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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/Parser.h"
15 #include "RAIIObjectsForParser.h"
16 #include "clang/Parse/ParseDiagnostic.h"
17 #include "clang/Sema/Designator.h"
18 #include "clang/Sema/Scope.h"
19 #include "llvm/ADT/SmallString.h"
20 #include "llvm/Support/raw_ostream.h"
21 using namespace clang;
22 
23 
24 /// MayBeDesignationStart - Return true if the current token might be the start
25 /// of a designator.  If we can tell it is impossible that it is a designator,
26 /// return false.
MayBeDesignationStart()27 bool Parser::MayBeDesignationStart() {
28   switch (Tok.getKind()) {
29   default:
30     return false;
31 
32   case tok::period:      // designator: '.' identifier
33     return true;
34 
35   case tok::l_square: {  // designator: array-designator
36     if (!PP.getLangOpts().CPlusPlus11)
37       return true;
38 
39     // C++11 lambda expressions and C99 designators can be ambiguous all the
40     // way through the closing ']' and to the next character. Handle the easy
41     // cases here, and fall back to tentative parsing if those fail.
42     switch (PP.LookAhead(0).getKind()) {
43     case tok::equal:
44     case tok::r_square:
45       // Definitely starts a lambda expression.
46       return false;
47 
48     case tok::amp:
49     case tok::kw_this:
50     case tok::identifier:
51       // We have to do additional analysis, because these could be the
52       // start of a constant expression or a lambda capture list.
53       break;
54 
55     default:
56       // Anything not mentioned above cannot occur following a '[' in a
57       // lambda expression.
58       return true;
59     }
60 
61     // Handle the complicated case below.
62     break;
63   }
64   case tok::identifier:  // designation: identifier ':'
65     return PP.LookAhead(0).is(tok::colon);
66   }
67 
68   // Parse up to (at most) the token after the closing ']' to determine
69   // whether this is a C99 designator or a lambda.
70   TentativeParsingAction Tentative(*this);
71 
72   LambdaIntroducer Intro;
73   bool SkippedInits = false;
74   Optional<unsigned> DiagID(ParseLambdaIntroducer(Intro, &SkippedInits));
75 
76   if (DiagID) {
77     // If this can't be a lambda capture list, it's a designator.
78     Tentative.Revert();
79     return true;
80   }
81 
82   // Once we hit the closing square bracket, we look at the next
83   // token. If it's an '=', this is a designator. Otherwise, it's a
84   // lambda expression. This decision favors lambdas over the older
85   // GNU designator syntax, which allows one to omit the '=', but is
86   // consistent with GCC.
87   tok::TokenKind Kind = Tok.getKind();
88   // FIXME: If we didn't skip any inits, parse the lambda from here
89   // rather than throwing away then reparsing the LambdaIntroducer.
90   Tentative.Revert();
91   return Kind == tok::equal;
92 }
93 
CheckArrayDesignatorSyntax(Parser & P,SourceLocation Loc,Designation & Desig)94 static void CheckArrayDesignatorSyntax(Parser &P, SourceLocation Loc,
95                                        Designation &Desig) {
96   // If we have exactly one array designator, this used the GNU
97   // 'designation: array-designator' extension, otherwise there should be no
98   // designators at all!
99   if (Desig.getNumDesignators() == 1 &&
100       (Desig.getDesignator(0).isArrayDesignator() ||
101        Desig.getDesignator(0).isArrayRangeDesignator()))
102     P.Diag(Loc, diag::ext_gnu_missing_equal_designator);
103   else if (Desig.getNumDesignators() > 0)
104     P.Diag(Loc, diag::err_expected_equal_designator);
105 }
106 
107 /// ParseInitializerWithPotentialDesignator - Parse the 'initializer' production
108 /// checking to see if the token stream starts with a designator.
109 ///
110 ///       designation:
111 ///         designator-list '='
112 /// [GNU]   array-designator
113 /// [GNU]   identifier ':'
114 ///
115 ///       designator-list:
116 ///         designator
117 ///         designator-list designator
118 ///
119 ///       designator:
120 ///         array-designator
121 ///         '.' identifier
122 ///
123 ///       array-designator:
124 ///         '[' constant-expression ']'
125 /// [GNU]   '[' constant-expression '...' constant-expression ']'
126 ///
127 /// NOTE: [OBC] allows '[ objc-receiver objc-message-args ]' as an
128 /// initializer (because it is an expression).  We need to consider this case
129 /// when parsing array designators.
130 ///
ParseInitializerWithPotentialDesignator()131 ExprResult Parser::ParseInitializerWithPotentialDesignator() {
132 
133   // If this is the old-style GNU extension:
134   //   designation ::= identifier ':'
135   // Handle it as a field designator.  Otherwise, this must be the start of a
136   // normal expression.
137   if (Tok.is(tok::identifier)) {
138     const IdentifierInfo *FieldName = Tok.getIdentifierInfo();
139 
140     SmallString<256> NewSyntax;
141     llvm::raw_svector_ostream(NewSyntax) << '.' << FieldName->getName()
142                                          << " = ";
143 
144     SourceLocation NameLoc = ConsumeToken(); // Eat the identifier.
145 
146     assert(Tok.is(tok::colon) && "MayBeDesignationStart not working properly!");
147     SourceLocation ColonLoc = ConsumeToken();
148 
149     Diag(NameLoc, diag::ext_gnu_old_style_field_designator)
150       << FixItHint::CreateReplacement(SourceRange(NameLoc, ColonLoc),
151                                       NewSyntax);
152 
153     Designation D;
154     D.AddDesignator(Designator::getField(FieldName, SourceLocation(), NameLoc));
155     return Actions.ActOnDesignatedInitializer(D, ColonLoc, true,
156                                               ParseInitializer());
157   }
158 
159   // Desig - This is initialized when we see our first designator.  We may have
160   // an objc message send with no designator, so we don't want to create this
161   // eagerly.
162   Designation Desig;
163 
164   // Parse each designator in the designator list until we find an initializer.
165   while (Tok.is(tok::period) || Tok.is(tok::l_square)) {
166     if (Tok.is(tok::period)) {
167       // designator: '.' identifier
168       SourceLocation DotLoc = ConsumeToken();
169 
170       if (Tok.isNot(tok::identifier)) {
171         Diag(Tok.getLocation(), diag::err_expected_field_designator);
172         return ExprError();
173       }
174 
175       Desig.AddDesignator(Designator::getField(Tok.getIdentifierInfo(), DotLoc,
176                                                Tok.getLocation()));
177       ConsumeToken(); // Eat the identifier.
178       continue;
179     }
180 
181     // We must have either an array designator now or an objc message send.
182     assert(Tok.is(tok::l_square) && "Unexpected token!");
183 
184     // Handle the two forms of array designator:
185     //   array-designator: '[' constant-expression ']'
186     //   array-designator: '[' constant-expression '...' constant-expression ']'
187     //
188     // Also, we have to handle the case where the expression after the
189     // designator an an objc message send: '[' objc-message-expr ']'.
190     // Interesting cases are:
191     //   [foo bar]         -> objc message send
192     //   [foo]             -> array designator
193     //   [foo ... bar]     -> array designator
194     //   [4][foo bar]      -> obsolete GNU designation with objc message send.
195     //
196     // We do not need to check for an expression starting with [[ here. If it
197     // contains an Objective-C message send, then it is not an ill-formed
198     // attribute. If it is a lambda-expression within an array-designator, then
199     // it will be rejected because a constant-expression cannot begin with a
200     // lambda-expression.
201     InMessageExpressionRAIIObject InMessage(*this, true);
202 
203     BalancedDelimiterTracker T(*this, tok::l_square);
204     T.consumeOpen();
205     SourceLocation StartLoc = T.getOpenLocation();
206 
207     ExprResult Idx;
208 
209     // If Objective-C is enabled and this is a typename (class message
210     // send) or send to 'super', parse this as a message send
211     // expression.  We handle C++ and C separately, since C++ requires
212     // much more complicated parsing.
213     if  (getLangOpts().ObjC1 && getLangOpts().CPlusPlus) {
214       // Send to 'super'.
215       if (Tok.is(tok::identifier) && Tok.getIdentifierInfo() == Ident_super &&
216           NextToken().isNot(tok::period) &&
217           getCurScope()->isInObjcMethodScope()) {
218         CheckArrayDesignatorSyntax(*this, StartLoc, Desig);
219         return ParseAssignmentExprWithObjCMessageExprStart(
220             StartLoc, ConsumeToken(), nullptr, nullptr);
221       }
222 
223       // Parse the receiver, which is either a type or an expression.
224       bool IsExpr;
225       void *TypeOrExpr;
226       if (ParseObjCXXMessageReceiver(IsExpr, TypeOrExpr)) {
227         SkipUntil(tok::r_square, StopAtSemi);
228         return ExprError();
229       }
230 
231       // If the receiver was a type, we have a class message; parse
232       // the rest of it.
233       if (!IsExpr) {
234         CheckArrayDesignatorSyntax(*this, StartLoc, Desig);
235         return ParseAssignmentExprWithObjCMessageExprStart(StartLoc,
236                                                            SourceLocation(),
237                                    ParsedType::getFromOpaquePtr(TypeOrExpr),
238                                                            nullptr);
239       }
240 
241       // If the receiver was an expression, we still don't know
242       // whether we have a message send or an array designator; just
243       // adopt the expression for further analysis below.
244       // FIXME: potentially-potentially evaluated expression above?
245       Idx = ExprResult(static_cast<Expr*>(TypeOrExpr));
246     } else if (getLangOpts().ObjC1 && Tok.is(tok::identifier)) {
247       IdentifierInfo *II = Tok.getIdentifierInfo();
248       SourceLocation IILoc = Tok.getLocation();
249       ParsedType ReceiverType;
250       // Three cases. This is a message send to a type: [type foo]
251       // This is a message send to super:  [super foo]
252       // This is a message sent to an expr:  [super.bar foo]
253       switch (Actions.getObjCMessageKind(
254           getCurScope(), II, IILoc, II == Ident_super,
255           NextToken().is(tok::period), ReceiverType)) {
256       case Sema::ObjCSuperMessage:
257         CheckArrayDesignatorSyntax(*this, StartLoc, Desig);
258         return ParseAssignmentExprWithObjCMessageExprStart(
259             StartLoc, ConsumeToken(), nullptr, nullptr);
260 
261       case Sema::ObjCClassMessage:
262         CheckArrayDesignatorSyntax(*this, StartLoc, Desig);
263         ConsumeToken(); // the identifier
264         if (!ReceiverType) {
265           SkipUntil(tok::r_square, StopAtSemi);
266           return ExprError();
267         }
268 
269         // Parse type arguments and protocol qualifiers.
270         if (Tok.is(tok::less)) {
271           SourceLocation NewEndLoc;
272           TypeResult NewReceiverType
273             = parseObjCTypeArgsAndProtocolQualifiers(IILoc, ReceiverType,
274                                                      /*consumeLastToken=*/true,
275                                                      NewEndLoc);
276           if (!NewReceiverType.isUsable()) {
277             SkipUntil(tok::r_square, StopAtSemi);
278             return ExprError();
279           }
280 
281           ReceiverType = NewReceiverType.get();
282         }
283 
284         return ParseAssignmentExprWithObjCMessageExprStart(StartLoc,
285                                                            SourceLocation(),
286                                                            ReceiverType,
287                                                            nullptr);
288 
289       case Sema::ObjCInstanceMessage:
290         // Fall through; we'll just parse the expression and
291         // (possibly) treat this like an Objective-C message send
292         // later.
293         break;
294       }
295     }
296 
297     // Parse the index expression, if we haven't already gotten one
298     // above (which can only happen in Objective-C++).
299     // Note that we parse this as an assignment expression, not a constant
300     // expression (allowing *=, =, etc) to handle the objc case.  Sema needs
301     // to validate that the expression is a constant.
302     // FIXME: We also need to tell Sema that we're in a
303     // potentially-potentially evaluated context.
304     if (!Idx.get()) {
305       Idx = ParseAssignmentExpression();
306       if (Idx.isInvalid()) {
307         SkipUntil(tok::r_square, StopAtSemi);
308         return Idx;
309       }
310     }
311 
312     // Given an expression, we could either have a designator (if the next
313     // tokens are '...' or ']' or an objc message send.  If this is an objc
314     // message send, handle it now.  An objc-message send is the start of
315     // an assignment-expression production.
316     if (getLangOpts().ObjC1 && Tok.isNot(tok::ellipsis) &&
317         Tok.isNot(tok::r_square)) {
318       CheckArrayDesignatorSyntax(*this, Tok.getLocation(), Desig);
319       return ParseAssignmentExprWithObjCMessageExprStart(
320           StartLoc, SourceLocation(), nullptr, Idx.get());
321     }
322 
323     // If this is a normal array designator, remember it.
324     if (Tok.isNot(tok::ellipsis)) {
325       Desig.AddDesignator(Designator::getArray(Idx.get(), StartLoc));
326     } else {
327       // Handle the gnu array range extension.
328       Diag(Tok, diag::ext_gnu_array_range);
329       SourceLocation EllipsisLoc = ConsumeToken();
330 
331       ExprResult RHS(ParseConstantExpression());
332       if (RHS.isInvalid()) {
333         SkipUntil(tok::r_square, StopAtSemi);
334         return RHS;
335       }
336       Desig.AddDesignator(Designator::getArrayRange(Idx.get(),
337                                                     RHS.get(),
338                                                     StartLoc, EllipsisLoc));
339     }
340 
341     T.consumeClose();
342     Desig.getDesignator(Desig.getNumDesignators() - 1).setRBracketLoc(
343                                                         T.getCloseLocation());
344   }
345 
346   // Okay, we're done with the designator sequence.  We know that there must be
347   // at least one designator, because the only case we can get into this method
348   // without a designator is when we have an objc message send.  That case is
349   // handled and returned from above.
350   assert(!Desig.empty() && "Designator is empty?");
351 
352   // Handle a normal designator sequence end, which is an equal.
353   if (Tok.is(tok::equal)) {
354     SourceLocation EqualLoc = ConsumeToken();
355     return Actions.ActOnDesignatedInitializer(Desig, EqualLoc, false,
356                                               ParseInitializer());
357   }
358 
359   // We read some number of designators and found something that isn't an = or
360   // an initializer.  If we have exactly one array designator, this
361   // is the GNU 'designation: array-designator' extension.  Otherwise, it is a
362   // parse error.
363   if (Desig.getNumDesignators() == 1 &&
364       (Desig.getDesignator(0).isArrayDesignator() ||
365        Desig.getDesignator(0).isArrayRangeDesignator())) {
366     Diag(Tok, diag::ext_gnu_missing_equal_designator)
367       << FixItHint::CreateInsertion(Tok.getLocation(), "= ");
368     return Actions.ActOnDesignatedInitializer(Desig, Tok.getLocation(),
369                                               true, ParseInitializer());
370   }
371 
372   Diag(Tok, diag::err_expected_equal_designator);
373   return ExprError();
374 }
375 
376 
377 /// ParseBraceInitializer - Called when parsing an initializer that has a
378 /// leading open brace.
379 ///
380 ///       initializer: [C99 6.7.8]
381 ///         '{' initializer-list '}'
382 ///         '{' initializer-list ',' '}'
383 /// [GNU]   '{' '}'
384 ///
385 ///       initializer-list:
386 ///         designation[opt] initializer ...[opt]
387 ///         initializer-list ',' designation[opt] initializer ...[opt]
388 ///
ParseBraceInitializer()389 ExprResult Parser::ParseBraceInitializer() {
390   InMessageExpressionRAIIObject InMessage(*this, false);
391 
392   BalancedDelimiterTracker T(*this, tok::l_brace);
393   T.consumeOpen();
394   SourceLocation LBraceLoc = T.getOpenLocation();
395 
396   /// InitExprs - This is the actual list of expressions contained in the
397   /// initializer.
398   ExprVector InitExprs;
399 
400   if (Tok.is(tok::r_brace)) {
401     // Empty initializers are a C++ feature and a GNU extension to C.
402     if (!getLangOpts().CPlusPlus)
403       Diag(LBraceLoc, diag::ext_gnu_empty_initializer);
404     // Match the '}'.
405     return Actions.ActOnInitList(LBraceLoc, None, ConsumeBrace());
406   }
407 
408   bool InitExprsOk = true;
409 
410   while (1) {
411     // Handle Microsoft __if_exists/if_not_exists if necessary.
412     if (getLangOpts().MicrosoftExt && (Tok.is(tok::kw___if_exists) ||
413         Tok.is(tok::kw___if_not_exists))) {
414       if (ParseMicrosoftIfExistsBraceInitializer(InitExprs, InitExprsOk)) {
415         if (Tok.isNot(tok::comma)) break;
416         ConsumeToken();
417       }
418       if (Tok.is(tok::r_brace)) break;
419       continue;
420     }
421 
422     // Parse: designation[opt] initializer
423 
424     // If we know that this cannot be a designation, just parse the nested
425     // initializer directly.
426     ExprResult SubElt;
427     if (MayBeDesignationStart())
428       SubElt = ParseInitializerWithPotentialDesignator();
429     else
430       SubElt = ParseInitializer();
431 
432     if (Tok.is(tok::ellipsis))
433       SubElt = Actions.ActOnPackExpansion(SubElt.get(), ConsumeToken());
434 
435     SubElt = Actions.CorrectDelayedTyposInExpr(SubElt.get());
436 
437     // If we couldn't parse the subelement, bail out.
438     if (SubElt.isUsable()) {
439       InitExprs.push_back(SubElt.get());
440     } else {
441       InitExprsOk = false;
442 
443       // We have two ways to try to recover from this error: if the code looks
444       // grammatically ok (i.e. we have a comma coming up) try to continue
445       // parsing the rest of the initializer.  This allows us to emit
446       // diagnostics for later elements that we find.  If we don't see a comma,
447       // assume there is a parse error, and just skip to recover.
448       // FIXME: This comment doesn't sound right. If there is a r_brace
449       // immediately, it can't be an error, since there is no other way of
450       // leaving this loop except through this if.
451       if (Tok.isNot(tok::comma)) {
452         SkipUntil(tok::r_brace, StopBeforeMatch);
453         break;
454       }
455     }
456 
457     // If we don't have a comma continued list, we're done.
458     if (Tok.isNot(tok::comma)) break;
459 
460     // TODO: save comma locations if some client cares.
461     ConsumeToken();
462 
463     // Handle trailing comma.
464     if (Tok.is(tok::r_brace)) break;
465   }
466 
467   bool closed = !T.consumeClose();
468 
469   if (InitExprsOk && closed)
470     return Actions.ActOnInitList(LBraceLoc, InitExprs,
471                                  T.getCloseLocation());
472 
473   return ExprError(); // an error occurred.
474 }
475 
476 
477 // Return true if a comma (or closing brace) is necessary after the
478 // __if_exists/if_not_exists statement.
ParseMicrosoftIfExistsBraceInitializer(ExprVector & InitExprs,bool & InitExprsOk)479 bool Parser::ParseMicrosoftIfExistsBraceInitializer(ExprVector &InitExprs,
480                                                     bool &InitExprsOk) {
481   bool trailingComma = false;
482   IfExistsCondition Result;
483   if (ParseMicrosoftIfExistsCondition(Result))
484     return false;
485 
486   BalancedDelimiterTracker Braces(*this, tok::l_brace);
487   if (Braces.consumeOpen()) {
488     Diag(Tok, diag::err_expected) << tok::l_brace;
489     return false;
490   }
491 
492   switch (Result.Behavior) {
493   case IEB_Parse:
494     // Parse the declarations below.
495     break;
496 
497   case IEB_Dependent:
498     Diag(Result.KeywordLoc, diag::warn_microsoft_dependent_exists)
499       << Result.IsIfExists;
500     // Fall through to skip.
501 
502   case IEB_Skip:
503     Braces.skipToEnd();
504     return false;
505   }
506 
507   while (!isEofOrEom()) {
508     trailingComma = false;
509     // If we know that this cannot be a designation, just parse the nested
510     // initializer directly.
511     ExprResult SubElt;
512     if (MayBeDesignationStart())
513       SubElt = ParseInitializerWithPotentialDesignator();
514     else
515       SubElt = ParseInitializer();
516 
517     if (Tok.is(tok::ellipsis))
518       SubElt = Actions.ActOnPackExpansion(SubElt.get(), ConsumeToken());
519 
520     // If we couldn't parse the subelement, bail out.
521     if (!SubElt.isInvalid())
522       InitExprs.push_back(SubElt.get());
523     else
524       InitExprsOk = false;
525 
526     if (Tok.is(tok::comma)) {
527       ConsumeToken();
528       trailingComma = true;
529     }
530 
531     if (Tok.is(tok::r_brace))
532       break;
533   }
534 
535   Braces.consumeClose();
536 
537   return !trailingComma;
538 }
539