Fix libcxx formatters for changes in r300140.

[lhames]

Summary

LLVM r300140 changed the layout and field names of __compressed_pair, which
broke LLDB's std::vector, std::map and std::unsorted_map formatters.

This patch attempts to fix these formatters by having them interogate the
__compressed_pair values to determine whether they're pre- or post-r300140
variants, then access them accordingly.

[EricWF]

LLVM r300140 changed the layout and field names of __compressed_pair,

I sure hope it doesn't break the ABI layout of __compressed_pair.

[lhames]

In D32554#738632, @EricWF wrote:

LLVM r300140 changed the layout and field names of __compressed_pair,

I sure hope it doesn't break the ABI layout of __compressed_pair.

Sorry - that was a poorly chosen phrase. I don't believe it changes the binary representation, just the conceptual layout of the class (from a pair of fields to a descendent of two singletons), which changes how it's represented in DWARF.

[EricWF]

just making sure I didn't make a mistake.

[jingham]

That looks good. I'm not quite sure why the std::map formatter makes statics for the ConstStrings it's going to use, but the other two look them up each time. I can't imagine it will matter IRL which one you use, and you didn't change the oddity, so...

[lhames]

In D32554#738880, @jingham wrote:

That looks good. I'm not quite sure why the std::map formatter makes statics for the ConstStrings it's going to use, but the other two look them up each time. I can't imagine it will matter IRL which one you use, and you didn't change the oddity, so...

Yeah - I stuck as close as possible to the existing functions here. I'll clean up the oddities in a separate patch. :)

source/Plugins/Language/CPlusPlus/LibCxxMap.cpp

lldb_private::formatters::LibcxxStdMapSyntheticFrontEnd::
   if (valobj_sp)
     Update();
 }
 
 size_t lldb_private::formatters::LibcxxStdMapSyntheticFrontEnd::
     CalculateNumChildren() {
   static ConstString g___pair3_("__pair3_");
   static ConstString g___first_("__first_");
+  static ConstString g___value_("__value_");
 
   if (m_count != UINT32_MAX)
     return m_count;
   if (m_tree == nullptr)
     return 0;
   ValueObjectSP m_item(m_tree->GetChildMemberWithName(g___pair3_, true));
   if (!m_item)
     return 0;
+
+  switch (m_item->GetCompilerType().GetNumDirectBaseClasses()) {
+  case 1:
+    // Assume a pre llvm r300140 __compressed_pair implementation:
     m_item = m_item->GetChildMemberWithName(g___first_, true);
+    break;
+  case 2: {
+    // Assume a post llvm r300140 __compressed_pair implementation:
+    ValueObjectSP first_elem_parent = m_item->GetChildAtIndex(0, true);
+    m_item = first_elem_parent->GetChildMemberWithName(g___value_, true);
+    break;
+  }
+  default:
+    return false;
+  }
+
   if (!m_item)
     return 0;
   m_count = m_item->GetValueAsUnsigned(0);
   return m_count;
 }
 
 bool lldb_private::formatters::LibcxxStdMapSyntheticFrontEnd::GetDataType() {
   static ConstString g___value_("__value_");

source/Plugins/Language/CPlusPlus/LibCxxUnorderedMap.cpp

if (!node_sp || error.Fail())
       return lldb::ValueObjectSP();
 
     ValueObjectSP value_sp =
         node_sp->GetChildMemberWithName(ConstString("__value_"), true);
     ValueObjectSP hash_sp =
         node_sp->GetChildMemberWithName(ConstString("__hash_"), true);
     if (!hash_sp || !value_sp) {
       if (!m_element_type) {
-        auto first_sp = m_backend.GetChildAtNamePath({ConstString("__table_"),
-                                                      ConstString("__p1_"),
-                                                      ConstString("__first_")});
+        auto p1_sp = m_backend.GetChildAtNamePath({ConstString("__table_"),
+                                                   ConstString("__p1_")});
+        if (!p1_sp)
+          return nullptr;
+
+        ValueObjectSP first_sp = nullptr;
+        switch (p1_sp->GetCompilerType().GetNumDirectBaseClasses()) {
+        case 1:
+          // Assume a pre llvm r300140 __compressed_pair implementation:
+          first_sp = p1_sp->GetChildMemberWithName(ConstString("__first_"),
+                                                   true);
+          break;
+        case 2: {
+          // Assume a post llvm r300140 __compressed_pair implementation:
+          ValueObjectSP first_elem_parent_sp =
+            p1_sp->GetChildAtIndex(0, true);
+          first_sp = p1_sp->GetChildMemberWithName(ConstString("__value_"),
+                                                   true);
+          break;
+        }
+        default:
+          return nullptr;
+        }
+
         if (!first_sp)
           return nullptr;
         m_element_type = first_sp->GetCompilerType();
         lldb::TemplateArgumentKind kind;
         m_element_type = m_element_type.GetTemplateArgument(0, kind);
         m_element_type = m_element_type.GetPointeeType();
         m_node_type = m_element_type;
         m_element_type = m_element_type.GetTemplateArgument(0, kind);
bool lldb_private::formatters::LibcxxStdUnorderedMapSyntheticFrontEnd::
     Update() {
   m_num_elements = UINT32_MAX;
   m_next_element = nullptr;
   m_elements_cache.clear();
   ValueObjectSP table_sp =
       m_backend.GetChildMemberWithName(ConstString("__table_"), true);
   if (!table_sp)
     return false;
-  ValueObjectSP num_elements_sp = table_sp->GetChildAtNamePath(
-      {ConstString("__p2_"), ConstString("__first_")});
+
+  ValueObjectSP p2_sp = table_sp->GetChildMemberWithName(
+    ConstString("__p2_"), true);
+  ValueObjectSP num_elements_sp = nullptr;
+  llvm::SmallVector<ConstString, 3> next_path;
+  switch (p2_sp->GetCompilerType().GetNumDirectBaseClasses()) {
+  case 1:
+    // Assume a pre llvm r300140 __compressed_pair implementation:
+    num_elements_sp = p2_sp->GetChildMemberWithName(
+      ConstString("__first_"), true);
+    next_path.append({ConstString("__p1_"), ConstString("__first_"),
+                      ConstString("__next_")});
+    break;
+  case 2: {
+    // Assume a post llvm r300140 __compressed_pair implementation:
+    ValueObjectSP first_elem_parent = p2_sp->GetChildAtIndex(0, true);
+    num_elements_sp = first_elem_parent->GetChildMemberWithName(
+      ConstString("__value_"), true);
+    next_path.append({ConstString("__p1_"), ConstString("__value_"),
+                      ConstString("__next_")});
+    break;
+  }
+  default:
+    return false;
+  }
+
   if (!num_elements_sp)
     return false;
   m_num_elements = num_elements_sp->GetValueAsUnsigned(0);
-  m_tree =
-      table_sp
-          ->GetChildAtNamePath({ConstString("__p1_"), ConstString("__first_"),
-                                ConstString("__next_")})
-          .get();
+  m_tree = table_sp->GetChildAtNamePath(next_path).get();
   if (m_num_elements > 0)
     m_next_element =
-        table_sp
-            ->GetChildAtNamePath({ConstString("__p1_"), ConstString("__first_"),
-                                  ConstString("__next_")})
-            .get();
+        table_sp->GetChildAtNamePath(next_path).get();
   return false;
 }
 
 bool lldb_private::formatters::LibcxxStdUnorderedMapSyntheticFrontEnd::
     MightHaveChildren() {
   return true;
 }
 

source/Plugins/Language/CPlusPlus/LibCxxVector.cpp

 }
 
 bool lldb_private::formatters::LibcxxStdVectorSyntheticFrontEnd::Update() {
   m_start = m_finish = nullptr;
   ValueObjectSP data_type_finder_sp(
       m_backend.GetChildMemberWithName(ConstString("__end_cap_"), true));
   if (!data_type_finder_sp)
     return false;
+
+  switch (data_type_finder_sp->GetCompilerType().GetNumDirectBaseClasses()) {
+  case 1:
+    // Assume a pre llvm r300140 __compressed_pair implementation:
     data_type_finder_sp = data_type_finder_sp->GetChildMemberWithName(
       ConstString("__first_"), true);
+    break;
+  case 2: {
+    // Assume a post llvm r300140 __compressed_pair implementation:
+    ValueObjectSP first_elem_parent_sp =
+      data_type_finder_sp->GetChildAtIndex(0, true);
+    data_type_finder_sp = first_elem_parent_sp->GetChildMemberWithName(
+      ConstString("__value_"), true);
+    break;
+  }
+  default:
+    return false;
+  }
+
   if (!data_type_finder_sp)
     return false;
   m_element_type = data_type_finder_sp->GetCompilerType().GetPointeeType();
   m_element_size = m_element_type.GetByteSize(nullptr);
 
   if (m_element_size > 0) {
     // store raw pointers or end up with a circular dependency
     m_start =