`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
*  Assumes that setDescendants includes all in-mempool descendants of anything
     *  already in it.  */
    void CalculateDescendants(txiter it, setEntries &setDescendants);
    /** The minimum fee to get into the mempool, which may itself not be enough
      *  for larger-sized transactions.
      *  The incrementalRelayFee policy variable is used to bound the time it
      *  takes the fee rate to go back down all the way to 0. When the feerate
      *  would otherwise be half of this, it is set to 0 instead.
      */
    CFeeRate GetMinFee(size_t sizelimit) const;
    /** Remove transactions from the mempool until its dynamic size is <= sizelimit.
      *  pvNoSpendsRemaining, if set, will be populated with the list of outpoints
      *  which are not in mempool which no longer have any spends in this mempool.
      */
    void TrimToSize(size_t sizelimit, std::vector<COutPoint>* pvNoSpendsRemaining=nullptr);
    
    int Expire(int64_t time);
    
    bool TransactionWithinChainLimit(const uint256& txid, size_t chainLimit) const;
    unsigned long size()
    {
        LOCK(cs);
        return mapTx.size();
    }
    uint64_t GetTotalTxSize() const
    {
        LOCK(cs);
        return totalTxSize;
    }
    bool exists(uint256 hash) const