• make BlockUntilSyncedToCurrentChain() const

The method checks the chain tip for the best block, and calls SyncWithValidationInterfaceQueue() (a standalone function) if necessary.

• wallet: make CanGenerateKeys() const

This method simply checks if HD is or can be enabled and does not require mutability.

• wallet: make KeypoolCountExternalKeys() const

This method returns the sum of the key pool sizes. It does no modification.

• wallet: make CanGetAddresses() const

CWallet::CanGetAddresses() is used to check whether the wallet has available or is able to produce keys for addresses. It uses the ScriptPubKeyMan::CanGetAddresses(), which in turn uses the const KeypoolCountExternalKeys() method, all which do counting and no modifications.

• wallet/db: make IsDummy() const

This method does a simple check and no modifications.

• wallet/db: make Backup() const

This method is the to-disk equivalent of serialize methods which are also const.

• wallet: use constant CWallets in rpcdump.cpp

• GetWalletAddressesForKey is, as the name implies, immutable; the one change besides the parameter constness is a [] -> .at() change, to a verified-existing key.
• dumpprivkey and dumpwallet are both similarly immutable, for obvious reasons.
  • wallet/spkm: make GetOldestKeyPoolTime() const

The method checks the oldest key time for key pools and returns the oldest. It does no modifications.

• wallet: make getters const
• wallet: make BackupWallet() const
• wallet: make ReserveDestination pwallet ivar const
• wallet: use constant CWallets in rpcwallet.cpp

• GetAvoidReuseFlag: simply gets the flag, without modifying the wallet
• ListReceived: helper function to produce lists
• ListTransactions: produces a list of transactions, without modifications; two cases of map [] -> .at() for verified-existing keys
• DescribeWalletAddress: generates a description of a given wallet address without changing the wallet
• The following functions produce a list without making any modifications to the wallet:
  • listaddressgroupings
  • listreceivedbyaddress
  • listreceivedbylabel
  • listtransactions
  • listsinceblock
  • listlockunspent
  • listunspent
  • listlabels
  • getreceivedbyaddress
  • getreceivedbylabel
  • getaddressesbylabel
• signmessage: uses the wallet to procure a private key for signing, but does no modifications
• getbalance, getunconfirmedbalance: calculates the wallet balance, without any modifications
• gettransaction: procures transaction without any modifications
• backupwallet: makes a backup of the wallet to disk, without changing said wallet
• getwalletinfo: produces info about wallet without any modifications
• signrawtransactionwithwallet: modifies incoming transaction on the fly by signing with private key procured from within wallet; no modifications to wallet
• getaddressinfo: gets information about the given address, with no modifications done to the wallet; one case of [] -> .at() and one ::iterator -> ::const_iterator
• walletprocesspsbt: processes the given PSBT on the fly, without modifying the wallet

This is a backport of Core PR18241