[lldb][Formatters] Make libc++ and libstdc++ std::shared_ptr formatters consistent with each other

[Michael137]

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 #147141

[llvmbot]

@llvm/pr-subscribers-lldb

Author: Michael Buch (Michael137)

Changes

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 #147141

---

Full diff: https://github.com/llvm/llvm-project/pull/147165.diff

3 Files Affected:

• (modified) lldb/source/Plugins/Language/CPlusPlus/LibCxx.cpp (+23-16)
• (modified) lldb/source/Plugins/Language/CPlusPlus/LibCxx.h (+1)
• (modified) lldb/source/Plugins/Language/CPlusPlus/LibStdcpp.cpp (+16-11)

diff --git a/lldb/source/Plugins/Language/CPlusPlus/LibCxx.cpp b/lldb/source/Plugins/Language/CPlusPlus/LibCxx.cpp
index 104521b8c3e71..aa13e66a1b550 100644
--- a/lldb/source/Plugins/Language/CPlusPlus/LibCxx.cpp
+++ b/lldb/source/Plugins/Language/CPlusPlus/LibCxx.cpp
@@ -238,7 +238,8 @@ 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();
 }
@@ -251,7 +252,7 @@ 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();
@@ -259,20 +260,17 @@ lldb_private::formatters::LibcxxSharedPtrSyntheticFrontEnd::GetChildAtIndex(
     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();
@@ -281,6 +279,7 @@ 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)
@@ -290,6 +289,12 @@ 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
@@ -300,10 +305,12 @@ lldb_private::formatters::LibcxxSharedPtrSyntheticFrontEnd::Update() {
 llvm::Expected<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 llvm::createStringError("Type has no child named '%s'",
                                  name.AsCString());
 }
diff --git a/lldb/source/Plugins/Language/CPlusPlus/LibCxx.h b/lldb/source/Plugins/Language/CPlusPlus/LibCxx.h
index 56501302d116f..6115ccde38ad2 100644
--- a/lldb/source/Plugins/Language/CPlusPlus/LibCxx.h
+++ b/lldb/source/Plugins/Language/CPlusPlus/LibCxx.h
@@ -108,6 +108,7 @@ 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
index 28b7c01ab1b5b..7668a87ce447e 100644
--- a/lldb/source/Plugins/Language/CPlusPlus/LibStdcpp.cpp
+++ b/lldb/source/Plugins/Language/CPlusPlus/LibStdcpp.cpp
@@ -77,8 +77,7 @@ 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
@@ -266,15 +265,20 @@ 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();
 }
@@ -293,7 +297,6 @@ 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;
 }
@@ -302,8 +305,10 @@ llvm::Expected<size_t>
 LibStdcppSharedPtrSyntheticFrontEnd::GetIndexOfChildWithName(ConstString name) {
   if (name == "pointer")
     return 0;
+
   if (name == "object" || name == "$$dereference$$")
     return 1;
+
   return llvm::createStringError("Type has no child named '%s'",
                                  name.AsCString());
 }

[labath]

Ah, I see you've done that already.

Not required, but I noticed that the pointer child still contains the goo:

(lldb) v a.__ptr_
(std::shared_ptr<int>::element_type *) a.__ptr_ = 0x000055555555a2b8

If we do the casting centrally, we could have both of these appear the same way.

[Michael137]

Ah, I see you've done that already.

Not required, but I noticed that the pointer child still contains the goo:

(lldb) v a.__ptr_
(std::shared_ptr<int>::element_type *) a.__ptr_ = 0x000055555555a2b8

If we do the casting centrally, we could have both of these appear the same way.

Good point. I'll address that separately once I merge the combined tests