FormatString.cpp

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// FormatString.cpp - Common stuff for handling printf/scanf formats -*- C++ -*-
//
// 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
//
//===----------------------------------------------------------------------===//
//
// Shared details for processing format strings of printf and scanf
// (and friends).
//
//===----------------------------------------------------------------------===//
 
#include "FormatStringParsing.h"
#include "clang/Basic/LangOptions.h"
#include "clang/Basic/TargetInfo.h"
#include "llvm/ADT/StringExtras.h"
#include "llvm/Support/ConvertUTF.h"
#include <optional>
 
using clang::analyze_format_string::ArgType;
using clang::analyze_format_string::ConversionSpecifier;
using clang::analyze_format_string::FormatSpecifier;
using clang::analyze_format_string::FormatStringHandler;
using clang::analyze_format_string::LengthModifier;
using clang::analyze_format_string::OptionalAmount;
using namespace clang;
 
// Key function to FormatStringHandler.
FormatStringHandler::~FormatStringHandler() {}
 
//===----------------------------------------------------------------------===//
// Functions for parsing format strings components in both printf and
// scanf format strings.
//===----------------------------------------------------------------------===//
 
OptionalAmount clang::analyze_format_string::ParseAmount(const char *&Beg,
                                                         const char *E) {
  const char *I = Beg;
  UpdateOnReturn<const char *> UpdateBeg(Beg, I);
 
  unsigned accumulator = 0;
  bool hasDigits = false;
 
  for (; I != E; ++I) {
    char c = *I;
    if (c >= '0' && c <= '9') {
      hasDigits = true;
      accumulator = (accumulator * 10) + (c - '0');
      continue;
    }
 
    if (hasDigits)
      return OptionalAmount(OptionalAmount::Constant, accumulator, Beg, I - Beg,
                            false);
 
    break;
  }
 
  return OptionalAmount();
}
 
static bool ParseWidthModifier(const char *&I, const char *E,
                               unsigned &BitWidth, unsigned &ModifierLength) {
  StringRef W = StringRef(I, E - I).take_while(llvm::isDigit);
  if (W.empty() || W.front() == '0')
    return false;
 
  if (W.getAsInteger(10, BitWidth))
    return false;
 
  I = W.end();
  ModifierLength += W.size();
 
  return true;
}
 
OptionalAmount clang::analyze_format_string::ParseNonPositionAmount(
    const char *&Beg, const char *E, unsigned &argIndex) {
  if (*Beg == '*') {
    ++Beg;
    return OptionalAmount(OptionalAmount::Arg, argIndex++, Beg, 0, false);
  }
 
  return ParseAmount(Beg, E);
}
 
OptionalAmount clang::analyze_format_string::ParsePositionAmount(
    FormatStringHandler &H, const char *Start, const char *&Beg, const char *E,
    PositionContext p) {
  if (*Beg == '*') {
    const char *I = Beg + 1;
    const OptionalAmount &Amt = ParseAmount(I, E);
 
    if (Amt.getHowSpecified() == OptionalAmount::NotSpecified) {
      H.HandleInvalidPosition(Beg, I - Beg, p);
      return OptionalAmount(false);
    }
 
    if (I == E) {
      // No more characters left?
      H.HandleIncompleteSpecifier(Start, E - Start);
      return OptionalAmount(false);
    }
 
    assert(Amt.getHowSpecified() == OptionalAmount::Constant);
 
    if (*I == '$') {
      // Handle positional arguments
 
      // Special case: '*0$', since this is an easy mistake.
      if (Amt.getConstantAmount() == 0) {
        H.HandleZeroPosition(Beg, I - Beg + 1);
        return OptionalAmount(false);
      }
 
      const char *Tmp = Beg;
      Beg = ++I;
 
      return OptionalAmount(OptionalAmount::Arg, Amt.getConstantAmount() - 1,
                            Tmp, 0, true);
    }
 
    H.HandleInvalidPosition(Beg, I - Beg, p);
    return OptionalAmount(false);
  }
 
  return ParseAmount(Beg, E);
}
 
bool clang::analyze_format_string::ParseFieldWidth(
    FormatStringHandler &H, FormatSpecifier &CS, const char *Start,
    const char *&Beg, const char *E, unsigned *argIndex) {
  // FIXME: Support negative field widths.
  if (argIndex) {
    CS.setFieldWidth(ParseNonPositionAmount(Beg, E, *argIndex));
  } else {
    const OptionalAmount Amt = ParsePositionAmount(
        H, Start, Beg, E, analyze_format_string::FieldWidthPos);
 
    if (Amt.isInvalid())
      return true;
    CS.setFieldWidth(Amt);
  }
  return false;
}
 
bool clang::analyze_format_string::ParseArgPosition(FormatStringHandler &H,
                                                    FormatSpecifier &FS,
                                                    const char *Start,
                                                    const char *&Beg,
                                                    const char *E) {
  const char *I = Beg;
 
  const OptionalAmount &Amt = ParseAmount(I, E);
 
  if (I == E) {
    // No more characters left?
    H.HandleIncompleteSpecifier(Start, E - Start);
    return true;
  }
 
  if (Amt.getHowSpecified() == OptionalAmount::Constant && *(I++) == '$') {
    // Warn that positional arguments are non-standard.
    H.HandlePosition(Start, I - Start);
 
    // Special case: '%0$', since this is an easy mistake.
    if (Amt.getConstantAmount() == 0) {
      H.HandleZeroPosition(Start, I - Start);
      return true;
    }
 
    FS.setArgIndex(Amt.getConstantAmount() - 1);
    FS.setUsesPositionalArg();
    // Update the caller's pointer if we decided to consume
    // these characters.
    Beg = I;
    return false;
  }
 
  return false;
}
 
bool clang::analyze_format_string::ParseVectorModifier(FormatStringHandler &H,
                                                       FormatSpecifier &FS,
                                                       const char *&I,
                                                       const char *E,
                                                       const LangOptions &LO) {
  if (!LO.OpenCL)
    return false;
 
  const char *Start = I;
  if (*I == 'v') {
    ++I;
 
    if (I == E) {
      H.HandleIncompleteSpecifier(Start, E - Start);
      return true;
    }
 
    OptionalAmount NumElts = ParseAmount(I, E);
    if (NumElts.getHowSpecified() != OptionalAmount::Constant) {
      H.HandleIncompleteSpecifier(Start, E - Start);
      return true;
    }
 
    FS.setVectorNumElts(NumElts);
  }
 
  return false;
}
 
bool clang::analyze_format_string::ParseLengthModifier(FormatSpecifier &FS,
                                                       const char *&I,
                                                       const char *E,
                                                       const LangOptions &LO,
                                                       bool IsScanf) {
  LengthModifier::Kind lmKind = LengthModifier::None;
  const char *lmPosition = I;
  switch (*I) {
  default:
    return false;
  case 'h':
    ++I;
    if (I != E && *I == 'h') {
      ++I;
      lmKind = LengthModifier::AsChar;
    } else if (I != E && *I == 'l' && LO.OpenCL) {
      ++I;
      lmKind = LengthModifier::AsShortLong;
    } else {
      lmKind = LengthModifier::AsShort;
    }
    break;
  case 'l':
    ++I;
    if (I != E && *I == 'l') {
      ++I;
      lmKind = LengthModifier::AsLongLong;
    } else {
      lmKind = LengthModifier::AsLong;
    }
    break;
  case 'j':
    lmKind = LengthModifier::AsIntMax;
    ++I;
    break;
  case 'z':
    lmKind = LengthModifier::AsSizeT;
    ++I;
    break;
  case 't':
    lmKind = LengthModifier::AsPtrDiff;
    ++I;
    break;
  case 'L':
    lmKind = LengthModifier::AsLongDouble;
    ++I;
    break;
  case 'q':
    lmKind = LengthModifier::AsQuad;
    ++I;
    break;
  case 'a':
    if (IsScanf && !LO.C99 && !LO.CPlusPlus11) {
      // For scanf in C90, look at the next character to see if this should
      // be parsed as the GNU extension 'a' length modifier. If not, this
      // will be parsed as a conversion specifier.
      ++I;
      if (I != E && (*I == 's' || *I == 'S' || *I == '[')) {
        lmKind = LengthModifier::AsAllocate;
        break;
      }
      --I;
    }
    return false;
  case 'm':
    if (IsScanf) {
      lmKind = LengthModifier::AsMAllocate;
      ++I;
      break;
    }
    return false;
  // printf: AsInt64, AsInt32, AsInt3264
  // scanf:  AsInt64
  case 'I':
    if (I + 1 != E && I + 2 != E) {
      if (I[1] == '6' && I[2] == '4') {
        I += 3;
        lmKind = LengthModifier::AsInt64;
        break;
      }
      if (IsScanf)
        return false;
 
      if (I[1] == '3' && I[2] == '2') {
        I += 3;
        lmKind = LengthModifier::AsInt32;
        break;
      }
    }
    ++I;
    lmKind = LengthModifier::AsInt3264;
    break;
  case 'H':
    if (LO.C23) {
      lmKind = LengthModifier::AsDecimal32;
      ++I;
      break;
    }
    return false;
  case 'D':
    if (LO.C23) {
      ++I;
      if (I != E && *I == 'D') {
        ++I;
        lmKind = LengthModifier::AsDecimal128;
      } else {
        lmKind = LengthModifier::AsDecimal64;
      }
      break;
    }
    return false;
  case 'w':
    if (LO.C23) {
      const char *WidthModifier = I + 1;
      unsigned BitWidth = 0;
      unsigned ModifierLength = 1;
 
      LengthModifier::Kind WidthKind = LengthModifier::AsIntN;
      if (WidthModifier != E && *WidthModifier == 'f') {
        WidthModifier = I + 2;
        ModifierLength = 2;
        WidthKind = LengthModifier::AsFastIntN;
      }
 
      if (ParseWidthModifier(WidthModifier, E, BitWidth, ModifierLength)) {
        I = WidthModifier;
        FS.setLengthModifier(
            LengthModifier(lmPosition, WidthKind, BitWidth, ModifierLength));
        return true;
      }
    }
    lmKind = LengthModifier::AsWide;
    ++I;
    break;
  }
  LengthModifier lm(lmPosition, lmKind);
  FS.setLengthModifier(lm);
  return true;
}
 
bool clang::analyze_format_string::ParseUTF8InvalidSpecifier(
    const char *SpecifierBegin, const char *FmtStrEnd, unsigned &Len) {
  if (SpecifierBegin + 1 >= FmtStrEnd)
    return false;
 
  const llvm::UTF8 *SB =
      reinterpret_cast<const llvm::UTF8 *>(SpecifierBegin + 1);
  const llvm::UTF8 *SE = reinterpret_cast<const llvm::UTF8 *>(FmtStrEnd);
  const char FirstByte = *SB;
 
  // If the invalid specifier is a multibyte UTF-8 string, return the
  // total length accordingly so that the conversion specifier can be
  // properly updated to reflect a complete UTF-8 specifier.
  unsigned NumBytes = llvm::getNumBytesForUTF8(FirstByte);
  if (NumBytes == 1)
    return false;
  if (SB + NumBytes > SE)
    return false;
 
  Len = NumBytes + 1;
  return true;
}
 
//===----------------------------------------------------------------------===//
// Methods on ArgType.
//===----------------------------------------------------------------------===//
 
static bool namedTypeToLengthModifierKind(ASTContext &Ctx, QualType QT,
                                          LengthModifier::Kind &K) {
  if (!Ctx.getLangOpts().C99 && !Ctx.getLangOpts().CPlusPlus)
    return false;
  for (/**/; const auto *TT = QT->getAs<TypedefType>(); QT = TT->desugar()) {
    const auto *TD = TT->getDecl();
    const auto *DC = TT->getDecl()->getDeclContext();
    if (DC->isTranslationUnit() || DC->isStdNamespace()) {
      StringRef Name = TD->getIdentifier()->getName();
      if (Name == "size_t") {
        K = LengthModifier::AsSizeT;
        return true;
      } else if (Name == "ssize_t" /*Not C99, but common in Unix.*/) {
        K = LengthModifier::AsSizeT;
        return true;
      } else if (Name == "ptrdiff_t") {
        K = LengthModifier::AsPtrDiff;
        return true;
      } else if (Name == "intmax_t") {
        K = LengthModifier::AsIntMax;
        return true;
      } else if (Name == "uintmax_t") {
        K = LengthModifier::AsIntMax;
        return true;
      }
    }
  }
  if (const auto *PST = QT->getAs<PredefinedSugarType>()) {
    using Kind = PredefinedSugarType::Kind;
    switch (PST->getKind()) {
    case Kind::SizeT:
    case Kind::SignedSizeT:
      K = LengthModifier::AsSizeT;
      return true;
    case Kind::PtrdiffT:
      K = LengthModifier::AsPtrDiff;
      return true;
    }
    llvm_unreachable("unexpected kind");
  }
  return false;
}
 
// Check whether T and E are compatible size_t/ptrdiff_t types. E must be
// consistent with LE.
// T is the type of the actual expression in the code to be checked, and E is
// the expected type parsed from the format string.
static clang::analyze_format_string::ArgType::MatchKind
matchesSizeTPtrdiffT(ASTContext &C, QualType T, QualType E) {
  using MatchKind = clang::analyze_format_string::ArgType::MatchKind;
 
  if (!T->isIntegerType() || T->isBooleanType())
    return MatchKind::NoMatch;
 
  if (C.hasSameType(T, E))
    return MatchKind::Match;
 
  if (C.getCorrespondingSignedType(T.getCanonicalType()) !=
      C.getCorrespondingSignedType(E.getCanonicalType()))
    return MatchKind::NoMatch;
 
  return MatchKind::NoMatchSignedness;
}
 
clang::analyze_format_string::ArgType::MatchKind
ArgType::matchesType(ASTContext &C, QualType argTy) const {
  // When using the format attribute in C++, you can receive a function or an
  // array that will necessarily decay to a pointer when passed to the final
  // format consumer. Apply decay before type comparison.
  if (argTy->canDecayToPointerType())
    argTy = C.getDecayedType(argTy);
 
  if (Ptr) {
    // It has to be a pointer.
    const PointerType *PT = argTy->getAs<PointerType>();
    if (!PT)
      return NoMatch;
 
    // We cannot write through a const qualified pointer.
    if (PT->getPointeeType().isConstQualified())
      return NoMatch;
 
    argTy = PT->getPointeeType();
  }
 
  if (const auto *OBT = argTy->getAs<OverflowBehaviorType>())
    argTy = OBT->getUnderlyingType();
 
  switch (K) {
  case InvalidTy:
    llvm_unreachable("ArgType must be valid");
 
  case UnsupportedTy:
    return NoMatch;
 
  case UnknownTy:
    return Match;
 
  case AnyCharTy: {
    if (const auto *ED = argTy->getAsEnumDecl()) {
      // If the enum is incomplete we know nothing about the underlying type.
      // Assume that it's 'int'. Do not use the underlying type for a scoped
      // enumeration.
      if (!ED->isComplete())
        return NoMatch;
      if (!ED->isScoped())
        argTy = ED->getIntegerType();
    }
 
    if (const auto *BT = argTy->getAs<BuiltinType>()) {
      // The types are perfectly matched?
      switch (BT->getKind()) {
      default:
        break;
      case BuiltinType::Char_S:
      case BuiltinType::SChar:
      case BuiltinType::UChar:
      case BuiltinType::Char_U:
        return Match;
      case BuiltinType::Bool:
        if (!Ptr)
          return Match;
        break;
      }
      // "Partially matched" because of promotions?
      if (!Ptr) {
        switch (BT->getKind()) {
        default:
          break;
        case BuiltinType::Int:
        case BuiltinType::UInt:
          return MatchPromotion;
        case BuiltinType::Short:
        case BuiltinType::UShort:
        case BuiltinType::WChar_S:
        case BuiltinType::WChar_U:
          return NoMatchPromotionTypeConfusion;
        }
      }
    }
    return NoMatch;
  }
 
  case SpecificTy: {
    if (TK == TypeKind::SizeT || TK == TypeKind::PtrdiffT) {
      return matchesSizeTPtrdiffT(C, argTy, T);
    }
 
    if (const auto *ED = argTy->getAsEnumDecl()) {
      // If the enum is incomplete we know nothing about the underlying type.
      // Assume that it's 'int'. Do not use the underlying type for a scoped
      // enumeration as that needs an exact match.
      if (!ED->isComplete())
        argTy = C.IntTy;
      else if (!ED->isScoped())
        argTy = ED->getIntegerType();
    }
 
    if (argTy->isSaturatedFixedPointType())
      argTy = C.getCorrespondingUnsaturatedType(argTy);
 
    argTy = C.getCanonicalType(argTy).getUnqualifiedType();
 
    if (T == argTy)
      return Match;
    if (const auto *BT = argTy->getAs<BuiltinType>()) {
      // Check if the only difference between them is signed vs unsigned
      // if true, return match signedness.
      switch (BT->getKind()) {
      default:
        break;
      case BuiltinType::Bool:
        if (Ptr && (T == C.UnsignedCharTy || T == C.SignedCharTy))
          return NoMatch;
        [[fallthrough]];
      case BuiltinType::Char_S:
      case BuiltinType::SChar:
        if (T == C.UnsignedShortTy || T == C.ShortTy)
          return NoMatchTypeConfusion;
        if (T == C.UnsignedCharTy)
          return NoMatchSignedness;
        if (T == C.SignedCharTy)
          return Match;
        break;
      case BuiltinType::Char_U:
      case BuiltinType::UChar:
        if (T == C.UnsignedShortTy || T == C.ShortTy)
          return NoMatchTypeConfusion;
        if (T == C.UnsignedCharTy)
          return Match;
        if (T == C.SignedCharTy)
          return NoMatchSignedness;
        break;
      case BuiltinType::Short:
        if (T == C.UnsignedShortTy)
          return NoMatchSignedness;
        break;
      case BuiltinType::UShort:
        if (T == C.ShortTy)
          return NoMatchSignedness;
        break;
      case BuiltinType::Int:
        if (T == C.UnsignedIntTy)
          return NoMatchSignedness;
        break;
      case BuiltinType::UInt:
        if (T == C.IntTy)
          return NoMatchSignedness;
        break;
      case BuiltinType::Long:
        if (T == C.UnsignedLongTy)
          return NoMatchSignedness;
        break;
      case BuiltinType::ULong:
        if (T == C.LongTy)
          return NoMatchSignedness;
        break;
      case BuiltinType::LongLong:
        if (T == C.UnsignedLongLongTy)
          return NoMatchSignedness;
        break;
      case BuiltinType::ULongLong:
        if (T == C.LongLongTy)
          return NoMatchSignedness;
        break;
      }
      // "Partially matched" because of promotions?
      if (!Ptr) {
        switch (BT->getKind()) {
        default:
          break;
        case BuiltinType::Bool:
          if (T == C.IntTy || T == C.UnsignedIntTy)
            return MatchPromotion;
          break;
        case BuiltinType::Int:
        case BuiltinType::UInt:
          if (T == C.SignedCharTy || T == C.UnsignedCharTy || T == C.ShortTy ||
              T == C.UnsignedShortTy || T == C.WCharTy || T == C.WideCharTy)
            return MatchPromotion;
          break;
        case BuiltinType::Char_U:
          if (T == C.UnsignedIntTy)
            return MatchPromotion;
          if (T == C.UnsignedShortTy)
            return NoMatchPromotionTypeConfusion;
          break;
        case BuiltinType::Char_S:
          if (T == C.IntTy)
            return MatchPromotion;
          if (T == C.ShortTy)
            return NoMatchPromotionTypeConfusion;
          break;
        case BuiltinType::Half:
        case BuiltinType::Float:
          if (T == C.DoubleTy)
            return MatchPromotion;
          break;
        case BuiltinType::Short:
        case BuiltinType::UShort:
          if (T == C.SignedCharTy || T == C.UnsignedCharTy)
            return NoMatchPromotionTypeConfusion;
          break;
        case BuiltinType::WChar_U:
        case BuiltinType::WChar_S:
          if (T != C.WCharTy && T != C.WideCharTy)
            return NoMatchPromotionTypeConfusion;
        }
      }
    }
    return NoMatch;
  }
 
  case CStrTy:
    if (const auto *PT = argTy->getAs<PointerType>();
        PT && PT->getPointeeType()->isCharType())
      return Match;
    return NoMatch;
 
  case WCStrTy:
    if (const auto *PT = argTy->getAs<PointerType>();
        PT &&
        C.hasSameUnqualifiedType(PT->getPointeeType(), C.getWideCharType()))
      return Match;
    return NoMatch;
 
  case WIntTy: {
    QualType WInt = C.getCanonicalType(C.getWIntType()).getUnqualifiedType();
 
    if (C.getCanonicalType(argTy).getUnqualifiedType() == WInt)
      return Match;
 
    QualType PromoArg = C.isPromotableIntegerType(argTy)
                            ? C.getPromotedIntegerType(argTy)
                            : argTy;
    PromoArg = C.getCanonicalType(PromoArg).getUnqualifiedType();
 
    // If the promoted argument is the corresponding signed type of the
    // wint_t type, then it should match.
    if (PromoArg->hasSignedIntegerRepresentation() &&
        C.getCorrespondingUnsignedType(PromoArg) == WInt)
      return Match;
 
    return WInt == PromoArg ? Match : NoMatch;
  }
 
  case CPointerTy:
    if (const auto *PT = argTy->getAs<PointerType>()) {
      QualType PointeeTy = PT->getPointeeType();
      if (PointeeTy->isVoidType() || (!Ptr && PointeeTy->isCharType()))
        return Match;
      return NoMatchPedantic;
    }
 
    // nullptr_t* is not a double pointer, so reject when something like
    // void** is expected.
    // In C++, nullptr is promoted to void*. In C23, va_arg(ap, void*) is not
    // undefined when the next argument is of type nullptr_t.
    if (!Ptr && argTy->isNullPtrType())
      return C.getLangOpts().CPlusPlus ? MatchPromotion : Match;
 
    if (argTy->isObjCObjectPointerType() || argTy->isBlockPointerType())
      return NoMatchPedantic;
 
    return NoMatch;
 
  case ObjCPointerTy: {
    if (argTy->getAs<ObjCObjectPointerType>() ||
        argTy->getAs<BlockPointerType>())
      return Match;
 
    // Handle implicit toll-free bridging.
    if (const PointerType *PT = argTy->getAs<PointerType>()) {
      // Things such as CFTypeRef are really just opaque pointers
      // to C structs representing CF types that can often be bridged
      // to Objective-C objects.  Since the compiler doesn't know which
      // structs can be toll-free bridged, we just accept them all.
      QualType pointee = PT->getPointeeType();
      if (pointee->isStructureType() || pointee->isVoidType())
        return Match;
    }
    return NoMatch;
  }
  }
 
  llvm_unreachable("Invalid ArgType Kind!");
}
 
static analyze_format_string::ArgType::MatchKind
integerTypeMatch(ASTContext &C, QualType A, QualType B, bool CheckSign) {
  using MK = analyze_format_string::ArgType::MatchKind;
 
  uint64_t IntSize = C.getTypeSize(C.IntTy);
  uint64_t ASize = C.getTypeSize(A);
  uint64_t BSize = C.getTypeSize(B);
  if (std::max(ASize, IntSize) != std::max(BSize, IntSize))
    return MK::NoMatch;
  if (CheckSign && A->isSignedIntegerType() != B->isSignedIntegerType())
    return MK::NoMatchSignedness;
  if (ASize != BSize)
    return MK::MatchPromotion;
  return MK::Match;
}
 
analyze_format_string::ArgType::MatchKind
ArgType::matchesArgType(ASTContext &C, const ArgType &Other) const {
  using AK = analyze_format_string::ArgType::Kind;
 
  // Per matchesType.
  if (K == AK::InvalidTy || Other.K == AK::InvalidTy)
    return NoMatch;
  if (K == AK::UnsupportedTy || Other.K == AK::UnsupportedTy)
    return NoMatch;
  if (K == AK::UnknownTy || Other.K == AK::UnknownTy)
    return Match;
 
  // Handle whether either (or both, or neither) sides has Ptr set,
  // in addition to whether either (or both, or neither) sides is a SpecificTy
  // that is a pointer.
  ArgType Left = *this;
  bool LeftWasPointer = false;
  ArgType Right = Other;
  bool RightWasPointer = false;
  if (Left.Ptr) {
    Left.Ptr = false;
    LeftWasPointer = true;
  } else if (Left.K == AK::SpecificTy && Left.T->isPointerType()) {
    Left.T = Left.T->getPointeeType();
    LeftWasPointer = true;
  }
  if (Right.Ptr) {
    Right.Ptr = false;
    RightWasPointer = true;
  } else if (Right.K == AK::SpecificTy && Right.T->isPointerType()) {
    Right.T = Right.T->getPointeeType();
    RightWasPointer = true;
  }
 
  if (LeftWasPointer != RightWasPointer)
    return NoMatch;
 
  // Ensure that if at least one side is a SpecificTy, then Left is a
  // SpecificTy.
  if (Right.K == AK::SpecificTy)
    std::swap(Left, Right);
 
  if (Left.K == AK::SpecificTy) {
    if (Right.K == AK::SpecificTy) {
      if (Left.TK != TypeKind::DontCare) {
        return matchesSizeTPtrdiffT(C, Right.T, Left.T);
      } else if (Right.TK != TypeKind::DontCare) {
        return matchesSizeTPtrdiffT(C, Left.T, Right.T);
      }
 
      auto Canon1 = C.getCanonicalType(Left.T);
      auto Canon2 = C.getCanonicalType(Right.T);
      if (Canon1 == Canon2)
        return Match;
 
      auto *BT1 = QualType(Canon1)->getAs<BuiltinType>();
      auto *BT2 = QualType(Canon2)->getAs<BuiltinType>();
      if (BT1 == nullptr || BT2 == nullptr)
        return NoMatch;
      if (BT1 == BT2)
        return Match;
 
      if (!LeftWasPointer && BT1->isInteger() && BT2->isInteger())
        return integerTypeMatch(C, Canon1, Canon2, true);
      return NoMatch;
    } else if (Right.K == AK::AnyCharTy) {
      if (!LeftWasPointer && Left.T->isIntegerType())
        return integerTypeMatch(C, Left.T, C.CharTy, false);
      return NoMatch;
    } else if (Right.K == AK::WIntTy) {
      if (!LeftWasPointer && Left.T->isIntegerType())
        return integerTypeMatch(C, Left.T, C.WIntTy, true);
      return NoMatch;
    }
    // It's hypothetically possible to create an AK::SpecificTy ArgType
    // that matches another kind of ArgType, but in practice Clang doesn't
    // do that, so ignore that case.
    return NoMatch;
  }
 
  return Left.K == Right.K ? Match : NoMatch;
}
 
ArgType ArgType::makeVectorType(ASTContext &C, unsigned NumElts) const {
  // Check for valid vector element types.
  if (T.isNull())
    return ArgType::Invalid();
 
  QualType Vec = C.getExtVectorType(T, NumElts);
  return ArgType(Vec, Name);
}
 
ArgType ArgType::makeIntNType(ASTContext &Ctx, const LengthModifier &LengthMod,
                              bool Signed) {
  bool IsFast = LengthMod.getKind() == LengthModifier::AsFastIntN;
  QualType Ty =
      IsFast ? Ctx.getLeastIntTypeForBitwidth(LengthMod.getBitWidth(), Signed)
             : Ctx.getIntTypeForBitwidth(LengthMod.getBitWidth(), Signed);
  if (Ty.isNull())
    return ArgType::Invalid();
 
  ArgType Res(Ty);
  Res.TK = IsFast ? (Signed ? TypeKind::FastIntN : TypeKind::FastUIntN)
                  : (Signed ? TypeKind::IntN : TypeKind::UIntN);
  Res.BitWidth = LengthMod.getBitWidth();
  return Res;
}
 
QualType ArgType::getRepresentativeType(ASTContext &C) const {
  QualType Res;
  switch (K) {
  case InvalidTy:
    llvm_unreachable("No representative type for Invalid ArgType");
  case UnknownTy:
    llvm_unreachable("No representative type for Unknown ArgType");
  case UnsupportedTy:
    llvm_unreachable("No representative type for Unsupported ArgType");
  case AnyCharTy:
    Res = C.CharTy;
    break;
  case SpecificTy:
    if (TK == TypeKind::PtrdiffT || TK == TypeKind::SizeT)
      // Using Name as name, so no need to show the uglified name.
      Res = T->getCanonicalTypeInternal();
    else
      Res = T;
    break;
  case CStrTy:
    Res = C.getPointerType(C.CharTy);
    break;
  case WCStrTy:
    Res = C.getPointerType(C.getWideCharType());
    break;
  case ObjCPointerTy:
    Res = C.ObjCBuiltinIdTy;
    break;
  case CPointerTy:
    Res = C.VoidPtrTy;
    break;
  case WIntTy: {
    Res = C.getWIntType();
    break;
  }
  }
 
  if (Ptr)
    Res = C.getPointerType(Res);
  return Res;
}
 
std::string ArgType::getRepresentativeTypeName(ASTContext &C) const {
  std::string S;
  if (K != UnsupportedTy)
    S = getRepresentativeType(C).getAsString(C.getPrintingPolicy());
 
  std::string Alias;
  if (Name) {
    // Use a specific name for this type, e.g. "size_t".
    Alias = Name;
  } else {
    const char *Prefix = nullptr;
    switch (TK) {
    case TypeKind::IntN:
      Prefix = "int";
      break;
    case TypeKind::UIntN:
      Prefix = "uint";
      break;
    case TypeKind::FastIntN:
      Prefix = "int_fast";
      break;
    case TypeKind::FastUIntN:
      Prefix = "uint_fast";
      break;
    case TypeKind::DontCare:
    case TypeKind::SizeT:
    case TypeKind::PtrdiffT:
      break;
    }
    if (Prefix) {
      Alias = Prefix;
      Alias += std::to_string(BitWidth);
      Alias += "_t";
    }
  }
  if (!Alias.empty()) {
    if (Ptr) {
      // If ArgType is actually a pointer to T, append an asterisk.
      Alias += (Alias[Alias.size() - 1] == '*') ? "*" : " *";
    }
    // If Alias is the same as the underlying type, e.g. wchar_t, then drop it.
    if (S == Alias)
      Alias.clear();
  }
 
  if (Alias.empty())
    return std::string("'") + S + "'";
 
  return std::string("'") + Alias + "'" +
         (K == UnsupportedTy ? "" : " (aka '" + S + "')");
}
 
//===----------------------------------------------------------------------===//
// Methods on OptionalAmount.
//===----------------------------------------------------------------------===//
 
ArgType
analyze_format_string::OptionalAmount::getArgType(ASTContext &Ctx) const {
  return Ctx.IntTy;
}
 
//===----------------------------------------------------------------------===//
// Methods on LengthModifier.
//===----------------------------------------------------------------------===//
 
StringRef analyze_format_string::LengthModifier::toString() const {
  switch (kind) {
  case AsChar:
    return "hh";
  case AsShort:
    return "h";
  case AsShortLong:
    return "hl";
  case AsLong: // or AsWideChar
    return "l";
  case AsLongLong:
    return "ll";
  case AsQuad:
    return "q";
  case AsIntMax:
    return "j";
  case AsSizeT:
    return "z";
  case AsPtrDiff:
    return "t";
  case AsInt32:
    return "I32";
  case AsInt3264:
    return "I";
  case AsInt64:
    return "I64";
  case AsLongDouble:
    return "L";
  case AsDecimal32:
    return "H";
  case AsDecimal64:
    return "D";
  case AsDecimal128:
    return "DD";
  case AsIntN:
  case AsFastIntN:
    return StringRef(Position, getLength());
  case AsAllocate:
    return "a";
  case AsMAllocate:
    return "m";
  case AsWide:
    return "w";
  case None:
    return "";
  }
  llvm_unreachable("Invalid LengthModifier Kind!");
}
 
//===----------------------------------------------------------------------===//
// Methods on ConversionSpecifier.
//===----------------------------------------------------------------------===//
 
const char *ConversionSpecifier::toString() const {
  switch (kind) {
  case bArg:
    return "b";
  case BArg:
    return "B";
  case dArg:
    return "d";
  case DArg:
    return "D";
  case iArg:
    return "i";
  case oArg:
    return "o";
  case OArg:
    return "O";
  case uArg:
    return "u";
  case UArg:
    return "U";
  case xArg:
    return "x";
  case XArg:
    return "X";
  case fArg:
    return "f";
  case FArg:
    return "F";
  case eArg:
    return "e";
  case EArg:
    return "E";
  case gArg:
    return "g";
  case GArg:
    return "G";
  case aArg:
    return "a";
  case AArg:
    return "A";
  case cArg:
    return "c";
  case sArg:
    return "s";
  case pArg:
    return "p";
  case PArg:
    return "P";
  case nArg:
    return "n";
  case PercentArg:
    return "%";
  case ScanListArg:
    return "[";
  case InvalidSpecifier:
    return nullptr;
 
  // POSIX unicode extensions.
  case CArg:
    return "C";
  case SArg:
    return "S";
 
  // Objective-C specific specifiers.
  case ObjCObjArg:
    return "@";
 
  // FreeBSD kernel specific specifiers.
  case FreeBSDbArg:
    return "b";
  case FreeBSDDArg:
    return "D";
  case FreeBSDrArg:
    return "r";
  case FreeBSDyArg:
    return "y";
 
  // GlibC specific specifiers.
  case PrintErrno:
    return "m";
 
  // MS specific specifiers.
  case ZArg:
    return "Z";
 
  // ISO/IEC TR 18037 (fixed-point) specific specifiers.
  case rArg:
    return "r";
  case RArg:
    return "R";
  case kArg:
    return "k";
  case KArg:
    return "K";
  }
  return nullptr;
}
 
std::optional<ConversionSpecifier>
ConversionSpecifier::getStandardSpecifier() const {
  ConversionSpecifier::Kind NewKind;
 
  switch (getKind()) {
  default:
    return std::nullopt;
  case DArg:
    NewKind = dArg;
    break;
  case UArg:
    NewKind = uArg;
    break;
  case OArg:
    NewKind = oArg;
    break;
  }
 
  ConversionSpecifier FixedCS(*this);
  FixedCS.setKind(NewKind);
  return FixedCS;
}
 
//===----------------------------------------------------------------------===//
// Methods on OptionalAmount.
//===----------------------------------------------------------------------===//
 
void OptionalAmount::toString(raw_ostream &os) const {
  switch (hs) {
  case Invalid:
  case NotSpecified:
    return;
  case Arg:
    if (UsesDotPrefix)
      os << ".";
    if (usesPositionalArg())
      os << "*" << getPositionalArgIndex() << "$";
    else
      os << "*";
    break;
  case Constant:
    if (UsesDotPrefix)
      os << ".";
    os << amt;
    break;
  }
}
 
bool FormatSpecifier::hasValidLengthModifier(const TargetInfo &Target,
                                             const LangOptions &LO) const {
  switch (LM.getKind()) {
  case LengthModifier::None:
    return true;
 
  // Handle most integer flags
  case LengthModifier::AsShort:
    // Length modifier only applies to FP vectors.
    if (LO.OpenCL && CS.isDoubleArg())
      return !VectorNumElts.isInvalid();
 
    if (CS.isFixedPointArg())
      return true;
 
    if (Target.getTriple().isOSMSVCRT()) {
      switch (CS.getKind()) {
      case ConversionSpecifier::cArg:
      case ConversionSpecifier::CArg:
      case ConversionSpecifier::sArg:
      case ConversionSpecifier::SArg:
      case ConversionSpecifier::ZArg:
        return true;
      default:
        break;
      }
    }
    [[fallthrough]];
  case LengthModifier::AsChar:
  case LengthModifier::AsLongLong:
  case LengthModifier::AsQuad:
  case LengthModifier::AsIntMax:
  case LengthModifier::AsSizeT:
  case LengthModifier::AsPtrDiff:
    switch (CS.getKind()) {
    case ConversionSpecifier::bArg:
    case ConversionSpecifier::BArg:
    case ConversionSpecifier::dArg:
    case ConversionSpecifier::DArg:
    case ConversionSpecifier::iArg:
    case ConversionSpecifier::oArg:
    case ConversionSpecifier::OArg:
    case ConversionSpecifier::uArg:
    case ConversionSpecifier::UArg:
    case ConversionSpecifier::xArg:
    case ConversionSpecifier::XArg:
    case ConversionSpecifier::nArg:
      return true;
    case ConversionSpecifier::FreeBSDrArg:
    case ConversionSpecifier::FreeBSDyArg:
      return Target.getTriple().isOSFreeBSD() || Target.getTriple().isPS();
    default:
      return false;
    }
 
  case LengthModifier::AsShortLong:
    return LO.OpenCL && !VectorNumElts.isInvalid();
 
  // Handle 'l' flag
  case LengthModifier::AsLong: // or AsWideChar
    if (CS.isDoubleArg()) {
      // Invalid for OpenCL FP scalars.
      if (LO.OpenCL && VectorNumElts.isInvalid())
        return false;
      return true;
    }
 
    if (CS.isFixedPointArg())
      return true;
 
    switch (CS.getKind()) {
    case ConversionSpecifier::bArg:
    case ConversionSpecifier::BArg:
    case ConversionSpecifier::dArg:
    case ConversionSpecifier::DArg:
    case ConversionSpecifier::iArg:
    case ConversionSpecifier::oArg:
    case ConversionSpecifier::OArg:
    case ConversionSpecifier::uArg:
    case ConversionSpecifier::UArg:
    case ConversionSpecifier::xArg:
    case ConversionSpecifier::XArg:
    case ConversionSpecifier::nArg:
    case ConversionSpecifier::cArg:
    case ConversionSpecifier::sArg:
    case ConversionSpecifier::ScanListArg:
    case ConversionSpecifier::ZArg:
      return true;
    case ConversionSpecifier::FreeBSDrArg:
    case ConversionSpecifier::FreeBSDyArg:
      return Target.getTriple().isOSFreeBSD() || Target.getTriple().isPS();
    default:
      return false;
    }
 
  case LengthModifier::AsLongDouble:
    switch (CS.getKind()) {
    case ConversionSpecifier::aArg:
    case ConversionSpecifier::AArg:
    case ConversionSpecifier::fArg:
    case ConversionSpecifier::FArg:
    case ConversionSpecifier::eArg:
    case ConversionSpecifier::EArg:
    case ConversionSpecifier::gArg:
    case ConversionSpecifier::GArg:
      return true;
    // GNU libc extension.
    case ConversionSpecifier::dArg:
    case ConversionSpecifier::iArg:
    case ConversionSpecifier::oArg:
    case ConversionSpecifier::uArg:
    case ConversionSpecifier::xArg:
    case ConversionSpecifier::XArg:
      return !Target.getTriple().isOSDarwin() &&
             !Target.getTriple().isOSWindows();
    default:
      return false;
    }
 
  case LengthModifier::AsIntN:
  case LengthModifier::AsFastIntN: {
    if (!LO.C23)
      return false;
 
    TargetInfo::IntType TargetType =
        LM.getKind() == LengthModifier::AsIntN
            ? Target.getIntTypeByWidth(LM.getBitWidth(), /*IsSigned=*/true)
            : Target.getLeastIntTypeByWidth(LM.getBitWidth(),
                                            /*IsSigned=*/true);
    if (TargetType == TargetInfo::NoInt)
      return false;
 
    switch (CS.getKind()) {
    case ConversionSpecifier::bArg:
    case ConversionSpecifier::BArg:
    case ConversionSpecifier::dArg:
    case ConversionSpecifier::iArg:
    case ConversionSpecifier::oArg:
    case ConversionSpecifier::uArg:
    case ConversionSpecifier::xArg:
    case ConversionSpecifier::XArg:
    case ConversionSpecifier::nArg:
      return true;
    default:
      return false;
    }
  }
 
  case LengthModifier::AsAllocate:
    switch (CS.getKind()) {
    case ConversionSpecifier::sArg:
    case ConversionSpecifier::SArg:
    case ConversionSpecifier::ScanListArg:
      return true;
    default:
      return false;
    }
 
  case LengthModifier::AsMAllocate:
    switch (CS.getKind()) {
    case ConversionSpecifier::cArg:
    case ConversionSpecifier::CArg:
    case ConversionSpecifier::sArg:
    case ConversionSpecifier::SArg:
    case ConversionSpecifier::ScanListArg:
      return true;
    default:
      return false;
    }
  case LengthModifier::AsInt32:
  case LengthModifier::AsInt3264:
  case LengthModifier::AsInt64:
    switch (CS.getKind()) {
    case ConversionSpecifier::dArg:
    case ConversionSpecifier::iArg:
    case ConversionSpecifier::oArg:
    case ConversionSpecifier::uArg:
    case ConversionSpecifier::xArg:
    case ConversionSpecifier::XArg:
      return Target.getTriple().isOSMSVCRT();
    default:
      return false;
    }
  case LengthModifier::AsWide:
    switch (CS.getKind()) {
    case ConversionSpecifier::cArg:
    case ConversionSpecifier::CArg:
    case ConversionSpecifier::sArg:
    case ConversionSpecifier::SArg:
    case ConversionSpecifier::ZArg:
      return Target.getTriple().isOSMSVCRT();
    default:
      return false;
    }
 
  case LengthModifier::AsDecimal32:
  case LengthModifier::AsDecimal64:
  case LengthModifier::AsDecimal128:
    switch (CS.getKind()) {
    case ConversionSpecifier::aArg:
    case ConversionSpecifier::AArg:
    case ConversionSpecifier::eArg:
    case ConversionSpecifier::EArg:
    case ConversionSpecifier::fArg:
    case ConversionSpecifier::FArg:
    case ConversionSpecifier::gArg:
    case ConversionSpecifier::GArg:
      return LO.C23;
    default:
      return false;
    }
  }
  llvm_unreachable("Invalid LengthModifier Kind!");
}
 
bool FormatSpecifier::hasStandardLengthModifier() const {
  switch (LM.getKind()) {
  case LengthModifier::None:
  case LengthModifier::AsChar:
  case LengthModifier::AsShort:
  case LengthModifier::AsLong:
  case LengthModifier::AsLongLong:
  case LengthModifier::AsIntMax:
  case LengthModifier::AsSizeT:
  case LengthModifier::AsPtrDiff:
  case LengthModifier::AsLongDouble:
  case LengthModifier::AsDecimal32:
  case LengthModifier::AsDecimal64:
  case LengthModifier::AsDecimal128:
  case LengthModifier::AsIntN:
  case LengthModifier::AsFastIntN:
    return true;
  case LengthModifier::AsAllocate:
  case LengthModifier::AsMAllocate:
  case LengthModifier::AsQuad:
  case LengthModifier::AsInt32:
  case LengthModifier::AsInt3264:
  case LengthModifier::AsInt64:
  case LengthModifier::AsWide:
  case LengthModifier::AsShortLong: // ???
    return false;
  }
  llvm_unreachable("Invalid LengthModifier Kind!");
}
 
bool FormatSpecifier::hasStandardConversionSpecifier(
    const LangOptions &LangOpt) const {
  switch (CS.getKind()) {
  case ConversionSpecifier::bArg:
  case ConversionSpecifier::BArg:
  case ConversionSpecifier::cArg:
  case ConversionSpecifier::dArg:
  case ConversionSpecifier::iArg:
  case ConversionSpecifier::oArg:
  case ConversionSpecifier::uArg:
  case ConversionSpecifier::xArg:
  case ConversionSpecifier::XArg:
  case ConversionSpecifier::fArg:
  case ConversionSpecifier::FArg:
  case ConversionSpecifier::eArg:
  case ConversionSpecifier::EArg:
  case ConversionSpecifier::gArg:
  case ConversionSpecifier::GArg:
  case ConversionSpecifier::aArg:
  case ConversionSpecifier::AArg:
  case ConversionSpecifier::sArg:
  case ConversionSpecifier::pArg:
  case ConversionSpecifier::nArg:
  case ConversionSpecifier::ObjCObjArg:
  case ConversionSpecifier::ScanListArg:
  case ConversionSpecifier::PercentArg:
  case ConversionSpecifier::PArg:
    return true;
  case ConversionSpecifier::CArg:
  case ConversionSpecifier::SArg:
    return LangOpt.ObjC;
  case ConversionSpecifier::InvalidSpecifier:
  case ConversionSpecifier::FreeBSDbArg:
  case ConversionSpecifier::FreeBSDDArg:
  case ConversionSpecifier::FreeBSDrArg:
  case ConversionSpecifier::FreeBSDyArg:
  case ConversionSpecifier::PrintErrno:
  case ConversionSpecifier::DArg:
  case ConversionSpecifier::OArg:
  case ConversionSpecifier::UArg:
  case ConversionSpecifier::ZArg:
    return false;
  case ConversionSpecifier::rArg:
  case ConversionSpecifier::RArg:
  case ConversionSpecifier::kArg:
  case ConversionSpecifier::KArg:
    return LangOpt.FixedPoint;
  }
  llvm_unreachable("Invalid ConversionSpecifier Kind!");
}
 
bool FormatSpecifier::hasStandardLengthConversionCombination() const {
  if (LM.getKind() == LengthModifier::AsLongDouble) {
    switch (CS.getKind()) {
    case ConversionSpecifier::dArg:
    case ConversionSpecifier::iArg:
    case ConversionSpecifier::oArg:
    case ConversionSpecifier::uArg:
    case ConversionSpecifier::xArg:
    case ConversionSpecifier::XArg:
      return false;
    default:
      return true;
    }
  }
  return true;
}
 
std::optional<LengthModifier>
FormatSpecifier::getCorrectedLengthModifier() const {
  if (CS.isAnyIntArg() || CS.getKind() == ConversionSpecifier::nArg) {
    if (LM.getKind() == LengthModifier::AsLongDouble ||
        LM.getKind() == LengthModifier::AsQuad) {
      LengthModifier FixedLM(LM);
      FixedLM.setKind(LengthModifier::AsLongLong);
      return FixedLM;
    }
  }
 
  return std::nullopt;
}
 
bool FormatSpecifier::namedTypeToLengthModifier(ASTContext &Ctx, QualType QT,
                                                LengthModifier &LM) {
  if (LengthModifier::Kind Out = LengthModifier::Kind::None;
      namedTypeToLengthModifierKind(Ctx, QT, Out)) {
    LM.setKind(Out);
    return true;
  }
  return false;
}