protocol: make message types constexpr

As a side effect the names of the constants do not have to be
repeated in `src/protocol.cpp`.

src/protocol.cpp

@@ -7,46 +7,6 @@
 
 #include <common/system.h>
 
-#include <atomic>
-
-namespace NetMsgType {
-const char* VERSION = "version";
-const char* VERACK = "verack";
-const char* ADDR = "addr";
-const char* ADDRV2 = "addrv2";
-const char* SENDADDRV2 = "sendaddrv2";
-const char* INV = "inv";
-const char* GETDATA = "getdata";
-const char* MERKLEBLOCK = "merkleblock";
-const char* GETBLOCKS = "getblocks";
-const char* GETHEADERS = "getheaders";
-const char* TX = "tx";
-const char* HEADERS = "headers";
-const char* BLOCK = "block";
-const char* GETADDR = "getaddr";
-const char* MEMPOOL = "mempool";
-const char* PING = "ping";
-const char* PONG = "pong";
-const char* NOTFOUND = "notfound";
-const char* FILTERLOAD = "filterload";
-const char* FILTERADD = "filteradd";
-const char* FILTERCLEAR = "filterclear";
-const char* SENDHEADERS = "sendheaders";
-const char* FEEFILTER = "feefilter";
-const char* SENDCMPCT = "sendcmpct";
-const char* CMPCTBLOCK = "cmpctblock";
-const char* GETBLOCKTXN = "getblocktxn";
-const char* BLOCKTXN = "blocktxn";
-const char* GETCFILTERS = "getcfilters";
-const char* CFILTER = "cfilter";
-const char* GETCFHEADERS = "getcfheaders";
-const char* CFHEADERS = "cfheaders";
-const char* GETCFCHECKPT = "getcfcheckpt";
-const char* CFCHECKPT = "cfcheckpt";
-const char* WTXIDRELAY = "wtxidrelay";
-const char* SENDTXRCNCL = "sendtxrcncl";
-} // namespace NetMsgType
-
 CMessageHeader::CMessageHeader(const MessageStartChars& pchMessageStartIn, const char* pszCommand, unsigned int nMessageSizeIn)
     : pchMessageStart{pchMessageStartIn}
 {

src/protocol.h

@@ -58,103 +58,102 @@ public:
  * to update ALL_NET_MESSAGE_TYPES below.
  */
 namespace NetMsgType {
-
 /**
  * The version message provides information about the transmitting node to the
  * receiving node at the beginning of a connection.
  */
-extern const char* VERSION;
+inline constexpr const char* VERSION{"version"};
 /**
  * The verack message acknowledges a previously-received version message,
  * informing the connecting node that it can begin to send other messages.
  */
-extern const char* VERACK;
+inline constexpr const char* VERACK{"verack"};
 /**
  * The addr (IP address) message relays connection information for peers on the
  * network.
  */
-extern const char* ADDR;
+inline constexpr const char* ADDR{"addr"};
 /**
  * The addrv2 message relays connection information for peers on the network just
  * like the addr message, but is extended to allow gossiping of longer node
  * addresses (see BIP155).
  */
-extern const char *ADDRV2;
+inline constexpr const char* ADDRV2{"addrv2"};
 /**
  * The sendaddrv2 message signals support for receiving ADDRV2 messages (BIP155).
  * It also implies that its sender can encode as ADDRV2 and would send ADDRV2
  * instead of ADDR to a peer that has signaled ADDRV2 support by sending SENDADDRV2.
  */
-extern const char *SENDADDRV2;
+inline constexpr const char* SENDADDRV2{"sendaddrv2"};
 /**
  * The inv message (inventory message) transmits one or more inventories of
  * objects known to the transmitting peer.
  */
-extern const char* INV;
+inline constexpr const char* INV{"inv"};
 /**
  * The getdata message requests one or more data objects from another node.
  */
-extern const char* GETDATA;
+inline constexpr const char* GETDATA{"getdata"};
 /**
  * The merkleblock message is a reply to a getdata message which requested a
  * block using the inventory type MSG_MERKLEBLOCK.
  * @since protocol version 70001 as described by BIP37.
  */
-extern const char* MERKLEBLOCK;
+inline constexpr const char* MERKLEBLOCK{"merkleblock"};
 /**
  * The getblocks message requests an inv message that provides block header
  * hashes starting from a particular point in the block chain.
  */
-extern const char* GETBLOCKS;
+inline constexpr const char* GETBLOCKS{"getblocks"};
 /**
  * The getheaders message requests a headers message that provides block
  * headers starting from a particular point in the block chain.
  * @since protocol version 31800.
  */
-extern const char* GETHEADERS;
+inline constexpr const char* GETHEADERS{"getheaders"};
 /**
  * The tx message transmits a single transaction.
  */
-extern const char* TX;
+inline constexpr const char* TX{"tx"};
 /**
  * The headers message sends one or more block headers to a node which
  * previously requested certain headers with a getheaders message.
  * @since protocol version 31800.
  */
-extern const char* HEADERS;
+inline constexpr const char* HEADERS{"headers"};
 /**
  * The block message transmits a single serialized block.
  */
-extern const char* BLOCK;
+inline constexpr const char* BLOCK{"block"};
 /**
  * The getaddr message requests an addr message from the receiving node,
  * preferably one with lots of IP addresses of other receiving nodes.
  */
-extern const char* GETADDR;
+inline constexpr const char* GETADDR{"getaddr"};
 /**
  * The mempool message requests the TXIDs of transactions that the receiving
  * node has verified as valid but which have not yet appeared in a block.
  * @since protocol version 60002 as described by BIP35.
  *   Only available with service bit NODE_BLOOM, see also BIP111.
  */
-extern const char* MEMPOOL;
+inline constexpr const char* MEMPOOL{"mempool"};
 /**
  * The ping message is sent periodically to help confirm that the receiving
  * peer is still connected.
  */
-extern const char* PING;
+inline constexpr const char* PING{"ping"};
 /**
  * The pong message replies to a ping message, proving to the pinging node that
  * the ponging node is still alive.
  * @since protocol version 60001 as described by BIP31.
  */
-extern const char* PONG;
+inline constexpr const char* PONG{"pong"};
 /**
  * The notfound message is a reply to a getdata message which requested an
  * object the receiving node does not have available for relay.
  * @since protocol version 70001.
  */
-extern const char* NOTFOUND;
+inline constexpr const char* NOTFOUND{"notfound"};
 /**
  * The filterload message tells the receiving peer to filter all relayed
  * transactions and requested merkle blocks through the provided filter.
@@ -162,7 +161,7 @@ extern const char* NOTFOUND;
  *   Only available with service bit NODE_BLOOM since protocol version
  *   70011 as described by BIP111.
  */
-extern const char* FILTERLOAD;
+inline constexpr const char* FILTERLOAD{"filterload"};
 /**
  * The filteradd message tells the receiving peer to add a single element to a
  * previously-set bloom filter, such as a new public key.
@@ -170,7 +169,7 @@ extern const char* FILTERLOAD;
  *   Only available with service bit NODE_BLOOM since protocol version
  *   70011 as described by BIP111.
  */
-extern const char* FILTERADD;
+inline constexpr const char* FILTERADD{"filteradd"};
 /**
  * The filterclear message tells the receiving peer to remove a previously-set
  * bloom filter.
@@ -178,19 +177,19 @@ extern const char* FILTERADD;
  *   Only available with service bit NODE_BLOOM since protocol version
  *   70011 as described by BIP111.
  */
-extern const char* FILTERCLEAR;
+inline constexpr const char* FILTERCLEAR{"filterclear"};
 /**
  * Indicates that a node prefers to receive new block announcements via a
  * "headers" message rather than an "inv".
  * @since protocol version 70012 as described by BIP130.
  */
-extern const char* SENDHEADERS;
+inline constexpr const char* SENDHEADERS{"sendheaders"};
 /**
  * The feefilter message tells the receiving peer not to inv us any txs
  * which do not meet the specified min fee rate.
  * @since protocol version 70013 as described by BIP133
  */
-extern const char* FEEFILTER;
+inline constexpr const char* FEEFILTER{"feefilter"};
 /**
  * Contains a 1-byte bool and 8-byte LE version number.
  * Indicates that a node is willing to provide blocks via "cmpctblock" messages.
@@ -198,36 +197,36 @@ extern const char* FEEFILTER;
  * "cmpctblock" message rather than an "inv", depending on message contents.
  * @since protocol version 70014 as described by BIP 152
  */
-extern const char* SENDCMPCT;
+inline constexpr const char* SENDCMPCT{"sendcmpct"};
 /**
  * Contains a CBlockHeaderAndShortTxIDs object - providing a header and
  * list of "short txids".
  * @since protocol version 70014 as described by BIP 152
  */
-extern const char* CMPCTBLOCK;
+inline constexpr const char* CMPCTBLOCK{"cmpctblock"};
 /**
  * Contains a BlockTransactionsRequest
  * Peer should respond with "blocktxn" message.
  * @since protocol version 70014 as described by BIP 152
  */
-extern const char* GETBLOCKTXN;
+inline constexpr const char* GETBLOCKTXN{"getblocktxn"};
 /**
  * Contains a BlockTransactions.
  * Sent in response to a "getblocktxn" message.
  * @since protocol version 70014 as described by BIP 152
  */
-extern const char* BLOCKTXN;
+inline constexpr const char* BLOCKTXN{"blocktxn"};
 /**
  * getcfilters requests compact filters for a range of blocks.
  * Only available with service bit NODE_COMPACT_FILTERS as described by
  * BIP 157 & 158.
  */
-extern const char* GETCFILTERS;
+inline constexpr const char* GETCFILTERS{"getcfilters"};
 /**
  * cfilter is a response to a getcfilters request containing a single compact
  * filter.
  */
-extern const char* CFILTER;
+inline constexpr const char* CFILTER{"cfilter"};
 /**
  * getcfheaders requests a compact filter header and the filter hashes for a
  * range of blocks, which can then be used to reconstruct the filter headers
@@ -235,36 +234,36 @@ extern const char* CFILTER;
  * Only available with service bit NODE_COMPACT_FILTERS as described by
  * BIP 157 & 158.
  */
-extern const char* GETCFHEADERS;
+inline constexpr const char* GETCFHEADERS{"getcfheaders"};
 /**
  * cfheaders is a response to a getcfheaders request containing a filter header
  * and a vector of filter hashes for each subsequent block in the requested range.
  */
-extern const char* CFHEADERS;
+inline constexpr const char* CFHEADERS{"cfheaders"};
 /**
  * getcfcheckpt requests evenly spaced compact filter headers, enabling
  * parallelized download and validation of the headers between them.
  * Only available with service bit NODE_COMPACT_FILTERS as described by
  * BIP 157 & 158.
  */
-extern const char* GETCFCHECKPT;
+inline constexpr const char* GETCFCHECKPT{"getcfcheckpt"};
 /**
  * cfcheckpt is a response to a getcfcheckpt request containing a vector of
  * evenly spaced filter headers for blocks on the requested chain.
  */
-extern const char* CFCHECKPT;
+inline constexpr const char* CFCHECKPT{"cfcheckpt"};
 /**
  * Indicates that a node prefers to relay transactions via wtxid, rather than
  * txid.
  * @since protocol version 70016 as described by BIP 339.
  */
-extern const char* WTXIDRELAY;
+inline constexpr const char* WTXIDRELAY{"wtxidrelay"};
 /**
  * Contains a 4-byte version number and an 8-byte salt.
  * The salt is used to compute short txids needed for efficient
  * txreconciliation, as described by BIP 330.
  */
-extern const char* SENDTXRCNCL;
+inline constexpr const char* SENDTXRCNCL{"sendtxrcncl"};
 }; // namespace NetMsgType
 
 /** All known message types (see above). Keep this in the same order as the list of messages above. */