[lldb][DataFormatter] Move std::unordered_map::iterator formatter into LibCxxUnorderedMap.cpp (#97752)

Similar to how we moved the `std::map::iterator` formatter in
#97687, do the same for
`std::unordered_map::iterator`.

Again the `unordered_map` and `unordered_map::iterator` formatters try
to do very similar things: retrieve data out of the map. The iterator
formatter does this in a fragile way (similar to how `std::map` does it,
see #97579). Thus we will be
refactoring the `std::unordered_map::iterator` in upcoming patches.
Having it in `LibCxxUnorderedMap` will allow us to re-use some of the
logic (and we won't have to repeat some of the clarification comments).

Author: Michael137

lldb/source/Plugins/Language/CPlusPlus/LibCxx.cpp

@@ -202,155 +202,6 @@ bool lldb_private::formatters::LibcxxUniquePointerSummaryProvider(
   return true;
 }
 
-lldb_private::formatters::LibCxxUnorderedMapIteratorSyntheticFrontEnd::
-    LibCxxUnorderedMapIteratorSyntheticFrontEnd(lldb::ValueObjectSP valobj_sp)
-    : SyntheticChildrenFrontEnd(*valobj_sp) {
-  if (valobj_sp)
-    Update();
-}
-
-lldb::ChildCacheState lldb_private::formatters::
-    LibCxxUnorderedMapIteratorSyntheticFrontEnd::Update() {
-  m_pair_sp.reset();
-  m_iter_ptr = nullptr;
-
-  ValueObjectSP valobj_sp = m_backend.GetSP();
-  if (!valobj_sp)
-    return lldb::ChildCacheState::eRefetch;
-
-  TargetSP target_sp(valobj_sp->GetTargetSP());
-
-  if (!target_sp)
-    return lldb::ChildCacheState::eRefetch;
-
-  if (!valobj_sp)
-    return lldb::ChildCacheState::eRefetch;
-
-  auto exprPathOptions = ValueObject::GetValueForExpressionPathOptions()
-                             .DontCheckDotVsArrowSyntax()
-                             .SetSyntheticChildrenTraversal(
-                                 ValueObject::GetValueForExpressionPathOptions::
-                                     SyntheticChildrenTraversal::None);
-
-  // This must be a ValueObject* because it is a child of the ValueObject we
-  // are producing children for it if were a ValueObjectSP, we would end up
-  // with a loop (iterator -> synthetic -> child -> parent == iterator) and
-  // that would in turn leak memory by never allowing the ValueObjects to die
-  // and free their memory.
-  m_iter_ptr =
-      valobj_sp
-          ->GetValueForExpressionPath(".__i_.__node_", nullptr, nullptr,
-                                      exprPathOptions, nullptr)
-          .get();
-
-  if (m_iter_ptr) {
-    auto iter_child(valobj_sp->GetChildMemberWithName("__i_"));
-    if (!iter_child) {
-      m_iter_ptr = nullptr;
-      return lldb::ChildCacheState::eRefetch;
-    }
-
-    CompilerType node_type(iter_child->GetCompilerType()
-                               .GetTypeTemplateArgument(0)
-                               .GetPointeeType());
-
-    CompilerType pair_type(node_type.GetTypeTemplateArgument(0));
-
-    std::string name;
-    uint64_t bit_offset_ptr;
-    uint32_t bitfield_bit_size_ptr;
-    bool is_bitfield_ptr;
-
-    pair_type = pair_type.GetFieldAtIndex(
-        0, name, &bit_offset_ptr, &bitfield_bit_size_ptr, &is_bitfield_ptr);
-    if (!pair_type) {
-      m_iter_ptr = nullptr;
-      return lldb::ChildCacheState::eRefetch;
-    }
-
-    uint64_t addr = m_iter_ptr->GetValueAsUnsigned(LLDB_INVALID_ADDRESS);
-    m_iter_ptr = nullptr;
-
-    if (addr == 0 || addr == LLDB_INVALID_ADDRESS)
-      return lldb::ChildCacheState::eRefetch;
-
-    auto ts = pair_type.GetTypeSystem();
-    auto ast_ctx = ts.dyn_cast_or_null<TypeSystemClang>();
-    if (!ast_ctx)
-      return lldb::ChildCacheState::eRefetch;
-
-    // Mimick layout of std::__hash_iterator::__node_ and read it in
-    // from process memory.
-    //
-    // The following shows the contiguous block of memory:
-    //
-    //         +-----------------------------+ class __hash_node_base
-    // __node_ | __next_pointer __next_;     |
-    //         +-----------------------------+ class __hash_node
-    //         | size_t __hash_;             |
-    //         | __node_value_type __value_; | <<< our key/value pair
-    //         +-----------------------------+
-    //
-    CompilerType tree_node_type = ast_ctx->CreateStructForIdentifier(
-        llvm::StringRef(),
-        {{"__next_",
-          ast_ctx->GetBasicType(lldb::eBasicTypeVoid).GetPointerType()},
-         {"__hash_", ast_ctx->GetBasicType(lldb::eBasicTypeUnsignedLongLong)},
-         {"__value_", pair_type}});
-    std::optional<uint64_t> size = tree_node_type.GetByteSize(nullptr);
-    if (!size)
-      return lldb::ChildCacheState::eRefetch;
-    WritableDataBufferSP buffer_sp(new DataBufferHeap(*size, 0));
-    ProcessSP process_sp(target_sp->GetProcessSP());
-    Status error;
-    process_sp->ReadMemory(addr, buffer_sp->GetBytes(),
-                           buffer_sp->GetByteSize(), error);
-    if (error.Fail())
-      return lldb::ChildCacheState::eRefetch;
-    DataExtractor extractor(buffer_sp, process_sp->GetByteOrder(),
-                            process_sp->GetAddressByteSize());
-    auto pair_sp = CreateValueObjectFromData(
-        "pair", extractor, valobj_sp->GetExecutionContextRef(), tree_node_type);
-    if (pair_sp)
-      m_pair_sp = pair_sp->GetChildAtIndex(2);
-  }
-
-  return lldb::ChildCacheState::eRefetch;
-}
-
-llvm::Expected<uint32_t> lldb_private::formatters::
-    LibCxxUnorderedMapIteratorSyntheticFrontEnd::CalculateNumChildren() {
-  return 2;
-}
-
-lldb::ValueObjectSP lldb_private::formatters::
-    LibCxxUnorderedMapIteratorSyntheticFrontEnd::GetChildAtIndex(uint32_t idx) {
-  if (m_pair_sp)
-    return m_pair_sp->GetChildAtIndex(idx);
-  return lldb::ValueObjectSP();
-}
-
-bool lldb_private::formatters::LibCxxUnorderedMapIteratorSyntheticFrontEnd::
-    MightHaveChildren() {
-  return true;
-}
-
-size_t lldb_private::formatters::LibCxxUnorderedMapIteratorSyntheticFrontEnd::
-    GetIndexOfChildWithName(ConstString name) {
-  if (name == "first")
-    return 0;
-  if (name == "second")
-    return 1;
-  return UINT32_MAX;
-}
-
-SyntheticChildrenFrontEnd *
-lldb_private::formatters::LibCxxUnorderedMapIteratorSyntheticFrontEndCreator(
-    CXXSyntheticChildren *, lldb::ValueObjectSP valobj_sp) {
-  return (valobj_sp ? new LibCxxUnorderedMapIteratorSyntheticFrontEnd(valobj_sp)
-                    : nullptr);
-}
-
 /*
  (lldb) fr var ibeg --raw --ptr-depth 1 -T
  (std::__1::__wrap_iter<int *>) ibeg = {

lldb/source/Plugins/Language/CPlusPlus/LibCxx.h

@@ -87,56 +87,6 @@ bool LibcxxContainerSummaryProvider(ValueObject &valobj, Stream &stream,
 bool LibcxxSpanSummaryProvider(ValueObject &valobj, Stream &stream,
                                const TypeSummaryOptions &options);
 
-/// Formats libcxx's std::unordered_map iterators
-///
-/// In raw form a std::unordered_map::iterator is represented as follows:
-///
-/// (lldb) var it --raw --ptr-depth 1
-/// (std::__1::__hash_map_iterator<
-///    std::__1::__hash_iterator<
-///      std::__1::__hash_node<
-///        std::__1::__hash_value_type<
-///            std::__1::basic_string<char, std::__1::char_traits<char>,
-///            std::__1::allocator<char> >, std::__1::basic_string<char,
-///            std::__1::char_traits<char>, std::__1::allocator<char> > >,
-///        void *> *> >)
-///  it = {
-///   __i_ = {
-///     __node_ = 0x0000600001700040 {
-///       __next_ = 0x0000600001704000
-///     }
-///   }
-/// }
-class LibCxxUnorderedMapIteratorSyntheticFrontEnd
-    : public SyntheticChildrenFrontEnd {
-public:
-  LibCxxUnorderedMapIteratorSyntheticFrontEnd(lldb::ValueObjectSP valobj_sp);
-
-  ~LibCxxUnorderedMapIteratorSyntheticFrontEnd() override = default;
-
-  llvm::Expected<uint32_t> CalculateNumChildren() override;
-
-  lldb::ValueObjectSP GetChildAtIndex(uint32_t idx) override;
-
-  lldb::ChildCacheState Update() override;
-
-  bool MightHaveChildren() override;
-
-  size_t GetIndexOfChildWithName(ConstString name) override;
-
-private:
-  ValueObject *m_iter_ptr = nullptr; ///< Held, not owned. Child of iterator
-                                     ///< ValueObject supplied at construction.
-
-  lldb::ValueObjectSP m_pair_sp; ///< ValueObject for the key/value pair
-                                 ///< that the iterator currently points
-                                 ///< to.
-};
-
-SyntheticChildrenFrontEnd *
-LibCxxUnorderedMapIteratorSyntheticFrontEndCreator(CXXSyntheticChildren *,
-                                                   lldb::ValueObjectSP);
-
 SyntheticChildrenFrontEnd *
 LibCxxVectorIteratorSyntheticFrontEndCreator(CXXSyntheticChildren *,
                                              lldb::ValueObjectSP);
@@ -230,6 +180,10 @@ SyntheticChildrenFrontEnd *
 LibcxxStdUnorderedMapSyntheticFrontEndCreator(CXXSyntheticChildren *,
                                               lldb::ValueObjectSP);
 
+SyntheticChildrenFrontEnd *
+LibCxxUnorderedMapIteratorSyntheticFrontEndCreator(CXXSyntheticChildren *,
+                                                   lldb::ValueObjectSP);
+
 SyntheticChildrenFrontEnd *
 LibcxxInitializerListSyntheticFrontEndCreator(CXXSyntheticChildren *,
                                               lldb::ValueObjectSP);