SymbolFile/DWARF/DWARFUnit.cpp

//===-- DWARFUnit.cpp -------------------------------------------*- 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
//
//===----------------------------------------------------------------------===//

#include "DWARFUnit.h"

#include "lldb/Core/Module.h"
#include "lldb/Host/StringConvert.h"
#include "lldb/Symbol/ObjectFile.h"
#include "lldb/Utility/LLDBAssert.h"
#include "lldb/Utility/StreamString.h"
#include "lldb/Utility/Timer.h"
#include "llvm/Object/Error.h"

#include "DWARFCompileUnit.h"
#include "DWARFDebugAranges.h"
#include "DWARFDebugInfo.h"
#include "DWARFTypeUnit.h"
#include "LogChannelDWARF.h"
#include "SymbolFileDWARFDwo.h"

using namespace lldb;
using namespace lldb_private;
using namespace std;

extern int g_verbose;

DWARFUnit::DWARFUnit(SymbolFileDWARF *dwarf, lldb::user_id_t uid,
                     const DWARFUnitHeader &header,
                     const DWARFAbbreviationDeclarationSet &abbrevs,
                     DIERef::Section section)
    : UserID(uid), m_dwarf(dwarf), m_header(header), m_abbrevs(&abbrevs),
      m_cancel_scopes(false), m_section(section) {}

DWARFUnit::~DWARFUnit() = default;

// Parses first DIE of a compile unit.
void DWARFUnit::ExtractUnitDIEIfNeeded() {
  {
    llvm::sys::ScopedReader lock(m_first_die_mutex);
    if (m_first_die)
      return; // Already parsed
  }
  llvm::sys::ScopedWriter lock(m_first_die_mutex);
  if (m_first_die)
    return; // Already parsed

  static Timer::Category func_cat(LLVM_PRETTY_FUNCTION);
  Timer scoped_timer(func_cat, "%8.8x: DWARFUnit::ExtractUnitDIEIfNeeded()",
                     GetOffset());

  // Set the offset to that of the first DIE and calculate the start of the
  // next compilation unit header.
  lldb::offset_t offset = GetFirstDIEOffset();

  // We are in our compile unit, parse starting at the offset we were told to
  // parse
  const DWARFDataExtractor &data = GetData();
  if (offset < GetNextUnitOffset() &&
      m_first_die.Extract(data, this, &offset)) {
    AddUnitDIE(m_first_die);
    return;
  }
}

// Parses a compile unit and indexes its DIEs if it hasn't already been done.
// It will leave this compile unit extracted forever.
void DWARFUnit::ExtractDIEsIfNeeded() {
  m_cancel_scopes = true;

  {
    llvm::sys::ScopedReader lock(m_die_array_mutex);
    if (!m_die_array.empty())
      return; // Already parsed
  }
  llvm::sys::ScopedWriter lock(m_die_array_mutex);
  if (!m_die_array.empty())
    return; // Already parsed

  ExtractDIEsRWLocked();
}

// Parses a compile unit and indexes its DIEs if it hasn't already been done.
// It will clear this compile unit after returned instance gets out of scope,
// no other ScopedExtractDIEs instance is running for this compile unit
// and no ExtractDIEsIfNeeded() has been executed during this ScopedExtractDIEs
// lifetime.
DWARFUnit::ScopedExtractDIEs DWARFUnit::ExtractDIEsScoped() {
  ScopedExtractDIEs scoped(this);

  {
    llvm::sys::ScopedReader lock(m_die_array_mutex);
    if (!m_die_array.empty())
      return scoped; // Already parsed
  }
  llvm::sys::ScopedWriter lock(m_die_array_mutex);
  if (!m_die_array.empty())
    return scoped; // Already parsed

  // Otherwise m_die_array would be already populated.
  lldbassert(!m_cancel_scopes);

  ExtractDIEsRWLocked();
  scoped.m_clear_dies = true;
  return scoped;
}

DWARFUnit::ScopedExtractDIEs::ScopedExtractDIEs(DWARFUnit *cu) : m_cu(cu) {
  lldbassert(m_cu);
  m_cu->m_die_array_scoped_mutex.lock_shared();
}

DWARFUnit::ScopedExtractDIEs::~ScopedExtractDIEs() {
  if (!m_cu)
    return;
  m_cu->m_die_array_scoped_mutex.unlock_shared();
  if (!m_clear_dies || m_cu->m_cancel_scopes)
    return;
  // Be sure no other ScopedExtractDIEs is running anymore.
  llvm::sys::ScopedWriter lock_scoped(m_cu->m_die_array_scoped_mutex);
  llvm::sys::ScopedWriter lock(m_cu->m_die_array_mutex);
  if (m_cu->m_cancel_scopes)
    return;
  m_cu->ClearDIEsRWLocked();
}

DWARFUnit::ScopedExtractDIEs::ScopedExtractDIEs(ScopedExtractDIEs &&rhs)
    : m_cu(rhs.m_cu), m_clear_dies(rhs.m_clear_dies) {
  rhs.m_cu = nullptr;
}

DWARFUnit::ScopedExtractDIEs &DWARFUnit::ScopedExtractDIEs::operator=(
    DWARFUnit::ScopedExtractDIEs &&rhs) {
  m_cu = rhs.m_cu;
  rhs.m_cu = nullptr;
  m_clear_dies = rhs.m_clear_dies;
  return *this;
}

// Parses a compile unit and indexes its DIEs, m_die_array_mutex must be
// held R/W and m_die_array must be empty.
void DWARFUnit::ExtractDIEsRWLocked() {
  llvm::sys::ScopedWriter first_die_lock(m_first_die_mutex);

  static Timer::Category func_cat(LLVM_PRETTY_FUNCTION);
  Timer scoped_timer(func_cat, "%8.8x: DWARFUnit::ExtractDIEsIfNeeded()",
                     GetOffset());

  // Set the offset to that of the first DIE and calculate the start of the
  // next compilation unit header.
  lldb::offset_t offset = GetFirstDIEOffset();
  lldb::offset_t next_cu_offset = GetNextUnitOffset();

  DWARFDebugInfoEntry die;

  uint32_t depth = 0;
  // We are in our compile unit, parse starting at the offset we were told to
  // parse
  const DWARFDataExtractor &data = GetData();
  std::vector<uint32_t> die_index_stack;
  die_index_stack.reserve(32);
  die_index_stack.push_back(0);
  bool prev_die_had_children = false;
  while (offset < next_cu_offset && die.Extract(data, this, &offset)) {
    const bool null_die = die.IsNULL();
    if (depth == 0) {
      assert(m_die_array.empty() && "Compile unit DIE already added");

      // The average bytes per DIE entry has been seen to be around 14-20 so
      // lets pre-reserve half of that since we are now stripping the NULL
      // tags.

      // Only reserve the memory if we are adding children of the main
      // compile unit DIE. The compile unit DIE is always the first entry, so
      // if our size is 1, then we are adding the first compile unit child
      // DIE and should reserve the memory.
      m_die_array.reserve(GetDebugInfoSize() / 24);
      m_die_array.push_back(die);

      if (!m_first_die)
        AddUnitDIE(m_die_array.front());
    } else {
      if (null_die) {
        if (prev_die_had_children) {
          // This will only happen if a DIE says is has children but all it
          // contains is a NULL tag. Since we are removing the NULL DIEs from
          // the list (saves up to 25% in C++ code), we need a way to let the
          // DIE know that it actually doesn't have children.
          if (!m_die_array.empty())
            m_die_array.back().SetHasChildren(false);
        }
      } else {
        die.SetParentIndex(m_die_array.size() - die_index_stack[depth - 1]);

        if (die_index_stack.back())
          m_die_array[die_index_stack.back()].SetSiblingIndex(
              m_die_array.size() - die_index_stack.back());

        // Only push the DIE if it isn't a NULL DIE
        m_die_array.push_back(die);
      }
    }

    if (null_die) {
      // NULL DIE.
      if (!die_index_stack.empty())
        die_index_stack.pop_back();

      if (depth > 0)
        --depth;
      prev_die_had_children = false;
    } else {
      die_index_stack.back() = m_die_array.size() - 1;
      // Normal DIE
      const bool die_has_children = die.HasChildren();
      if (die_has_children) {
        die_index_stack.push_back(0);
        ++depth;
      }
      prev_die_had_children = die_has_children;
    }

    if (depth == 0)
      break; // We are done with this compile unit!
  }

  if (!m_die_array.empty()) {
    if (m_first_die) {
      // Only needed for the assertion.
      m_first_die.SetHasChildren(m_die_array.front().HasChildren());
      lldbassert(m_first_die == m_die_array.front());
    }
    m_first_die = m_die_array.front();
  }

  m_die_array.shrink_to_fit();

  if (m_dwo_symbol_file) {
    DWARFUnit *dwo_cu = m_dwo_symbol_file->GetCompileUnit();
    dwo_cu->ExtractDIEsIfNeeded();
  }
}

// This is used when a split dwarf is enabled.
// A skeleton compilation unit may contain the DW_AT_str_offsets_base attribute
// that points to the first string offset of the CU contribution to the
// .debug_str_offsets. At the same time, the corresponding split debug unit also
// may use DW_FORM_strx* forms pointing to its own .debug_str_offsets.dwo and
// for that case, we should find the offset (skip the section header).
static void SetDwoStrOffsetsBase(DWARFUnit *dwo_cu) {
  lldb::offset_t baseOffset = 0;

  const DWARFDataExtractor &strOffsets =
      dwo_cu->GetSymbolFileDWARF()->GetDWARFContext().getOrLoadStrOffsetsData();
  uint64_t length = strOffsets.GetU32(&baseOffset);
  if (length == 0xffffffff)
    length = strOffsets.GetU64(&baseOffset);

  // Check version.
  if (strOffsets.GetU16(&baseOffset) < 5)
    return;

  // Skip padding.
  baseOffset += 2;

  dwo_cu->SetStrOffsetsBase(baseOffset);
}

// m_die_array_mutex must be already held as read/write.
void DWARFUnit::AddUnitDIE(const DWARFDebugInfoEntry &cu_die) {
  dw_addr_t addr_base = cu_die.GetAttributeValueAsUnsigned(
      this, DW_AT_addr_base, LLDB_INVALID_ADDRESS);
  if (addr_base != LLDB_INVALID_ADDRESS)
    SetAddrBase(addr_base);

  dw_addr_t ranges_base = cu_die.GetAttributeValueAsUnsigned(
      this, DW_AT_rnglists_base, LLDB_INVALID_ADDRESS);
  if (ranges_base != LLDB_INVALID_ADDRESS)
    SetRangesBase(ranges_base);

  SetStrOffsetsBase(
      cu_die.GetAttributeValueAsUnsigned(this, DW_AT_str_offsets_base, 0));

  uint64_t base_addr = cu_die.GetAttributeValueAsAddress(this, DW_AT_low_pc,
                                                         LLDB_INVALID_ADDRESS);
  if (base_addr == LLDB_INVALID_ADDRESS)
    base_addr = cu_die.GetAttributeValueAsAddress(this, DW_AT_entry_pc, 0);
  SetBaseAddress(base_addr);

  std::unique_ptr<SymbolFileDWARFDwo> dwo_symbol_file =
      m_dwarf->GetDwoSymbolFileForCompileUnit(*this, cu_die);
  if (!dwo_symbol_file)
    return;

  DWARFUnit *dwo_cu = dwo_symbol_file->GetCompileUnit();
  if (!dwo_cu)
    return; // Can't fetch the compile unit from the dwo file.

  DWARFBaseDIE dwo_cu_die = dwo_cu->GetUnitDIEOnly();
  if (!dwo_cu_die.IsValid())
    return; // Can't fetch the compile unit DIE from the dwo file.

  uint64_t main_dwo_id =
      cu_die.GetAttributeValueAsUnsigned(this, DW_AT_GNU_dwo_id, 0);
  uint64_t sub_dwo_id =
      dwo_cu_die.GetAttributeValueAsUnsigned(DW_AT_GNU_dwo_id, 0);
  if (main_dwo_id != sub_dwo_id)
    return; // The 2 dwo ID isn't match. Don't use the dwo file as it belongs to
  // a differectn compilation.

  m_dwo_symbol_file = std::move(dwo_symbol_file);

  // Here for DWO CU we want to use the address base set in the skeleton unit
  // (DW_AT_addr_base) if it is available and use the DW_AT_GNU_addr_base
  // otherwise. We do that because pre-DWARF v5 could use the DW_AT_GNU_*
  // attributes which were applicable to the DWO units. The corresponding
  // DW_AT_* attributes standardized in DWARF v5 are also applicable to the main
  // unit in contrast.
  if (addr_base == LLDB_INVALID_ADDRESS)
    addr_base =
        cu_die.GetAttributeValueAsUnsigned(this, DW_AT_GNU_addr_base, 0);
  dwo_cu->SetAddrBase(addr_base);

  if (ranges_base == LLDB_INVALID_ADDRESS)
    ranges_base =
        cu_die.GetAttributeValueAsUnsigned(this, DW_AT_GNU_ranges_base, 0);
  dwo_cu->SetRangesBase(ranges_base);

  dwo_cu->SetBaseObjOffset(GetOffset());

  SetDwoStrOffsetsBase(dwo_cu);
}

DWARFDIE DWARFUnit::LookupAddress(const dw_addr_t address) {
  if (DIE()) {
    const DWARFDebugAranges &func_aranges = GetFunctionAranges();

    // Re-check the aranges auto pointer contents in case it was created above
    if (!func_aranges.IsEmpty())
      return GetDIE(func_aranges.FindAddress(address));
  }
  return DWARFDIE();
}

size_t DWARFUnit::AppendDIEsWithTag(const dw_tag_t tag,
                                    std::vector<DWARFDIE> &dies,
                                    uint32_t depth) const {
  size_t old_size = dies.size();
  {
    llvm::sys::ScopedReader lock(m_die_array_mutex);
    DWARFDebugInfoEntry::const_iterator pos;
    DWARFDebugInfoEntry::const_iterator end = m_die_array.end();
    for (pos = m_die_array.begin(); pos != end; ++pos) {
      if (pos->Tag() == tag)
        dies.emplace_back(this, &(*pos));
    }
  }

  // Return the number of DIEs added to the collection
  return dies.size() - old_size;
}

size_t DWARFUnit::GetDebugInfoSize() const {
  return GetLengthByteSize() + GetLength() - GetHeaderByteSize();
}

const DWARFAbbreviationDeclarationSet *DWARFUnit::GetAbbreviations() const {
  return m_abbrevs;
}

dw_offset_t DWARFUnit::GetAbbrevOffset() const {
  return m_abbrevs ? m_abbrevs->GetOffset() : DW_INVALID_OFFSET;
}

void DWARFUnit::SetAddrBase(dw_addr_t addr_base) { m_addr_base = addr_base; }

void DWARFUnit::SetRangesBase(dw_addr_t ranges_base) {
  m_ranges_base = ranges_base;
}

void DWARFUnit::SetBaseObjOffset(dw_offset_t base_obj_offset) {
  m_base_obj_offset = base_obj_offset;
}

void DWARFUnit::SetStrOffsetsBase(dw_offset_t str_offsets_base) {
  m_str_offsets_base = str_offsets_base;
}

// It may be called only with m_die_array_mutex held R/W.
void DWARFUnit::ClearDIEsRWLocked() {
  m_die_array.clear();
  m_die_array.shrink_to_fit();

  if (m_dwo_symbol_file)
    m_dwo_symbol_file->GetCompileUnit()->ClearDIEsRWLocked();
}

lldb::ByteOrder DWARFUnit::GetByteOrder() const {
  return m_dwarf->GetObjectFile()->GetByteOrder();
}

TypeSystem *DWARFUnit::GetTypeSystem() {
  if (m_dwarf)
    return m_dwarf->GetTypeSystemForLanguage(GetLanguageType());
  else
    return nullptr;
}

void DWARFUnit::SetBaseAddress(dw_addr_t base_addr) { m_base_addr = base_addr; }

// Compare function DWARFDebugAranges::Range structures
static bool CompareDIEOffset(const DWARFDebugInfoEntry &die,
                             const dw_offset_t die_offset) {
  return die.GetOffset() < die_offset;
}

// GetDIE()
//
// Get the DIE (Debug Information Entry) with the specified offset by first
// checking if the DIE is contained within this compile unit and grabbing the
// DIE from this compile unit. Otherwise we grab the DIE from the DWARF file.
DWARFDIE
DWARFUnit::GetDIE(dw_offset_t die_offset) {
  if (die_offset != DW_INVALID_OFFSET) {
    if (GetDwoSymbolFile())
      return GetDwoSymbolFile()->GetCompileUnit()->GetDIE(die_offset);

    if (ContainsDIEOffset(die_offset)) {
      ExtractDIEsIfNeeded();
      DWARFDebugInfoEntry::const_iterator end = m_die_array.cend();
      DWARFDebugInfoEntry::const_iterator pos =
          lower_bound(m_die_array.cbegin(), end, die_offset, CompareDIEOffset);
      if (pos != end) {
        if (die_offset == (*pos).GetOffset())
          return DWARFDIE(this, &(*pos));
      }
    } else
      GetSymbolFileDWARF()->GetObjectFile()->GetModule()->ReportError(
          "GetDIE for DIE 0x%" PRIx32 " is outside of its CU 0x%" PRIx32,
          die_offset, GetOffset());
  }
  return DWARFDIE(); // Not found
}

uint8_t DWARFUnit::GetAddressByteSize(const DWARFUnit *cu) {
  if (cu)
    return cu->GetAddressByteSize();
  return DWARFUnit::GetDefaultAddressSize();
}

uint8_t DWARFUnit::GetDefaultAddressSize() { return 4; }

void *DWARFUnit::GetUserData() const { return m_user_data; }

void DWARFUnit::SetUserData(void *d) {
  m_user_data = d;
  if (m_dwo_symbol_file)
    m_dwo_symbol_file->GetCompileUnit()->SetUserData(d);
}

bool DWARFUnit::Supports_DW_AT_APPLE_objc_complete_type() {
  return GetProducer() != eProducerLLVMGCC;
}

bool DWARFUnit::DW_AT_decl_file_attributes_are_invalid() {
  // llvm-gcc makes completely invalid decl file attributes and won't ever be
  // fixed, so we need to know to ignore these.
  return GetProducer() == eProducerLLVMGCC;
}

bool DWARFUnit::Supports_unnamed_objc_bitfields() {
  if (GetProducer() == eProducerClang) {
    const uint32_t major_version = GetProducerVersionMajor();
    return major_version > 425 ||
           (major_version == 425 && GetProducerVersionUpdate() >= 13);
  }
  return true; // Assume all other compilers didn't have incorrect ObjC bitfield
               // info
}

SymbolFileDWARF *DWARFUnit::GetSymbolFileDWARF() const { return m_dwarf; }

void DWARFUnit::ParseProducerInfo() {
  m_producer_version_major = UINT32_MAX;
  m_producer_version_minor = UINT32_MAX;
  m_producer_version_update = UINT32_MAX;

  const DWARFDebugInfoEntry *die = GetUnitDIEPtrOnly();
  if (die) {

    const char *producer_cstr =
        die->GetAttributeValueAsString(this, DW_AT_producer, nullptr);
    if (producer_cstr) {
      RegularExpression llvm_gcc_regex(
          llvm::StringRef("^4\\.[012]\\.[01] \\(Based on Apple "
                          "Inc\\. build [0-9]+\\) \\(LLVM build "
                          "[\\.0-9]+\\)$"));
      if (llvm_gcc_regex.Execute(llvm::StringRef(producer_cstr))) {
        m_producer = eProducerLLVMGCC;
      } else if (strstr(producer_cstr, "clang")) {
        static RegularExpression g_clang_version_regex(
            llvm::StringRef("clang-([0-9]+)\\.([0-9]+)\\.([0-9]+)"));
        RegularExpression::Match regex_match(3);
        if (g_clang_version_regex.Execute(llvm::StringRef(producer_cstr),
                                          &regex_match)) {
          std::string str;
          if (regex_match.GetMatchAtIndex(producer_cstr, 1, str))
            m_producer_version_major =
                StringConvert::ToUInt32(str.c_str(), UINT32_MAX, 10);
          if (regex_match.GetMatchAtIndex(producer_cstr, 2, str))
            m_producer_version_minor =
                StringConvert::ToUInt32(str.c_str(), UINT32_MAX, 10);
          if (regex_match.GetMatchAtIndex(producer_cstr, 3, str))
            m_producer_version_update =
                StringConvert::ToUInt32(str.c_str(), UINT32_MAX, 10);
        }
        m_producer = eProducerClang;
      } else if (strstr(producer_cstr, "GNU"))
        m_producer = eProducerGCC;
    }
  }
  if (m_producer == eProducerInvalid)
    m_producer = eProcucerOther;
}

DWARFProducer DWARFUnit::GetProducer() {
  if (m_producer == eProducerInvalid)
    ParseProducerInfo();
  return m_producer;
}

uint32_t DWARFUnit::GetProducerVersionMajor() {
  if (m_producer_version_major == 0)
    ParseProducerInfo();
  return m_producer_version_major;
}

uint32_t DWARFUnit::GetProducerVersionMinor() {
  if (m_producer_version_minor == 0)
    ParseProducerInfo();
  return m_producer_version_minor;
}

uint32_t DWARFUnit::GetProducerVersionUpdate() {
  if (m_producer_version_update == 0)
    ParseProducerInfo();
  return m_producer_version_update;
}
LanguageType DWARFUnit::LanguageTypeFromDWARF(uint64_t val) {
  // Note: user languages between lo_user and hi_user must be handled
  // explicitly here.
  switch (val) {
  case DW_LANG_Mips_Assembler:
    return eLanguageTypeMipsAssembler;
  case DW_LANG_GOOGLE_RenderScript:
    return eLanguageTypeExtRenderScript;
  default:
    return static_cast<LanguageType>(val);
  }
}

LanguageType DWARFUnit::GetLanguageType() {
  if (m_language_type != eLanguageTypeUnknown)
    return m_language_type;

  const DWARFDebugInfoEntry *die = GetUnitDIEPtrOnly();
  if (die)
    m_language_type = LanguageTypeFromDWARF(
        die->GetAttributeValueAsUnsigned(this, DW_AT_language, 0));
  return m_language_type;
}

bool DWARFUnit::GetIsOptimized() {
  if (m_is_optimized == eLazyBoolCalculate) {
    const DWARFDebugInfoEntry *die = GetUnitDIEPtrOnly();
    if (die) {
      m_is_optimized = eLazyBoolNo;
      if (die->GetAttributeValueAsUnsigned(this, DW_AT_APPLE_optimized, 0) ==
          1) {
        m_is_optimized = eLazyBoolYes;
      }
    }
  }
  return m_is_optimized == eLazyBoolYes;
}

FileSpec::Style DWARFUnit::GetPathStyle() {
  if (!m_comp_dir)
    ComputeCompDirAndGuessPathStyle();
  return m_comp_dir->GetPathStyle();
}

const FileSpec &DWARFUnit::GetCompilationDirectory() {
  if (!m_comp_dir)
    ComputeCompDirAndGuessPathStyle();
  return *m_comp_dir;
}

// DWARF2/3 suggests the form hostname:pathname for compilation directory.
// Remove the host part if present.
static llvm::StringRef
removeHostnameFromPathname(llvm::StringRef path_from_dwarf) {
  llvm::StringRef host, path;
  std::tie(host, path) = path_from_dwarf.split(':');

  if (host.contains('/'))
    return path_from_dwarf;

  // check whether we have a windows path, and so the first character is a
  // drive-letter not a hostname.
  if (host.size() == 1 && llvm::isAlpha(host[0]) && path.startswith("\\"))
    return path_from_dwarf;

  return path;
}

static FileSpec resolveCompDir(const FileSpec &path) {
  bool is_symlink = SymbolFileDWARF::GetSymlinkPaths().FindFileIndex(
                        0, path, /*full*/ true) != UINT32_MAX;

  if (!is_symlink)
    return path;

  namespace fs = llvm::sys::fs;
  if (fs::get_file_type(path.GetPath(), false) != fs::file_type::symlink_file)
    return path;

  FileSpec resolved_symlink;
  const auto error = FileSystem::Instance().Readlink(path, resolved_symlink);
  if (error.Success())
    return resolved_symlink;

  return path;
}

void DWARFUnit::ComputeCompDirAndGuessPathStyle() {
  m_comp_dir = FileSpec();
  const DWARFDebugInfoEntry *die = GetUnitDIEPtrOnly();
  if (!die)
    return;

  llvm::StringRef comp_dir = removeHostnameFromPathname(
      die->GetAttributeValueAsString(this, DW_AT_comp_dir, nullptr));
  if (!comp_dir.empty()) {
    FileSpec::Style comp_dir_style =
        FileSpec::GuessPathStyle(comp_dir).getValueOr(FileSpec::Style::native);
    m_comp_dir = resolveCompDir(FileSpec(comp_dir, comp_dir_style));
  } else {
    // Try to detect the style based on the DW_AT_name attribute, but just store
    // the detected style in the m_comp_dir field.
    const char *name =
        die->GetAttributeValueAsString(this, DW_AT_name, nullptr);
    m_comp_dir = FileSpec(
        "", FileSpec::GuessPathStyle(name).getValueOr(FileSpec::Style::native));
  }
}

SymbolFileDWARFDwo *DWARFUnit::GetDwoSymbolFile() const {
  return m_dwo_symbol_file.get();
}

dw_offset_t DWARFUnit::GetBaseObjOffset() const { return m_base_obj_offset; }

const DWARFDebugAranges &DWARFUnit::GetFunctionAranges() {
  if (m_func_aranges_up == nullptr) {
    m_func_aranges_up.reset(new DWARFDebugAranges());
    const DWARFDebugInfoEntry *die = DIEPtr();
    if (die)
      die->BuildFunctionAddressRangeTable(this, m_func_aranges_up.get());

    if (m_dwo_symbol_file) {
      DWARFUnit *dwo_cu = m_dwo_symbol_file->GetCompileUnit();
      const DWARFDebugInfoEntry *dwo_die = dwo_cu->DIEPtr();
      if (dwo_die)
        dwo_die->BuildFunctionAddressRangeTable(dwo_cu,
                                                m_func_aranges_up.get());
    }

    const bool minimize = false;
    m_func_aranges_up->Sort(minimize);
  }
  return *m_func_aranges_up;
}

llvm::Expected<DWARFUnitHeader>
DWARFUnitHeader::extract(const DWARFDataExtractor &data, DIERef::Section section,
                         lldb::offset_t *offset_ptr) {
  DWARFUnitHeader header;
  header.m_offset = *offset_ptr;
  header.m_length = data.GetDWARFInitialLength(offset_ptr);
  header.m_version = data.GetU16(offset_ptr);
  if (header.m_version == 5) {
    header.m_unit_type = data.GetU8(offset_ptr);
    header.m_addr_size = data.GetU8(offset_ptr);
    header.m_abbr_offset = data.GetDWARFOffset(offset_ptr);
    if (header.m_unit_type == llvm::dwarf::DW_UT_skeleton)
      header.m_dwo_id = data.GetU64(offset_ptr);
  } else {
    header.m_abbr_offset = data.GetDWARFOffset(offset_ptr);
    header.m_addr_size = data.GetU8(offset_ptr);
    header.m_unit_type =
        section == DIERef::Section::DebugTypes ? DW_UT_type : DW_UT_compile;
  }

  if (header.IsTypeUnit()) {
    header.m_type_hash = data.GetU64(offset_ptr);
    header.m_type_offset = data.GetDWARFOffset(offset_ptr);
  }

  bool length_OK = data.ValidOffset(header.GetNextUnitOffset() - 1);
  bool version_OK = SymbolFileDWARF::SupportedVersion(header.m_version);
  bool addr_size_OK = (header.m_addr_size == 4) || (header.m_addr_size == 8);
  bool type_offset_OK =
      !header.IsTypeUnit() || (header.m_type_offset <= header.GetLength());

  if (!length_OK)
    return llvm::make_error<llvm::object::GenericBinaryError>(
        "Invalid unit length");
  if (!version_OK)
    return llvm::make_error<llvm::object::GenericBinaryError>(
        "Unsupported unit version");
  if (!addr_size_OK)
    return llvm::make_error<llvm::object::GenericBinaryError>(
        "Invalid unit address size");
  if (!type_offset_OK)
    return llvm::make_error<llvm::object::GenericBinaryError>(
        "Type offset out of range");

  return header;
}

llvm::Expected<DWARFUnitSP>
DWARFUnit::extract(SymbolFileDWARF *dwarf, user_id_t uid,
                   const DWARFDataExtractor &debug_info, DIERef::Section section,
                   lldb::offset_t *offset_ptr) {
  assert(debug_info.ValidOffset(*offset_ptr));

  auto expected_header =
      DWARFUnitHeader::extract(debug_info, section, offset_ptr);
  if (!expected_header)
    return expected_header.takeError();

  const DWARFDebugAbbrev *abbr = dwarf->DebugAbbrev();
  if (!abbr)
    return llvm::make_error<llvm::object::GenericBinaryError>(
        "No debug_abbrev data");

  bool abbr_offset_OK =
      dwarf->GetDWARFContext().getOrLoadAbbrevData().ValidOffset(
          expected_header->GetAbbrOffset());
  if (!abbr_offset_OK)
    return llvm::make_error<llvm::object::GenericBinaryError>(
        "Abbreviation offset for unit is not valid");

  const DWARFAbbreviationDeclarationSet *abbrevs =
      abbr->GetAbbreviationDeclarationSet(expected_header->GetAbbrOffset());
  if (!abbrevs)
    return llvm::make_error<llvm::object::GenericBinaryError>(
        "No abbrev exists at the specified offset.");

  if (expected_header->IsTypeUnit())
    return DWARFUnitSP(
        new DWARFTypeUnit(dwarf, uid, *expected_header, *abbrevs, section));
  return DWARFUnitSP(
      new DWARFCompileUnit(dwarf, uid, *expected_header, *abbrevs, section));
}

const lldb_private::DWARFDataExtractor &DWARFUnit::GetData() const {
  return m_section == DIERef::Section::DebugTypes
             ? m_dwarf->GetDWARFContext().getOrLoadDebugTypesData()
             : m_dwarf->GetDWARFContext().getOrLoadDebugInfoData();
}

uint32_t DWARFUnit::GetHeaderByteSize() const {
  switch (m_header.GetUnitType()) {
  case llvm::dwarf::DW_UT_compile:
  case llvm::dwarf::DW_UT_partial:
    return GetVersion() < 5 ? 11 : 12;
  case llvm::dwarf::DW_UT_skeleton:
  case llvm::dwarf::DW_UT_split_compile:
    return 20;
  case llvm::dwarf::DW_UT_type:
  case llvm::dwarf::DW_UT_split_type:
    return GetVersion() < 5 ? 23 : 24;
  }
  llvm_unreachable("invalid UnitType.");
}

llvm::Expected<DWARFRangeList>
DWARFUnit::FindRnglistFromOffset(dw_offset_t offset) const {
  const DWARFDebugRangesBase *debug_ranges;
  llvm::StringRef section;
  if (GetVersion() <= 4) {
    debug_ranges = m_dwarf->GetDebugRanges();
    section = "debug_ranges";
  } else {
    debug_ranges = m_dwarf->GetDebugRngLists();
    section = "debug_rnglists";
  }
  if (!debug_ranges)
    return llvm::make_error<llvm::object::GenericBinaryError>("No " + section +
                                                              " section");

  DWARFRangeList ranges;
  debug_ranges->FindRanges(this, offset, ranges);
  return ranges;
}

llvm::Expected<DWARFRangeList>
DWARFUnit::FindRnglistFromIndex(uint32_t index) const {
  const DWARFDebugRangesBase *debug_rnglists = m_dwarf->GetDebugRngLists();
  if (!debug_rnglists)
    return llvm::make_error<llvm::object::GenericBinaryError>(
        "No debug_rnglists section");
  return FindRnglistFromOffset(debug_rnglists->GetOffset(index));
}