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/Designator.h"
15 #include "clang/Parse/Parser.h"
16 #include "clang/Parse/ParseDiagnostic.h"
17 #include "llvm/ADT/SmallString.h"
18 using namespace clang;
19 
20 
21 /// MayBeDesignationStart - Return true if this token might be the start of a
22 /// designator.  If we can tell it is impossible that it is a designator, return
23 /// false.
24 static bool MayBeDesignationStart(tok::TokenKind K, Preprocessor &PP) {
25   switch (K) {
26   default: return false;
27   case tok::period:      // designator: '.' identifier
28   case tok::l_square:    // designator: array-designator
29       return true;
30   case tok::identifier:  // designation: identifier ':'
31     return PP.LookAhead(0).is(tok::colon);
32   }
33 }
34 
35 /// ParseInitializerWithPotentialDesignator - Parse the 'initializer' production
36 /// checking to see if the token stream starts with a designator.
37 ///
38 ///       designation:
39 ///         designator-list '='
40 /// [GNU]   array-designator
41 /// [GNU]   identifier ':'
42 ///
43 ///       designator-list:
44 ///         designator
45 ///         designator-list designator
46 ///
47 ///       designator:
48 ///         array-designator
49 ///         '.' identifier
50 ///
51 ///       array-designator:
52 ///         '[' constant-expression ']'
53 /// [GNU]   '[' constant-expression '...' constant-expression ']'
54 ///
55 /// NOTE: [OBC] allows '[ objc-receiver objc-message-args ]' as an
56 /// initializer (because it is an expression).  We need to consider this case
57 /// when parsing array designators.
58 ///
59 Parser::OwningExprResult Parser::ParseInitializerWithPotentialDesignator() {
60 
61   // If this is the old-style GNU extension:
62   //   designation ::= identifier ':'
63   // Handle it as a field designator.  Otherwise, this must be the start of a
64   // normal expression.
65   if (Tok.is(tok::identifier)) {
66     const IdentifierInfo *FieldName = Tok.getIdentifierInfo();
67 
68     std::string NewSyntax(".");
69     NewSyntax += FieldName->getName();
70     NewSyntax += " = ";
71 
72     SourceLocation NameLoc = ConsumeToken(); // Eat the identifier.
73 
74     assert(Tok.is(tok::colon) && "MayBeDesignationStart not working properly!");
75     SourceLocation ColonLoc = ConsumeToken();
76 
77     Diag(Tok, diag::ext_gnu_old_style_field_designator)
78       << CodeModificationHint::CreateReplacement(SourceRange(NameLoc,
79                                                              ColonLoc),
80                                                  NewSyntax);
81 
82     Designation D;
83     D.AddDesignator(Designator::getField(FieldName, SourceLocation(), NameLoc));
84     return Actions.ActOnDesignatedInitializer(D, ColonLoc, true,
85                                               ParseInitializer());
86   }
87 
88   // Desig - This is initialized when we see our first designator.  We may have
89   // an objc message send with no designator, so we don't want to create this
90   // eagerly.
91   Designation Desig;
92 
93   // Parse each designator in the designator list until we find an initializer.
94   while (Tok.is(tok::period) || Tok.is(tok::l_square)) {
95     if (Tok.is(tok::period)) {
96       // designator: '.' identifier
97       SourceLocation DotLoc = ConsumeToken();
98 
99       if (Tok.isNot(tok::identifier)) {
100         Diag(Tok.getLocation(), diag::err_expected_field_designator);
101         return ExprError();
102       }
103 
104       Desig.AddDesignator(Designator::getField(Tok.getIdentifierInfo(), DotLoc,
105                                                Tok.getLocation()));
106       ConsumeToken(); // Eat the identifier.
107       continue;
108     }
109 
110     // We must have either an array designator now or an objc message send.
111     assert(Tok.is(tok::l_square) && "Unexpected token!");
112 
113     // Handle the two forms of array designator:
114     //   array-designator: '[' constant-expression ']'
115     //   array-designator: '[' constant-expression '...' constant-expression ']'
116     //
117     // Also, we have to handle the case where the expression after the
118     // designator an an objc message send: '[' objc-message-expr ']'.
119     // Interesting cases are:
120     //   [foo bar]         -> objc message send
121     //   [foo]             -> array designator
122     //   [foo ... bar]     -> array designator
123     //   [4][foo bar]      -> obsolete GNU designation with objc message send.
124     //
125     SourceLocation StartLoc = ConsumeBracket();
126 
127     // If Objective-C is enabled and this is a typename or other identifier
128     // receiver, parse this as a message send expression.
129     if (getLang().ObjC1 && isTokObjCMessageIdentifierReceiver()) {
130       // If we have exactly one array designator, this used the GNU
131       // 'designation: array-designator' extension, otherwise there should be no
132       // designators at all!
133       if (Desig.getNumDesignators() == 1 &&
134           (Desig.getDesignator(0).isArrayDesignator() ||
135            Desig.getDesignator(0).isArrayRangeDesignator()))
136         Diag(StartLoc, diag::ext_gnu_missing_equal_designator);
137       else if (Desig.getNumDesignators() > 0)
138         Diag(Tok, diag::err_expected_equal_designator);
139 
140       IdentifierInfo *Name = Tok.getIdentifierInfo();
141       SourceLocation NameLoc = ConsumeToken();
142       return ParseAssignmentExprWithObjCMessageExprStart(
143                        StartLoc, NameLoc, Name, ExprArg(Actions));
144     }
145 
146     // Note that we parse this as an assignment expression, not a constant
147     // expression (allowing *=, =, etc) to handle the objc case.  Sema needs
148     // to validate that the expression is a constant.
149     OwningExprResult Idx(ParseAssignmentExpression());
150     if (Idx.isInvalid()) {
151       SkipUntil(tok::r_square);
152       return move(Idx);
153     }
154 
155     // Given an expression, we could either have a designator (if the next
156     // tokens are '...' or ']' or an objc message send.  If this is an objc
157     // message send, handle it now.  An objc-message send is the start of
158     // an assignment-expression production.
159     if (getLang().ObjC1 && Tok.isNot(tok::ellipsis) &&
160         Tok.isNot(tok::r_square)) {
161 
162       // If we have exactly one array designator, this used the GNU
163       // 'designation: array-designator' extension, otherwise there should be no
164       // designators at all!
165       if (Desig.getNumDesignators() == 1 &&
166           (Desig.getDesignator(0).isArrayDesignator() ||
167            Desig.getDesignator(0).isArrayRangeDesignator()))
168         Diag(StartLoc, diag::ext_gnu_missing_equal_designator);
169       else if (Desig.getNumDesignators() > 0)
170         Diag(Tok, diag::err_expected_equal_designator);
171 
172       return ParseAssignmentExprWithObjCMessageExprStart(StartLoc,
173                                                          SourceLocation(),
174                                                          0, move(Idx));
175     }
176 
177     // If this is a normal array designator, remember it.
178     if (Tok.isNot(tok::ellipsis)) {
179       Desig.AddDesignator(Designator::getArray(Idx.release(), StartLoc));
180     } else {
181       // Handle the gnu array range extension.
182       Diag(Tok, diag::ext_gnu_array_range);
183       SourceLocation EllipsisLoc = ConsumeToken();
184 
185       OwningExprResult RHS(ParseConstantExpression());
186       if (RHS.isInvalid()) {
187         SkipUntil(tok::r_square);
188         return move(RHS);
189       }
190       Desig.AddDesignator(Designator::getArrayRange(Idx.release(),
191                                                     RHS.release(),
192                                                     StartLoc, EllipsisLoc));
193     }
194 
195     SourceLocation EndLoc = MatchRHSPunctuation(tok::r_square, StartLoc);
196     Desig.getDesignator(Desig.getNumDesignators() - 1).setRBracketLoc(EndLoc);
197   }
198 
199   // Okay, we're done with the designator sequence.  We know that there must be
200   // at least one designator, because the only case we can get into this method
201   // without a designator is when we have an objc message send.  That case is
202   // handled and returned from above.
203   assert(!Desig.empty() && "Designator is empty?");
204 
205   // Handle a normal designator sequence end, which is an equal.
206   if (Tok.is(tok::equal)) {
207     SourceLocation EqualLoc = ConsumeToken();
208     return Actions.ActOnDesignatedInitializer(Desig, EqualLoc, false,
209                                               ParseInitializer());
210   }
211 
212   // We read some number of designators and found something that isn't an = or
213   // an initializer.  If we have exactly one array designator, this
214   // is the GNU 'designation: array-designator' extension.  Otherwise, it is a
215   // parse error.
216   if (Desig.getNumDesignators() == 1 &&
217       (Desig.getDesignator(0).isArrayDesignator() ||
218        Desig.getDesignator(0).isArrayRangeDesignator())) {
219     Diag(Tok, diag::ext_gnu_missing_equal_designator)
220       << CodeModificationHint::CreateInsertion(Tok.getLocation(), "= ");
221     return Actions.ActOnDesignatedInitializer(Desig, Tok.getLocation(),
222                                               true, ParseInitializer());
223   }
224 
225   Diag(Tok, diag::err_expected_equal_designator);
226   return ExprError();
227 }
228 
229 
230 /// ParseBraceInitializer - Called when parsing an initializer that has a
231 /// leading open brace.
232 ///
233 ///       initializer: [C99 6.7.8]
234 ///         '{' initializer-list '}'
235 ///         '{' initializer-list ',' '}'
236 /// [GNU]   '{' '}'
237 ///
238 ///       initializer-list:
239 ///         designation[opt] initializer
240 ///         initializer-list ',' designation[opt] initializer
241 ///
242 Parser::OwningExprResult Parser::ParseBraceInitializer() {
243   SourceLocation LBraceLoc = ConsumeBrace();
244 
245   /// InitExprs - This is the actual list of expressions contained in the
246   /// initializer.
247   ExprVector InitExprs(Actions);
248 
249   if (Tok.is(tok::r_brace)) {
250     // Empty initializers are a C++ feature and a GNU extension to C.
251     if (!getLang().CPlusPlus)
252       Diag(LBraceLoc, diag::ext_gnu_empty_initializer);
253     // Match the '}'.
254     return Actions.ActOnInitList(LBraceLoc, Action::MultiExprArg(Actions),
255                                  ConsumeBrace());
256   }
257 
258   bool InitExprsOk = true;
259 
260   while (1) {
261     // Parse: designation[opt] initializer
262 
263     // If we know that this cannot be a designation, just parse the nested
264     // initializer directly.
265     OwningExprResult SubElt(Actions);
266     if (MayBeDesignationStart(Tok.getKind(), PP))
267       SubElt = ParseInitializerWithPotentialDesignator();
268     else
269       SubElt = ParseInitializer();
270 
271     // If we couldn't parse the subelement, bail out.
272     if (!SubElt.isInvalid()) {
273       InitExprs.push_back(SubElt.release());
274     } else {
275       InitExprsOk = false;
276 
277       // We have two ways to try to recover from this error: if the code looks
278       // gramatically ok (i.e. we have a comma coming up) try to continue
279       // parsing the rest of the initializer.  This allows us to emit
280       // diagnostics for later elements that we find.  If we don't see a comma,
281       // assume there is a parse error, and just skip to recover.
282       // FIXME: This comment doesn't sound right. If there is a r_brace
283       // immediately, it can't be an error, since there is no other way of
284       // leaving this loop except through this if.
285       if (Tok.isNot(tok::comma)) {
286         SkipUntil(tok::r_brace, false, true);
287         break;
288       }
289     }
290 
291     // If we don't have a comma continued list, we're done.
292     if (Tok.isNot(tok::comma)) break;
293 
294     // TODO: save comma locations if some client cares.
295     ConsumeToken();
296 
297     // Handle trailing comma.
298     if (Tok.is(tok::r_brace)) break;
299   }
300   if (InitExprsOk && Tok.is(tok::r_brace))
301     return Actions.ActOnInitList(LBraceLoc, move_arg(InitExprs),
302                                  ConsumeBrace());
303 
304   // Match the '}'.
305   MatchRHSPunctuation(tok::r_brace, LBraceLoc);
306   return ExprError(); // an error occurred.
307 }
308 
309