DiagnosticIDs.cpp

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//===--- DiagnosticIDs.cpp - Diagnostic IDs Handling ----------------------===//
//
// 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 Diagnostic IDs-related interfaces.
//
//===----------------------------------------------------------------------===//
 
#include "clang/Basic/DiagnosticIDs.h"
#include "clang/Basic/AllDiagnostics.h"
#include "clang/Basic/DiagnosticCategories.h"
#include "clang/Basic/LangOptions.h"
#include "clang/Basic/SourceManager.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/StringTable.h"
#include "llvm/Support/Compiler.h"
#include "llvm/Support/ErrorHandling.h"
#include <map>
#include <optional>
using namespace clang;
 
//===----------------------------------------------------------------------===//
// Builtin Diagnostic information
//===----------------------------------------------------------------------===//
 
namespace {
 
struct StaticDiagInfoRec;
 
#define GET_DIAG_STABLE_ID_ARRAYS
#include "clang/Basic/DiagnosticStableIDs.inc"
#undef GET_DIAG_STABLE_ID_ARRAYS
 
// Store the descriptions in a separate table to avoid pointers that need to
// be relocated, and also decrease the amount of data needed on 64-bit
// platforms. See "How To Write Shared Libraries" by Ulrich Drepper.
struct StaticDiagInfoDescriptionStringTable {
#define DIAG(ENUM, CLASS, DEFAULT_SEVERITY, DESC, GROUP, SFINAE, NOWERROR,     \
             SHOWINSYSHEADER, SHOWINSYSMACRO, DEFERRABLE, CATEGORY, STABLE_ID, \
             LEGACY_STABLE_IDS)                                                \
  char ENUM##_desc[sizeof(DESC)];
#include "clang/Basic/AllDiagnosticKinds.inc"
#undef DIAG
};
 
const StaticDiagInfoDescriptionStringTable StaticDiagInfoDescriptions = {
#define DIAG(ENUM, CLASS, DEFAULT_SEVERITY, DESC, GROUP, SFINAE, NOWERROR,     \
             SHOWINSYSHEADER, SHOWINSYSMACRO, DEFERRABLE, CATEGORY, STABLE_ID, \
             LEGACY_STABLE_IDS)                                                \
  DESC,
#include "clang/Basic/AllDiagnosticKinds.inc"
#undef DIAG
};
 
extern const StaticDiagInfoRec StaticDiagInfo[];
 
// Stored separately from StaticDiagInfoRec to pack better.  Otherwise,
// StaticDiagInfoRec would have extra padding on 64-bit platforms.
const uint32_t StaticDiagInfoDescriptionOffsets[] = {
#define DIAG(ENUM, CLASS, DEFAULT_SEVERITY, DESC, GROUP, SFINAE, NOWERROR,     \
             SHOWINSYSHEADER, SHOWINSYSMACRO, DEFERRABLE, CATEGORY, STABLE_ID, \
             LEGACY_STABLE_IDS)                                                \
  offsetof(StaticDiagInfoDescriptionStringTable, ENUM##_desc),
#include "clang/Basic/AllDiagnosticKinds.inc"
#undef DIAG
};
 
const uint32_t StaticDiagInfoStableIDOffsets[] = {
#define DIAG(ENUM, CLASS, DEFAULT_SEVERITY, DESC, GROUP, SFINAE, NOWERROR,     \
             SHOWINSYSHEADER, SHOWINSYSMACRO, DEFERRABLE, CATEGORY, STABLE_ID, \
             LEGACY_STABLE_IDS)                                                \
  STABLE_ID,
#include "clang/Basic/AllDiagnosticKinds.inc"
#undef DIAG
};
 
const uint32_t StaticDiagInfoLegacyStableIDStartOffsets[] = {
#define DIAG(ENUM, CLASS, DEFAULT_SEVERITY, DESC, GROUP, SFINAE, NOWERROR,     \
             SHOWINSYSHEADER, SHOWINSYSMACRO, DEFERRABLE, CATEGORY, STABLE_ID, \
             LEGACY_STABLE_IDS)                                                \
  LEGACY_STABLE_IDS,
#include "clang/Basic/AllDiagnosticKinds.inc"
#undef DIAG
};
 
enum DiagnosticClass {
  CLASS_NOTE = DiagnosticIDs::CLASS_NOTE,
  CLASS_REMARK = DiagnosticIDs::CLASS_REMARK,
  CLASS_WARNING = DiagnosticIDs::CLASS_WARNING,
  CLASS_EXTENSION = DiagnosticIDs::CLASS_EXTENSION,
  CLASS_ERROR = DiagnosticIDs::CLASS_ERROR,
  CLASS_TRAP = DiagnosticIDs::CLASS_TRAP,
};
 
struct StaticDiagInfoRec {
  uint16_t DiagID;
  LLVM_PREFERRED_TYPE(diag::Severity)
  uint16_t DefaultSeverity : 3;
  LLVM_PREFERRED_TYPE(DiagnosticClass)
  uint16_t Class : 3;
  LLVM_PREFERRED_TYPE(DiagnosticIDs::SFINAEResponse)
  uint16_t SFINAE : 2;
  LLVM_PREFERRED_TYPE(diag::DiagCategory)
  uint16_t Category : 6;
  LLVM_PREFERRED_TYPE(bool)
  uint16_t WarnNoWerror : 1;
  LLVM_PREFERRED_TYPE(bool)
  uint16_t WarnShowInSystemHeader : 1;
  LLVM_PREFERRED_TYPE(bool)
  uint16_t WarnShowInSystemMacro : 1;
 
  LLVM_PREFERRED_TYPE(diag::Group)
  uint16_t OptionGroupIndex : 15;
  LLVM_PREFERRED_TYPE(bool)
  uint16_t Deferrable : 1;
 
  uint16_t DescriptionLen;
 
  unsigned getOptionGroupIndex() const {
    return OptionGroupIndex;
  }
 
  StringRef getDescription() const {
    size_t MyIndex = this - &StaticDiagInfo[0];
    uint32_t StringOffset = StaticDiagInfoDescriptionOffsets[MyIndex];
    const char* Table = reinterpret_cast<const char*>(&StaticDiagInfoDescriptions);
    return StringRef(&Table[StringOffset], DescriptionLen);
  }
 
  StringRef getStableID() const {
    size_t MyIndex = this - &StaticDiagInfo[0];
    uint32_t StringOffset = StaticDiagInfoStableIDOffsets[MyIndex];
    return DiagStableIDs[StringOffset];
  }
 
  llvm::SmallVector<StringRef, 4> getLegacyStableIDs() const {
    llvm::SmallVector<StringRef, 4> Result;
    size_t MyIndex = this - &StaticDiagInfo[0];
    uint32_t StartOffset = StaticDiagInfoLegacyStableIDStartOffsets[MyIndex];
    for (uint32_t Offset = StartOffset; DiagLegacyStableIDs[Offset] != 0;
         ++Offset) {
      Result.push_back(DiagStableIDs[DiagLegacyStableIDs[Offset]]);
    }
 
    return Result;
  }
 
  diag::Flavor getFlavor() const {
    return Class == CLASS_REMARK ? diag::Flavor::Remark
                                 : diag::Flavor::WarningOrError;
  }
 
  bool operator<(const StaticDiagInfoRec &RHS) const {
    return DiagID < RHS.DiagID;
  }
};
 
#define STRINGIFY_NAME(NAME) #NAME
#define VALIDATE_DIAG_SIZE(NAME)                                               \
  static_assert(                                                               \
      static_cast<unsigned>(diag::NUM_BUILTIN_##NAME##_DIAGNOSTICS) <          \
          static_cast<unsigned>(diag::DIAG_START_##NAME) +                     \
              static_cast<unsigned>(diag::DIAG_SIZE_##NAME),                   \
      STRINGIFY_NAME(                                                          \
          DIAG_SIZE_##NAME) " is insufficient to contain all "                 \
                            "diagnostics, it may need to be made larger in "   \
                            "DiagnosticIDs.h.");
VALIDATE_DIAG_SIZE(COMMON)
VALIDATE_DIAG_SIZE(DRIVER)
VALIDATE_DIAG_SIZE(FRONTEND)
VALIDATE_DIAG_SIZE(SERIALIZATION)
VALIDATE_DIAG_SIZE(LEX)
VALIDATE_DIAG_SIZE(PARSE)
VALIDATE_DIAG_SIZE(AST)
VALIDATE_DIAG_SIZE(COMMENT)
VALIDATE_DIAG_SIZE(CROSSTU)
VALIDATE_DIAG_SIZE(SEMA)
VALIDATE_DIAG_SIZE(ANALYSIS)
VALIDATE_DIAG_SIZE(REFACTORING)
VALIDATE_DIAG_SIZE(INSTALLAPI)
VALIDATE_DIAG_SIZE(TRAP)
#undef VALIDATE_DIAG_SIZE
#undef STRINGIFY_NAME
 
const StaticDiagInfoRec StaticDiagInfo[] = {
// clang-format off
#define DIAG(ENUM, CLASS, DEFAULT_SEVERITY, DESC, GROUP, SFINAE, NOWERROR,     \
             SHOWINSYSHEADER, SHOWINSYSMACRO, DEFERRABLE, CATEGORY, STABLE_ID, \
             LEGACY_STABLE_IDS)                                                \
  {                                                                            \
      diag::ENUM,                                                              \
      DEFAULT_SEVERITY,                                                        \
      CLASS,                                                                   \
      DiagnosticIDs::SFINAE,                                                   \
      CATEGORY,                                                                \
      NOWERROR,                                                                \
      SHOWINSYSHEADER,                                                         \
      SHOWINSYSMACRO,                                                          \
      GROUP,                                                                   \
      DEFERRABLE,                                                              \
      STR_SIZE(DESC, uint16_t)},
#include "clang/Basic/DiagnosticCommonKinds.inc"
#include "clang/Basic/DiagnosticDriverKinds.inc"
#include "clang/Basic/DiagnosticFrontendKinds.inc"
#include "clang/Basic/DiagnosticSerializationKinds.inc"
#include "clang/Basic/DiagnosticLexKinds.inc"
#include "clang/Basic/DiagnosticParseKinds.inc"
#include "clang/Basic/DiagnosticASTKinds.inc"
#include "clang/Basic/DiagnosticCommentKinds.inc"
#include "clang/Basic/DiagnosticCrossTUKinds.inc"
#include "clang/Basic/DiagnosticSemaKinds.inc"
#include "clang/Basic/DiagnosticAnalysisKinds.inc"
#include "clang/Basic/DiagnosticRefactoringKinds.inc"
#include "clang/Basic/DiagnosticInstallAPIKinds.inc"
#include "clang/Basic/DiagnosticTrapKinds.inc"
// clang-format on
#undef DIAG
};
 
} // namespace
 
static const unsigned StaticDiagInfoSize = std::size(StaticDiagInfo);
 
/// GetDiagInfo - Return the StaticDiagInfoRec entry for the specified DiagID,
/// or null if the ID is invalid.
static const StaticDiagInfoRec *GetDiagInfo(unsigned DiagID) {
  // Out of bounds diag. Can't be in the table.
  using namespace diag;
  if (DiagID >= DIAG_UPPER_LIMIT || DiagID <= DIAG_START_COMMON)
    return nullptr;
 
  // Compute the index of the requested diagnostic in the static table.
  // 1. Add the number of diagnostics in each category preceding the
  //    diagnostic and of the category the diagnostic is in. This gives us
  //    the offset of the category in the table.
  // 2. Subtract the number of IDs in each category from our ID. This gives us
  //    the offset of the diagnostic in the category.
  // This is cheaper than a binary search on the table as it doesn't touch
  // memory at all.
  unsigned Offset = 0;
  unsigned ID = DiagID - DIAG_START_COMMON - 1;
#define CATEGORY(NAME, PREV) \
  if (DiagID > DIAG_START_##NAME) { \
    Offset += NUM_BUILTIN_##PREV##_DIAGNOSTICS - DIAG_START_##PREV - 1; \
    ID -= DIAG_START_##NAME - DIAG_START_##PREV; \
  }
CATEGORY(DRIVER, COMMON)
CATEGORY(FRONTEND, DRIVER)
CATEGORY(SERIALIZATION, FRONTEND)
CATEGORY(LEX, SERIALIZATION)
CATEGORY(PARSE, LEX)
CATEGORY(AST, PARSE)
CATEGORY(COMMENT, AST)
CATEGORY(CROSSTU, COMMENT)
CATEGORY(SEMA, CROSSTU)
CATEGORY(ANALYSIS, SEMA)
CATEGORY(REFACTORING, ANALYSIS)
CATEGORY(INSTALLAPI, REFACTORING)
CATEGORY(TRAP, INSTALLAPI)
#undef CATEGORY
 
  // Avoid out of bounds reads.
  if (ID + Offset >= StaticDiagInfoSize)
    return nullptr;
 
  assert(ID < StaticDiagInfoSize && Offset < StaticDiagInfoSize);
 
  const StaticDiagInfoRec *Found = &StaticDiagInfo[ID + Offset];
  // If the diag id doesn't match we found a different diag, abort. This can
  // happen when this function is called with an ID that points into a hole in
  // the diagID space.
  if (Found->DiagID != DiagID)
    return nullptr;
  return Found;
}
 
//===----------------------------------------------------------------------===//
// Custom Diagnostic information
//===----------------------------------------------------------------------===//
 
namespace clang {
namespace diag {
using CustomDiagDesc = DiagnosticIDs::CustomDiagDesc;
class CustomDiagInfo {
  std::vector<CustomDiagDesc> DiagInfo;
  std::map<CustomDiagDesc, unsigned> DiagIDs;
  std::map<diag::Group, std::vector<unsigned>> GroupToDiags;
 
public:
  /// getDescription - Return the description of the specified custom
  /// diagnostic.
  const CustomDiagDesc &getDescription(unsigned DiagID) const {
    assert(DiagID - DIAG_UPPER_LIMIT < DiagInfo.size() &&
           "Invalid diagnostic ID");
    return DiagInfo[DiagID - DIAG_UPPER_LIMIT];
  }
 
  unsigned getOrCreateDiagID(DiagnosticIDs::CustomDiagDesc D) {
    // Check to see if it already exists.
    std::map<CustomDiagDesc, unsigned>::iterator I = DiagIDs.lower_bound(D);
    if (I != DiagIDs.end() && I->first == D)
      return I->second;
 
    // If not, assign a new ID.
    unsigned ID = DiagInfo.size() + DIAG_UPPER_LIMIT;
    DiagIDs.insert(std::make_pair(D, ID));
    DiagInfo.push_back(D);
    if (auto Group = D.GetGroup())
      GroupToDiags[*Group].emplace_back(ID);
    return ID;
  }
 
  ArrayRef<unsigned> getDiagsInGroup(diag::Group G) const {
    if (auto Diags = GroupToDiags.find(G); Diags != GroupToDiags.end())
      return Diags->second;
    return {};
  }
};
 
} // namespace diag
} // namespace clang
 
DiagnosticMapping DiagnosticIDs::getDefaultMapping(unsigned DiagID) const {
  DiagnosticMapping Info = DiagnosticMapping::Make(
      diag::Severity::Fatal, /*IsUser=*/false, /*IsPragma=*/false);
 
  if (IsCustomDiag(DiagID)) {
    Info.setSeverity(
        CustomDiagInfo->getDescription(DiagID).GetDefaultSeverity());
  } else if (const StaticDiagInfoRec *StaticInfo = GetDiagInfo(DiagID)) {
    Info.setSeverity((diag::Severity)StaticInfo->DefaultSeverity);
 
    if (StaticInfo->WarnNoWerror) {
      assert(Info.getSeverity() == diag::Severity::Warning &&
             "Unexpected mapping with no-Werror bit!");
      Info.setNoWarningAsError(true);
    }
  }
 
  return Info;
}
 
void DiagnosticIDs::initCustomDiagMapping(DiagnosticMapping &Mapping,
                                          unsigned DiagID) {
  assert(IsCustomDiag(DiagID));
  const auto &Diag = CustomDiagInfo->getDescription(DiagID);
  if (auto Group = Diag.GetGroup()) {
    GroupInfo GroupInfo = GroupInfos[static_cast<size_t>(*Group)];
    if (static_cast<diag::Severity>(GroupInfo.Severity) != diag::Severity())
      Mapping.setSeverity(static_cast<diag::Severity>(GroupInfo.Severity));
    Mapping.setNoWarningAsError(GroupInfo.HasNoWarningAsError);
  } else {
    Mapping.setSeverity(Diag.GetDefaultSeverity());
    Mapping.setNoWarningAsError(true);
    Mapping.setNoErrorAsFatal(true);
  }
}
 
/// getCategoryNumberForDiag - Return the category number that a specified
/// DiagID belongs to, or 0 if no category.
unsigned DiagnosticIDs::getCategoryNumberForDiag(unsigned DiagID) {
  if (const StaticDiagInfoRec *Info = GetDiagInfo(DiagID))
    return Info->Category;
  return 0;
}
 
namespace {
  // The diagnostic category names.
  struct StaticDiagCategoryRec {
    const char *NameStr;
    uint8_t NameLen;
 
    StringRef getName() const {
      return StringRef(NameStr, NameLen);
    }
  };
}
 
static const StaticDiagCategoryRec CategoryNameTable[] = {
#define GET_CATEGORY_TABLE
#define CATEGORY(X, ENUM) { X, STR_SIZE(X, uint8_t) },
#include "clang/Basic/DiagnosticGroups.inc"
#undef GET_CATEGORY_TABLE
  { nullptr, 0 }
};
 
/// getNumberOfCategories - Return the number of categories
unsigned DiagnosticIDs::getNumberOfCategories() {
  return std::size(CategoryNameTable) - 1;
}
 
/// getCategoryNameFromID - Given a category ID, return the name of the
/// category, an empty string if CategoryID is zero, or null if CategoryID is
/// invalid.
StringRef DiagnosticIDs::getCategoryNameFromID(unsigned CategoryID) {
  if (CategoryID >= getNumberOfCategories())
   return StringRef();
  return CategoryNameTable[CategoryID].getName();
}
 
 
 
DiagnosticIDs::SFINAEResponse
DiagnosticIDs::getDiagnosticSFINAEResponse(unsigned DiagID) {
  if (const StaticDiagInfoRec *Info = GetDiagInfo(DiagID))
    return static_cast<DiagnosticIDs::SFINAEResponse>(Info->SFINAE);
  return SFINAE_Report;
}
 
bool DiagnosticIDs::isDeferrable(unsigned DiagID) {
  if (const StaticDiagInfoRec *Info = GetDiagInfo(DiagID))
    return Info->Deferrable;
  return false;
}
 
//===----------------------------------------------------------------------===//
// Common Diagnostic implementation
//===----------------------------------------------------------------------===//
 
DiagnosticIDs::DiagnosticIDs() {}
 
DiagnosticIDs::~DiagnosticIDs() {}
 
/// getCustomDiagID - Return an ID for a diagnostic with the specified message
/// and level.  If this is the first request for this diagnostic, it is
/// registered and created, otherwise the existing ID is returned.
///
/// \param FormatString A fixed diagnostic format string that will be hashed and
/// mapped to a unique DiagID.
unsigned DiagnosticIDs::getCustomDiagID(CustomDiagDesc Diag) {
  if (!CustomDiagInfo)
    CustomDiagInfo.reset(new diag::CustomDiagInfo());
  return CustomDiagInfo->getOrCreateDiagID(Diag);
}
 
bool DiagnosticIDs::isWarningOrExtension(unsigned DiagID) const {
  return DiagID < diag::DIAG_UPPER_LIMIT
             ? getDiagClass(DiagID) != CLASS_ERROR
             : CustomDiagInfo->getDescription(DiagID).GetClass() != CLASS_ERROR;
}
 
/// Determine whether the given built-in diagnostic ID is a
/// Note.
bool DiagnosticIDs::isNote(unsigned DiagID) const {
  return DiagID < diag::DIAG_UPPER_LIMIT && getDiagClass(DiagID) == CLASS_NOTE;
}
 
/// isExtensionDiag - Determine whether the given built-in diagnostic
/// ID is for an extension of some sort.  This also returns EnabledByDefault,
/// which is set to indicate whether the diagnostic is ignored by default (in
/// which case -pedantic enables it) or treated as a warning/error by default.
///
bool DiagnosticIDs::isExtensionDiag(unsigned DiagID,
                                    bool &EnabledByDefault) const {
  if (IsCustomDiag(DiagID) || getDiagClass(DiagID) != CLASS_EXTENSION)
    return false;
 
  EnabledByDefault =
      getDefaultMapping(DiagID).getSeverity() != diag::Severity::Ignored;
  return true;
}
 
bool DiagnosticIDs::isDefaultMappingAsError(unsigned DiagID) const {
  return getDefaultMapping(DiagID).getSeverity() >= diag::Severity::Error;
}
 
/// getDescription - Given a diagnostic ID, return a description of the
/// issue.
StringRef DiagnosticIDs::getDescription(unsigned DiagID) const {
  if (const StaticDiagInfoRec *Info = GetDiagInfo(DiagID))
    return Info->getDescription();
  assert(CustomDiagInfo && "Invalid CustomDiagInfo");
  return CustomDiagInfo->getDescription(DiagID).GetDescription();
}
 
/// getStableID - Given a diagnostic ID, return the stable ID of the diagnostic.
std::string DiagnosticIDs::getStableID(unsigned DiagID) const {
  if (const StaticDiagInfoRec *Info = GetDiagInfo(DiagID))
    return Info->getStableID().str();
  assert(CustomDiagInfo && "Invalid CustomDiagInfo");
  // TODO: Stable IDs for custom diagnostics?
  // If we have to go through every custom diagnostic and add a stable ID, we
  // should instead just go replace them all with declared diagnostics.
  return std::to_string(DiagID);
}
 
/// getLegacyStableIDs - Given a diagnostic ID, return the previous stable IDs
/// of the diagnostic.
SmallVector<StringRef, 4>
DiagnosticIDs::getLegacyStableIDs(unsigned DiagID) const {
  if (const StaticDiagInfoRec *Info = GetDiagInfo(DiagID))
    return Info->getLegacyStableIDs();
  assert(CustomDiagInfo && "Invalid CustomDiagInfo");
  // TODO: Stable IDs for custom diagnostics?
  // If we have to go through every custom diagnostic and add a stable ID, we
  // should instead just go replace them all with declared diagnostics.
  return {};
}
 
static DiagnosticIDs::Level toLevel(diag::Severity SV) {
  switch (SV) {
  case diag::Severity::Ignored:
    return DiagnosticIDs::Ignored;
  case diag::Severity::Remark:
    return DiagnosticIDs::Remark;
  case diag::Severity::Warning:
    return DiagnosticIDs::Warning;
  case diag::Severity::Error:
    return DiagnosticIDs::Error;
  case diag::Severity::Fatal:
    return DiagnosticIDs::Fatal;
  }
  llvm_unreachable("unexpected severity");
}
 
/// getDiagnosticLevel - Based on the way the client configured the
/// DiagnosticsEngine object, classify the specified diagnostic ID into a Level,
/// by consumable the DiagnosticClient.
DiagnosticIDs::Level
DiagnosticIDs::getDiagnosticLevel(unsigned DiagID, SourceLocation Loc,
                                  const DiagnosticsEngine &Diag) const {
  unsigned DiagClass = getDiagClass(DiagID);
  if (DiagClass == CLASS_NOTE) return DiagnosticIDs::Note;
  return toLevel(getDiagnosticSeverity(DiagID, Loc, Diag));
}
 
/// Based on the way the client configured the Diagnostic
/// object, classify the specified diagnostic ID into a Level, consumable by
/// the DiagnosticClient.
///
/// \param Loc The source location we are interested in finding out the
/// diagnostic state. Can be null in order to query the latest state.
diag::Severity
DiagnosticIDs::getDiagnosticSeverity(unsigned DiagID, SourceLocation Loc,
                                     const DiagnosticsEngine &Diag) const {
  bool IsCustomDiag = DiagnosticIDs::IsCustomDiag(DiagID);
  assert(getDiagClass(DiagID) != CLASS_NOTE);
 
  // Specific non-error diagnostics may be mapped to various levels from ignored
  // to error.  Errors can only be mapped to fatal.
  diag::Severity Result = diag::Severity::Fatal;
 
  // Get the mapping information, or compute it lazily.
  DiagnosticsEngine::DiagState *State = Diag.GetDiagStateForLoc(Loc);
  DiagnosticMapping Mapping = State->getOrAddMapping((diag::kind)DiagID);
 
  // TODO: Can a null severity really get here?
  if (Mapping.getSeverity() != diag::Severity())
    Result = Mapping.getSeverity();
 
  // Upgrade ignored diagnostics if -Weverything is enabled.
  if (State->EnableAllWarnings && Result == diag::Severity::Ignored &&
      !Mapping.isUser() &&
      (IsCustomDiag || getDiagClass(DiagID) != CLASS_REMARK))
    Result = diag::Severity::Warning;
 
  // Ignore -pedantic diagnostics inside __extension__ blocks.
  // (The diagnostics controlled by -pedantic are the extension diagnostics
  // that are not enabled by default.)
  bool EnabledByDefault = false;
  bool IsExtensionDiag = isExtensionDiag(DiagID, EnabledByDefault);
  if (Diag.AllExtensionsSilenced && IsExtensionDiag && !EnabledByDefault)
    return diag::Severity::Ignored;
 
  // For extension diagnostics that haven't been explicitly mapped, check if we
  // should upgrade the diagnostic. Skip if the user explicitly suppressed it
  // (e.g. -Wno-foo).
  if (IsExtensionDiag &&
      !(Mapping.isUser() && Result == diag::Severity::Ignored)) {
    if (Mapping.hasNoWarningAsError())
      Result = std::max(Result,
                        std::min(State->ExtBehavior, diag::Severity::Warning));
    else
      Result = std::max(Result, State->ExtBehavior);
  }
 
  // At this point, ignored errors can no longer be upgraded.
  if (Result == diag::Severity::Ignored)
    return Result;
 
  // Honor -w: this disables all messages which are not Error/Fatal by
  // default (disregarding attempts to upgrade severity from Warning to Error),
  // as well as disabling all messages which are currently mapped to Warning
  // (whether by default or downgraded from Error via e.g. -Wno-error or #pragma
  // diagnostic.)
  // FIXME: Should -w be ignored for custom warnings without a group?
  if (State->IgnoreAllWarnings) {
    if ((!IsCustomDiag || CustomDiagInfo->getDescription(DiagID).GetGroup()) &&
        (Result == diag::Severity::Warning ||
         (Result >= diag::Severity::Error &&
          !isDefaultMappingAsError((diag::kind)DiagID))))
      return diag::Severity::Ignored;
  }
 
  // If -Werror is enabled, map warnings to errors unless explicitly disabled.
  if (Result == diag::Severity::Warning) {
    if (State->WarningsAsErrors && !Mapping.hasNoWarningAsError())
      Result = diag::Severity::Error;
  }
 
  // If -Wfatal-errors is enabled, map errors to fatal unless explicitly
  // disabled.
  if (Result == diag::Severity::Error) {
    if (State->ErrorsAsFatal && !Mapping.hasNoErrorAsFatal())
      Result = diag::Severity::Fatal;
  }
 
  // If explicitly requested, map fatal errors to errors.
  if (Result == diag::Severity::Fatal &&
      DiagID != diag::fatal_too_many_errors && Diag.FatalsAsError)
    Result = diag::Severity::Error;
 
  // Rest of the mappings are only applicable for diagnostics associated with a
  // SourceLocation, bail out early for others.
  if (!Diag.hasSourceManager())
    return Result;
 
  const auto &SM = Diag.getSourceManager();
  // If we are in a system header, we ignore it. We look at the diagnostic class
  // because we also want to ignore extensions and warnings in -Werror and
  // -pedantic-errors modes, which *map* warnings/extensions to errors.
  //
  // We check both the location-specific state and the ForceSystemWarnings
  // override. In some cases (like template instantiations from system modules),
  // the location-specific state might have suppression enabled, but the
  // engine might have an override (e.g. AllowWarningInSystemHeaders) to show
  // the warning.
  if (State->SuppressSystemWarnings && !Diag.getForceSystemWarnings() &&
      Loc.isValid() && SM.isInSystemHeader(SM.getExpansionLoc(Loc))) {
    bool ShowInSystemHeader = true;
    if (IsCustomDiag)
      ShowInSystemHeader =
          CustomDiagInfo->getDescription(DiagID).ShouldShowInSystemHeader();
    else if (const StaticDiagInfoRec *Rec = GetDiagInfo(DiagID))
      ShowInSystemHeader = Rec->WarnShowInSystemHeader;
 
    if (!ShowInSystemHeader)
      return diag::Severity::Ignored;
  }
  // We also ignore warnings due to system macros. As above, we respect the
  // ForceSystemWarnings override.
  if (State->SuppressSystemWarnings && !Diag.getForceSystemWarnings() &&
      Loc.isValid()) {
 
    bool ShowInSystemMacro = true;
    if (const StaticDiagInfoRec *Rec = GetDiagInfo(DiagID))
      ShowInSystemMacro = Rec->WarnShowInSystemMacro;
 
    if (!ShowInSystemMacro && SM.isInSystemMacro(Loc))
      return diag::Severity::Ignored;
  }
  // Clang-diagnostics pragmas always take precedence over suppression mapping.
  if (!Mapping.isPragma() && Diag.isSuppressedViaMapping(DiagID, Loc))
    return diag::Severity::Ignored;
 
  return Result;
}
 
DiagnosticIDs::Class DiagnosticIDs::getDiagClass(unsigned DiagID) const {
  if (IsCustomDiag(DiagID))
    return Class(CustomDiagInfo->getDescription(DiagID).GetClass());
 
  if (const StaticDiagInfoRec *Info = GetDiagInfo(DiagID))
    return Class(Info->Class);
  return CLASS_INVALID;
}
 
#define GET_DIAG_ARRAYS
#include "clang/Basic/DiagnosticGroups.inc"
#undef GET_DIAG_ARRAYS
 
namespace {
  struct WarningOption {
    uint16_t NameOffset;
    uint16_t Members;
    uint16_t SubGroups;
    StringRef Documentation;
 
    StringRef getName() const { return DiagGroupNames[NameOffset]; }
  };
}
 
// Second the table of options, sorted by name for fast binary lookup.
static const WarningOption OptionTable[] = {
#define DIAG_ENTRY(GroupName, FlagNameOffset, Members, SubGroups, Docs)        \
  {FlagNameOffset, Members, SubGroups, Docs},
#include "clang/Basic/DiagnosticGroups.inc"
#undef DIAG_ENTRY
};
 
/// Given a diagnostic group ID, return its documentation.
StringRef DiagnosticIDs::getWarningOptionDocumentation(diag::Group Group) {
  return OptionTable[static_cast<int>(Group)].Documentation;
}
 
StringRef DiagnosticIDs::getWarningOptionForGroup(diag::Group Group) {
  return OptionTable[static_cast<int>(Group)].getName();
}
 
std::optional<diag::Group>
DiagnosticIDs::getGroupForWarningOption(StringRef Name) {
  const auto *Found = llvm::partition_point(
      OptionTable, [=](const WarningOption &O) { return O.getName() < Name; });
  if (Found == std::end(OptionTable) || Found->getName() != Name)
    return std::nullopt;
  return static_cast<diag::Group>(Found - OptionTable);
}
 
std::optional<diag::Group>
DiagnosticIDs::getGroupForDiag(unsigned DiagID) const {
  if (IsCustomDiag(DiagID)) {
    assert(CustomDiagInfo);
    return CustomDiagInfo->getDescription(DiagID).GetGroup();
  }
  if (const StaticDiagInfoRec *Info = GetDiagInfo(DiagID))
    return static_cast<diag::Group>(Info->getOptionGroupIndex());
  return std::nullopt;
}
 
/// getWarningOptionForDiag - Return the lowest-level warning option that
/// enables the specified diagnostic.  If there is no -Wfoo flag that controls
/// the diagnostic, this returns null.
StringRef DiagnosticIDs::getWarningOptionForDiag(unsigned DiagID) {
  if (auto G = getGroupForDiag(DiagID))
    return getWarningOptionForGroup(*G);
  return StringRef();
}
 
std::vector<std::string> DiagnosticIDs::getDiagnosticFlags() {
  std::vector<std::string> Res{"-W", "-Wno-"};
  for (StringRef Name : DiagGroupNames) {
    if (Name.empty())
      continue;
 
    Res.push_back((Twine("-W") + Name).str());
    Res.push_back((Twine("-Wno-") + Name).str());
  }
 
  return Res;
}
 
/// Return \c true if any diagnostics were found in this group, even if they
/// were filtered out due to having the wrong flavor.
static bool getDiagnosticsInGroup(diag::Flavor Flavor,
                                  const WarningOption *Group,
                                  SmallVectorImpl<diag::kind> &Diags,
                                  diag::CustomDiagInfo *CustomDiagInfo) {
  // An empty group is considered to be a warning group: we have empty groups
  // for GCC compatibility, and GCC does not have remarks.
  if (!Group->Members && !Group->SubGroups)
    return Flavor == diag::Flavor::Remark;
 
  bool NotFound = true;
 
  // Add the members of the option diagnostic set.
  const int16_t *Member = DiagArrays + Group->Members;
  for (; *Member != -1; ++Member) {
    if (GetDiagInfo(*Member)->getFlavor() == Flavor) {
      NotFound = false;
      Diags.push_back(*Member);
    }
  }
 
  // Add the members of the subgroups.
  const int16_t *SubGroups = DiagSubGroups + Group->SubGroups;
  for (; *SubGroups != (int16_t)-1; ++SubGroups) {
    if (CustomDiagInfo)
      llvm::copy(
          CustomDiagInfo->getDiagsInGroup(static_cast<diag::Group>(*SubGroups)),
          std::back_inserter(Diags));
    NotFound &= getDiagnosticsInGroup(Flavor, &OptionTable[(short)*SubGroups],
                                      Diags, CustomDiagInfo);
  }
 
  return NotFound;
}
 
bool
DiagnosticIDs::getDiagnosticsInGroup(diag::Flavor Flavor, StringRef Group,
                                     SmallVectorImpl<diag::kind> &Diags) const {
  if (std::optional<diag::Group> G = getGroupForWarningOption(Group)) {
    if (CustomDiagInfo)
      llvm::copy(CustomDiagInfo->getDiagsInGroup(*G),
                 std::back_inserter(Diags));
    return ::getDiagnosticsInGroup(Flavor,
                                   &OptionTable[static_cast<unsigned>(*G)],
                                   Diags, CustomDiagInfo.get());
  }
  return true;
}
 
template <class Func>
static void forEachSubGroupImpl(const WarningOption *Group, Func func) {
  for (const int16_t *SubGroups = DiagSubGroups + Group->SubGroups;
       *SubGroups != -1; ++SubGroups) {
    func(static_cast<size_t>(*SubGroups));
    forEachSubGroupImpl(&OptionTable[*SubGroups], func);
  }
}
 
template <class Func>
static void forEachSubGroup(diag::Group Group, Func func) {
  const WarningOption *WarningOpt = &OptionTable[static_cast<size_t>(Group)];
  func(static_cast<size_t>(Group));
  ::forEachSubGroupImpl(WarningOpt, std::move(func));
}
 
void DiagnosticIDs::setGroupSeverity(StringRef Group, diag::Severity Sev) {
  if (std::optional<diag::Group> G = getGroupForWarningOption(Group)) {
    ::forEachSubGroup(*G, [&](size_t SubGroup) {
      GroupInfos[SubGroup].Severity = static_cast<unsigned>(Sev);
    });
  }
}
 
void DiagnosticIDs::setGroupNoWarningsAsError(StringRef Group, bool Val) {
  if (std::optional<diag::Group> G = getGroupForWarningOption(Group)) {
    ::forEachSubGroup(*G, [&](size_t SubGroup) {
      GroupInfos[static_cast<size_t>(*G)].HasNoWarningAsError = Val;
    });
  }
}
 
void DiagnosticIDs::getAllDiagnostics(diag::Flavor Flavor,
                                      std::vector<diag::kind> &Diags) {
  for (unsigned i = 0; i != StaticDiagInfoSize; ++i)
    if (StaticDiagInfo[i].getFlavor() == Flavor)
      Diags.push_back(StaticDiagInfo[i].DiagID);
}
 
StringRef DiagnosticIDs::getNearestOption(diag::Flavor Flavor,
                                          StringRef Group) {
  StringRef Best;
  unsigned BestDistance = Group.size() + 1; // Maximum threshold.
  for (const WarningOption &O : OptionTable) {
    // Don't suggest ignored warning flags.
    if (!O.Members && !O.SubGroups)
      continue;
 
    unsigned Distance = O.getName().edit_distance(Group, true, BestDistance);
    if (Distance > BestDistance)
      continue;
 
    // Don't suggest groups that are not of this kind.
    llvm::SmallVector<diag::kind, 8> Diags;
    if (::getDiagnosticsInGroup(Flavor, &O, Diags, nullptr) || Diags.empty())
      continue;
 
    if (Distance == BestDistance) {
      // Two matches with the same distance, don't prefer one over the other.
      Best = "";
    } else if (Distance < BestDistance) {
      // This is a better match.
      Best = O.getName();
      BestDistance = Distance;
    }
  }
 
  return Best;
}
 
unsigned DiagnosticIDs::getCXXCompatDiagId(const LangOptions &LangOpts,
                                           unsigned CompatDiagId) {
  struct CompatDiag {
    unsigned StdVer;
    unsigned DiagId;
    unsigned PreDiagId;
  };
 
  // We encode the standard version such that C++98 < C++11 < C++14 etc. The
  // actual numbers don't really matter for this, but the definitions of the
  // compat diags in the Tablegen file use the standard version number (i.e.
  // 98, 11, 14, etc.), so we base the encoding here on that.
#define DIAG_COMPAT_IDS_BEGIN()
#define DIAG_COMPAT_IDS_END()
#define DIAG_COMPAT_ID(Value, Name, Std, Diag, DiagPre)                        \
  {Std == 98 ? 1998 : 2000 + Std, diag::Diag, diag::DiagPre},
  static constexpr CompatDiag Diags[]{
#include "clang/Basic/DiagnosticAllCompatIDs.inc"
  };
#undef DIAG_COMPAT_ID
#undef DIAG_COMPAT_IDS_BEGIN
#undef DIAG_COMPAT_IDS_END
 
  assert(CompatDiagId < std::size(Diags) && "Invalid compat diag id");
 
  unsigned StdVer = [&] {
    if (LangOpts.CPlusPlus26)
      return 2026;
    if (LangOpts.CPlusPlus23)
      return 2023;
    if (LangOpts.CPlusPlus20)
      return 2020;
    if (LangOpts.CPlusPlus17)
      return 2017;
    if (LangOpts.CPlusPlus14)
      return 2014;
    if (LangOpts.CPlusPlus11)
      return 2011;
    return 1998;
  }();
 
  const CompatDiag &D = Diags[CompatDiagId];
  return StdVer >= D.StdVer ? D.DiagId : D.PreDiagId;
}
 
bool DiagnosticIDs::isUnrecoverable(unsigned DiagID) const {
  // Only errors may be unrecoverable.
  if (getDiagClass(DiagID) < CLASS_ERROR)
    return false;
 
  if (DiagID == diag::err_unavailable ||
      DiagID == diag::err_unavailable_message)
    return false;
 
  // All ARC errors are currently considered recoverable, with the exception of
  // err_arc_may_not_respond. This specific error is treated as unrecoverable
  // because sending a message with an unknown selector could lead to crashes
  // within CodeGen if the resulting expression is used to initialize a C++
  // auto variable, where type deduction is required.
  if (isARCDiagnostic(DiagID) && DiagID != diag::err_arc_may_not_respond)
    return false;
 
  if (isCodegenABICheckDiagnostic(DiagID))
    return false;
 
  return true;
}
 
bool DiagnosticIDs::isARCDiagnostic(unsigned DiagID) {
  unsigned cat = getCategoryNumberForDiag(DiagID);
  return DiagnosticIDs::getCategoryNameFromID(cat).starts_with("ARC ");
}
 
bool DiagnosticIDs::isCodegenABICheckDiagnostic(unsigned DiagID) {
  unsigned cat = getCategoryNumberForDiag(DiagID);
  return DiagnosticIDs::getCategoryNameFromID(cat) == "Codegen ABI Check";
}