lib/Parse/ParseInit.cpp

   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