[Lldb-commits] [lldb] Teach LLDB's pretty-printer about libc++'s various `std::vector` layouts (PR #202438)

[Michael Buch via lldb-commits]

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@@ -126,40 +128,50 @@ lldb_private::formatters::LibcxxStdVectorSyntheticFrontEnd::GetChildAtIndex(
                                            m_element_type);
 }
 
-static ValueObjectSP GetDataPointer(ValueObject &root) {
-  auto [cap_sp, is_compressed_pair] =
-      GetValueOrOldCompressedPair(root, "__cap_", "__end_cap_");
-  if (!cap_sp)
-    return nullptr;
-
-  if (is_compressed_pair)
-    return GetFirstValueOfLibCXXCompressedPair(*cap_sp);
-
-  return cap_sp;
-}
-
 lldb::ChildCacheState
 lldb_private::formatters::LibcxxStdVectorSyntheticFrontEnd::Update() {
   m_start = m_finish = nullptr;
-  ValueObjectSP data_sp(GetDataPointer(m_backend));
 
-  if (!data_sp)
+  // Determine if this version of libc++'s `std::vector` uses `__vector_layout`.
+  ValueObjectSP layout_sp = m_backend.GetChildMemberWithName("__layout_");
+  ValueObject *target = layout_sp ? layout_sp.get() : &m_backend;
+
+  ValueObjectSP begin_sp = target->GetChildMemberWithName("__begin_");
+  if (!begin_sp)
     return lldb::ChildCacheState::eRefetch;
 
-  m_element_type = data_sp->GetCompilerType().GetPointeeType();
+  m_element_type = begin_sp->GetCompilerType().GetPointeeType();
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Michael137 wrote:

Can we add some tests to confirm that this works with the old-style compressed-pair (before the `no_unique_address` refactor)

https://github.com/llvm/llvm-project/pull/202438