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      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/Basic/TargetInfo.h"
     21 #include "clang/Lex/CodeCompletionHandler.h"
     22 #include "clang/Lex/LexDiagnostic.h"
     23 #include "clang/Lex/LiteralSupport.h"
     24 #include "clang/Lex/MacroInfo.h"
     25 #include "llvm/ADT/APSInt.h"
     26 #include "llvm/Support/ErrorHandling.h"
     27 #include "llvm/Support/SaveAndRestore.h"
     28 using namespace clang;
     29 
     30 namespace {
     31 
     32 /// PPValue - Represents the value of a subexpression of a preprocessor
     33 /// conditional and the source range covered by it.
     34 class PPValue {
     35   SourceRange Range;
     36 public:
     37   llvm::APSInt Val;
     38 
     39   // Default ctor - Construct an 'invalid' PPValue.
     40   PPValue(unsigned BitWidth) : Val(BitWidth) {}
     41 
     42   unsigned getBitWidth() const { return Val.getBitWidth(); }
     43   bool isUnsigned() const { return Val.isUnsigned(); }
     44 
     45   const SourceRange &getRange() const { return Range; }
     46 
     47   void setRange(SourceLocation L) { Range.setBegin(L); Range.setEnd(L); }
     48   void setRange(SourceLocation B, SourceLocation E) {
     49     Range.setBegin(B); Range.setEnd(E);
     50   }
     51   void setBegin(SourceLocation L) { Range.setBegin(L); }
     52   void setEnd(SourceLocation L) { Range.setEnd(L); }
     53 };
     54 
     55 }
     56 
     57 static bool EvaluateDirectiveSubExpr(PPValue &LHS, unsigned MinPrec,
     58                                      Token &PeekTok, bool ValueLive,
     59                                      Preprocessor &PP);
     60 
     61 /// DefinedTracker - This struct is used while parsing expressions to keep track
     62 /// of whether !defined(X) has been seen.
     63 ///
     64 /// With this simple scheme, we handle the basic forms:
     65 ///    !defined(X)   and !defined X
     66 /// but we also trivially handle (silly) stuff like:
     67 ///    !!!defined(X) and +!defined(X) and !+!+!defined(X) and !(defined(X)).
     68 struct DefinedTracker {
     69   /// Each time a Value is evaluated, it returns information about whether the
     70   /// parsed value is of the form defined(X), !defined(X) or is something else.
     71   enum TrackerState {
     72     DefinedMacro,        // defined(X)
     73     NotDefinedMacro,     // !defined(X)
     74     Unknown              // Something else.
     75   } State;
     76   /// TheMacro - When the state is DefinedMacro or NotDefinedMacro, this
     77   /// indicates the macro that was checked.
     78   IdentifierInfo *TheMacro;
     79 };
     80 
     81 /// EvaluateDefined - Process a 'defined(sym)' expression.
     82 static bool EvaluateDefined(PPValue &Result, Token &PeekTok, DefinedTracker &DT,
     83                             bool ValueLive, Preprocessor &PP) {
     84   SourceLocation beginLoc(PeekTok.getLocation());
     85   Result.setBegin(beginLoc);
     86 
     87   // Get the next token, don't expand it.
     88   PP.LexUnexpandedNonComment(PeekTok);
     89 
     90   // Two options, it can either be a pp-identifier or a (.
     91   SourceLocation LParenLoc;
     92   if (PeekTok.is(tok::l_paren)) {
     93     // Found a paren, remember we saw it and skip it.
     94     LParenLoc = PeekTok.getLocation();
     95     PP.LexUnexpandedNonComment(PeekTok);
     96   }
     97 
     98   if (PeekTok.is(tok::code_completion)) {
     99     if (PP.getCodeCompletionHandler())
    100       PP.getCodeCompletionHandler()->CodeCompleteMacroName(false);
    101     PP.setCodeCompletionReached();
    102     PP.LexUnexpandedNonComment(PeekTok);
    103   }
    104 
    105   // If we don't have a pp-identifier now, this is an error.
    106   if (PP.CheckMacroName(PeekTok, 0))
    107     return true;
    108 
    109   // Otherwise, we got an identifier, is it defined to something?
    110   IdentifierInfo *II = PeekTok.getIdentifierInfo();
    111   Result.Val = II->hasMacroDefinition();
    112   Result.Val.setIsUnsigned(false);  // Result is signed intmax_t.
    113 
    114   MacroDirective *Macro = nullptr;
    115   // If there is a macro, mark it used.
    116   if (Result.Val != 0 && ValueLive) {
    117     Macro = PP.getMacroDirective(II);
    118     PP.markMacroAsUsed(Macro->getMacroInfo());
    119   }
    120 
    121   // Save macro token for callback.
    122   Token macroToken(PeekTok);
    123 
    124   // If we are in parens, ensure we have a trailing ).
    125   if (LParenLoc.isValid()) {
    126     // Consume identifier.
    127     Result.setEnd(PeekTok.getLocation());
    128     PP.LexUnexpandedNonComment(PeekTok);
    129 
    130     if (PeekTok.isNot(tok::r_paren)) {
    131       PP.Diag(PeekTok.getLocation(), diag::err_pp_expected_after)
    132           << "'defined'" << tok::r_paren;
    133       PP.Diag(LParenLoc, diag::note_matching) << tok::l_paren;
    134       return true;
    135     }
    136     // Consume the ).
    137     Result.setEnd(PeekTok.getLocation());
    138     PP.LexNonComment(PeekTok);
    139   } else {
    140     // Consume identifier.
    141     Result.setEnd(PeekTok.getLocation());
    142     PP.LexNonComment(PeekTok);
    143   }
    144 
    145   // Invoke the 'defined' callback.
    146   if (PPCallbacks *Callbacks = PP.getPPCallbacks()) {
    147     MacroDirective *MD = Macro;
    148     // Pass the MacroInfo for the macro name even if the value is dead.
    149     if (!MD && Result.Val != 0)
    150       MD = PP.getMacroDirective(II);
    151     Callbacks->Defined(macroToken, MD,
    152                        SourceRange(beginLoc, PeekTok.getLocation()));
    153   }
    154 
    155   // Success, remember that we saw defined(X).
    156   DT.State = DefinedTracker::DefinedMacro;
    157   DT.TheMacro = II;
    158   return false;
    159 }
    160 
    161 /// EvaluateValue - Evaluate the token PeekTok (and any others needed) and
    162 /// return the computed value in Result.  Return true if there was an error
    163 /// parsing.  This function also returns information about the form of the
    164 /// expression in DT.  See above for information on what DT means.
    165 ///
    166 /// If ValueLive is false, then this value is being evaluated in a context where
    167 /// the result is not used.  As such, avoid diagnostics that relate to
    168 /// evaluation.
    169 static bool EvaluateValue(PPValue &Result, Token &PeekTok, DefinedTracker &DT,
    170                           bool ValueLive, Preprocessor &PP) {
    171   DT.State = DefinedTracker::Unknown;
    172 
    173   if (PeekTok.is(tok::code_completion)) {
    174     if (PP.getCodeCompletionHandler())
    175       PP.getCodeCompletionHandler()->CodeCompletePreprocessorExpression();
    176     PP.setCodeCompletionReached();
    177     PP.LexNonComment(PeekTok);
    178   }
    179 
    180   // If this token's spelling is a pp-identifier, check to see if it is
    181   // 'defined' or if it is a macro.  Note that we check here because many
    182   // keywords are pp-identifiers, so we can't check the kind.
    183   if (IdentifierInfo *II = PeekTok.getIdentifierInfo()) {
    184     // Handle "defined X" and "defined(X)".
    185     if (II->isStr("defined"))
    186       return(EvaluateDefined(Result, PeekTok, DT, ValueLive, PP));
    187 
    188     // If this identifier isn't 'defined' or one of the special
    189     // preprocessor keywords and it wasn't macro expanded, it turns
    190     // into a simple 0, unless it is the C++ keyword "true", in which case it
    191     // turns into "1".
    192     if (ValueLive &&
    193         II->getTokenID() != tok::kw_true &&
    194         II->getTokenID() != tok::kw_false)
    195       PP.Diag(PeekTok, diag::warn_pp_undef_identifier) << II;
    196     Result.Val = II->getTokenID() == tok::kw_true;
    197     Result.Val.setIsUnsigned(false);  // "0" is signed intmax_t 0.
    198     Result.setRange(PeekTok.getLocation());
    199     PP.LexNonComment(PeekTok);
    200     return false;
    201   }
    202 
    203   switch (PeekTok.getKind()) {
    204   default:  // Non-value token.
    205     PP.Diag(PeekTok, diag::err_pp_expr_bad_token_start_expr);
    206     return true;
    207   case tok::eod:
    208   case tok::r_paren:
    209     // If there is no expression, report and exit.
    210     PP.Diag(PeekTok, diag::err_pp_expected_value_in_expr);
    211     return true;
    212   case tok::numeric_constant: {
    213     SmallString<64> IntegerBuffer;
    214     bool NumberInvalid = false;
    215     StringRef Spelling = PP.getSpelling(PeekTok, IntegerBuffer,
    216                                               &NumberInvalid);
    217     if (NumberInvalid)
    218       return true; // a diagnostic was already reported
    219 
    220     NumericLiteralParser Literal(Spelling, PeekTok.getLocation(), PP);
    221     if (Literal.hadError)
    222       return true; // a diagnostic was already reported.
    223 
    224     if (Literal.isFloatingLiteral() || Literal.isImaginary) {
    225       PP.Diag(PeekTok, diag::err_pp_illegal_floating_literal);
    226       return true;
    227     }
    228     assert(Literal.isIntegerLiteral() && "Unknown ppnumber");
    229 
    230     // Complain about, and drop, any ud-suffix.
    231     if (Literal.hasUDSuffix())
    232       PP.Diag(PeekTok, diag::err_pp_invalid_udl) << /*integer*/1;
    233 
    234     // 'long long' is a C99 or C++11 feature.
    235     if (!PP.getLangOpts().C99 && Literal.isLongLong) {
    236       if (PP.getLangOpts().CPlusPlus)
    237         PP.Diag(PeekTok,
    238              PP.getLangOpts().CPlusPlus11 ?
    239              diag::warn_cxx98_compat_longlong : diag::ext_cxx11_longlong);
    240       else
    241         PP.Diag(PeekTok, diag::ext_c99_longlong);
    242     }
    243 
    244     // Parse the integer literal into Result.
    245     if (Literal.GetIntegerValue(Result.Val)) {
    246       // Overflow parsing integer literal.
    247       if (ValueLive) PP.Diag(PeekTok, diag::err_integer_too_large);
    248       Result.Val.setIsUnsigned(true);
    249     } else {
    250       // Set the signedness of the result to match whether there was a U suffix
    251       // or not.
    252       Result.Val.setIsUnsigned(Literal.isUnsigned);
    253 
    254       // Detect overflow based on whether the value is signed.  If signed
    255       // and if the value is too large, emit a warning "integer constant is so
    256       // large that it is unsigned" e.g. on 12345678901234567890 where intmax_t
    257       // is 64-bits.
    258       if (!Literal.isUnsigned && Result.Val.isNegative()) {
    259         // Octal, hexadecimal, and binary literals are implicitly unsigned if
    260         // the value does not fit into a signed integer type.
    261         if (ValueLive && Literal.getRadix() == 10)
    262           PP.Diag(PeekTok, diag::ext_integer_too_large_for_signed);
    263         Result.Val.setIsUnsigned(true);
    264       }
    265     }
    266 
    267     // Consume the token.
    268     Result.setRange(PeekTok.getLocation());
    269     PP.LexNonComment(PeekTok);
    270     return false;
    271   }
    272   case tok::char_constant:          // 'x'
    273   case tok::wide_char_constant:     // L'x'
    274   case tok::utf16_char_constant:    // u'x'
    275   case tok::utf32_char_constant: {  // U'x'
    276     // Complain about, and drop, any ud-suffix.
    277     if (PeekTok.hasUDSuffix())
    278       PP.Diag(PeekTok, diag::err_pp_invalid_udl) << /*character*/0;
    279 
    280     SmallString<32> CharBuffer;
    281     bool CharInvalid = false;
    282     StringRef ThisTok = PP.getSpelling(PeekTok, CharBuffer, &CharInvalid);
    283     if (CharInvalid)
    284       return true;
    285 
    286     CharLiteralParser Literal(ThisTok.begin(), ThisTok.end(),
    287                               PeekTok.getLocation(), PP, PeekTok.getKind());
    288     if (Literal.hadError())
    289       return true;  // A diagnostic was already emitted.
    290 
    291     // Character literals are always int or wchar_t, expand to intmax_t.
    292     const TargetInfo &TI = PP.getTargetInfo();
    293     unsigned NumBits;
    294     if (Literal.isMultiChar())
    295       NumBits = TI.getIntWidth();
    296     else if (Literal.isWide())
    297       NumBits = TI.getWCharWidth();
    298     else if (Literal.isUTF16())
    299       NumBits = TI.getChar16Width();
    300     else if (Literal.isUTF32())
    301       NumBits = TI.getChar32Width();
    302     else
    303       NumBits = TI.getCharWidth();
    304 
    305     // Set the width.
    306     llvm::APSInt Val(NumBits);
    307     // Set the value.
    308     Val = Literal.getValue();
    309     // Set the signedness. UTF-16 and UTF-32 are always unsigned
    310     if (!Literal.isUTF16() && !Literal.isUTF32())
    311       Val.setIsUnsigned(!PP.getLangOpts().CharIsSigned);
    312 
    313     if (Result.Val.getBitWidth() > Val.getBitWidth()) {
    314       Result.Val = Val.extend(Result.Val.getBitWidth());
    315     } else {
    316       assert(Result.Val.getBitWidth() == Val.getBitWidth() &&
    317              "intmax_t smaller than char/wchar_t?");
    318       Result.Val = Val;
    319     }
    320 
    321     // Consume the token.
    322     Result.setRange(PeekTok.getLocation());
    323     PP.LexNonComment(PeekTok);
    324     return false;
    325   }
    326   case tok::l_paren: {
    327     SourceLocation Start = PeekTok.getLocation();
    328     PP.LexNonComment(PeekTok);  // Eat the (.
    329     // Parse the value and if there are any binary operators involved, parse
    330     // them.
    331     if (EvaluateValue(Result, PeekTok, DT, ValueLive, PP)) return true;
    332 
    333     // If this is a silly value like (X), which doesn't need parens, check for
    334     // !(defined X).
    335     if (PeekTok.is(tok::r_paren)) {
    336       // Just use DT unmodified as our result.
    337     } else {
    338       // Otherwise, we have something like (x+y), and we consumed '(x'.
    339       if (EvaluateDirectiveSubExpr(Result, 1, PeekTok, ValueLive, PP))
    340         return true;
    341 
    342       if (PeekTok.isNot(tok::r_paren)) {
    343         PP.Diag(PeekTok.getLocation(), diag::err_pp_expected_rparen)
    344           << Result.getRange();
    345         PP.Diag(Start, diag::note_matching) << tok::l_paren;
    346         return true;
    347       }
    348       DT.State = DefinedTracker::Unknown;
    349     }
    350     Result.setRange(Start, PeekTok.getLocation());
    351     PP.LexNonComment(PeekTok);  // Eat the ).
    352     return false;
    353   }
    354   case tok::plus: {
    355     SourceLocation Start = PeekTok.getLocation();
    356     // Unary plus doesn't modify the value.
    357     PP.LexNonComment(PeekTok);
    358     if (EvaluateValue(Result, PeekTok, DT, ValueLive, PP)) return true;
    359     Result.setBegin(Start);
    360     return false;
    361   }
    362   case tok::minus: {
    363     SourceLocation Loc = PeekTok.getLocation();
    364     PP.LexNonComment(PeekTok);
    365     if (EvaluateValue(Result, PeekTok, DT, ValueLive, PP)) return true;
    366     Result.setBegin(Loc);
    367 
    368     // C99 6.5.3.3p3: The sign of the result matches the sign of the operand.
    369     Result.Val = -Result.Val;
    370 
    371     // -MININT is the only thing that overflows.  Unsigned never overflows.
    372     bool Overflow = !Result.isUnsigned() && Result.Val.isMinSignedValue();
    373 
    374     // If this operator is live and overflowed, report the issue.
    375     if (Overflow && ValueLive)
    376       PP.Diag(Loc, diag::warn_pp_expr_overflow) << Result.getRange();
    377 
    378     DT.State = DefinedTracker::Unknown;
    379     return false;
    380   }
    381 
    382   case tok::tilde: {
    383     SourceLocation Start = PeekTok.getLocation();
    384     PP.LexNonComment(PeekTok);
    385     if (EvaluateValue(Result, PeekTok, DT, ValueLive, PP)) return true;
    386     Result.setBegin(Start);
    387 
    388     // C99 6.5.3.3p4: The sign of the result matches the sign of the operand.
    389     Result.Val = ~Result.Val;
    390     DT.State = DefinedTracker::Unknown;
    391     return false;
    392   }
    393 
    394   case tok::exclaim: {
    395     SourceLocation Start = PeekTok.getLocation();
    396     PP.LexNonComment(PeekTok);
    397     if (EvaluateValue(Result, PeekTok, DT, ValueLive, PP)) return true;
    398     Result.setBegin(Start);
    399     Result.Val = !Result.Val;
    400     // C99 6.5.3.3p5: The sign of the result is 'int', aka it is signed.
    401     Result.Val.setIsUnsigned(false);
    402 
    403     if (DT.State == DefinedTracker::DefinedMacro)
    404       DT.State = DefinedTracker::NotDefinedMacro;
    405     else if (DT.State == DefinedTracker::NotDefinedMacro)
    406       DT.State = DefinedTracker::DefinedMacro;
    407     return false;
    408   }
    409 
    410   // FIXME: Handle #assert
    411   }
    412 }
    413 
    414 
    415 
    416 /// getPrecedence - Return the precedence of the specified binary operator
    417 /// token.  This returns:
    418 ///   ~0 - Invalid token.
    419 ///   14 -> 3 - various operators.
    420 ///    0 - 'eod' or ')'
    421 static unsigned getPrecedence(tok::TokenKind Kind) {
    422   switch (Kind) {
    423   default: return ~0U;
    424   case tok::percent:
    425   case tok::slash:
    426   case tok::star:                 return 14;
    427   case tok::plus:
    428   case tok::minus:                return 13;
    429   case tok::lessless:
    430   case tok::greatergreater:       return 12;
    431   case tok::lessequal:
    432   case tok::less:
    433   case tok::greaterequal:
    434   case tok::greater:              return 11;
    435   case tok::exclaimequal:
    436   case tok::equalequal:           return 10;
    437   case tok::amp:                  return 9;
    438   case tok::caret:                return 8;
    439   case tok::pipe:                 return 7;
    440   case tok::ampamp:               return 6;
    441   case tok::pipepipe:             return 5;
    442   case tok::question:             return 4;
    443   case tok::comma:                return 3;
    444   case tok::colon:                return 2;
    445   case tok::r_paren:              return 0;// Lowest priority, end of expr.
    446   case tok::eod:                  return 0;// Lowest priority, end of directive.
    447   }
    448 }
    449 
    450 
    451 /// EvaluateDirectiveSubExpr - Evaluate the subexpression whose first token is
    452 /// PeekTok, and whose precedence is PeekPrec.  This returns the result in LHS.
    453 ///
    454 /// If ValueLive is false, then this value is being evaluated in a context where
    455 /// the result is not used.  As such, avoid diagnostics that relate to
    456 /// evaluation, such as division by zero warnings.
    457 static bool EvaluateDirectiveSubExpr(PPValue &LHS, unsigned MinPrec,
    458                                      Token &PeekTok, bool ValueLive,
    459                                      Preprocessor &PP) {
    460   unsigned PeekPrec = getPrecedence(PeekTok.getKind());
    461   // If this token isn't valid, report the error.
    462   if (PeekPrec == ~0U) {
    463     PP.Diag(PeekTok.getLocation(), diag::err_pp_expr_bad_token_binop)
    464       << LHS.getRange();
    465     return true;
    466   }
    467 
    468   while (1) {
    469     // If this token has a lower precedence than we are allowed to parse, return
    470     // it so that higher levels of the recursion can parse it.
    471     if (PeekPrec < MinPrec)
    472       return false;
    473 
    474     tok::TokenKind Operator = PeekTok.getKind();
    475 
    476     // If this is a short-circuiting operator, see if the RHS of the operator is
    477     // dead.  Note that this cannot just clobber ValueLive.  Consider
    478     // "0 && 1 ? 4 : 1 / 0", which is parsed as "(0 && 1) ? 4 : (1 / 0)".  In
    479     // this example, the RHS of the && being dead does not make the rest of the
    480     // expr dead.
    481     bool RHSIsLive;
    482     if (Operator == tok::ampamp && LHS.Val == 0)
    483       RHSIsLive = false;   // RHS of "0 && x" is dead.
    484     else if (Operator == tok::pipepipe && LHS.Val != 0)
    485       RHSIsLive = false;   // RHS of "1 || x" is dead.
    486     else if (Operator == tok::question && LHS.Val == 0)
    487       RHSIsLive = false;   // RHS (x) of "0 ? x : y" is dead.
    488     else
    489       RHSIsLive = ValueLive;
    490 
    491     // Consume the operator, remembering the operator's location for reporting.
    492     SourceLocation OpLoc = PeekTok.getLocation();
    493     PP.LexNonComment(PeekTok);
    494 
    495     PPValue RHS(LHS.getBitWidth());
    496     // Parse the RHS of the operator.
    497     DefinedTracker DT;
    498     if (EvaluateValue(RHS, PeekTok, DT, RHSIsLive, PP)) return true;
    499 
    500     // Remember the precedence of this operator and get the precedence of the
    501     // operator immediately to the right of the RHS.
    502     unsigned ThisPrec = PeekPrec;
    503     PeekPrec = getPrecedence(PeekTok.getKind());
    504 
    505     // If this token isn't valid, report the error.
    506     if (PeekPrec == ~0U) {
    507       PP.Diag(PeekTok.getLocation(), diag::err_pp_expr_bad_token_binop)
    508         << RHS.getRange();
    509       return true;
    510     }
    511 
    512     // Decide whether to include the next binop in this subexpression.  For
    513     // example, when parsing x+y*z and looking at '*', we want to recursively
    514     // handle y*z as a single subexpression.  We do this because the precedence
    515     // of * is higher than that of +.  The only strange case we have to handle
    516     // here is for the ?: operator, where the precedence is actually lower than
    517     // the LHS of the '?'.  The grammar rule is:
    518     //
    519     // conditional-expression ::=
    520     //    logical-OR-expression ? expression : conditional-expression
    521     // where 'expression' is actually comma-expression.
    522     unsigned RHSPrec;
    523     if (Operator == tok::question)
    524       // The RHS of "?" should be maximally consumed as an expression.
    525       RHSPrec = getPrecedence(tok::comma);
    526     else  // All others should munch while higher precedence.
    527       RHSPrec = ThisPrec+1;
    528 
    529     if (PeekPrec >= RHSPrec) {
    530       if (EvaluateDirectiveSubExpr(RHS, RHSPrec, PeekTok, RHSIsLive, PP))
    531         return true;
    532       PeekPrec = getPrecedence(PeekTok.getKind());
    533     }
    534     assert(PeekPrec <= ThisPrec && "Recursion didn't work!");
    535 
    536     // Usual arithmetic conversions (C99 6.3.1.8p1): result is unsigned if
    537     // either operand is unsigned.
    538     llvm::APSInt Res(LHS.getBitWidth());
    539     switch (Operator) {
    540     case tok::question:       // No UAC for x and y in "x ? y : z".
    541     case tok::lessless:       // Shift amount doesn't UAC with shift value.
    542     case tok::greatergreater: // Shift amount doesn't UAC with shift value.
    543     case tok::comma:          // Comma operands are not subject to UACs.
    544     case tok::pipepipe:       // Logical || does not do UACs.
    545     case tok::ampamp:         // Logical && does not do UACs.
    546       break;                  // No UAC
    547     default:
    548       Res.setIsUnsigned(LHS.isUnsigned()|RHS.isUnsigned());
    549       // If this just promoted something from signed to unsigned, and if the
    550       // value was negative, warn about it.
    551       if (ValueLive && Res.isUnsigned()) {
    552         if (!LHS.isUnsigned() && LHS.Val.isNegative())
    553           PP.Diag(OpLoc, diag::warn_pp_convert_lhs_to_positive)
    554             << LHS.Val.toString(10, true) + " to " +
    555                LHS.Val.toString(10, false)
    556             << LHS.getRange() << RHS.getRange();
    557         if (!RHS.isUnsigned() && RHS.Val.isNegative())
    558           PP.Diag(OpLoc, diag::warn_pp_convert_rhs_to_positive)
    559             << RHS.Val.toString(10, true) + " to " +
    560                RHS.Val.toString(10, false)
    561             << LHS.getRange() << RHS.getRange();
    562       }
    563       LHS.Val.setIsUnsigned(Res.isUnsigned());
    564       RHS.Val.setIsUnsigned(Res.isUnsigned());
    565     }
    566 
    567     bool Overflow = false;
    568     switch (Operator) {
    569     default: llvm_unreachable("Unknown operator token!");
    570     case tok::percent:
    571       if (RHS.Val != 0)
    572         Res = LHS.Val % RHS.Val;
    573       else if (ValueLive) {
    574         PP.Diag(OpLoc, diag::err_pp_remainder_by_zero)
    575           << LHS.getRange() << RHS.getRange();
    576         return true;
    577       }
    578       break;
    579     case tok::slash:
    580       if (RHS.Val != 0) {
    581         if (LHS.Val.isSigned())
    582           Res = llvm::APSInt(LHS.Val.sdiv_ov(RHS.Val, Overflow), false);
    583         else
    584           Res = LHS.Val / RHS.Val;
    585       } else if (ValueLive) {
    586         PP.Diag(OpLoc, diag::err_pp_division_by_zero)
    587           << LHS.getRange() << RHS.getRange();
    588         return true;
    589       }
    590       break;
    591 
    592     case tok::star:
    593       if (Res.isSigned())
    594         Res = llvm::APSInt(LHS.Val.smul_ov(RHS.Val, Overflow), false);
    595       else
    596         Res = LHS.Val * RHS.Val;
    597       break;
    598     case tok::lessless: {
    599       // Determine whether overflow is about to happen.
    600       unsigned ShAmt = static_cast<unsigned>(RHS.Val.getLimitedValue());
    601       if (LHS.isUnsigned()) {
    602         Overflow = ShAmt >= LHS.Val.getBitWidth();
    603         if (Overflow)
    604           ShAmt = LHS.Val.getBitWidth()-1;
    605         Res = LHS.Val << ShAmt;
    606       } else {
    607         Res = llvm::APSInt(LHS.Val.sshl_ov(ShAmt, Overflow), false);
    608       }
    609       break;
    610     }
    611     case tok::greatergreater: {
    612       // Determine whether overflow is about to happen.
    613       unsigned ShAmt = static_cast<unsigned>(RHS.Val.getLimitedValue());
    614       if (ShAmt >= LHS.getBitWidth())
    615         Overflow = true, ShAmt = LHS.getBitWidth()-1;
    616       Res = LHS.Val >> ShAmt;
    617       break;
    618     }
    619     case tok::plus:
    620       if (LHS.isUnsigned())
    621         Res = LHS.Val + RHS.Val;
    622       else
    623         Res = llvm::APSInt(LHS.Val.sadd_ov(RHS.Val, Overflow), false);
    624       break;
    625     case tok::minus:
    626       if (LHS.isUnsigned())
    627         Res = LHS.Val - RHS.Val;
    628       else
    629         Res = llvm::APSInt(LHS.Val.ssub_ov(RHS.Val, Overflow), false);
    630       break;
    631     case tok::lessequal:
    632       Res = LHS.Val <= RHS.Val;
    633       Res.setIsUnsigned(false);  // C99 6.5.8p6, result is always int (signed)
    634       break;
    635     case tok::less:
    636       Res = LHS.Val < RHS.Val;
    637       Res.setIsUnsigned(false);  // C99 6.5.8p6, result is always int (signed)
    638       break;
    639     case tok::greaterequal:
    640       Res = LHS.Val >= RHS.Val;
    641       Res.setIsUnsigned(false);  // C99 6.5.8p6, result is always int (signed)
    642       break;
    643     case tok::greater:
    644       Res = LHS.Val > RHS.Val;
    645       Res.setIsUnsigned(false);  // C99 6.5.8p6, result is always int (signed)
    646       break;
    647     case tok::exclaimequal:
    648       Res = LHS.Val != RHS.Val;
    649       Res.setIsUnsigned(false);  // C99 6.5.9p3, result is always int (signed)
    650       break;
    651     case tok::equalequal:
    652       Res = LHS.Val == RHS.Val;
    653       Res.setIsUnsigned(false);  // C99 6.5.9p3, result is always int (signed)
    654       break;
    655     case tok::amp:
    656       Res = LHS.Val & RHS.Val;
    657       break;
    658     case tok::caret:
    659       Res = LHS.Val ^ RHS.Val;
    660       break;
    661     case tok::pipe:
    662       Res = LHS.Val | RHS.Val;
    663       break;
    664     case tok::ampamp:
    665       Res = (LHS.Val != 0 && RHS.Val != 0);
    666       Res.setIsUnsigned(false);  // C99 6.5.13p3, result is always int (signed)
    667       break;
    668     case tok::pipepipe:
    669       Res = (LHS.Val != 0 || RHS.Val != 0);
    670       Res.setIsUnsigned(false);  // C99 6.5.14p3, result is always int (signed)
    671       break;
    672     case tok::comma:
    673       // Comma is invalid in pp expressions in c89/c++ mode, but is valid in C99
    674       // if not being evaluated.
    675       if (!PP.getLangOpts().C99 || ValueLive)
    676         PP.Diag(OpLoc, diag::ext_pp_comma_expr)
    677           << LHS.getRange() << RHS.getRange();
    678       Res = RHS.Val; // LHS = LHS,RHS -> RHS.
    679       break;
    680     case tok::question: {
    681       // Parse the : part of the expression.
    682       if (PeekTok.isNot(tok::colon)) {
    683         PP.Diag(PeekTok.getLocation(), diag::err_expected)
    684             << tok::colon << LHS.getRange() << RHS.getRange();
    685         PP.Diag(OpLoc, diag::note_matching) << tok::question;
    686         return true;
    687       }
    688       // Consume the :.
    689       PP.LexNonComment(PeekTok);
    690 
    691       // Evaluate the value after the :.
    692       bool AfterColonLive = ValueLive && LHS.Val == 0;
    693       PPValue AfterColonVal(LHS.getBitWidth());
    694       DefinedTracker DT;
    695       if (EvaluateValue(AfterColonVal, PeekTok, DT, AfterColonLive, PP))
    696         return true;
    697 
    698       // Parse anything after the : with the same precedence as ?.  We allow
    699       // things of equal precedence because ?: is right associative.
    700       if (EvaluateDirectiveSubExpr(AfterColonVal, ThisPrec,
    701                                    PeekTok, AfterColonLive, PP))
    702         return true;
    703 
    704       // Now that we have the condition, the LHS and the RHS of the :, evaluate.
    705       Res = LHS.Val != 0 ? RHS.Val : AfterColonVal.Val;
    706       RHS.setEnd(AfterColonVal.getRange().getEnd());
    707 
    708       // Usual arithmetic conversions (C99 6.3.1.8p1): result is unsigned if
    709       // either operand is unsigned.
    710       Res.setIsUnsigned(RHS.isUnsigned() | AfterColonVal.isUnsigned());
    711 
    712       // Figure out the precedence of the token after the : part.
    713       PeekPrec = getPrecedence(PeekTok.getKind());
    714       break;
    715     }
    716     case tok::colon:
    717       // Don't allow :'s to float around without being part of ?: exprs.
    718       PP.Diag(OpLoc, diag::err_pp_colon_without_question)
    719         << LHS.getRange() << RHS.getRange();
    720       return true;
    721     }
    722 
    723     // If this operator is live and overflowed, report the issue.
    724     if (Overflow && ValueLive)
    725       PP.Diag(OpLoc, diag::warn_pp_expr_overflow)
    726         << LHS.getRange() << RHS.getRange();
    727 
    728     // Put the result back into 'LHS' for our next iteration.
    729     LHS.Val = Res;
    730     LHS.setEnd(RHS.getRange().getEnd());
    731   }
    732 }
    733 
    734 /// EvaluateDirectiveExpression - Evaluate an integer constant expression that
    735 /// may occur after a #if or #elif directive.  If the expression is equivalent
    736 /// to "!defined(X)" return X in IfNDefMacro.
    737 bool Preprocessor::
    738 EvaluateDirectiveExpression(IdentifierInfo *&IfNDefMacro) {
    739   SaveAndRestore<bool> PPDir(ParsingIfOrElifDirective, true);
    740   // Save the current state of 'DisableMacroExpansion' and reset it to false. If
    741   // 'DisableMacroExpansion' is true, then we must be in a macro argument list
    742   // in which case a directive is undefined behavior.  We want macros to be able
    743   // to recursively expand in order to get more gcc-list behavior, so we force
    744   // DisableMacroExpansion to false and restore it when we're done parsing the
    745   // expression.
    746   bool DisableMacroExpansionAtStartOfDirective = DisableMacroExpansion;
    747   DisableMacroExpansion = false;
    748 
    749   // Peek ahead one token.
    750   Token Tok;
    751   LexNonComment(Tok);
    752 
    753   // C99 6.10.1p3 - All expressions are evaluated as intmax_t or uintmax_t.
    754   unsigned BitWidth = getTargetInfo().getIntMaxTWidth();
    755 
    756   PPValue ResVal(BitWidth);
    757   DefinedTracker DT;
    758   if (EvaluateValue(ResVal, Tok, DT, true, *this)) {
    759     // Parse error, skip the rest of the macro line.
    760     if (Tok.isNot(tok::eod))
    761       DiscardUntilEndOfDirective();
    762 
    763     // Restore 'DisableMacroExpansion'.
    764     DisableMacroExpansion = DisableMacroExpansionAtStartOfDirective;
    765     return false;
    766   }
    767 
    768   // If we are at the end of the expression after just parsing a value, there
    769   // must be no (unparenthesized) binary operators involved, so we can exit
    770   // directly.
    771   if (Tok.is(tok::eod)) {
    772     // If the expression we parsed was of the form !defined(macro), return the
    773     // macro in IfNDefMacro.
    774     if (DT.State == DefinedTracker::NotDefinedMacro)
    775       IfNDefMacro = DT.TheMacro;
    776 
    777     // Restore 'DisableMacroExpansion'.
    778     DisableMacroExpansion = DisableMacroExpansionAtStartOfDirective;
    779     return ResVal.Val != 0;
    780   }
    781 
    782   // Otherwise, we must have a binary operator (e.g. "#if 1 < 2"), so parse the
    783   // operator and the stuff after it.
    784   if (EvaluateDirectiveSubExpr(ResVal, getPrecedence(tok::question),
    785                                Tok, true, *this)) {
    786     // Parse error, skip the rest of the macro line.
    787     if (Tok.isNot(tok::eod))
    788       DiscardUntilEndOfDirective();
    789 
    790     // Restore 'DisableMacroExpansion'.
    791     DisableMacroExpansion = DisableMacroExpansionAtStartOfDirective;
    792     return false;
    793   }
    794 
    795   // If we aren't at the tok::eod token, something bad happened, like an extra
    796   // ')' token.
    797   if (Tok.isNot(tok::eod)) {
    798     Diag(Tok, diag::err_pp_expected_eol);
    799     DiscardUntilEndOfDirective();
    800   }
    801 
    802   // Restore 'DisableMacroExpansion'.
    803   DisableMacroExpansion = DisableMacroExpansionAtStartOfDirective;
    804   return ResVal.Val != 0;
    805 }
    806