[lldb][Formatters] Make libc++ and libstdc++ std::shared_ptr formatters consistent with each other (llvm#147165)

Michael137 · Michael137 · commit d54d47c50dce · 2025-07-25T09:08:12.000+01:00
This patch adjusts the libcxx and libstdcxx std::shared_ptr formatters to look the same. Changes to libcxx: * Now creates a synthetic child called `pointer` (like we already do for `std::unique_ptr`) Changes to libstdcxx: * When asked to dereference the pointer, cast the type of the result ValueObject to the element type (which we get from the template argument to std::shared_ptr). Before: ``` (std::__shared_ptr<int, __gnu_cxx::_S_atomic>::element_type) *foo = 123 ``` After: ``` (int) *foo = 123 ``` Tested in llvm#147141 (cherry picked from commit 6fec6a9)
diff --git a/lldb/source/Plugins/Language/CPlusPlus/LibCxx.cpp b/lldb/source/Plugins/Language/CPlusPlus/LibCxx.cpp
@@ -237,7 +237,8 @@ lldb_private::formatters::LibCxxVectorIteratorSyntheticFrontEndCreator(
 
 lldb_private::formatters::LibcxxSharedPtrSyntheticFrontEnd::
     LibcxxSharedPtrSyntheticFrontEnd(lldb::ValueObjectSP valobj_sp)
-    : SyntheticChildrenFrontEnd(*valobj_sp), m_cntrl(nullptr) {
+    : SyntheticChildrenFrontEnd(*valobj_sp), m_cntrl(nullptr),
+      m_ptr_obj(nullptr) {
   if (valobj_sp)
     Update();
 }
@@ -250,28 +251,25 @@ llvm::Expected<uint32_t> lldb_private::formatters::
 lldb::ValueObjectSP
 lldb_private::formatters::LibcxxSharedPtrSyntheticFrontEnd::GetChildAtIndex(
     uint32_t idx) {
-  if (!m_cntrl)
+  if (!m_cntrl || !m_ptr_obj)
     return lldb::ValueObjectSP();
 
   ValueObjectSP valobj_sp = m_backend.GetSP();
   if (!valobj_sp)
     return lldb::ValueObjectSP();
 
   if (idx == 0)
-    return valobj_sp->GetChildMemberWithName("__ptr_");
+    return m_ptr_obj->GetSP();
 
   if (idx == 1) {
-    if (auto ptr_sp = valobj_sp->GetChildMemberWithName("__ptr_")) {
-      Status status;
-      auto value_type_sp =
-            valobj_sp->GetCompilerType()
-              .GetTypeTemplateArgument(0).GetPointerType();
-      ValueObjectSP cast_ptr_sp = ptr_sp->Cast(value_type_sp);
-      ValueObjectSP value_sp = cast_ptr_sp->Dereference(status);
-      if (status.Success()) {
-        return value_sp;
-      }
-    }
+    Status status;
+    auto value_type_sp = valobj_sp->GetCompilerType()
+                             .GetTypeTemplateArgument(0)
+                             .GetPointerType();
+    ValueObjectSP cast_ptr_sp = m_ptr_obj->Cast(value_type_sp);
+    ValueObjectSP value_sp = cast_ptr_sp->Dereference(status);
+    if (status.Success())
+      return value_sp;
   }
 
   return lldb::ValueObjectSP();
@@ -280,6 +278,7 @@ lldb_private::formatters::LibcxxSharedPtrSyntheticFrontEnd::GetChildAtIndex(
 lldb::ChildCacheState
 lldb_private::formatters::LibcxxSharedPtrSyntheticFrontEnd::Update() {
   m_cntrl = nullptr;
+  m_ptr_obj = nullptr;
 
   ValueObjectSP valobj_sp = m_backend.GetSP();
   if (!valobj_sp)
@@ -289,6 +288,12 @@ lldb_private::formatters::LibcxxSharedPtrSyntheticFrontEnd::Update() {
   if (!target_sp)
     return lldb::ChildCacheState::eRefetch;
 
+  auto ptr_obj_sp = valobj_sp->GetChildMemberWithName("__ptr_");
+  if (!ptr_obj_sp)
+    return lldb::ChildCacheState::eRefetch;
+
+  m_ptr_obj = ptr_obj_sp->Clone(ConstString("pointer")).get();
+
   lldb::ValueObjectSP cntrl_sp(valobj_sp->GetChildMemberWithName("__cntrl_"));
 
   m_cntrl = cntrl_sp.get(); // need to store the raw pointer to avoid a circular
@@ -303,10 +308,12 @@ bool lldb_private::formatters::LibcxxSharedPtrSyntheticFrontEnd::
 
 size_t lldb_private::formatters::LibcxxSharedPtrSyntheticFrontEnd::
     GetIndexOfChildWithName(ConstString name) {
-  if (name == "__ptr_")
+  if (name == "__ptr_" || name == "pointer")
     return 0;
-  if (name == "$$dereference$$")
+
+  if (name == "object" || name == "$$dereference$$")
     return 1;
+
   return UINT32_MAX;
 }
 
diff --git a/lldb/source/Plugins/Language/CPlusPlus/LibCxx.h b/lldb/source/Plugins/Language/CPlusPlus/LibCxx.h
@@ -110,6 +110,7 @@ class LibcxxSharedPtrSyntheticFrontEnd : public SyntheticChildrenFrontEnd {
 
 private:
   ValueObject *m_cntrl;
+  ValueObject *m_ptr_obj;
 };
 
 class LibcxxUniquePtrSyntheticFrontEnd : public SyntheticChildrenFrontEnd {
diff --git a/lldb/source/Plugins/Language/CPlusPlus/LibStdcpp.cpp b/lldb/source/Plugins/Language/CPlusPlus/LibStdcpp.cpp
@@ -80,8 +80,7 @@ class LibStdcppSharedPtrSyntheticFrontEnd : public SyntheticChildrenFrontEnd {
   // objects are only destroyed when every shared pointer to any of them
   // is destroyed, so we must not store a shared pointer to any ValueObject
   // derived from our backend ValueObject (since we're in the same cluster).
-  ValueObject* m_ptr_obj = nullptr; // Underlying pointer (held, not owned)
-  ValueObject* m_obj_obj = nullptr; // Underlying object (held, not owned)
+  ValueObject *m_ptr_obj = nullptr; // Underlying pointer (held, not owned)
 };
 
 } // end of anonymous namespace
@@ -385,15 +384,20 @@ lldb::ValueObjectSP
 LibStdcppSharedPtrSyntheticFrontEnd::GetChildAtIndex(uint32_t idx) {
   if (idx == 0)
     return m_ptr_obj->GetSP();
+
   if (idx == 1) {
-    if (m_ptr_obj && !m_obj_obj) {
-      Status error;
-      ValueObjectSP obj_obj = m_ptr_obj->Dereference(error);
-      if (error.Success())
-        m_obj_obj = obj_obj->Clone(ConstString("object")).get();
-    }
-    if (m_obj_obj)
-      return m_obj_obj->GetSP();
+    ValueObjectSP valobj_sp = m_backend.GetSP();
+    if (!valobj_sp)
+      return nullptr;
+
+    Status status;
+    auto value_type_sp = valobj_sp->GetCompilerType()
+                             .GetTypeTemplateArgument(0)
+                             .GetPointerType();
+    ValueObjectSP cast_ptr_sp = m_ptr_obj->Cast(value_type_sp);
+    ValueObjectSP value_sp = cast_ptr_sp->Dereference(status);
+    if (status.Success())
+      return value_sp;
   }
   return lldb::ValueObjectSP();
 }
@@ -412,7 +416,6 @@ lldb::ChildCacheState LibStdcppSharedPtrSyntheticFrontEnd::Update() {
     return lldb::ChildCacheState::eRefetch;
 
   m_ptr_obj = ptr_obj_sp->Clone(ConstString("pointer")).get();
-  m_obj_obj = nullptr;
 
   return lldb::ChildCacheState::eRefetch;
 }
@@ -423,8 +426,10 @@ size_t LibStdcppSharedPtrSyntheticFrontEnd::GetIndexOfChildWithName(
     ConstString name) {
   if (name == "pointer")
     return 0;
+
   if (name == "object" || name == "$$dereference$$")
     return 1;
+
   return UINT32_MAX;
 }
 
diff --git a/lldb/test/API/functionalities/data-formatter/data-formatter-stl/libcxx/shared_ptr/TestDataFormatterLibcxxSharedPtr.py b/lldb/test/API/functionalities/data-formatter/data-formatter-stl/libcxx/shared_ptr/TestDataFormatterLibcxxSharedPtr.py
@@ -22,7 +22,7 @@ def test_shared_ptr_variables(self):
             "sp_empty",
             type="std::shared_ptr<int>",
             summary="nullptr",
-            children=[ValueCheck(name="__ptr_")],
+            children=[ValueCheck(name="pointer")],
         )
         self.assertEqual(
             valobj.child[0].GetValueAsUnsigned(lldb.LLDB_INVALID_ADDRESS), 0
@@ -35,23 +35,23 @@ def test_shared_ptr_variables(self):
         valobj = self.expect_var_path(
             "sp_int",
             type="std::shared_ptr<int>",
-            children=[ValueCheck(name="__ptr_")],
+            children=[ValueCheck(name="pointer")],
         )
         self.assertRegex(valobj.summary, r"^10( strong=1)? weak=0$")
         self.assertNotEqual(valobj.child[0].unsigned, 0)
 
         valobj = self.expect_var_path(
             "sp_int_ref",
             type="std::shared_ptr<int> &",
-            children=[ValueCheck(name="__ptr_")],
+            children=[ValueCheck(name="pointer")],
         )
         self.assertRegex(valobj.summary, r"^10( strong=1)? weak=0$")
         self.assertNotEqual(valobj.child[0].unsigned, 0)
 
         valobj = self.expect_var_path(
             "sp_int_ref_ref",
             type="std::shared_ptr<int> &&",
-            children=[ValueCheck(name="__ptr_")],
+            children=[ValueCheck(name="pointer")],
         )
         self.assertRegex(valobj.summary, r"^10( strong=1)? weak=0$")
         self.assertNotEqual(valobj.child[0].unsigned, 0)
@@ -66,7 +66,7 @@ def test_shared_ptr_variables(self):
         valobj = self.expect_var_path(
             "sp_str",
             type="std::shared_ptr<" + string_type + ">",
-            children=[ValueCheck(name="__ptr_", summary='"hello"')],
+            children=[ValueCheck(name="pointer", summary='"hello"')],
         )
         self.assertRegex(valobj.summary, r'^"hello"( strong=1)? weak=0$')
 
@@ -85,7 +85,7 @@ def test_shared_ptr_variables(self):
                 ValueCheck(name="name", summary='"steph"'),
             ],
         )
-        self.assertEqual(str(valobj), '(User) *__ptr_ = (id = 30, name = "steph")')
+        self.assertEqual(str(valobj), '(User) *pointer = (id = 30, name = "steph")')
 
         self.expect_var_path("sp_user->id", type="int", value="30")
         self.expect_var_path("sp_user->name", type="std::string", summary='"steph"')
