`CompareModifiedEntry`, as used in

https://github.com/bitcoin/bitcoin/blob/3c098a8aa0780009c11b66b1a5d488a928629ebf/src/miner.h#L97-L112

will trigger a compile-time error in many `const` operations of index #1 of `indexed_modified_transaction_set` because `CompareModifiedEntry::operator()` is not `const`.

Most likely related to:

https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=224129
{
        LOCK(cs);
        return (mapTx.count(hash) != 0);
    }
    CTransactionRef get(const uint256& hash) const;
    TxMempoolInfo info(const uint256& hash) const;
    std::vector<TxMempoolInfo> infoAll() const;
    size_t DynamicMemoryUsage() const;
    boost::signals2::signal<void (CTransactionRef)> NotifyEntryAdded;
    boost::signals2::signal<void (CTransactionRef, MemPoolRemovalReason)> NotifyEntryRemoved;
private:
    /** UpdateForDescendants is used by UpdateTransactionsFromBlock to update
     *  the descendants for a single transaction that has been added to the
     *  mempool but may have child transactions in the mempool, eg during a
     *  chain reorg.  setExclude is the set of descendant transactions in the
     *  mempool that must not be accounted for (because any descendants in
     *  setExclude were added to the mempool after the transaction being
     *  updated and hence their state is already reflected in the parent
     *  state).
     *
     *  cachedDescendants will be updated with the descendants of the transaction
     *  being updated, so that future invocations don't need to walk the
     *  same transaction again, if encountered in another transaction chain.
     */
    void UpdateForDescendants(txiter updateIt,
            cacheMap &cachedDescendants,
            const std::set<uint256> &setExclude);
    
    void UpdateAncestorsOf(bool add, txiter hash, setEntries &setAncestors);