Add comments to DWARFCompileUnit length fields/methods

[jankratochvil]

Summary

All the methods have similar names and they return different lengths, document it.

Is such patch obvious enough to check it in without an approval?

[labath]

If you are confident that the behavior you are documenting is correct, I think you can submit patches like these without approval. If you do end up sending something up for review, please be sure to add "lldb-commits" as a subscriber.

lldb/trunk/source/Plugins/SymbolFile/DWARF/DWARFCompileUnit.h

public:
   size_t ExtractDIEsIfNeeded(bool cu_die_only);
   DWARFDIE LookupAddress(const dw_addr_t address);
   size_t AppendDIEsWithTag(const dw_tag_t tag,
                            DWARFDIECollection &matching_dies,
                            uint32_t depth = UINT32_MAX) const;
   void Clear();
   bool Verify(lldb_private::Stream *s) const;
   void Dump(lldb_private::Stream *s) const;
+  // Offset of the initial length field.
   dw_offset_t GetOffset() const { return m_offset; }
   lldb::user_id_t GetID() const;
-  uint32_t Size() const {
-    return m_is_dwarf64 ? 23
-                        : 11; /* Size in bytes of the compile unit header */
-  }
+  // Size in bytes of the initial length + compile unit header.
+  uint32_t Size() const { return m_is_dwarf64 ? 23 : 11; }
   bool ContainsDIEOffset(dw_offset_t die_offset) const {
     return die_offset >= GetFirstDIEOffset() &&
            die_offset < GetNextCompileUnitOffset();
   }
   dw_offset_t GetFirstDIEOffset() const { return m_offset + Size(); }
   dw_offset_t GetNextCompileUnitOffset() const {
-    return m_offset + m_length + (m_is_dwarf64 ? 12 : 4);
+    return m_offset + (m_is_dwarf64 ? 12 : 4) + m_length;
   }
+  // Size of the CU data (without initial length and without header).
   size_t GetDebugInfoSize() const {
-    return m_length + (m_is_dwarf64 ? 12 : 4) - Size(); /* Size in bytes of the
-                                                           .debug_info data
-                                                           associated with this
-                                                           compile unit. */
+    return (m_is_dwarf64 ? 12 : 4) + m_length - Size();
   }
+  // Size of the CU data incl. header but without initial length.
   uint32_t GetLength() const { return m_length; }
   uint16_t GetVersion() const { return m_version; }
   const DWARFAbbreviationDeclarationSet *GetAbbreviations() const {
     return m_abbrevs;
   }
   dw_offset_t GetAbbrevOffset() const;
   uint8_t GetAddressByteSize() const { return m_addr_size; }
   dw_addr_t GetBaseAddress() const { return m_base_addr; }
DWARFDebugInfoEntry::collection
       m_die_array; // The compile unit debug information entry item
   std::unique_ptr<DWARFDebugAranges> m_func_aranges_ap; // A table similar to
                                                         // the .debug_aranges
                                                         // table, but this one
                                                         // points to the exact
                                                         // DW_TAG_subprogram
                                                         // DIEs
   dw_addr_t m_base_addr;
+  // Offset of the initial length field.
   dw_offset_t m_offset;
   dw_offset_t m_length;
   uint16_t m_version;
   uint8_t m_addr_size;
   Producer m_producer;
   uint32_t m_producer_version_major;
   uint32_t m_producer_version_minor;
   uint32_t m_producer_version_update;