
369 }
370
371 Diag(Tok, diag::err_expected_equal_designator);
372 return ExprError();
373 }
374
375
376 /// ParseBraceInitializer - Called when parsing an initializer that has a
377 /// leading open brace.
378 ///
379 /// initializer: [C99 6.7.8]
380 /// '{' initializer-list '}'
381 /// '{' initializer-list ',' '}'
382 /// [GNU] '{' '}'
383 ///
384 /// initializer-list:
385 /// designation[opt] initializer ...[opt]
386 /// initializer-list ',' designation[opt] initializer ...[opt]
387 ///
ParseBraceInitializer()388 ExprResult Parser::ParseBraceInitializer() {
389 InMessageExpressionRAIIObject InMessage(*this, false);
390
391 BalancedDelimiterTracker T(*this, tok::l_brace);
392 T.consumeOpen();
393 SourceLocation LBraceLoc = T.getOpenLocation();
394
395 /// InitExprs - This is the actual list of expressions contained in the
396 /// initializer.
397 ExprVector InitExprs;
398
399 if (Tok.is(tok::r_brace)) {
400 // Empty initializers are a C++ feature and a GNU extension to C.
401 if (!getLangOpts().CPlusPlus)
402 Diag(LBraceLoc, diag::ext_gnu_empty_initializer);
403 // Match the '}'.
404 return Actions.ActOnInitList(LBraceLoc, None, ConsumeBrace());
405 }
406
407 // Enter an appropriate expression evaluation context for an initializer list.
408 EnterExpressionEvaluationContext EnterContext(
409 Actions, EnterExpressionEvaluationContext::InitList);
410
411 bool InitExprsOk = true;
412
413 while (1) {
414 // Handle Microsoft __if_exists/if_not_exists if necessary.
415 if (getLangOpts().MicrosoftExt && (Tok.is(tok::kw___if_exists) ||
416 Tok.is(tok::kw___if_not_exists))) {
417 if (ParseMicrosoftIfExistsBraceInitializer(InitExprs, InitExprsOk)) {
418 if (Tok.isNot(tok::comma)) break;
419 ConsumeToken();
420 }
421 if (Tok.is(tok::r_brace)) break;
422 continue;
423 }
424
425 // Parse: designation[opt] initializer
426
427 // If we know that this cannot be a designation, just parse the nested
428 // initializer directly.
429 ExprResult SubElt;
430 if (MayBeDesignationStart())
431 SubElt = ParseInitializerWithPotentialDesignator();
432 else
433 SubElt = ParseInitializer();
434
435 if (Tok.is(tok::ellipsis))
436 SubElt = Actions.ActOnPackExpansion(SubElt.get(), ConsumeToken());
437
438 SubElt = Actions.CorrectDelayedTyposInExpr(SubElt.get());
439
440 // If we couldn't parse the subelement, bail out.
441 if (SubElt.isUsable()) {
442 InitExprs.push_back(SubElt.get());
443 } else {
444 InitExprsOk = false;
445
446 // We have two ways to try to recover from this error: if the code looks
447 // grammatically ok (i.e. we have a comma coming up) try to continue
448 // parsing the rest of the initializer. This allows us to emit
449 // diagnostics for later elements that we find. If we don't see a comma,
450 // assume there is a parse error, and just skip to recover.
451 // FIXME: This comment doesn't sound right. If there is a r_brace
452 // immediately, it can't be an error, since there is no other way of
453 // leaving this loop except through this if.
454 if (Tok.isNot(tok::comma)) {
455 SkipUntil(tok::r_brace, StopBeforeMatch);
456 break;
457 }
458 }
459
460 // If we don't have a comma continued list, we're done.
461 if (Tok.isNot(tok::comma)) break;
462
463 // TODO: save comma locations if some client cares.
464 ConsumeToken();
465
466 // Handle trailing comma.
467 if (Tok.is(tok::r_brace)) break;
468 }
469
470 bool closed = !T.consumeClose();
471
472 if (InitExprsOk && closed)
473 return Actions.ActOnInitList(LBraceLoc, InitExprs,
474 T.getCloseLocation());
475
476 return ExprError(); // an error occurred.
477 }
478
479
480 // Return true if a comma (or closing brace) is necessary after the
481 // __if_exists/if_not_exists statement.
ParseMicrosoftIfExistsBraceInitializer(ExprVector & InitExprs,bool & InitExprsOk)482 bool Parser::ParseMicrosoftIfExistsBraceInitializer(ExprVector &InitExprs,
483 bool &InitExprsOk) {
484 bool trailingComma = false;
485 IfExistsCondition Result;
486 if (ParseMicrosoftIfExistsCondition(Result))
487 return false;
488
489 BalancedDelimiterTracker Braces(*this, tok::l_brace);
490 if (Braces.consumeOpen()) {
491 Diag(Tok, diag::err_expected) << tok::l_brace;
492 return false;
493 }
494
495 switch (Result.Behavior) {
496 case IEB_Parse:
497 // Parse the declarations below.
498 break;
499
500 case IEB_Dependent:
501 Diag(Result.KeywordLoc, diag::warn_microsoft_dependent_exists)
502 << Result.IsIfExists;
503 // Fall through to skip.
504 LLVM_FALLTHROUGH;
505
506 case IEB_Skip:
507 Braces.skipToEnd();
508 return false;
509 }
510
511 while (!isEofOrEom()) {
512 trailingComma = false;
513 // If we know that this cannot be a designation, just parse the nested
514 // initializer directly.
515 ExprResult SubElt;
516 if (MayBeDesignationStart())
517 SubElt = ParseInitializerWithPotentialDesignator();
518 else
519 SubElt = ParseInitializer();
520
521 if (Tok.is(tok::ellipsis))
522 SubElt = Actions.ActOnPackExpansion(SubElt.get(), ConsumeToken());
523
524 // If we couldn't parse the subelement, bail out.
525 if (!SubElt.isInvalid())
526 InitExprs.push_back(SubElt.get());
527 else
528 InitExprsOk = false;
529
530 if (Tok.is(tok::comma)) {
531 ConsumeToken();
532 trailingComma = true;
533 }
534
535 if (Tok.is(tok::r_brace))
536 break;
537 }
538
539 Braces.consumeClose();
540
541 return !trailingComma;
542 }
543