lib/Lex/PPExpressions.cpp

   1 //===--- PPExpressions.cpp - Preprocessor Expression Evaluation -----------===//
   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 the Preprocessor::EvaluateDirectiveExpression method,
  11 // which parses and evaluates integer constant expressions for #if directives.
  12 //
  13 //===----------------------------------------------------------------------===//
  14 //
  15 // FIXME: implement testing for #assert's.
  16 //
  17 //===----------------------------------------------------------------------===//
  18
  19 #include "clang/Lex/Preprocessor.h"
  20 #include "clang/Lex/MacroInfo.h"
  21 #include "clang/Lex/LiteralSupport.h"
  22 #include "clang/Lex/CodeCompletionHandler.h"
  23 #include "clang/Basic/TargetInfo.h"
  24 #include "clang/Lex/LexDiagnostic.h"
  25 #include "llvm/ADT/APSInt.h"
  26 using namespace clang;
  27
  28 namespace {
  29
  30 /// PPValue - Represents the value of a subexpression of a preprocessor
  31 /// conditional and the source range covered by it.
  32 class PPValue {
  33   SourceRange Range;
  34 public:
  35   llvm::APSInt Val;
  36
  37   // Default ctor - Construct an 'invalid' PPValue.
  38   PPValue(unsigned BitWidth) : Val(BitWidth) {}
  39
  40   unsigned getBitWidth() const { return Val.getBitWidth(); }
  41   bool isUnsigned() const { return Val.isUnsigned(); }
  42
  43   const SourceRange &getRange() const { return Range; }
  44
  45   void setRange(SourceLocation L) { Range.setBegin(L); Range.setEnd(L); }
  46   void setRange(SourceLocation B, SourceLocation E) {
  47     Range.setBegin(B); Range.setEnd(E);
  48   }
  49   void setBegin(SourceLocation L) { Range.setBegin(L); }
  50   void setEnd(SourceLocation L) { Range.setEnd(L); }
  51 };
  52
  53 }
  54
  55 static bool EvaluateDirectiveSubExpr(PPValue &LHS, unsigned MinPrec,
  56                                      Token &PeekTok, bool ValueLive,
  57                                      Preprocessor &PP);
  58
  59 /// DefinedTracker - This struct is used while parsing expressions to keep track
  60 /// of whether !defined(X) has been seen.
  61 ///
  62 /// With this simple scheme, we handle the basic forms:
  63 ///    !defined(X)   and !defined X
  64 /// but we also trivially handle (silly) stuff like:
  65 ///    !!!defined(X) and +!defined(X) and !+!+!defined(X) and !(defined(X)).
  66 struct DefinedTracker {
  67   /// Each time a Value is evaluated, it returns information about whether the
  68   /// parsed value is of the form defined(X), !defined(X) or is something else.
  69   enum TrackerState {
  70     DefinedMacro,        // defined(X)
  71     NotDefinedMacro,     // !defined(X)
  72     Unknown              // Something else.
  73   } State;
  74   /// TheMacro - When the state is DefinedMacro or NotDefinedMacro, this
  75   /// indicates the macro that was checked.
  76   IdentifierInfo *TheMacro;
  77 };
  78
  79 /// EvaluateDefined - Process a 'defined(sym)' expression.
  80 static bool EvaluateDefined(PPValue &Result, Token &PeekTok, DefinedTracker &DT,
  81                             bool ValueLive, Preprocessor &PP) {
  82   IdentifierInfo *II;
  83   Result.setBegin(PeekTok.getLocation());
  84
  85   // Get the next token, don't expand it.
  86   PP.LexUnexpandedToken(PeekTok);
  87
  88   // Two options, it can either be a pp-identifier or a (.
  89   SourceLocation LParenLoc;
  90   if (PeekTok.is(tok::l_paren)) {
  91     // Found a paren, remember we saw it and skip it.
  92     LParenLoc = PeekTok.getLocation();
  93     PP.LexUnexpandedToken(PeekTok);
  94   }
  95
  96   if (PeekTok.is(tok::code_completion)) {
  97     if (PP.getCodeCompletionHandler())
  98       PP.getCodeCompletionHandler()->CodeCompleteMacroName(false);
  99     PP.LexUnexpandedToken(PeekTok);
 100   }
 101
 102   // If we don't have a pp-identifier now, this is an error.
 103   if ((II = PeekTok.getIdentifierInfo()) == 0) {
 104     PP.Diag(PeekTok, diag::err_pp_defined_requires_identifier);
 105     return true;
 106   }
 107
 108   // Otherwise, we got an identifier, is it defined to something?
 109   Result.Val = II->hasMacroDefinition();
 110   Result.Val.setIsUnsigned(false);  // Result is signed intmax_t.
 111
 112   // If there is a macro, mark it used.
 113   if (Result.Val != 0 && ValueLive) {
 114     MacroInfo *Macro = PP.getMacroInfo(II);
 115     PP.markMacroAsUsed(Macro);
 116   }
 117
 118   // Consume identifier.
 119   Result.setEnd(PeekTok.getLocation());
 120   PP.LexUnexpandedToken(PeekTok);
 121
 122   // If we are in parens, ensure we have a trailing ).
 123   if (LParenLoc.isValid()) {
 124     if (PeekTok.isNot(tok::r_paren)) {
 125       PP.Diag(PeekTok.getLocation(), diag::err_pp_missing_rparen) << "defined";
 126       PP.Diag(LParenLoc, diag::note_matching) << "(";
 127       return true;
 128     }
 129     // Consume the ).
 130     Result.setEnd(PeekTok.getLocation());
 131     PP.LexNonComment(PeekTok);
 132   }
 133
 134   // Success, remember that we saw defined(X).
 135   DT.State = DefinedTracker::DefinedMacro;
 136   DT.TheMacro = II;
 137   return false;
 138 }
 139
 140 /// EvaluateValue - Evaluate the token PeekTok (and any others needed) and
 141 /// return the computed value in Result.  Return true if there was an error
 142 /// parsing.  This function also returns information about the form of the
 143 /// expression in DT.  See above for information on what DT means.
 144 ///
 145 /// If ValueLive is false, then this value is being evaluated in a context where
 146 /// the result is not used.  As such, avoid diagnostics that relate to
 147 /// evaluation.
 148 static bool EvaluateValue(PPValue &Result, Token &PeekTok, DefinedTracker &DT,
 149                           bool ValueLive, Preprocessor &PP) {
 150   DT.State = DefinedTracker::Unknown;
 151
 152   if (PeekTok.is(tok::code_completion)) {
 153     if (PP.getCodeCompletionHandler())
 154       PP.getCodeCompletionHandler()->CodeCompletePreprocessorExpression();
 155     PP.LexUnexpandedToken(PeekTok);
 156   }
 157
 158   // If this token's spelling is a pp-identifier, check to see if it is
 159   // 'defined' or if it is a macro.  Note that we check here because many
 160   // keywords are pp-identifiers, so we can't check the kind.
 161   if (IdentifierInfo *II = PeekTok.getIdentifierInfo()) {
 162     // Handle "defined X" and "defined(X)".
 163     if (II->isStr("defined"))
 164       return(EvaluateDefined(Result, PeekTok, DT, ValueLive, PP));
 165
 166     // If this identifier isn't 'defined' or one of the special
 167     // preprocessor keywords and it wasn't macro expanded, it turns
 168     // into a simple 0, unless it is the C++ keyword "true", in which case it
 169     // turns into "1".
 170     if (ValueLive)
 171       PP.Diag(PeekTok, diag::warn_pp_undef_identifier) << II;
 172     Result.Val = II->getTokenID() == tok::kw_true;
 173     Result.Val.setIsUnsigned(false);  // "0" is signed intmax_t 0.
 174     Result.setRange(PeekTok.getLocation());
 175     PP.LexNonComment(PeekTok);
 176     return false;
 177   }
 178
 179   switch (PeekTok.getKind()) {
 180   default:  // Non-value token.
 181     PP.Diag(PeekTok, diag::err_pp_expr_bad_token_start_expr);
 182     return true;
 183   case tok::eom:
 184   case tok::r_paren:
 185     // If there is no expression, report and exit.
 186     PP.Diag(PeekTok, diag::err_pp_expected_value_in_expr);
 187     return true;
 188   case tok::numeric_constant: {
 189     llvm::SmallString<64> IntegerBuffer;
 190     bool NumberInvalid = false;
 191     llvm::StringRef Spelling = PP.getSpelling(PeekTok, IntegerBuffer,
 192                                               &NumberInvalid);
 193     if (NumberInvalid)
 194       return true; // a diagnostic was already reported
 195
 196     NumericLiteralParser Literal(Spelling.begin(), Spelling.end(),
 197                                  PeekTok.getLocation(), PP);
 198     if (Literal.hadError)
 199       return true; // a diagnostic was already reported.
 200
 201     if (Literal.isFloatingLiteral() || Literal.isImaginary) {
 202       PP.Diag(PeekTok, diag::err_pp_illegal_floating_literal);
 203       return true;
 204     }
 205     assert(Literal.isIntegerLiteral() && "Unknown ppnumber");
 206
 207     // long long is a C99 feature.
 208     if (!PP.getLangOptions().C99 && !PP.getLangOptions().CPlusPlus0x
 209         && Literal.isLongLong)
 210       PP.Diag(PeekTok, diag::ext_longlong);
 211
 212     // Parse the integer literal into Result.
 213     if (Literal.GetIntegerValue(Result.Val)) {
 214       // Overflow parsing integer literal.
 215       if (ValueLive) PP.Diag(PeekTok, diag::warn_integer_too_large);
 216       Result.Val.setIsUnsigned(true);
 217     } else {
 218       // Set the signedness of the result to match whether there was a U suffix
 219       // or not.
 220       Result.Val.setIsUnsigned(Literal.isUnsigned);
 221
 222       // Detect overflow based on whether the value is signed.  If signed
 223       // and if the value is too large, emit a warning "integer constant is so
 224       // large that it is unsigned" e.g. on 12345678901234567890 where intmax_t
 225       // is 64-bits.
 226       if (!Literal.isUnsigned && Result.Val.isNegative()) {
 227         // Don't warn for a hex literal: 0x8000..0 shouldn't warn.
 228         if (ValueLive && Literal.getRadix() != 16)
 229           PP.Diag(PeekTok, diag::warn_integer_too_large_for_signed);
 230         Result.Val.setIsUnsigned(true);
 231       }
 232     }
 233
 234     // Consume the token.
 235     Result.setRange(PeekTok.getLocation());
 236     PP.LexNonComment(PeekTok);
 237     return false;
 238   }
 239   case tok::char_constant: {   // 'x'
 240     llvm::SmallString<32> CharBuffer;
 241     bool CharInvalid = false;
 242     llvm::StringRef ThisTok = PP.getSpelling(PeekTok, CharBuffer, &CharInvalid);
 243     if (CharInvalid)
 244       return true;
 245
 246     CharLiteralParser Literal(ThisTok.begin(), ThisTok.end(),
 247                               PeekTok.getLocation(), PP);
 248     if (Literal.hadError())
 249       return true;  // A diagnostic was already emitted.
 250
 251     // Character literals are always int or wchar_t, expand to intmax_t.
 252     const TargetInfo &TI = PP.getTargetInfo();
 253     unsigned NumBits;
 254     if (Literal.isMultiChar())
 255       NumBits = TI.getIntWidth();
 256     else if (Literal.isWide())
 257       NumBits = TI.getWCharWidth();
 258     else
 259       NumBits = TI.getCharWidth();
 260
 261     // Set the width.
 262     llvm::APSInt Val(NumBits);
 263     // Set the value.
 264     Val = Literal.getValue();
 265     // Set the signedness.
 266     Val.setIsUnsigned(!PP.getLangOptions().CharIsSigned);
 267
 268     if (Result.Val.getBitWidth() > Val.getBitWidth()) {
 269       Result.Val = Val.extend(Result.Val.getBitWidth());
 270     } else {
 271       assert(Result.Val.getBitWidth() == Val.getBitWidth() &&
 272              "intmax_t smaller than char/wchar_t?");
 273       Result.Val = Val;
 274     }
 275
 276     // Consume the token.
 277     Result.setRange(PeekTok.getLocation());
 278     PP.LexNonComment(PeekTok);
 279     return false;
 280   }
 281   case tok::l_paren: {
 282     SourceLocation Start = PeekTok.getLocation();
 283     PP.LexNonComment(PeekTok);  // Eat the (.
 284     // Parse the value and if there are any binary operators involved, parse
 285     // them.
 286     if (EvaluateValue(Result, PeekTok, DT, ValueLive, PP)) return true;
 287
 288     // If this is a silly value like (X), which doesn't need parens, check for
 289     // !(defined X).
 290     if (PeekTok.is(tok::r_paren)) {
 291       // Just use DT unmodified as our result.
 292     } else {
 293       // Otherwise, we have something like (x+y), and we consumed '(x'.
 294       if (EvaluateDirectiveSubExpr(Result, 1, PeekTok, ValueLive, PP))
 295         return true;
 296
 297       if (PeekTok.isNot(tok::r_paren)) {
 298         PP.Diag(PeekTok.getLocation(), diag::err_pp_expected_rparen)
 299           << Result.getRange();
 300         PP.Diag(Start, diag::note_matching) << "(";
 301         return true;
 302       }
 303       DT.State = DefinedTracker::Unknown;
 304     }
 305     Result.setRange(Start, PeekTok.getLocation());
 306     PP.LexNonComment(PeekTok);  // Eat the ).
 307     return false;
 308   }
 309   case tok::plus: {
 310     SourceLocation Start = PeekTok.getLocation();
 311     // Unary plus doesn't modify the value.
 312     PP.LexNonComment(PeekTok);
 313     if (EvaluateValue(Result, PeekTok, DT, ValueLive, PP)) return true;
 314     Result.setBegin(Start);
 315     return false;
 316   }
 317   case tok::minus: {
 318     SourceLocation Loc = PeekTok.getLocation();
 319     PP.LexNonComment(PeekTok);
 320     if (EvaluateValue(Result, PeekTok, DT, ValueLive, PP)) return true;
 321     Result.setBegin(Loc);
 322
 323     // C99 6.5.3.3p3: The sign of the result matches the sign of the operand.
 324     Result.Val = -Result.Val;
 325
 326     // -MININT is the only thing that overflows.  Unsigned never overflows.
 327     bool Overflow = !Result.isUnsigned() && Result.Val.isMinSignedValue();
 328
 329     // If this operator is live and overflowed, report the issue.
 330     if (Overflow && ValueLive)
 331       PP.Diag(Loc, diag::warn_pp_expr_overflow) << Result.getRange();
 332
 333     DT.State = DefinedTracker::Unknown;
 334     return false;
 335   }
 336
 337   case tok::tilde: {
 338     SourceLocation Start = PeekTok.getLocation();
 339     PP.LexNonComment(PeekTok);
 340     if (EvaluateValue(Result, PeekTok, DT, ValueLive, PP)) return true;
 341     Result.setBegin(Start);
 342
 343     // C99 6.5.3.3p4: The sign of the result matches the sign of the operand.
 344     Result.Val = ~Result.Val;
 345     DT.State = DefinedTracker::Unknown;
 346     return false;
 347   }
 348
 349   case tok::exclaim: {
 350     SourceLocation Start = PeekTok.getLocation();
 351     PP.LexNonComment(PeekTok);
 352     if (EvaluateValue(Result, PeekTok, DT, ValueLive, PP)) return true;
 353     Result.setBegin(Start);
 354     Result.Val = !Result.Val;
 355     // C99 6.5.3.3p5: The sign of the result is 'int', aka it is signed.
 356     Result.Val.setIsUnsigned(false);
 357
 358     if (DT.State == DefinedTracker::DefinedMacro)
 359       DT.State = DefinedTracker::NotDefinedMacro;
 360     else if (DT.State == DefinedTracker::NotDefinedMacro)
 361       DT.State = DefinedTracker::DefinedMacro;
 362     return false;
 363   }
 364
 365   // FIXME: Handle #assert
 366   }
 367 }
 368
 369
 370
 371 /// getPrecedence - Return the precedence of the specified binary operator
 372 /// token.  This returns:
 373 ///   ~0 - Invalid token.
 374 ///   14 -> 3 - various operators.
 375 ///    0 - 'eom' or ')'
 376 static unsigned getPrecedence(tok::TokenKind Kind) {
 377   switch (Kind) {
 378   default: return ~0U;
 379   case tok::percent:
 380   case tok::slash:
 381   case tok::star:                 return 14;
 382   case tok::plus:
 383   case tok::minus:                return 13;
 384   case tok::lessless:
 385   case tok::greatergreater:       return 12;
 386   case tok::lessequal:
 387   case tok::less:
 388   case tok::greaterequal:
 389   case tok::greater:              return 11;
 390   case tok::exclaimequal:
 391   case tok::equalequal:           return 10;
 392   case tok::amp:                  return 9;
 393   case tok::caret:                return 8;
 394   case tok::pipe:                 return 7;
 395   case tok::ampamp:               return 6;
 396   case tok::pipepipe:             return 5;
 397   case tok::question:             return 4;
 398   case tok::comma:                return 3;
 399   case tok::colon:                return 2;
 400   case tok::r_paren:              return 0;   // Lowest priority, end of expr.
 401   case tok::eom:                  return 0;   // Lowest priority, end of macro.
 402   }
 403 }
 404
 405
 406 /// EvaluateDirectiveSubExpr - Evaluate the subexpression whose first token is
 407 /// PeekTok, and whose precedence is PeekPrec.  This returns the result in LHS.
 408 ///
 409 /// If ValueLive is false, then this value is being evaluated in a context where
 410 /// the result is not used.  As such, avoid diagnostics that relate to
 411 /// evaluation, such as division by zero warnings.
 412 static bool EvaluateDirectiveSubExpr(PPValue &LHS, unsigned MinPrec,
 413                                      Token &PeekTok, bool ValueLive,
 414                                      Preprocessor &PP) {
 415   unsigned PeekPrec = getPrecedence(PeekTok.getKind());
 416   // If this token isn't valid, report the error.
 417   if (PeekPrec == ~0U) {
 418     PP.Diag(PeekTok.getLocation(), diag::err_pp_expr_bad_token_binop)
 419       << LHS.getRange();
 420     return true;
 421   }
 422
 423   while (1) {
 424     // If this token has a lower precedence than we are allowed to parse, return
 425     // it so that higher levels of the recursion can parse it.
 426     if (PeekPrec < MinPrec)
 427       return false;
 428
 429     tok::TokenKind Operator = PeekTok.getKind();
 430
 431     // If this is a short-circuiting operator, see if the RHS of the operator is
 432     // dead.  Note that this cannot just clobber ValueLive.  Consider
 433     // "0 && 1 ? 4 : 1 / 0", which is parsed as "(0 && 1) ? 4 : (1 / 0)".  In
 434     // this example, the RHS of the && being dead does not make the rest of the
 435     // expr dead.
 436     bool RHSIsLive;
 437     if (Operator == tok::ampamp && LHS.Val == 0)
 438       RHSIsLive = false;   // RHS of "0 && x" is dead.
 439     else if (Operator == tok::pipepipe && LHS.Val != 0)
 440       RHSIsLive = false;   // RHS of "1 || x" is dead.
 441     else if (Operator == tok::question && LHS.Val == 0)
 442       RHSIsLive = false;   // RHS (x) of "0 ? x : y" is dead.
 443     else
 444       RHSIsLive = ValueLive;
 445
 446     // Consume the operator, remembering the operator's location for reporting.
 447     SourceLocation OpLoc = PeekTok.getLocation();
 448     PP.LexNonComment(PeekTok);
 449
 450     PPValue RHS(LHS.getBitWidth());
 451     // Parse the RHS of the operator.
 452     DefinedTracker DT;
 453     if (EvaluateValue(RHS, PeekTok, DT, RHSIsLive, PP)) return true;
 454
 455     // Remember the precedence of this operator and get the precedence of the
 456     // operator immediately to the right of the RHS.
 457     unsigned ThisPrec = PeekPrec;
 458     PeekPrec = getPrecedence(PeekTok.getKind());
 459
 460     // If this token isn't valid, report the error.
 461     if (PeekPrec == ~0U) {
 462       PP.Diag(PeekTok.getLocation(), diag::err_pp_expr_bad_token_binop)
 463         << RHS.getRange();
 464       return true;
 465     }
 466
 467     // Decide whether to include the next binop in this subexpression.  For
 468     // example, when parsing x+y*z and looking at '*', we want to recursively
 469     // handle y*z as a single subexpression.  We do this because the precedence
 470     // of * is higher than that of +.  The only strange case we have to handle
 471     // here is for the ?: operator, where the precedence is actually lower than
 472     // the LHS of the '?'.  The grammar rule is:
 473     //
 474     // conditional-expression ::=
 475     //    logical-OR-expression ? expression : conditional-expression
 476     // where 'expression' is actually comma-expression.
 477     unsigned RHSPrec;
 478     if (Operator == tok::question)
 479       // The RHS of "?" should be maximally consumed as an expression.
 480       RHSPrec = getPrecedence(tok::comma);
 481     else  // All others should munch while higher precedence.
 482       RHSPrec = ThisPrec+1;
 483
 484     if (PeekPrec >= RHSPrec) {
 485       if (EvaluateDirectiveSubExpr(RHS, RHSPrec, PeekTok, RHSIsLive, PP))
 486         return true;
 487       PeekPrec = getPrecedence(PeekTok.getKind());
 488     }
 489     assert(PeekPrec <= ThisPrec && "Recursion didn't work!");
 490
 491     // Usual arithmetic conversions (C99 6.3.1.8p1): result is unsigned if
 492     // either operand is unsigned.
 493     llvm::APSInt Res(LHS.getBitWidth());
 494     switch (Operator) {
 495     case tok::question:       // No UAC for x and y in "x ? y : z".
 496     case tok::lessless:       // Shift amount doesn't UAC with shift value.
 497     case tok::greatergreater: // Shift amount doesn't UAC with shift value.
 498     case tok::comma:          // Comma operands are not subject to UACs.
 499     case tok::pipepipe:       // Logical || does not do UACs.
 500     case tok::ampamp:         // Logical && does not do UACs.
 501       break;                  // No UAC
 502     default:
 503       Res.setIsUnsigned(LHS.isUnsigned()|RHS.isUnsigned());
 504       // If this just promoted something from signed to unsigned, and if the
 505       // value was negative, warn about it.
 506       if (ValueLive && Res.isUnsigned()) {
 507         if (!LHS.isUnsigned() && LHS.Val.isNegative())
 508           PP.Diag(OpLoc, diag::warn_pp_convert_lhs_to_positive)
 509             << LHS.Val.toString(10, true) + " to " +
 510                LHS.Val.toString(10, false)
 511             << LHS.getRange() << RHS.getRange();
 512         if (!RHS.isUnsigned() && RHS.Val.isNegative())
 513           PP.Diag(OpLoc, diag::warn_pp_convert_rhs_to_positive)
 514             << RHS.Val.toString(10, true) + " to " +
 515                RHS.Val.toString(10, false)
 516             << LHS.getRange() << RHS.getRange();
 517       }
 518       LHS.Val.setIsUnsigned(Res.isUnsigned());
 519       RHS.Val.setIsUnsigned(Res.isUnsigned());
 520     }
 521
 522     bool Overflow = false;
 523     switch (Operator) {
 524     default: assert(0 && "Unknown operator token!");
 525     case tok::percent:
 526       if (RHS.Val != 0)
 527         Res = LHS.Val % RHS.Val;
 528       else if (ValueLive) {
 529         PP.Diag(OpLoc, diag::err_pp_remainder_by_zero)
 530           << LHS.getRange() << RHS.getRange();
 531         return true;
 532       }
 533       break;
 534     case tok::slash:
 535       if (RHS.Val != 0) {
 536         if (LHS.Val.isSigned())
 537           Res = llvm::APSInt(LHS.Val.sdiv_ov(RHS.Val, Overflow), false);
 538         else
 539           Res = LHS.Val / RHS.Val;
 540       } else if (ValueLive) {
 541         PP.Diag(OpLoc, diag::err_pp_division_by_zero)
 542           << LHS.getRange() << RHS.getRange();
 543         return true;
 544       }
 545       break;
 546
 547     case tok::star:
 548       if (Res.isSigned())
 549         Res = llvm::APSInt(LHS.Val.smul_ov(RHS.Val, Overflow), false);
 550       else
 551         Res = LHS.Val * RHS.Val;
 552       break;
 553     case tok::lessless: {
 554       // Determine whether overflow is about to happen.
 555       unsigned ShAmt = static_cast<unsigned>(RHS.Val.getLimitedValue());
 556       if (LHS.isUnsigned()) {
 557         Overflow = ShAmt >= LHS.Val.getBitWidth();
 558         if (Overflow)
 559           ShAmt = LHS.Val.getBitWidth()-1;
 560         Res = LHS.Val << ShAmt;
 561       } else {
 562         Res = llvm::APSInt(LHS.Val.sshl_ov(ShAmt, Overflow), false);
 563       }
 564       break;
 565     }
 566     case tok::greatergreater: {
 567       // Determine whether overflow is about to happen.
 568       unsigned ShAmt = static_cast<unsigned>(RHS.Val.getLimitedValue());
 569       if (ShAmt >= LHS.getBitWidth())
 570         Overflow = true, ShAmt = LHS.getBitWidth()-1;
 571       Res = LHS.Val >> ShAmt;
 572       break;
 573     }
 574     case tok::plus:
 575       if (LHS.isUnsigned())
 576         Res = LHS.Val + RHS.Val;
 577       else
 578         Res = llvm::APSInt(LHS.Val.sadd_ov(RHS.Val, Overflow), false);
 579       break;
 580     case tok::minus:
 581       if (LHS.isUnsigned())
 582         Res = LHS.Val - RHS.Val;
 583       else
 584         Res = llvm::APSInt(LHS.Val.ssub_ov(RHS.Val, Overflow), false);
 585       break;
 586     case tok::lessequal:
 587       Res = LHS.Val <= RHS.Val;
 588       Res.setIsUnsigned(false);  // C99 6.5.8p6, result is always int (signed)
 589       break;
 590     case tok::less:
 591       Res = LHS.Val < RHS.Val;
 592       Res.setIsUnsigned(false);  // C99 6.5.8p6, result is always int (signed)
 593       break;
 594     case tok::greaterequal:
 595       Res = LHS.Val >= RHS.Val;
 596       Res.setIsUnsigned(false);  // C99 6.5.8p6, result is always int (signed)
 597       break;
 598     case tok::greater:
 599       Res = LHS.Val > RHS.Val;
 600       Res.setIsUnsigned(false);  // C99 6.5.8p6, result is always int (signed)
 601       break;
 602     case tok::exclaimequal:
 603       Res = LHS.Val != RHS.Val;
 604       Res.setIsUnsigned(false);  // C99 6.5.9p3, result is always int (signed)
 605       break;
 606     case tok::equalequal:
 607       Res = LHS.Val == RHS.Val;
 608       Res.setIsUnsigned(false);  // C99 6.5.9p3, result is always int (signed)
 609       break;
 610     case tok::amp:
 611       Res = LHS.Val & RHS.Val;
 612       break;
 613     case tok::caret:
 614       Res = LHS.Val ^ RHS.Val;
 615       break;
 616     case tok::pipe:
 617       Res = LHS.Val | RHS.Val;
 618       break;
 619     case tok::ampamp:
 620       Res = (LHS.Val != 0 && RHS.Val != 0);
 621       Res.setIsUnsigned(false);  // C99 6.5.13p3, result is always int (signed)
 622       break;
 623     case tok::pipepipe:
 624       Res = (LHS.Val != 0 || RHS.Val != 0);
 625       Res.setIsUnsigned(false);  // C99 6.5.14p3, result is always int (signed)
 626       break;
 627     case tok::comma:
 628       // Comma is invalid in pp expressions in c89/c++ mode, but is valid in C99
 629       // if not being evaluated.
 630       if (!PP.getLangOptions().C99 || ValueLive)
 631         PP.Diag(OpLoc, diag::ext_pp_comma_expr)
 632           << LHS.getRange() << RHS.getRange();
 633       Res = RHS.Val; // LHS = LHS,RHS -> RHS.
 634       break;
 635     case tok::question: {
 636       // Parse the : part of the expression.
 637       if (PeekTok.isNot(tok::colon)) {
 638         PP.Diag(PeekTok.getLocation(), diag::err_expected_colon)
 639           << LHS.getRange(), RHS.getRange();
 640         PP.Diag(OpLoc, diag::note_matching) << "?";
 641         return true;
 642       }
 643       // Consume the :.
 644       PP.LexNonComment(PeekTok);
 645
 646       // Evaluate the value after the :.
 647       bool AfterColonLive = ValueLive && LHS.Val == 0;
 648       PPValue AfterColonVal(LHS.getBitWidth());
 649       DefinedTracker DT;
 650       if (EvaluateValue(AfterColonVal, PeekTok, DT, AfterColonLive, PP))
 651         return true;
 652
 653       // Parse anything after the : with the same precedence as ?.  We allow
 654       // things of equal precedence because ?: is right associative.
 655       if (EvaluateDirectiveSubExpr(AfterColonVal, ThisPrec,
 656                                    PeekTok, AfterColonLive, PP))
 657         return true;
 658
 659       // Now that we have the condition, the LHS and the RHS of the :, evaluate.
 660       Res = LHS.Val != 0 ? RHS.Val : AfterColonVal.Val;
 661       RHS.setEnd(AfterColonVal.getRange().getEnd());
 662
 663       // Usual arithmetic conversions (C99 6.3.1.8p1): result is unsigned if
 664       // either operand is unsigned.
 665       Res.setIsUnsigned(RHS.isUnsigned() | AfterColonVal.isUnsigned());
 666
 667       // Figure out the precedence of the token after the : part.
 668       PeekPrec = getPrecedence(PeekTok.getKind());
 669       break;
 670     }
 671     case tok::colon:
 672       // Don't allow :'s to float around without being part of ?: exprs.
 673       PP.Diag(OpLoc, diag::err_pp_colon_without_question)
 674         << LHS.getRange() << RHS.getRange();
 675       return true;
 676     }
 677
 678     // If this operator is live and overflowed, report the issue.
 679     if (Overflow && ValueLive)
 680       PP.Diag(OpLoc, diag::warn_pp_expr_overflow)
 681         << LHS.getRange() << RHS.getRange();
 682
 683     // Put the result back into 'LHS' for our next iteration.
 684     LHS.Val = Res;
 685     LHS.setEnd(RHS.getRange().getEnd());
 686   }
 687
 688   return false;
 689 }
 690
 691 /// EvaluateDirectiveExpression - Evaluate an integer constant expression that
 692 /// may occur after a #if or #elif directive.  If the expression is equivalent
 693 /// to "!defined(X)" return X in IfNDefMacro.
 694 bool Preprocessor::
 695 EvaluateDirectiveExpression(IdentifierInfo *&IfNDefMacro) {
 696   // Save the current state of 'DisableMacroExpansion' and reset it to false. If
 697   // 'DisableMacroExpansion' is true, then we must be in a macro argument list
 698   // in which case a directive is undefined behavior.  We want macros to be able
 699   // to recursively expand in order to get more gcc-list behavior, so we force
 700   // DisableMacroExpansion to false and restore it when we're done parsing the
 701   // expression.
 702   bool DisableMacroExpansionAtStartOfDirective = DisableMacroExpansion;
 703   DisableMacroExpansion = false;
 704
 705   // Peek ahead one token.
 706   Token Tok;
 707   Lex(Tok);
 708
 709   // C99 6.10.1p3 - All expressions are evaluated as intmax_t or uintmax_t.
 710   unsigned BitWidth = getTargetInfo().getIntMaxTWidth();
 711
 712   PPValue ResVal(BitWidth);
 713   DefinedTracker DT;
 714   if (EvaluateValue(ResVal, Tok, DT, true, *this)) {
 715     // Parse error, skip the rest of the macro line.
 716     if (Tok.isNot(tok::eom))
 717       DiscardUntilEndOfDirective();
 718
 719     // Restore 'DisableMacroExpansion'.
 720     DisableMacroExpansion = DisableMacroExpansionAtStartOfDirective;
 721     return false;
 722   }
 723
 724   // If we are at the end of the expression after just parsing a value, there
 725   // must be no (unparenthesized) binary operators involved, so we can exit
 726   // directly.
 727   if (Tok.is(tok::eom)) {
 728     // If the expression we parsed was of the form !defined(macro), return the
 729     // macro in IfNDefMacro.
 730     if (DT.State == DefinedTracker::NotDefinedMacro)
 731       IfNDefMacro = DT.TheMacro;
 732
 733     // Restore 'DisableMacroExpansion'.
 734     DisableMacroExpansion = DisableMacroExpansionAtStartOfDirective;
 735     return ResVal.Val != 0;
 736   }
 737
 738   // Otherwise, we must have a binary operator (e.g. "#if 1 < 2"), so parse the
 739   // operator and the stuff after it.
 740   if (EvaluateDirectiveSubExpr(ResVal, getPrecedence(tok::question),
 741                                Tok, true, *this)) {
 742     // Parse error, skip the rest of the macro line.
 743     if (Tok.isNot(tok::eom))
 744       DiscardUntilEndOfDirective();
 745
 746     // Restore 'DisableMacroExpansion'.
 747     DisableMacroExpansion = DisableMacroExpansionAtStartOfDirective;
 748     return false;
 749   }
 750
 751   // If we aren't at the tok::eom token, something bad happened, like an extra
 752   // ')' token.
 753   if (Tok.isNot(tok::eom)) {
 754     Diag(Tok, diag::err_pp_expected_eol);
 755     DiscardUntilEndOfDirective();
 756   }
 757
 758   // Restore 'DisableMacroExpansion'.
 759   DisableMacroExpansion = DisableMacroExpansionAtStartOfDirective;
 760   return ResVal.Val != 0;
 761 }
 762