[lldb][DataFormatter][NFC] Move std::map iterator formatter into LibCxxMap.cpp (#97687)

The two formatters follow very similar techniques to retrieve data out
of the map. We're changing this for `std::map` in
#97579 and plan to change it in
the same way for the iterator formatter. Having them in the same place
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

@@ -202,194 +202,6 @@ bool lldb_private::formatters::LibcxxUniquePointerSummaryProvider(
   return true;
 }
 
-/*
- (lldb) fr var ibeg --raw --ptr-depth 1
- (std::__1::__map_iterator<std::__1::__tree_iterator<std::__1::pair<int,
- std::__1::basic_string<char, std::__1::char_traits<char>,
- std::__1::allocator<char> > >, std::__1::__tree_node<std::__1::pair<int,
- std::__1::basic_string<char, std::__1::char_traits<char>,
- std::__1::allocator<char> > >, void *> *, long> >) ibeg = {
- __i_ = {
- __ptr_ = 0x0000000100103870 {
- std::__1::__tree_node_base<void *> = {
- std::__1::__tree_end_node<std::__1::__tree_node_base<void *> *> = {
- __left_ = 0x0000000000000000
- }
- __right_ = 0x0000000000000000
- __parent_ = 0x00000001001038b0
- __is_black_ = true
- }
- __value_ = {
- first = 0
- second = { std::string }
- */
-
-lldb_private::formatters::LibCxxMapIteratorSyntheticFrontEnd::
-    LibCxxMapIteratorSyntheticFrontEnd(lldb::ValueObjectSP valobj_sp)
-    : SyntheticChildrenFrontEnd(*valobj_sp), m_pair_ptr(), m_pair_sp() {
-  if (valobj_sp)
-    Update();
-}
-
-lldb::ChildCacheState
-lldb_private::formatters::LibCxxMapIteratorSyntheticFrontEnd::Update() {
-  m_pair_sp.reset();
-  m_pair_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;
-
-  // 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_pair_ptr = valobj_sp
-                   ->GetValueForExpressionPath(
-                       ".__i_.__ptr_->__value_", nullptr, nullptr,
-                       ValueObject::GetValueForExpressionPathOptions()
-                           .DontCheckDotVsArrowSyntax()
-                           .SetSyntheticChildrenTraversal(
-                               ValueObject::GetValueForExpressionPathOptions::
-                                   SyntheticChildrenTraversal::None),
-                       nullptr)
-                   .get();
-
-  if (!m_pair_ptr) {
-    m_pair_ptr = valobj_sp
-                     ->GetValueForExpressionPath(
-                         ".__i_.__ptr_", nullptr, nullptr,
-                         ValueObject::GetValueForExpressionPathOptions()
-                             .DontCheckDotVsArrowSyntax()
-                             .SetSyntheticChildrenTraversal(
-                                 ValueObject::GetValueForExpressionPathOptions::
-                                     SyntheticChildrenTraversal::None),
-                         nullptr)
-                     .get();
-    if (m_pair_ptr) {
-      auto __i_(valobj_sp->GetChildMemberWithName("__i_"));
-      if (!__i_) {
-        m_pair_ptr = nullptr;
-        return lldb::ChildCacheState::eRefetch;
-      }
-      CompilerType pair_type(
-          __i_->GetCompilerType().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_pair_ptr = nullptr;
-        return lldb::ChildCacheState::eRefetch;
-      }
-
-      auto addr(m_pair_ptr->GetValueAsUnsigned(LLDB_INVALID_ADDRESS));
-      m_pair_ptr = nullptr;
-      if (addr && addr != LLDB_INVALID_ADDRESS) {
-        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::__tree_iterator::__ptr_ and read it in
-        // from process memory.
-        //
-        // The following shows the contiguous block of memory:
-        //
-        //        +-----------------------------+ class __tree_end_node
-        // __ptr_ | pointer __left_;            |
-        //        +-----------------------------+ class __tree_node_base
-        //        | pointer __right_;           |
-        //        | __parent_pointer __parent_; |
-        //        | bool __is_black_;           |
-        //        +-----------------------------+ class __tree_node
-        //        | __node_value_type __value_; | <<< our key/value pair
-        //        +-----------------------------+
-        //
-        CompilerType tree_node_type = ast_ctx->CreateStructForIdentifier(
-            llvm::StringRef(),
-            {{"ptr0",
-              ast_ctx->GetBasicType(lldb::eBasicTypeVoid).GetPointerType()},
-             {"ptr1",
-              ast_ctx->GetBasicType(lldb::eBasicTypeVoid).GetPointerType()},
-             {"ptr2",
-              ast_ctx->GetBasicType(lldb::eBasicTypeVoid).GetPointerType()},
-             {"cw", ast_ctx->GetBasicType(lldb::eBasicTypeBool)},
-             {"payload", 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(4);
-      }
-    }
-  }
-
-  return lldb::ChildCacheState::eRefetch;
-}
-
-llvm::Expected<uint32_t> lldb_private::formatters::
-    LibCxxMapIteratorSyntheticFrontEnd::CalculateNumChildren() {
-  return 2;
-}
-
-lldb::ValueObjectSP
-lldb_private::formatters::LibCxxMapIteratorSyntheticFrontEnd::GetChildAtIndex(
-    uint32_t idx) {
-  if (m_pair_ptr)
-    return m_pair_ptr->GetChildAtIndex(idx);
-  if (m_pair_sp)
-    return m_pair_sp->GetChildAtIndex(idx);
-  return lldb::ValueObjectSP();
-}
-
-bool lldb_private::formatters::LibCxxMapIteratorSyntheticFrontEnd::
-    MightHaveChildren() {
-  return true;
-}
-
-size_t lldb_private::formatters::LibCxxMapIteratorSyntheticFrontEnd::
-    GetIndexOfChildWithName(ConstString name) {
-  if (name == "first")
-    return 0;
-  if (name == "second")
-    return 1;
-  return UINT32_MAX;
-}
-
-lldb_private::formatters::LibCxxMapIteratorSyntheticFrontEnd::
-    ~LibCxxMapIteratorSyntheticFrontEnd() {
-  // this will be deleted when its parent dies (since it's a child object)
-  // delete m_pair_ptr;
-}
-
-SyntheticChildrenFrontEnd *
-lldb_private::formatters::LibCxxMapIteratorSyntheticFrontEndCreator(
-    CXXSyntheticChildren *, lldb::ValueObjectSP valobj_sp) {
-  return (valobj_sp ? new LibCxxMapIteratorSyntheticFrontEnd(valobj_sp)
-                    : nullptr);
-}
-
 lldb_private::formatters::LibCxxUnorderedMapIteratorSyntheticFrontEnd::
     LibCxxUnorderedMapIteratorSyntheticFrontEnd(lldb::ValueObjectSP valobj_sp)
     : SyntheticChildrenFrontEnd(*valobj_sp) {

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

@@ -87,31 +87,6 @@ bool LibcxxContainerSummaryProvider(ValueObject &valobj, Stream &stream,
 bool LibcxxSpanSummaryProvider(ValueObject &valobj, Stream &stream,
                                const TypeSummaryOptions &options);
 
-class LibCxxMapIteratorSyntheticFrontEnd : public SyntheticChildrenFrontEnd {
-public:
-  LibCxxMapIteratorSyntheticFrontEnd(lldb::ValueObjectSP valobj_sp);
-
-  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;
-
-  ~LibCxxMapIteratorSyntheticFrontEnd() override;
-
-private:
-  ValueObject *m_pair_ptr;
-  lldb::ValueObjectSP m_pair_sp;
-};
-
-SyntheticChildrenFrontEnd *
-LibCxxMapIteratorSyntheticFrontEndCreator(CXXSyntheticChildren *,
-                                          lldb::ValueObjectSP);
-
 /// Formats libcxx's std::unordered_map iterators
 ///
 /// In raw form a std::unordered_map::iterator is represented as follows:
@@ -247,6 +222,10 @@ SyntheticChildrenFrontEnd *
 LibcxxStdMapSyntheticFrontEndCreator(CXXSyntheticChildren *,
                                      lldb::ValueObjectSP);
 
+SyntheticChildrenFrontEnd *
+LibCxxMapIteratorSyntheticFrontEndCreator(CXXSyntheticChildren *,
+                                          lldb::ValueObjectSP);
+
 SyntheticChildrenFrontEnd *
 LibcxxStdUnorderedMapSyntheticFrontEndCreator(CXXSyntheticChildren *,
                                               lldb::ValueObjectSP);