"verify_lookup_length" is defined in BasicHashtable<F>, and it's called by "verify()" methods in:

ProtectionDomainCacheTable : Hashtable : BasicHashtable
Dictionary : TwoOopHashtable : Hashtable : BasicHashtable
SymbolEntryTable : Hashtable : BasicHashtable
ModuleEntryTable : Hashtable : BasicHashtable
PackageEntryTable : Hashtable : BasicHashtable
PlaceholderTable : TwoOopHashtable : Hashtable : BasicHashtable

where "SharedDictionary" is the only class extending "Dictionary".

"verify_lookup_length" uses "_lookup_count" and "_lookup_length" fields defined in BasicHashtable<F>, but the only class actually using those fields is "SharedDictionary", in all other cases they are not used, so "verify_lookup_length is a NOP for all the cases except "SharedDictionary".