llvmbot wrote:

<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-lldb

Author: nerix (Nerixyz)

<details>
<summary>Changes</summary>

This PR adds formatters for `std::map`, `std::set`, `std::multimap`, 
`std::multiset` as well as their iterators. It's done in one PR because the 
types are essentially the same (a tree) except for their value type. The 
iterators are required because of the tests.

`MsvcStlTreeIterSyntheticFrontEnd` is based on the libc++ equivalent. As 
opposed to `std::list`, there aren't that many duplicates, so I didn't create a 
generic type.

For reference, the tree is implemented in 
https://github.com/microsoft/STL/blob/313964b78a8fd5a52e7965e13781f735bcce13c5/stl/inc/xtree.

Towards #<!-- -->24834.

---

Patch is 32.66 KiB, truncated to 20.00 KiB below, full version: 
https://github.com/llvm/llvm-project/pull/148385.diff


10 Files Affected:

- (modified) lldb/source/Plugins/Language/CPlusPlus/CMakeLists.txt (+1) 
- (modified) lldb/source/Plugins/Language/CPlusPlus/CPlusPlusLanguage.cpp 
(+52-14) 
- (modified) lldb/source/Plugins/Language/CPlusPlus/MsvcStl.h (+12) 
- (added) lldb/source/Plugins/Language/CPlusPlus/MsvcStlTree.cpp (+404) 
- (modified) 
lldb/test/API/functionalities/data-formatter/data-formatter-stl/generic/map/TestDataFormatterStdMap.py
 (+10-1) 
- (modified) 
lldb/test/API/functionalities/data-formatter/data-formatter-stl/generic/map/main.cpp
 (+2) 
- (modified) 
lldb/test/API/functionalities/data-formatter/data-formatter-stl/generic/multimap/TestDataFormatterGenericMultiMap.py
 (+11-7) 
- (modified) 
lldb/test/API/functionalities/data-formatter/data-formatter-stl/generic/multiset/TestDataFormatterGenericMultiSet.py
 (+21-11) 
- (modified) 
lldb/test/API/functionalities/data-formatter/data-formatter-stl/generic/set/TestDataFormatterGenericSet.py
 (+27-11) 
- (modified) 
lldb/test/API/functionalities/data-formatter/data-formatter-stl/generic/set/main.cpp
 (+6) 


``````````diff
diff --git a/lldb/source/Plugins/Language/CPlusPlus/CMakeLists.txt 
b/lldb/source/Plugins/Language/CPlusPlus/CMakeLists.txt
index 296159ea28407..96773b43e3685 100644
--- a/lldb/source/Plugins/Language/CPlusPlus/CMakeLists.txt
+++ b/lldb/source/Plugins/Language/CPlusPlus/CMakeLists.txt
@@ -34,6 +34,7 @@ add_lldb_library(lldbPluginCPlusPlusLanguage PLUGIN
   LibStdcppTuple.cpp
   LibStdcppUniquePointer.cpp
   MsvcStl.cpp
+  MsvcStlTree.cpp
   MsvcStlSmartPointer.cpp
   MSVCUndecoratedNameParser.cpp
 
diff --git a/lldb/source/Plugins/Language/CPlusPlus/CPlusPlusLanguage.cpp 
b/lldb/source/Plugins/Language/CPlusPlus/CPlusPlusLanguage.cpp
index 2db3e6f0ca315..d7bf6783b8d3e 100644
--- a/lldb/source/Plugins/Language/CPlusPlus/CPlusPlusLanguage.cpp
+++ b/lldb/source/Plugins/Language/CPlusPlus/CPlusPlusLanguage.cpp
@@ -1409,7 +1409,7 @@ static void 
LoadLibStdcppFormatters(lldb::TypeCategoryImplSP cpp_category_sp) {
           stl_synth_flags,
           "lldb.formatters.cpp.gnu_libstdcpp.StdVectorSynthProvider")));
   cpp_category_sp->AddTypeSynthetic(
-      "^std::(__debug::)?map<.+> >(( )?&)?$", eFormatterMatchRegex,
+      "^std::__debug::map<.+> >(( )?&)?$", eFormatterMatchRegex,
       SyntheticChildrenSP(new ScriptedSyntheticChildren(
           stl_synth_flags,
           "lldb.formatters.cpp.gnu_libstdcpp.StdMapLikeSynthProvider")));
@@ -1419,17 +1419,17 @@ static void 
LoadLibStdcppFormatters(lldb::TypeCategoryImplSP cpp_category_sp) {
           stl_deref_flags,
           "lldb.formatters.cpp.gnu_libstdcpp.StdDequeSynthProvider")));
   cpp_category_sp->AddTypeSynthetic(
-      "^std::(__debug::)?set<.+> >(( )?&)?$", eFormatterMatchRegex,
+      "^std::__debug::set<.+> >(( )?&)?$", eFormatterMatchRegex,
       SyntheticChildrenSP(new ScriptedSyntheticChildren(
           stl_deref_flags,
           "lldb.formatters.cpp.gnu_libstdcpp.StdMapLikeSynthProvider")));
   cpp_category_sp->AddTypeSynthetic(
-      "^std::(__debug::)?multimap<.+> >(( )?&)?$", eFormatterMatchRegex,
+      "^std::__debug::multimap<.+> >(( )?&)?$", eFormatterMatchRegex,
       SyntheticChildrenSP(new ScriptedSyntheticChildren(
           stl_deref_flags,
           "lldb.formatters.cpp.gnu_libstdcpp.StdMapLikeSynthProvider")));
   cpp_category_sp->AddTypeSynthetic(
-      "^std::(__debug::)?multiset<.+> >(( )?&)?$", eFormatterMatchRegex,
+      "^std::__debug::multiset<.+> >(( )?&)?$", eFormatterMatchRegex,
       SyntheticChildrenSP(new ScriptedSyntheticChildren(
           stl_deref_flags,
           "lldb.formatters.cpp.gnu_libstdcpp.StdMapLikeSynthProvider")));
@@ -1470,15 +1470,15 @@ static void 
LoadLibStdcppFormatters(lldb::TypeCategoryImplSP cpp_category_sp) {
       "libstdc++ std::vector summary provider",
       "^std::(__debug::)?vector<.+>(( )?&)?$", stl_summary_flags, true);
 
-  AddCXXSummary(
-      cpp_category_sp, lldb_private::formatters::ContainerSizeSummaryProvider,
-      "libstdc++ std::map summary provider",
-      "^std::(__debug::)?map<.+> >(( )?&)?$", stl_summary_flags, true);
+  AddCXXSummary(cpp_category_sp,
+                lldb_private::formatters::ContainerSizeSummaryProvider,
+                "libstdc++ std::map summary provider",
+                "^std::__debug::map<.+> >(( )?&)?$", stl_summary_flags, true);
 
-  AddCXXSummary(
-      cpp_category_sp, lldb_private::formatters::ContainerSizeSummaryProvider,
-      "libstdc++ std::set summary provider",
-      "^std::(__debug::)?set<.+> >(( )?&)?$", stl_summary_flags, true);
+  AddCXXSummary(cpp_category_sp,
+                lldb_private::formatters::ContainerSizeSummaryProvider,
+                "libstdc++ std::set summary provider",
+                "^std::__debug::set<.+> >(( )?&)?$", stl_summary_flags, true);
 
   AddCXXSummary(
       cpp_category_sp, lldb_private::formatters::ContainerSizeSummaryProvider,
@@ -1488,12 +1488,12 @@ static void 
LoadLibStdcppFormatters(lldb::TypeCategoryImplSP cpp_category_sp) {
   AddCXXSummary(
       cpp_category_sp, lldb_private::formatters::ContainerSizeSummaryProvider,
       "libstdc++ std::multimap summary provider",
-      "^std::(__debug::)?multimap<.+> >(( )?&)?$", stl_summary_flags, true);
+      "^std::__debug::multimap<.+> >(( )?&)?$", stl_summary_flags, true);
 
   AddCXXSummary(
       cpp_category_sp, lldb_private::formatters::ContainerSizeSummaryProvider,
       "libstdc++ std::multiset summary provider",
-      "^std::(__debug::)?multiset<.+> >(( )?&)?$", stl_summary_flags, true);
+      "^std::__debug::multiset<.+> >(( )?&)?$", stl_summary_flags, true);
 
   AddCXXSummary(cpp_category_sp,
                 lldb_private::formatters::ContainerSizeSummaryProvider,
@@ -1599,6 +1599,18 @@ GenericSmartPointerSummaryProvider(ValueObject &valobj, 
Stream &stream,
   return LibStdcppSmartPointerSummaryProvider(valobj, stream, options);
 }
 
+static lldb_private::SyntheticChildrenFrontEnd *
+GenericMapLikeSyntheticFrontEndCreator(CXXSyntheticChildren *children,
+                                       lldb::ValueObjectSP valobj_sp) {
+  if (!valobj_sp)
+    return nullptr;
+
+  if (IsMsvcStlMapLike(*valobj_sp))
+    return MsvcStlMapLikeSyntheticFrontEndCreator(valobj_sp);
+  return new ScriptedSyntheticChildren::FrontEnd(
+      "lldb.formatters.cpp.gnu_libstdcpp.StdMapLikeSynthProvider", *valobj_sp);
+}
+
 /// Load formatters that are formatting types from more than one STL
 static void LoadCommonStlFormatters(lldb::TypeCategoryImplSP cpp_category_sp) {
   if (!cpp_category_sp)
@@ -1642,12 +1654,19 @@ static void 
LoadCommonStlFormatters(lldb::TypeCategoryImplSP cpp_category_sp) {
           },
           "MSVC STL/libstdc++ std::wstring summary provider"));
 
+  stl_summary_flags.SetDontShowChildren(false);
+  stl_summary_flags.SetSkipPointers(false);
+
   AddCXXSynthetic(cpp_category_sp, GenericSmartPointerSyntheticFrontEndCreator,
                   "std::shared_ptr synthetic children",
                   "^std::shared_ptr<.+>(( )?&)?$", stl_synth_flags, true);
   AddCXXSynthetic(cpp_category_sp, GenericSmartPointerSyntheticFrontEndCreator,
                   "std::weak_ptr synthetic children",
                   "^std::weak_ptr<.+>(( )?&)?$", stl_synth_flags, true);
+  AddCXXSynthetic(cpp_category_sp, GenericMapLikeSyntheticFrontEndCreator,
+                  "std::(multi)?map/set synthetic children",
+                  "^std::(multi)?(map|set)<.+>(( )?&)?$", stl_synth_flags,
+                  true);
 
   AddCXXSummary(cpp_category_sp, GenericSmartPointerSummaryProvider,
                 "MSVC STL/libstdc++ std::shared_ptr summary provider",
@@ -1655,6 +1674,10 @@ static void 
LoadCommonStlFormatters(lldb::TypeCategoryImplSP cpp_category_sp) {
   AddCXXSummary(cpp_category_sp, GenericSmartPointerSummaryProvider,
                 "MSVC STL/libstdc++ std::weak_ptr summary provider",
                 "^std::weak_ptr<.+>(( )?&)?$", stl_summary_flags, true);
+  AddCXXSummary(cpp_category_sp, ContainerSizeSummaryProvider,
+                "MSVC STL/libstdc++ std::(multi)?map/set summary provider",
+                "^std::(multi)?(map|set)<.+>(( )?&)?$", stl_summary_flags,
+                true);
 }
 
 static void LoadMsvcStlFormatters(lldb::TypeCategoryImplSP cpp_category_sp) {
@@ -1669,6 +1692,9 @@ static void 
LoadMsvcStlFormatters(lldb::TypeCategoryImplSP cpp_category_sp) {
       .SetDontShowValue(false)
       .SetShowMembersOneLiner(false)
       .SetHideItemNames(false);
+  SyntheticChildren::Flags stl_synth_flags;
+  stl_synth_flags.SetCascades(true).SetSkipPointers(false).SetSkipReferences(
+      false);
 
   using StringElementType = StringPrinter::StringElementType;
 
@@ -1690,6 +1716,18 @@ static void 
LoadMsvcStlFormatters(lldb::TypeCategoryImplSP cpp_category_sp) {
           stl_summary_flags,
           MsvcStlStringSummaryProvider<StringElementType::UTF32>,
           "MSVC STL std::u32string summary provider"));
+
+  stl_summary_flags.SetDontShowChildren(false);
+  stl_summary_flags.SetSkipPointers(false);
+
+  AddCXXSynthetic(cpp_category_sp, MsvcStlTreeIterSyntheticFrontEndCreator,
+                  "MSVC STL tree iterator synthetic children",
+                  "^std::_Tree(_const)?_iterator<.+>(( )?&)?$", 
stl_synth_flags,
+                  true);
+  AddCXXSummary(cpp_category_sp, MsvcStlTreeIterSummaryProvider,
+                "MSVC STL tree iterator summary",
+                "^std::_Tree(_const)?_iterator<.+>(( )?&)?$", 
stl_summary_flags,
+                true);
 }
 
 static void LoadSystemFormatters(lldb::TypeCategoryImplSP cpp_category_sp) {
diff --git a/lldb/source/Plugins/Language/CPlusPlus/MsvcStl.h 
b/lldb/source/Plugins/Language/CPlusPlus/MsvcStl.h
index edf3f4e8a5387..5506df35832ad 100644
--- a/lldb/source/Plugins/Language/CPlusPlus/MsvcStl.h
+++ b/lldb/source/Plugins/Language/CPlusPlus/MsvcStl.h
@@ -37,6 +37,18 @@ bool MsvcStlSmartPointerSummaryProvider(ValueObject &valobj, 
Stream &stream,
 lldb_private::SyntheticChildrenFrontEnd *
 MsvcStlSmartPointerSyntheticFrontEndCreator(lldb::ValueObjectSP valobj_sp);
 
+bool IsMsvcStlTreeIter(ValueObject &valobj);
+bool MsvcStlTreeIterSummaryProvider(ValueObject &valobj, Stream &stream,
+                                    const TypeSummaryOptions &options);
+lldb_private::SyntheticChildrenFrontEnd *
+MsvcStlTreeIterSyntheticFrontEndCreator(CXXSyntheticChildren *,
+                                        lldb::ValueObjectSP valobj_sp);
+
+// std::map,set,multimap,multiset
+bool IsMsvcStlMapLike(ValueObject &valobj);
+lldb_private::SyntheticChildrenFrontEnd *
+MsvcStlMapLikeSyntheticFrontEndCreator(lldb::ValueObjectSP valobj_sp);
+
 } // namespace formatters
 } // namespace lldb_private
 
diff --git a/lldb/source/Plugins/Language/CPlusPlus/MsvcStlTree.cpp 
b/lldb/source/Plugins/Language/CPlusPlus/MsvcStlTree.cpp
new file mode 100644
index 0000000000000..0530a3c302371
--- /dev/null
+++ b/lldb/source/Plugins/Language/CPlusPlus/MsvcStlTree.cpp
@@ -0,0 +1,404 @@
+//===-- MsvcStlTree.cpp 
---------------------------------------------------===//
+//
+// 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 "MsvcStl.h"
+
+#include "lldb/DataFormatters/FormattersHelpers.h"
+#include "lldb/Utility/Status.h"
+#include "lldb/ValueObject/ValueObject.h"
+#include "lldb/lldb-enumerations.h"
+#include "lldb/lldb-forward.h"
+#include <cstdint>
+#include <optional>
+
+using namespace lldb;
+using namespace lldb_private;
+using namespace lldb_private::formatters;
+
+// A Node looks as follows:
+// struct _Tree_node {
+//   _Tree_node *_Left;
+//   _Tree_node *_Parent;
+//   _Tree_node *_Right;
+//   char _Color;
+//   char _Isnil;         // true (!= 0) if head or nil node
+//   value_type _Myval;
+// };
+
+namespace {
+
+class MapEntry {
+public:
+  MapEntry() = default;
+  explicit MapEntry(ValueObjectSP entry_sp) : m_entry_sp(entry_sp) {}
+  explicit MapEntry(ValueObject *entry)
+      : m_entry_sp(entry ? entry->GetSP() : ValueObjectSP()) {}
+
+  ValueObjectSP left() const {
+    if (!m_entry_sp)
+      return m_entry_sp;
+    return m_entry_sp->GetSyntheticChildAtOffset(
+        0, m_entry_sp->GetCompilerType(), true);
+  }
+
+  ValueObjectSP right() const {
+    if (!m_entry_sp)
+      return m_entry_sp;
+    return m_entry_sp->GetSyntheticChildAtOffset(
+        2 * m_entry_sp->GetProcessSP()->GetAddressByteSize(),
+        m_entry_sp->GetCompilerType(), true);
+  }
+
+  ValueObjectSP parent() const {
+    if (!m_entry_sp)
+      return m_entry_sp;
+    return m_entry_sp->GetSyntheticChildAtOffset(
+         m_entry_sp->GetProcessSP()->GetAddressByteSize(),
+        m_entry_sp->GetCompilerType(), true);
+  }
+
+  uint64_t value() const {
+    if (!m_entry_sp)
+      return 0;
+    return m_entry_sp->GetValueAsUnsigned(0);
+  }
+
+  bool is_nil() const {
+    if (!m_entry_sp)
+      return true;
+    auto isnil_sp = m_entry_sp->GetChildMemberWithName("_Isnil");
+    if (!isnil_sp)
+      return true;
+    return isnil_sp->GetValueAsUnsigned(1) != 0;
+  }
+
+  bool error() const {
+    if (!m_entry_sp)
+      return true;
+    return m_entry_sp->GetError().Fail();
+  }
+
+  bool is_nullptr() const { return (value() == 0); }
+
+  ValueObjectSP GetEntry() const { return m_entry_sp; }
+
+  void SetEntry(ValueObjectSP entry) { m_entry_sp = entry; }
+
+  bool operator==(const MapEntry &rhs) const {
+    return (rhs.m_entry_sp.get() == m_entry_sp.get());
+  }
+
+private:
+  ValueObjectSP m_entry_sp;
+};
+
+class MapIterator {
+public:
+  MapIterator(ValueObject *entry, size_t depth = 0)
+      : m_entry(entry), m_max_depth(depth) {}
+
+  MapIterator() = default;
+
+  ValueObjectSP value() { return m_entry.GetEntry(); }
+
+  ValueObjectSP advance(size_t count) {
+    ValueObjectSP fail;
+    if (m_error)
+      return fail;
+    size_t steps = 0;
+    while (count > 0) {
+      next();
+      count--, steps++;
+      if (m_error || m_entry.is_nullptr() || (steps > m_max_depth))
+        return fail;
+    }
+    return m_entry.GetEntry();
+  }
+
+private:
+  /// Mimicks _Tree_unchecked_const_iterator::operator++()
+  void next() {
+    if (m_entry.is_nullptr())
+      return;
+    MapEntry right(m_entry.right());
+    if (!right.is_nil()) {
+      m_entry = tree_min(std::move(right));
+      return;
+    }
+    size_t steps = 0;
+    MapEntry pnode(m_entry.parent());
+    while(!pnode.is_nil() && m_entry.value() == 
MapEntry(pnode.right()).value()) {
+      m_entry = pnode;
+      steps++;
+      if (steps > m_max_depth) {
+        m_entry = MapEntry();
+        return;
+      }
+      pnode.SetEntry(m_entry.parent());
+    }
+    m_entry = std::move(pnode);
+  }
+
+  /// Mimicks MSVC STL's _Min() algorithm (finding the leftmost node in the 
subtree).
+  MapEntry tree_min(MapEntry pnode) {
+    if (pnode.is_nullptr())
+      return MapEntry();
+    MapEntry left(pnode.left());
+    size_t steps = 0;
+    while (!left.is_nil()) {
+      if (left.error()) {
+        m_error = true;
+        return MapEntry();
+      }
+      pnode = left;
+      left.SetEntry(pnode.left());
+      steps++;
+      if (steps > m_max_depth)
+        return MapEntry();
+    }
+    return pnode;
+  }
+
+  MapEntry m_entry;
+  size_t m_max_depth = 0;
+  bool m_error = false;
+};
+
+} // namespace
+
+namespace lldb_private {
+namespace formatters {
+class MsvcStlTreeSyntheticFrontEnd : public SyntheticChildrenFrontEnd {
+public:
+  MsvcStlTreeSyntheticFrontEnd(lldb::ValueObjectSP valobj_sp);
+
+  ~MsvcStlTreeSyntheticFrontEnd() override = default;
+
+  llvm::Expected<uint32_t> CalculateNumChildren() override;
+
+  lldb::ValueObjectSP GetChildAtIndex(uint32_t idx) override;
+
+  lldb::ChildCacheState Update() override;
+
+  llvm::Expected<size_t> GetIndexOfChildWithName(ConstString name) override;
+
+private:
+  /// Returns the ValueObject for the _Tree_node at index \ref idx.
+  ///
+  /// \param[in] idx The child index that we're looking to get the value for.
+  ///
+  /// \param[in] max_depth The maximum search depth after which we stop trying
+  ///                      to find the node for.
+  ///
+  /// \returns On success, returns the ValueObjectSP corresponding to the 
+  ///          _Tree_node's _Myval member.
+  ///          On failure, nullptr is returned.
+  ValueObjectSP GetValueAt(size_t idx, size_t max_depth);
+
+  ValueObject *m_tree = nullptr;
+  ValueObject *m_begin_node = nullptr;
+  size_t m_count = UINT32_MAX;
+  std::map<size_t, MapIterator> m_iterators;
+};
+
+class MsvcStlTreeIterSyntheticFrontEnd : public SyntheticChildrenFrontEnd {
+public:
+  MsvcStlTreeIterSyntheticFrontEnd(lldb::ValueObjectSP valobj_sp): 
SyntheticChildrenFrontEnd(*valobj_sp) {}
+
+  llvm::Expected<uint32_t> CalculateNumChildren() override {
+    if (!m_inner_sp)
+      return 0;
+    return m_inner_sp->GetNumChildren();
+  }
+
+  lldb::ValueObjectSP GetChildAtIndex(uint32_t idx) override {
+    if (!m_inner_sp)
+      return nullptr;
+    return m_inner_sp->GetChildAtIndex(idx);
+  }
+
+  lldb::ChildCacheState Update() override;
+
+  llvm::Expected<size_t> GetIndexOfChildWithName(ConstString name) override {
+    if (!m_inner_sp)
+      return llvm::createStringError("There are no children.");
+    return m_inner_sp->GetIndexOfChildWithName(name);
+  }
+
+  lldb::ValueObjectSP GetSyntheticValue() override {
+    return m_inner_sp;
+  }
+
+private:
+  ValueObjectSP m_inner_sp;
+};
+
+} // namespace formatters
+} // namespace lldb_private
+
+lldb_private::formatters::MsvcStlTreeSyntheticFrontEnd::
+    MsvcStlTreeSyntheticFrontEnd(lldb::ValueObjectSP valobj_sp)
+    : SyntheticChildrenFrontEnd(*valobj_sp) {
+  if (valobj_sp)
+    Update();
+}
+
+llvm::Expected<uint32_t> lldb_private::formatters::
+    MsvcStlTreeSyntheticFrontEnd::CalculateNumChildren() {
+  if (m_count != UINT32_MAX)
+    return m_count;
+
+  if (m_tree == nullptr)
+    return 0;
+
+  if (auto node_sp = m_tree->GetChildMemberWithName("_Mysize")) {
+    m_count = node_sp->GetValueAsUnsigned(0);
+    return m_count;
+  }
+
+  return llvm::createStringError("Failed to read size.");
+}
+
+ValueObjectSP
+lldb_private::formatters::MsvcStlTreeSyntheticFrontEnd::GetValueAt(
+    size_t idx, size_t max_depth) {
+  MapIterator iterator(m_begin_node, max_depth);
+
+  size_t advance_by = idx;
+  if (idx > 0) {
+    // If we have already created the iterator for the previous
+    // index, we can start from there and advance by 1.
+    auto cached_iterator = m_iterators.find(idx - 1);
+    if (cached_iterator != m_iterators.end()) {
+      iterator = cached_iterator->second;
+      advance_by = 1;
+    }
+  }
+
+  ValueObjectSP iterated_sp(iterator.advance(advance_by));
+  if (!iterated_sp)
+    // this tree is garbage - stop
+    return nullptr;
+
+  ValueObjectSP value_sp = iterated_sp->GetChildMemberWithName("_Myval");
+  if (!value_sp)
+    return nullptr;
+
+  m_iterators[idx] = iterator;
+
+  return value_sp;
+}
+
+lldb::ValueObjectSP
+lldb_private::formatters::MsvcStlTreeSyntheticFrontEnd::GetChildAtIndex(
+    uint32_t idx) {
+  uint32_t num_children = CalculateNumChildrenIgnoringErrors();
+  if (idx >= num_children)
+    return nullptr;
+
+  if (m_tree == nullptr || m_begin_node == nullptr)
+    return nullptr;
+
+  ValueObjectSP val_sp = GetValueAt(idx, /*max_depth=*/num_children);
+  if (!val_sp) {
+    // this will stop all future searches until an Update() happens
+    m_tree = nullptr;
+    return nullptr;
+  }
+
+  // at this point we have a valid pair
+  // we need to copy current_sp into a new object otherwise we will end up with
+  // all items named _Myval
+  StreamString name;
+  name.Printf("[%" PRIu64 "]", (uint64_t)idx);
+  return val_sp->Clone(ConstString(name.GetString()));
+}
+
+lldb::ChildCacheState
+lldb_private::formatters::MsvcStlTreeSyntheticFrontEnd::Update() {
+  m_count = UINT32_MAX;
+  m_tree = m_begin_node = nullptr;
+  m_iterators.clear();
+  m_tree = m_backend.GetChildAtNamePath({"_Mypair", "_Myval2", 
"_Myval2"}).get();
+  if (!m_tree)
+    return lldb::ChildCacheState::eRefetch;
+
+  m_begin_node = m_tree->GetChildAtNamePath({"_Myhead", "_Left"}).get();
+
+  return lldb::ChildCacheState::eRefetch;
+}
+
+llvm::Expected<size_t> lldb_private::formatters::MsvcStlTreeSyntheticFrontEnd::
+    GetIndexOfChildWithName(ConstString name) {
+  auto optional_idx = formatters::ExtractIndexFromString(name.GetCString());
+  if (!optional_idx) {
+    return llvm::createStringError("Type has no child named '%s'",
+                                   name.AsCString());
+  }
+  return *optional_idx;
+}
+
+lldb::ChildCacheState MsvcStlTreeIterSyntheticFrontEnd::Update() {
+  m_inner_sp = nullptr;
+  auto node_sp = m_backend.GetChildMemberWithName("_Ptr");
+  if (!node_sp)
+    return lldb::eRefetch;
+
+  MapEntry entry(node_sp.get());
+  if (entry.is_nil())
+    return lldb::eRefetch; // end
+
+  m_inner_sp = node_sp->GetChildMemberWithName("_Myval");
+  return lldb::eRefetch;
+}
+
+bool formatters::IsMsvcStlTreeIter(ValueObject &valobj) {
+  return valobj.GetChildMemberWithName("_Ptr") != nullptr;
+}
+
+bool formatters::MsvcStlTreeIterSummaryProvider(ValueObject &valobj, Stream 
&stream,
+                                    const TypeSummaryOptions &options) {
+                                      auto valobj_sp = 
valobj.GetNonSyntheticValue();
+                  ...
[truncated]

``````````

</details>


https://github.com/llvm/llvm-project/pull/148385
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