//===--- PPExpressions.cpp - Preprocessor Expression Evaluation -----------===//

//

// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.

// See https://llvm.org/LICENSE.txt for license information.

// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception

//

//===----------------------------------------------------------------------===//

//

// This file implements the Preprocessor::EvaluateDirectiveExpression method,

// which parses and evaluates integer constant expressions for #if directives.

//

//===----------------------------------------------------------------------===//

//

// FIXME: implement testing for #assert's.

//

//===----------------------------------------------------------------------===//

#include "clang/Basic/IdentifierTable.h"

#include "clang/Basic/SourceLocation.h"

#include "clang/Basic/SourceManager.h"

#include "clang/Basic/TargetInfo.h"

#include "clang/Basic/TokenKinds.h"

#include "clang/Lex/CodeCompletionHandler.h"

#include "clang/Lex/LexDiagnostic.h"

#include "clang/Lex/LiteralSupport.h"

#include "clang/Lex/MacroInfo.h"

#include "clang/Lex/PPCallbacks.h"

#include "clang/Lex/Preprocessor.h"

#include "clang/Lex/Token.h"

#include "llvm/ADT/APSInt.h"

#include "llvm/ADT/STLExtras.h"

#include "llvm/ADT/SmallString.h"

#include "llvm/ADT/StringExtras.h"

#include "llvm/ADT/StringRef.h"

#include "llvm/Support/ErrorHandling.h"

#include "llvm/Support/SaveAndRestore.h"

#include <cassert>

using namespace clang;

namespace {

/// PPValue - Represents the value of a subexpression of a preprocessor

/// conditional and the source range covered by it.

class PPValue {

  SourceRange Range;

  IdentifierInfo *II = nullptr;

public:

  llvm::APSInt Val;

  // Default ctor - Construct an 'invalid' PPValue.

  PPValue(unsigned BitWidth) : Val(BitWidth) {}

  // If this value was produced by directly evaluating an identifier, produce

  // that identifier.

  IdentifierInfo *getIdentifier() const { return II; }

  void setIdentifier(IdentifierInfo *II) { this->II = II; }

  unsigned getBitWidth() const { return Val.getBitWidth(); }

  bool isUnsigned() const { return Val.isUnsigned(); }

  SourceRange getRange() const { return Range; }

  void setRange(SourceLocation L) { Range.setBegin(L); Range.setEnd(L); }

  void setRange(SourceLocation B, SourceLocation E) {

    Range.setBegin(B); Range.setEnd(E);

  }

  void setBegin(SourceLocation L) { Range.setBegin(L); }

  void setEnd(SourceLocation L) { Range.setEnd(L); }

};

} // end anonymous namespace

static bool EvaluateDirectiveSubExpr(PPValue &LHS, unsigned MinPrec,

                                     Token &PeekTok, bool ValueLive,

                                     bool &IncludedUndefinedIds,

                                     Preprocessor &PP);

/// DefinedTracker - This struct is used while parsing expressions to keep track

/// of whether !defined(X) has been seen.

///

/// With this simple scheme, we handle the basic forms:

///    !defined(X)   and !defined X

/// but we also trivially handle (silly) stuff like:

///    !!!defined(X) and +!defined(X) and !+!+!defined(X) and !(defined(X)).

struct DefinedTracker {

  /// Each time a Value is evaluated, it returns information about whether the

  /// parsed value is of the form defined(X), !defined(X) or is something else.

  enum TrackerState {

    DefinedMacro,        // defined(X)

    NotDefinedMacro,     // !defined(X)

    Unknown              // Something else.

  } State;

  /// TheMacro - When the state is DefinedMacro or NotDefinedMacro, this

  /// indicates the macro that was checked.

  IdentifierInfo *TheMacro;

  bool IncludedUndefinedIds = false;

};

/// EvaluateDefined - Process a 'defined(sym)' expression.

static bool EvaluateDefined(PPValue &Result, Token &PeekTok, DefinedTracker &DT,

                            bool ValueLive, Preprocessor &PP) {

  SourceLocation beginLoc(PeekTok.getLocation());

  Result.setBegin(beginLoc);

  // Get the next token, don't expand it.

  PP.LexUnexpandedNonComment(PeekTok);

  // Two options, it can either be a pp-identifier or a (.

  SourceLocation LParenLoc;

  if (PeekTok.is(tok::l_paren)) {

    // Found a paren, remember we saw it and skip it.

    LParenLoc = PeekTok.getLocation();

    PP.LexUnexpandedNonComment(PeekTok);

  }

  if (PeekTok.is(tok::code_completion)) {

    if (PP.getCodeCompletionHandler())

      PP.getCodeCompletionHandler()->CodeCompleteMacroName(false);

    PP.setCodeCompletionReached();

    PP.LexUnexpandedNonComment(PeekTok);

  }

  // If we don't have a pp-identifier now, this is an error.

  if (PP.CheckMacroName(PeekTok, MU_Other))

    return true;

  // Otherwise, we got an identifier, is it defined to something?

  IdentifierInfo *II = PeekTok.getIdentifierInfo();

  MacroDefinition Macro = PP.getMacroDefinition(II);

  Result.Val = !!Macro;

  Result.Val.setIsUnsigned(false); // Result is signed intmax_t.

  DT.IncludedUndefinedIds = !Macro;

  PP.emitMacroExpansionWarnings(PeekTok);

  // If there is a macro, mark it used.

  if (Result.Val != 0 && ValueLive)

    PP.markMacroAsUsed(Macro.getMacroInfo());

  // Save macro token for callback.

  Token macroToken(PeekTok);

  // If we are in parens, ensure we have a trailing ).

  if (LParenLoc.isValid()) {

    // Consume identifier.

    Result.setEnd(PeekTok.getLocation());

    PP.LexUnexpandedNonComment(PeekTok);

    if (PeekTok.isNot(tok::r_paren)) {

      PP.Diag(PeekTok.getLocation(), diag::err_pp_expected_after)

          << "'defined'" << tok::r_paren;

      PP.Diag(LParenLoc, diag::note_matching) << tok::l_paren;

      return true;

    }

    // Consume the ).

    PP.LexNonComment(PeekTok);

    Result.setEnd(PeekTok.getLocation());

  } else {

    // Consume identifier.

    Result.setEnd(PeekTok.getLocation());

    PP.LexNonComment(PeekTok);

  }

  // [cpp.cond]p4:

  //   Prior to evaluation, macro invocations in the list of preprocessing

  //   tokens that will become the controlling constant expression are replaced

  //   (except for those macro names modified by the 'defined' unary operator),

  //   just as in normal text. If the token 'defined' is generated as a result

  //   of this replacement process or use of the 'defined' unary operator does

  //   not match one of the two specified forms prior to macro replacement, the

  //   behavior is undefined.

  // This isn't an idle threat, consider this program:

  //   #define FOO

  //   #define BAR defined(FOO)

  //   #if BAR

  //   ...

  //   #else

  //   ...

  //   #endif

  // clang and gcc will pick the #if branch while Visual Studio will take the

  // #else branch.  Emit a warning about this undefined behavior.

  if (beginLoc.isMacroID()) {

    bool IsFunctionTypeMacro =

        PP.getSourceManager()

            .getSLocEntry(PP.getSourceManager().getFileID(beginLoc))

            .getExpansion()

            .isFunctionMacroExpansion();

    // For object-type macros, it's easy to replace

    //   #define FOO defined(BAR)

    // with

    //   #if defined(BAR)

    //   #define FOO 1

    //   #else

    //   #define FOO 0

    //   #endif

    // and doing so makes sense since compilers handle this differently in

    // practice (see example further up).  But for function-type macros,

    // there is no good way to write

    //   # define FOO(x) (defined(M_ ## x) && M_ ## x)

    // in a different way, and compilers seem to agree on how to behave here.

    // So warn by default on object-type macros, but only warn in -pedantic

    // mode on function-type macros.

    if (IsFunctionTypeMacro)

      PP.Diag(beginLoc, diag::warn_defined_in_function_type_macro);

    else

      PP.Diag(beginLoc, diag::warn_defined_in_object_type_macro);

  }

  // Invoke the 'defined' callback.

  if (PPCallbacks *Callbacks = PP.getPPCallbacks()) {

    Callbacks->Defined(macroToken, Macro,

                       SourceRange(beginLoc, PeekTok.getLocation()));

  }

  // Success, remember that we saw defined(X).

  DT.State = DefinedTracker::DefinedMacro;

  DT.TheMacro = II;

  return false;

}

/// EvaluateValue - Evaluate the token PeekTok (and any others needed) and

/// return the computed value in Result.  Return true if there was an error

/// parsing.  This function also returns information about the form of the

/// expression in DT.  See above for information on what DT means.

///

/// If ValueLive is false, then this value is being evaluated in a context where

/// the result is not used.  As such, avoid diagnostics that relate to

/// evaluation.

static bool EvaluateValue(PPValue &Result, Token &PeekTok, DefinedTracker &DT,

                          bool ValueLive, Preprocessor &PP) {

  DT.State = DefinedTracker::Unknown;

  Result.setIdentifier(nullptr);

  if (PeekTok.is(tok::code_completion)) {

    if (PP.getCodeCompletionHandler())

      PP.getCodeCompletionHandler()->CodeCompletePreprocessorExpression();

    PP.setCodeCompletionReached();

    PP.LexNonComment(PeekTok);

  }

  switch (PeekTok.getKind()) {

  default:

    // If this token's spelling is a pp-identifier, check to see if it is

    // 'defined' or if it is a macro.  Note that we check here because many

    // keywords are pp-identifiers, so we can't check the kind.

    if (IdentifierInfo *II = PeekTok.getIdentifierInfo()) {

      // Handle "defined X" and "defined(X)".

      if (II->isStr("defined"))

        return EvaluateDefined(Result, PeekTok, DT, ValueLive, PP);

      if (!II->isCPlusPlusOperatorKeyword()) {

        // If this identifier isn't 'defined' or one of the special

        // preprocessor keywords and it wasn't macro expanded, it turns

        // into a simple 0

        if (ValueLive) {

          PP.Diag(PeekTok, diag::warn_pp_undef_identifier) << II;

          const DiagnosticsEngine &DiagEngine = PP.getDiagnostics();

          // If 'Wundef' is enabled, do not emit 'undef-prefix' diagnostics.

          if (DiagEngine.isIgnored(diag::warn_pp_undef_identifier,

                                   PeekTok.getLocation())) {

            const std::vector<std::string> UndefPrefixes =

                DiagEngine.getDiagnosticOptions().UndefPrefixes;

            const StringRef IdentifierName = II->getName();

            if (llvm::any_of(UndefPrefixes,

                             [&IdentifierName](const std::string &Prefix) {

                               return IdentifierName.starts_with(Prefix);

                             }))

              PP.Diag(PeekTok, diag::warn_pp_undef_prefix)

                  << AddFlagValue{llvm::join(UndefPrefixes, ",")} << II;

          }

        }

        Result.Val = 0;

        Result.Val.setIsUnsigned(false); // "0" is signed intmax_t 0.

        Result.setIdentifier(II);

        Result.setRange(PeekTok.getLocation());

        DT.IncludedUndefinedIds = true;

        PP.LexNonComment(PeekTok);

        return false;

      }

    }

    PP.Diag(PeekTok, diag::err_pp_expr_bad_token_start_expr);

    return true;

  case tok::eod:

  case tok::r_paren:

    // If there is no expression, report and exit.

    PP.Diag(PeekTok, diag::err_pp_expected_value_in_expr);

    return true;

  case tok::numeric_constant: {

    SmallString<64> IntegerBuffer;

    bool NumberInvalid = false;

    StringRef Spelling = PP.getSpelling(PeekTok, IntegerBuffer,

                                              &NumberInvalid);

    if (NumberInvalid)

      return true; // a diagnostic was already reported

    NumericLiteralParser Literal(Spelling, PeekTok.getLocation(),

                                 PP.getSourceManager(), PP.getLangOpts(),

                                 PP.getTargetInfo(), PP.getDiagnostics());

    if (Literal.hadError)

      return true; // a diagnostic was already reported.

    if (Literal.isFloatingLiteral() || Literal.isImaginary) {

      PP.Diag(PeekTok, diag::err_pp_illegal_floating_literal);

      return true;

    }

    assert(Literal.isIntegerLiteral() && "Unknown ppnumber");

    // Complain about, and drop, any ud-suffix.

    if (Literal.hasUDSuffix())

      PP.Diag(PeekTok, diag::err_pp_invalid_udl) << /*integer*/1;

    // 'long long' is a C99 or C++11 feature.

    if (!PP.getLangOpts().C99 && Literal.isLongLong) {

      if (PP.getLangOpts().CPlusPlus)

        PP.Diag(PeekTok,

             PP.getLangOpts().CPlusPlus11 ?

             diag::warn_cxx98_compat_longlong : diag::ext_cxx11_longlong);

      else

        PP.Diag(PeekTok, diag::ext_c99_longlong);

    }

    // 'z/uz' literals are a C++23 feature.

    if (Literal.isSizeT)

      PP.Diag(PeekTok, PP.getLangOpts().CPlusPlus

                           ? PP.getLangOpts().CPlusPlus23

                                 ? diag::warn_cxx20_compat_size_t_suffix

                                 : diag::ext_cxx23_size_t_suffix

                           : diag::err_cxx23_size_t_suffix);

    // 'wb/uwb' literals are a C23 feature. We explicitly do not support the

    // suffix in C++ as an extension because a library-based UDL that resolves

    // to a library type may be more appropriate there.

    if (Literal.isBitInt)

      PP.Diag(PeekTok, PP.getLangOpts().C23

                           ? diag::warn_c23_compat_bitint_suffix

                           : diag::ext_c23_bitint_suffix);

    // Parse the integer literal into Result.

    if (Literal.GetIntegerValue(Result.Val)) {

      // Overflow parsing integer literal.

      if (ValueLive)

        PP.Diag(PeekTok, diag::err_integer_literal_too_large)

            << /* Unsigned */ 1;

      Result.Val.setIsUnsigned(true);

    } else {

      // Set the signedness of the result to match whether there was a U suffix

      // or not.

      Result.Val.setIsUnsigned(Literal.isUnsigned);

      // Detect overflow based on whether the value is signed.  If signed

      // and if the value is too large, emit a warning "integer constant is so

      // large that it is unsigned" e.g. on 12345678901234567890 where intmax_t

      // is 64-bits.

      if (!Literal.isUnsigned && Result.Val.isNegative()) {

        // Octal, hexadecimal, and binary literals are implicitly unsigned if

        // the value does not fit into a signed integer type.

        if (ValueLive && Literal.getRadix() == 10)

          PP.Diag(PeekTok, diag::ext_integer_literal_too_large_for_signed);

        Result.Val.setIsUnsigned(true);

      }

    }

    // Consume the token.

    Result.setRange(PeekTok.getLocation());

    PP.LexNonComment(PeekTok);

    return false;

  }

  case tok::char_constant:          // 'x'

  case tok::wide_char_constant:     // L'x'

  case tok::utf8_char_constant:     // u8'x'

  case tok::utf16_char_constant:    // u'x'

  case tok::utf32_char_constant: {  // U'x'

    // Complain about, and drop, any ud-suffix.

    if (PeekTok.hasUDSuffix())

      PP.Diag(PeekTok, diag::err_pp_invalid_udl) << /*character*/0;

    SmallString<32> CharBuffer;

    bool CharInvalid = false;

    StringRef ThisTok = PP.getSpelling(PeekTok, CharBuffer, &CharInvalid);

    if (CharInvalid)

      return true;

    CharLiteralParser Literal(ThisTok.begin(), ThisTok.end(),

                              PeekTok.getLocation(), PP, PeekTok.getKind());

    if (Literal.hadError())

      return true;  // A diagnostic was already emitted.

    // Character literals are always int or wchar_t, expand to intmax_t.

    const TargetInfo &TI = PP.getTargetInfo();

    unsigned NumBits;

    if (Literal.isMultiChar())

      NumBits = TI.getIntWidth();

    else if (Literal.isWide())

      NumBits = TI.getWCharWidth();

    else if (Literal.isUTF16())

      NumBits = TI.getChar16Width();

    else if (Literal.isUTF32())

      NumBits = TI.getChar32Width();

    else // char or char8_t

      NumBits = TI.getCharWidth();

    // Set the width.

    llvm::APSInt Val(NumBits);

    // Set the value.

    Val = Literal.getValue();

    // Set the signedness. UTF-16 and UTF-32 are always unsigned

    // UTF-8 is unsigned if -fchar8_t is specified.

    if (Literal.isWide())

      Val.setIsUnsigned(!TargetInfo::isTypeSigned(TI.getWCharType()));

    else if (Literal.isUTF16() || Literal.isUTF32())

      Val.setIsUnsigned(true);

    else if (Literal.isUTF8()) {

      if (PP.getLangOpts().CPlusPlus)

        Val.setIsUnsigned(

            PP.getLangOpts().Char8 ? true : !PP.getLangOpts().CharIsSigned);

      else

        Val.setIsUnsigned(true);

    } else

      Val.setIsUnsigned(!PP.getLangOpts().CharIsSigned);

    if (Result.Val.getBitWidth() > Val.getBitWidth()) {

      Result.Val = Val.extend(Result.Val.getBitWidth());

    } else {

      assert(Result.Val.getBitWidth() == Val.getBitWidth() &&

             "intmax_t smaller than char/wchar_t?");

      Result.Val = Val;

    }

    // Consume the token.

    Result.setRange(PeekTok.getLocation());

    PP.LexNonComment(PeekTok);

    return false;

  }

  case tok::l_paren: {

    SourceLocation Start = PeekTok.getLocation();

    PP.LexNonComment(PeekTok);  // Eat the (.

    // Parse the value and if there are any binary operators involved, parse

    // them.

    if (EvaluateValue(Result, PeekTok, DT, ValueLive, PP)) return true;

    // If this is a silly value like (X), which doesn't need parens, check for

    // !(defined X).

    if (PeekTok.is(tok::r_paren)) {

      // Just use DT unmodified as our result.

    } else {

      // Otherwise, we have something like (x+y), and we consumed '(x'.

      if (EvaluateDirectiveSubExpr(Result, 1, PeekTok, ValueLive,

                                   DT.IncludedUndefinedIds, PP))

        return true;

      if (PeekTok.isNot(tok::r_paren)) {

        PP.Diag(PeekTok.getLocation(), diag::err_pp_expected_rparen)

          << Result.getRange();

        PP.Diag(Start, diag::note_matching) << tok::l_paren;

        return true;

      }

      DT.State = DefinedTracker::Unknown;

    }

    Result.setRange(Start, PeekTok.getLocation());

    Result.setIdentifier(nullptr);

    PP.LexNonComment(PeekTok);  // Eat the ).

    return false;

  }

  case tok::plus: {

    SourceLocation Start = PeekTok.getLocation();

    // Unary plus doesn't modify the value.

    PP.LexNonComment(PeekTok);

    if (EvaluateValue(Result, PeekTok, DT, ValueLive, PP)) return true;

    Result.setBegin(Start);

    Result.setIdentifier(nullptr);

    return false;

  }

  case tok::minus: {

    SourceLocation Loc = PeekTok.getLocation();

    PP.LexNonComment(PeekTok);

    if (EvaluateValue(Result, PeekTok, DT, ValueLive, PP)) return true;

    Result.setBegin(Loc);

    Result.setIdentifier(nullptr);

    // C99 6.5.3.3p3: The sign of the result matches the sign of the operand.

    Result.Val = -Result.Val;

    // -MININT is the only thing that overflows.  Unsigned never overflows.

    bool Overflow = !Result.isUnsigned() && Result.Val.isMinSignedValue();

    // If this operator is live and overflowed, report the issue.

    if (Overflow && ValueLive)

      PP.Diag(Loc, diag::warn_pp_expr_overflow) << Result.getRange();

    DT.State = DefinedTracker::Unknown;

    return false;

  }

  case tok::tilde: {

    SourceLocation Start = PeekTok.getLocation();

    PP.LexNonComment(PeekTok);

    if (EvaluateValue(Result, PeekTok, DT, ValueLive, PP)) return true;

    Result.setBegin(Start);

    Result.setIdentifier(nullptr);

    // C99 6.5.3.3p4: The sign of the result matches the sign of the operand.

    Result.Val = ~Result.Val;

    DT.State = DefinedTracker::Unknown;

    return false;

  }

  case tok::exclaim: {

    SourceLocation Start = PeekTok.getLocation();

    PP.LexNonComment(PeekTok);

    if (EvaluateValue(Result, PeekTok, DT, ValueLive, PP)) return true;

    Result.setBegin(Start);

    Result.Val = !Result.Val;

    // C99 6.5.3.3p5: The sign of the result is 'int', aka it is signed.

    Result.Val.setIsUnsigned(false);

    Result.setIdentifier(nullptr);

    if (DT.State == DefinedTracker::DefinedMacro)

      DT.State = DefinedTracker::NotDefinedMacro;

    else if (DT.State == DefinedTracker::NotDefinedMacro)

      DT.State = DefinedTracker::DefinedMacro;

    return false;

  }

  case tok::kw_true:

  case tok::kw_false:

    Result.Val = PeekTok.getKind() == tok::kw_true;

    Result.Val.setIsUnsigned(false); // "0" is signed intmax_t 0.

    Result.setIdentifier(PeekTok.getIdentifierInfo());

    Result.setRange(PeekTok.getLocation());

    PP.LexNonComment(PeekTok);

    return false;

  // FIXME: Handle #assert

  }

}

/// getPrecedence - Return the precedence of the specified binary operator

/// token.  This returns:

///   ~0 - Invalid token.

///   14 -> 3 - various operators.

///    0 - 'eod' or ')'

static unsigned getPrecedence(tok::TokenKind Kind) {

  switch (Kind) {

  default: return ~0U;

  case tok::percent:

  case tok::slash:

  case tok::star:                 return 14;

  case tok::plus:

  case tok::minus:                return 13;

  case tok::lessless:

  case tok::greatergreater:       return 12;

  case tok::lessequal:

  case tok::less:

  case tok::greaterequal:

  case tok::greater:              return 11;

  case tok::exclaimequal:

  case tok::equalequal:           return 10;

  case tok::amp:                  return 9;

  case tok::caret:                return 8;

  case tok::pipe:                 return 7;

  case tok::ampamp:               return 6;

  case tok::pipepipe:             return 5;

  case tok::question:             return 4;

  case tok::comma:                return 3;

  case tok::colon:                return 2;

  case tok::r_paren:              return 0;// Lowest priority, end of expr.

  case tok::eod:                  return 0;// Lowest priority, end of directive.

  }

}

static void diagnoseUnexpectedOperator(Preprocessor &PP, PPValue &LHS,

                                       Token &Tok) {

  if (Tok.is(tok::l_paren) && LHS.getIdentifier())

    PP.Diag(LHS.getRange().getBegin(), diag::err_pp_expr_bad_token_lparen)

        << LHS.getIdentifier();

  else

    PP.Diag(Tok.getLocation(), diag::err_pp_expr_bad_token_binop)

        << LHS.getRange();

}

/// EvaluateDirectiveSubExpr - Evaluate the subexpression whose first token is

/// PeekTok, and whose precedence is PeekPrec.  This returns the result in LHS.

///

/// If ValueLive is false, then this value is being evaluated in a context where

/// the result is not used.  As such, avoid diagnostics that relate to

/// evaluation, such as division by zero warnings.

static bool EvaluateDirectiveSubExpr(PPValue &LHS, unsigned MinPrec,

                                     Token &PeekTok, bool ValueLive,

                                     bool &IncludedUndefinedIds,

                                     Preprocessor &PP) {

  unsigned PeekPrec = getPrecedence(PeekTok.getKind());

  // If this token isn't valid, report the error.

  if (PeekPrec == ~0U) {

    diagnoseUnexpectedOperator(PP, LHS, PeekTok);

    return true;

  }

  while (true) {

    // If this token has a lower precedence than we are allowed to parse, return

    // it so that higher levels of the recursion can parse it.

    if (PeekPrec < MinPrec)

      return false;

    tok::TokenKind Operator = PeekTok.getKind();

    // If this is a short-circuiting operator, see if the RHS of the operator is

    // dead.  Note that this cannot just clobber ValueLive.  Consider

    // "0 && 1 ? 4 : 1 / 0", which is parsed as "(0 && 1) ? 4 : (1 / 0)".  In

    // this example, the RHS of the && being dead does not make the rest of the

    // expr dead.

    bool RHSIsLive;

    if (Operator == tok::ampamp && LHS.Val == 0)

      RHSIsLive = false;   // RHS of "0 && x" is dead.

    else if (Operator == tok::pipepipe && LHS.Val != 0)

      RHSIsLive = false;   // RHS of "1 || x" is dead.

    else if (Operator == tok::question && LHS.Val == 0)

      RHSIsLive = false;   // RHS (x) of "0 ? x : y" is dead.

    else

      RHSIsLive = ValueLive;

    // Consume the operator, remembering the operator's location for reporting.

    SourceLocation OpLoc = PeekTok.getLocation();

    PP.LexNonComment(PeekTok);

    PPValue RHS(LHS.getBitWidth());

    // Parse the RHS of the operator.

    DefinedTracker DT;

    if (EvaluateValue(RHS, PeekTok, DT, RHSIsLive, PP)) return true;

    IncludedUndefinedIds = DT.IncludedUndefinedIds;

    // Remember the precedence of this operator and get the precedence of the

    // operator immediately to the right of the RHS.

    unsigned ThisPrec = PeekPrec;

    PeekPrec = getPrecedence(PeekTok.getKind());

    // If this token isn't valid, report the error.

    if (PeekPrec == ~0U) {

      diagnoseUnexpectedOperator(PP, RHS, PeekTok);

      return true;

    }

    // Decide whether to include the next binop in this subexpression.  For

    // example, when parsing x+y*z and looking at '*', we want to recursively

    // handle y*z as a single subexpression.  We do this because the precedence

    // of * is higher than that of +.  The only strange case we have to handle

    // here is for the ?: operator, where the precedence is actually lower than

    // the LHS of the '?'.  The grammar rule is:

    //

    // conditional-expression ::=

    //    logical-OR-expression ? expression : conditional-expression

    // where 'expression' is actually comma-expression.

    unsigned RHSPrec;

    if (Operator == tok::question)

      // The RHS of "?" should be maximally consumed as an expression.

      RHSPrec = getPrecedence(tok::comma);

    else  // All others should munch while higher precedence.

      RHSPrec = ThisPrec+1;

    if (PeekPrec >= RHSPrec) {

      if (EvaluateDirectiveSubExpr(RHS, RHSPrec, PeekTok, RHSIsLive,

                                   IncludedUndefinedIds, PP))

        return true;

      PeekPrec = getPrecedence(PeekTok.getKind());

    }

    assert(PeekPrec <= ThisPrec && "Recursion didn't work!");

    // Usual arithmetic conversions (C99 6.3.1.8p1): result is unsigned if

    // either operand is unsigned.

    llvm::APSInt Res(LHS.getBitWidth());

    switch (Operator) {

    case tok::question:       // No UAC for x and y in "x ? y : z".

    case tok::lessless:       // Shift amount doesn't UAC with shift value.

    case tok::greatergreater: // Shift amount doesn't UAC with shift value.

    case tok::comma:          // Comma operands are not subject to UACs.

    case tok::pipepipe:       // Logical || does not do UACs.

    case tok::ampamp:         // Logical && does not do UACs.

      break;                  // No UAC

    default:

      Res.setIsUnsigned(LHS.isUnsigned() || RHS.isUnsigned());

      // If this just promoted something from signed to unsigned, and if the

      // value was negative, warn about it.

      if (ValueLive && Res.isUnsigned()) {

        if (!LHS.isUnsigned() && LHS.Val.isNegative())

          PP.Diag(OpLoc, diag::warn_pp_convert_to_positive) << 0

            << toString(LHS.Val, 10, true) + " to " +

               toString(LHS.Val, 10, false)

            << LHS.getRange() << RHS.getRange();

        if (!RHS.isUnsigned() && RHS.Val.isNegative())

          PP.Diag(OpLoc, diag::warn_pp_convert_to_positive) << 1

            << toString(RHS.Val, 10, true) + " to " +

               toString(RHS.Val, 10, false)

            << LHS.getRange() << RHS.getRange();

      }

      LHS.Val.setIsUnsigned(Res.isUnsigned());

      RHS.Val.setIsUnsigned(Res.isUnsigned());

    }

    bool Overflow = false;

    switch (Operator) {

    default: llvm_unreachable("Unknown operator token!");

    case tok::percent:

      if (RHS.Val != 0)

        Res = LHS.Val % RHS.Val;

      else if (ValueLive) {

        PP.Diag(OpLoc, diag::err_pp_remainder_by_zero)

          << LHS.getRange() << RHS.getRange();

        return true;

      }

      break;

    case tok::slash:

      if (RHS.Val != 0) {

        if (LHS.Val.isSigned())

          Res = llvm::APSInt(LHS.Val.sdiv_ov(RHS.Val, Overflow), false);

        else

          Res = LHS.Val / RHS.Val;

      } else if (ValueLive) {

        PP.Diag(OpLoc, diag::err_pp_division_by_zero)

          << LHS.getRange() << RHS.getRange();

        return true;

      }

      break;

    case tok::star:

      if (Res.isSigned())

        Res = llvm::APSInt(LHS.Val.smul_ov(RHS.Val, Overflow), false);

      else

        Res = LHS.Val * RHS.Val;

      break;

    case tok::lessless: {

      // Determine whether overflow is about to happen.

      if (LHS.isUnsigned())

        Res = LHS.Val.ushl_ov(RHS.Val, Overflow);

      else

        Res = llvm::APSInt(LHS.Val.sshl_ov(RHS.Val, Overflow), false);

      break;

    }

    case tok::greatergreater: {

      // Determine whether overflow is about to happen.

      unsigned ShAmt = static_cast<unsigned>(RHS.Val.getLimitedValue());

      if (ShAmt >= LHS.getBitWidth()) {

        Overflow = true;

        ShAmt = LHS.getBitWidth()-1;

      }

      Res = LHS.Val >> ShAmt;

      break;

    }

    case tok::plus:

      if (LHS.isUnsigned())

        Res = LHS.Val + RHS.Val;

      else

        Res = llvm::APSInt(LHS.Val.sadd_ov(RHS.Val, Overflow), false);

      break;

    case tok::minus:

      if (LHS.isUnsigned())

        Res = LHS.Val - RHS.Val;

      else

        Res = llvm::APSInt(LHS.Val.ssub_ov(RHS.Val, Overflow), false);

      break;

    case tok::lessequal:

      Res = LHS.Val <= RHS.Val;

      Res.setIsUnsigned(false);  // C99 6.5.8p6, result is always int (signed)

      break;

    case tok::less:

      Res = LHS.Val < RHS.Val;

      Res.setIsUnsigned(false);  // C99 6.5.8p6, result is always int (signed)

      break;

    case tok::greaterequal:

      Res = LHS.Val >= RHS.Val;

      Res.setIsUnsigned(false);  // C99 6.5.8p6, result is always int (signed)

      break;

    case tok::greater:

      Res = LHS.Val > RHS.Val;

      Res.setIsUnsigned(false);  // C99 6.5.8p6, result is always int (signed)

      break;

    case tok::exclaimequal:

      Res = LHS.Val != RHS.Val;

      Res.setIsUnsigned(false);  // C99 6.5.9p3, result is always int (signed)

      break;

    case tok::equalequal:

      Res = LHS.Val == RHS.Val;

      Res.setIsUnsigned(false);  // C99 6.5.9p3, result is always int (signed)

      break;

    case tok::amp:

      Res = LHS.Val & RHS.Val;

      break;

    case tok::caret:

      Res = LHS.Val ^ RHS.Val;

      break;

    case tok::pipe:

      Res = LHS.Val | RHS.Val;

      break;

    case tok::ampamp:

      Res = (LHS.Val != 0 && RHS.Val != 0);

      Res.setIsUnsigned(false);  // C99 6.5.13p3, result is always int (signed)

      break;

    case tok::pipepipe:

      Res = (LHS.Val != 0 || RHS.Val != 0);

      Res.setIsUnsigned(false);  // C99 6.5.14p3, result is always int (signed)

      break;

    case tok::comma:

      // Comma is invalid in pp expressions in c89/c++ mode, but is valid in C99

      // if not being evaluated.

      if (!PP.getLangOpts().C99 || ValueLive)

        PP.Diag(OpLoc, diag::ext_pp_comma_expr)

          << LHS.getRange() << RHS.getRange();

      Res = RHS.Val; // LHS = LHS,RHS -> RHS.

      break;

    case tok::question: {

      // Parse the : part of the expression.

      if (PeekTok.isNot(tok::colon)) {

        PP.Diag(PeekTok.getLocation(), diag::err_expected)

            << tok::colon << LHS.getRange() << RHS.getRange();

        PP.Diag(OpLoc, diag::note_matching) << tok::question;

        return true;

      }

      // Consume the :.

      PP.LexNonComment(PeekTok);

      // Evaluate the value after the :.

      bool AfterColonLive = ValueLive && LHS.Val == 0;

      PPValue AfterColonVal(LHS.getBitWidth());

      DefinedTracker DT;

      if (EvaluateValue(AfterColonVal, PeekTok, DT, AfterColonLive, PP))

        return true;

      // Parse anything after the : with the same precedence as ?.  We allow

      // things of equal precedence because ?: is right associative.

      if (EvaluateDirectiveSubExpr(AfterColonVal, ThisPrec,

                                   PeekTok, AfterColonLive,

                                   IncludedUndefinedIds, PP))

        return true;

      // Now that we have the condition, the LHS and the RHS of the :, evaluate.

      Res = LHS.Val != 0 ? RHS.Val : AfterColonVal.Val;

      RHS.setEnd(AfterColonVal.getRange().getEnd());

      // Usual arithmetic conversions (C99 6.3.1.8p1): result is unsigned if

      // either operand is unsigned.

      Res.setIsUnsigned(RHS.isUnsigned() || AfterColonVal.isUnsigned());

      // Figure out the precedence of the token after the : part.

      PeekPrec = getPrecedence(PeekTok.getKind());

      break;

    }

    case tok::colon:

      // Don't allow :'s to float around without being part of ?: exprs.

      PP.Diag(OpLoc, diag::err_pp_colon_without_question)

        << LHS.getRange() << RHS.getRange();

      return true;

    }

    // If this operator is live and overflowed, report the issue.

    if (Overflow && ValueLive)

      PP.Diag(OpLoc, diag::warn_pp_expr_overflow)

        << LHS.getRange() << RHS.getRange();

    // Put the result back into 'LHS' for our next iteration.

    LHS.Val = Res;

    LHS.setEnd(RHS.getRange().getEnd());

    RHS.setIdentifier(nullptr);

  }

}

/// EvaluateDirectiveExpression - Evaluate an integer constant expression that

/// may occur after a #if or #elif directive.  If the expression is equivalent

/// to "!defined(X)" return X in IfNDefMacro.

Preprocessor::DirectiveEvalResult

Preprocessor::EvaluateDirectiveExpression(IdentifierInfo *&IfNDefMacro) {

  SaveAndRestore PPDir(ParsingIfOrElifDirective, true);

  // Save the current state of 'DisableMacroExpansion' and reset it to false. If

  // 'DisableMacroExpansion' is true, then we must be in a macro argument list

  // in which case a directive is undefined behavior.  We want macros to be able

  // to recursively expand in order to get more gcc-list behavior, so we force

  // DisableMacroExpansion to false and restore it when we're done parsing the

  // expression.

  bool DisableMacroExpansionAtStartOfDirective = DisableMacroExpansion;

  DisableMacroExpansion = false;

  // Peek ahead one token.

  Token Tok;

  LexNonComment(Tok);

  // C99 6.10.1p3 - All expressions are evaluated as intmax_t or uintmax_t.

  unsigned BitWidth = getTargetInfo().getIntMaxTWidth();

  PPValue ResVal(BitWidth);

  DefinedTracker DT;

  SourceLocation ExprStartLoc = SourceMgr.getExpansionLoc(Tok.getLocation());

  if (EvaluateValue(ResVal, Tok, DT, true, *this)) {