[NFC][lldb] Document a few ivars on the value object system.

Author: augusto2112

lldb/include/lldb/Expression/ExpressionVariable.h

@@ -108,7 +108,14 @@ class ExpressionVariable
   FlagType m_flags; // takes elements of Flags
 
   // these should be private
+  /// A value object whose value's data lives in host (lldb's) memory.
   lldb::ValueObjectSP m_frozen_sp;
+  /// The ValueObject counterpart to m_frozen_sp that tracks the value in
+  /// inferior memory. This object may not always exist; its presence depends on
+  /// whether it is logical for the value to exist in the inferior memory. For
+  /// example, when evaluating a C++ expression that generates an r-value, such
+  /// as a single function call, there is no memory address in the inferior to
+  /// track.
   lldb::ValueObjectSP m_live_sp;
 };
 

lldb/include/lldb/ValueObject/ValueObjectConstResultImpl.h

@@ -66,6 +66,10 @@ class ValueObjectConstResultImpl {
 
 private:
   ValueObject *m_impl_backend;
+  /// The memory address in the inferior process that this ValueObject tracks.
+  /// This address is used to request additional memory when the actual data
+  /// size exceeds the initial local buffer size, such as when a dynamic type
+  /// resolution results in a type larger than its statically determined type.
   lldb::addr_t m_live_address;
   AddressType m_live_address_type;
   lldb::ValueObjectSP m_address_of_backend;

lldb/source/Expression/Materializer.cpp

@@ -1187,6 +1187,7 @@ class EntityResultVariable : public Materializer::Entity {
 
 private:
   CompilerType m_type;
+  /// If this result entity can (and should) track the value on inferior memory.
   bool m_is_program_reference;
   bool m_keep_in_memory;