Merge bitcoin/bitcoin#23413: Replace MakeSpan helper with Span deduction guide

11daf6ceb1 More Span simplifications (Pieter Wuille)
568dd2f839 Replace MakeSpan helper with Span deduction guide (Pieter Wuille)

Pull request description:

  C++17 supports [user-defined deduction guides](https://en.cppreference.com/w/cpp/language/class_template_argument_deduction), allowing class constructors to be invoked without specifying class template arguments. Instead, the code can contain rules to infer the template arguments from the constructor argument types.

  This alleviates the need for the `MakeSpan` helper. Convert the existing MakeSpan rules into deduction rules for `Span` itself, and replace all invocations of `MakeSpan` with just `Span` ones.

ACKs for top commit:
  MarcoFalke:
    re-ACK 11daf6ceb1 Only change is removing a hunk in the tests 🌕

Tree-SHA512: 10f3e82e4338f39d9b7b407cd11aac7ebe1e9191b58e3d7f4e5e338a4636c0e126b4a1d912127c7446f57ba356c8d6544482e47f97901efea6a54fffbfd7895f

src/base58.cpp

@@ -149,7 +149,7 @@ std::string EncodeBase58Check(Span<const unsigned char> input)
         return false;
     }
     // re-calculate the checksum, ensure it matches the included 4-byte checksum
-    uint256 hash = Hash(MakeSpan(vchRet).first(vchRet.size() - 4));
+    uint256 hash = Hash(Span{vchRet}.first(vchRet.size() - 4));
     if (memcmp(&hash, &vchRet[vchRet.size() - 4], 4) != 0) {
         vchRet.clear();
         return false;

src/compressor.h

@@ -65,12 +65,12 @@ struct ScriptCompression
     void Ser(Stream &s, const CScript& script) {
         CompressedScript compr;
         if (CompressScript(script, compr)) {
-            s << MakeSpan(compr);
+            s << Span{compr};
             return;
         }
         unsigned int nSize = script.size() + nSpecialScripts;
         s << VARINT(nSize);
-        s << MakeSpan(script);
+        s << Span{script};
     }
 
     template<typename Stream>
@@ -79,7 +79,7 @@ struct ScriptCompression
         s >> VARINT(nSize);
         if (nSize < nSpecialScripts) {
             CompressedScript vch(GetSpecialScriptSize(nSize), 0x00);
-            s >> MakeSpan(vch);
+            s >> Span{vch};
             DecompressScript(script, nSize, vch);
             return;
         }
@@ -90,7 +90,7 @@ struct ScriptCompression
             s.ignore(nSize);
         } else {
             script.resize(nSize);
-            s >> MakeSpan(script);
+            s >> Span{script};
         }
     }
 };

src/net.cpp

@@ -761,7 +761,7 @@ CNetMessage V1TransportDeserializer::GetMessage(const std::chrono::microseconds
     if (memcmp(hash.begin(), hdr.pchChecksum, CMessageHeader::CHECKSUM_SIZE) != 0) {
         LogPrint(BCLog::NET, "Header error: Wrong checksum (%s, %u bytes), expected %s was %s, peer=%d\n",
                  SanitizeString(msg.m_command), msg.m_message_size,
-                 HexStr(Span<uint8_t>(hash.begin(), hash.begin() + CMessageHeader::CHECKSUM_SIZE)),
+                 HexStr(Span{hash}.first(CMessageHeader::CHECKSUM_SIZE)),
                  HexStr(hdr.pchChecksum),
                  m_node_id);
         reject_message = true;
@@ -1583,8 +1583,9 @@ void CConnman::SocketHandlerConnected(const std::vector<CNode*>& nodes,
             if (nBytes > 0)
             {
                 bool notify = false;
-                if (!pnode->ReceiveMsgBytes(Span<const uint8_t>(pchBuf, nBytes), notify))
+                if (!pnode->ReceiveMsgBytes({pchBuf, (size_t)nBytes}, notify)) {
                     pnode->CloseSocketDisconnect();
+                }
                 RecordBytesRecv(nBytes);
                 if (notify) {
                     size_t nSizeAdded = 0;

src/net_processing.cpp

@@ -1815,7 +1815,7 @@ void PeerManagerImpl::ProcessGetBlockData(CNode& pfrom, Peer& peer, const CInv&
         if (!ReadRawBlockFromDisk(block_data, pindex, m_chainparams.MessageStart())) {
             assert(!"cannot load block from disk");
         }
-        m_connman.PushMessage(&pfrom, msgMaker.Make(NetMsgType::BLOCK, MakeSpan(block_data)));
+        m_connman.PushMessage(&pfrom, msgMaker.Make(NetMsgType::BLOCK, Span{block_data}));
         // Don't set pblock as we've sent the block
     } else {
         // Send block from disk

src/netaddress.cpp

@@ -196,7 +196,7 @@ static void Checksum(Span<const uint8_t> addr_pubkey, uint8_t (&checksum)[CHECKS
 
     SHA3_256 hasher;
 
-    hasher.Write(MakeSpan(prefix).first(prefix_len));
+    hasher.Write(Span{prefix}.first(prefix_len));
     hasher.Write(addr_pubkey);
     hasher.Write(VERSION);
 
@@ -303,7 +303,7 @@ CNetAddr::CNetAddr(const struct in_addr& ipv4Addr)
 
 CNetAddr::CNetAddr(const struct in6_addr& ipv6Addr, const uint32_t scope)
 {
-    SetLegacyIPv6(Span<const uint8_t>(reinterpret_cast<const uint8_t*>(&ipv6Addr), sizeof(ipv6Addr)));
+    SetLegacyIPv6({reinterpret_cast<const uint8_t*>(&ipv6Addr), sizeof(ipv6Addr)});
     m_scope_id = scope;
 }
 
@@ -693,13 +693,13 @@ uint32_t CNetAddr::GetLinkedIPv4() const
         return ReadBE32(m_addr.data());
     } else if (IsRFC6052() || IsRFC6145()) {
         // mapped IPv4, SIIT translated IPv4: the IPv4 address is the last 4 bytes of the address
-        return ReadBE32(MakeSpan(m_addr).last(ADDR_IPV4_SIZE).data());
+        return ReadBE32(Span{m_addr}.last(ADDR_IPV4_SIZE).data());
     } else if (IsRFC3964()) {
         // 6to4 tunneled IPv4: the IPv4 address is in bytes 2-6
-        return ReadBE32(MakeSpan(m_addr).subspan(2, ADDR_IPV4_SIZE).data());
+        return ReadBE32(Span{m_addr}.subspan(2, ADDR_IPV4_SIZE).data());
     } else if (IsRFC4380()) {
         // Teredo tunneled IPv4: the IPv4 address is in the last 4 bytes of the address, but bitflipped
-        return ~ReadBE32(MakeSpan(m_addr).last(ADDR_IPV4_SIZE).data());
+        return ~ReadBE32(Span{m_addr}.last(ADDR_IPV4_SIZE).data());
     }
     assert(false);
 }

src/netaddress.h

@@ -433,7 +433,7 @@ private:
 
         if (SetNetFromBIP155Network(bip155_net, address_size)) {
             m_addr.resize(address_size);
-            s >> MakeSpan(m_addr);
+            s >> Span{m_addr};
 
             if (m_net != NET_IPV6) {
                 return;

src/policy/policy.cpp

@@ -251,7 +251,7 @@ bool IsWitnessStandard(const CTransaction& tx, const CCoinsViewCache& mapInputs)
         // - No annexes
         if (witnessversion == 1 && witnessprogram.size() == WITNESS_V1_TAPROOT_SIZE && !p2sh) {
             // Taproot spend (non-P2SH-wrapped, version 1, witness program size 32; see BIP 341)
-            auto stack = MakeSpan(tx.vin[i].scriptWitness.stack);
+            Span stack{tx.vin[i].scriptWitness.stack};
             if (stack.size() >= 2 && !stack.back().empty() && stack.back()[0] == ANNEX_TAG) {
                 // Annexes are nonstandard as long as no semantics are defined for them.
                 return false;

src/psbt.h

@@ -81,7 +81,7 @@ struct PSBTInput
         if (final_script_sig.empty() && final_script_witness.IsNull()) {
             // Write any partial signatures
             for (auto sig_pair : partial_sigs) {
-                SerializeToVector(s, PSBT_IN_PARTIAL_SIG, MakeSpan(sig_pair.second.first));
+                SerializeToVector(s, PSBT_IN_PARTIAL_SIG, Span{sig_pair.second.first});
                 s << sig_pair.second.second;
             }
 

src/pubkey.h

@@ -157,13 +157,13 @@ public:
     //! Get the KeyID of this public key (hash of its serialization)
     CKeyID GetID() const
     {
-        return CKeyID(Hash160(MakeSpan(vch).first(size())));
+        return CKeyID(Hash160(Span{vch}.first(size())));
     }
 
     //! Get the 256-bit hash of this public key.
     uint256 GetHash() const
     {
-        return Hash(MakeSpan(vch).first(size()));
+        return Hash(Span{vch}.first(size()));
     }
 
     /*
@@ -240,7 +240,7 @@ public:
     explicit XOnlyPubKey(Span<const unsigned char> bytes);
 
     /** Construct an x-only pubkey from a normal pubkey. */
-    explicit XOnlyPubKey(const CPubKey& pubkey) : XOnlyPubKey(Span<const unsigned char>(pubkey.begin() + 1, pubkey.begin() + 33)) {}
+    explicit XOnlyPubKey(const CPubKey& pubkey) : XOnlyPubKey(Span{pubkey}.subspan(1, 32)) {}
 
     /** Verify a Schnorr signature against this public key.
      *

src/rpc/util.cpp

@@ -317,7 +317,7 @@ public:
         UniValue obj(UniValue::VOBJ);
         obj.pushKV("iswitness", true);
         obj.pushKV("witness_version", (int)id.version);
-        obj.pushKV("witness_program", HexStr(Span<const unsigned char>(id.program, id.length)));
+        obj.pushKV("witness_program", HexStr({id.program, id.length}));
         return obj;
     }
 };

src/script/descriptor.cpp

@@ -631,7 +631,7 @@ public:
             out.origins.emplace(entry.first.GetID(), std::make_pair<CPubKey, KeyOriginInfo>(CPubKey(entry.first), std::move(entry.second)));
         }
 
-        output_scripts = MakeScripts(pubkeys, MakeSpan(subscripts), out);
+        output_scripts = MakeScripts(pubkeys, Span{subscripts}, out);
         return true;
     }
 
@@ -974,10 +974,10 @@ std::unique_ptr<PubkeyProvider> ParsePubkeyInner(uint32_t key_exp_index, const S
     }
     KeyPath path;
     DeriveType type = DeriveType::NO;
-    if (split.back() == MakeSpan("*").first(1)) {
+    if (split.back() == Span{"*"}.first(1)) {
         split.pop_back();
         type = DeriveType::UNHARDENED;
-    } else if (split.back() == MakeSpan("*'").first(2) || split.back() == MakeSpan("*h").first(2)) {
+    } else if (split.back() == Span{"*'"}.first(2) || split.back() == Span{"*h"}.first(2)) {
         split.pop_back();
         type = DeriveType::HARDENED;
     }
@@ -1252,7 +1252,7 @@ std::unique_ptr<PubkeyProvider> InferXOnlyPubkey(const XOnlyPubKey& xkey, ParseS
 std::unique_ptr<DescriptorImpl> InferScript(const CScript& script, ParseScriptContext ctx, const SigningProvider& provider)
 {
     if (ctx == ParseScriptContext::P2TR && script.size() == 34 && script[0] == 32 && script[33] == OP_CHECKSIG) {
-        XOnlyPubKey key{Span<const unsigned char>{script.data() + 1, script.data() + 33}};
+        XOnlyPubKey key{Span{script}.subspan(1, 32)};
         return std::make_unique<PKDescriptor>(InferXOnlyPubkey(key, ctx, provider));
     }
 

src/script/interpreter.cpp

@@ -1858,7 +1858,7 @@ uint256 ComputeTaprootMerkleRoot(Span<const unsigned char> control, const uint25
     uint256 k = tapleaf_hash;
     for (int i = 0; i < path_len; ++i) {
         CHashWriter ss_branch{HASHER_TAPBRANCH};
-        Span<const unsigned char> node(control.data() + TAPROOT_CONTROL_BASE_SIZE + TAPROOT_CONTROL_NODE_SIZE * i, TAPROOT_CONTROL_NODE_SIZE);
+        Span node{Span{control}.subspan(TAPROOT_CONTROL_BASE_SIZE + TAPROOT_CONTROL_NODE_SIZE * i, TAPROOT_CONTROL_NODE_SIZE)};
         if (std::lexicographical_compare(k.begin(), k.end(), node.begin(), node.end())) {
             ss_branch << k << node;
         } else {
@@ -1874,7 +1874,7 @@ static bool VerifyTaprootCommitment(const std::vector<unsigned char>& control, c
     assert(control.size() >= TAPROOT_CONTROL_BASE_SIZE);
     assert(program.size() >= uint256::size());
     //! The internal pubkey (x-only, so no Y coordinate parity).
-    const XOnlyPubKey p{Span<const unsigned char>{control.data() + 1, control.data() + TAPROOT_CONTROL_BASE_SIZE}};
+    const XOnlyPubKey p{Span{control}.subspan(1, TAPROOT_CONTROL_BASE_SIZE - 1)};
     //! The output pubkey (taken from the scriptPubKey).
     const XOnlyPubKey q{program};
     // Compute the Merkle root from the leaf and the provided path.
@@ -1886,7 +1886,7 @@ static bool VerifyTaprootCommitment(const std::vector<unsigned char>& control, c
 static bool VerifyWitnessProgram(const CScriptWitness& witness, int witversion, const std::vector<unsigned char>& program, unsigned int flags, const BaseSignatureChecker& checker, ScriptError* serror, bool is_p2sh)
 {
     CScript exec_script; //!< Actually executed script (last stack item in P2WSH; implied P2PKH script in P2WPKH; leaf script in P2TR)
-    Span<const valtype> stack{witness.stack};
+    Span stack{witness.stack};
     ScriptExecutionData execdata;
 
     if (witversion == 0) {

src/script/sign.cpp

@@ -167,7 +167,7 @@ static bool SignTaprootScript(const SigningProvider& provider, const BaseSignatu
 
     // <xonly pubkey> OP_CHECKSIG
     if (script.size() == 34 && script[33] == OP_CHECKSIG && script[0] == 0x20) {
-        XOnlyPubKey pubkey(MakeSpan(script).subspan(1, 32));
+        XOnlyPubKey pubkey{Span{script}.subspan(1, 32)};
         std::vector<unsigned char> sig;
         if (CreateTaprootScriptSig(creator, sigdata, provider, sig, pubkey, leaf_hash, sigversion)) {
             result = Vector(std::move(sig));

src/script/sign.h

@@ -149,7 +149,7 @@ void SerializeHDKeypaths(Stream& s, const std::map<CPubKey, KeyOriginInfo>& hd_k
         if (!keypath_pair.first.IsValid()) {
             throw std::ios_base::failure("Invalid CPubKey being serialized");
         }
-        SerializeToVector(s, type, MakeSpan(keypath_pair.first));
+        SerializeToVector(s, type, Span{keypath_pair.first});
         WriteCompactSize(s, (keypath_pair.second.path.size() + 1) * sizeof(uint32_t));
         s << keypath_pair.second.fingerprint;
         for (const auto& path : keypath_pair.second.path) {

src/signet.cpp

@@ -38,7 +38,7 @@ static bool FetchAndClearCommitmentSection(const Span<const uint8_t> header, CSc
     std::vector<uint8_t> pushdata;
     while (witness_commitment.GetOp(pc, opcode, pushdata)) {
         if (pushdata.size() > 0) {
-            if (!found_header && pushdata.size() > (size_t) header.size() && Span<const uint8_t>(pushdata.data(), header.size()) == header) {
+            if (!found_header && pushdata.size() > (size_t)header.size() && Span{pushdata}.first(header.size()) == header) {
                 // pushdata only counts if it has the header _and_ some data
                 result.insert(result.end(), pushdata.begin() + header.size(), pushdata.end());
                 pushdata.erase(pushdata.begin() + header.size(), pushdata.end());

src/span.h

@@ -222,13 +222,15 @@ public:
     template <typename O> friend class Span;
 };
 
-// MakeSpan helps constructing a Span of the right type automatically.
+// Deduction guides for Span
-/** MakeSpan for arrays: */
+// For the pointer/size based and iterator based constructor:
-template <typename A, int N> Span<A> constexpr MakeSpan(A (&a)[N]) { return Span<A>(a, N); }
+template <typename T, typename EndOrSize> Span(T*, EndOrSize) -> Span<T>;
-/** MakeSpan for temporaries / rvalue references, only supporting const output. */
+// For the array constructor:
-template <typename V> constexpr auto MakeSpan(V&& v SPAN_ATTR_LIFETIMEBOUND) -> typename std::enable_if<!std::is_lvalue_reference<V>::value, Span<const typename std::remove_pointer<decltype(v.data())>::type>>::type { return std::forward<V>(v); }
+template <typename T, std::size_t N> Span(T (&)[N]) -> Span<T>;
-/** MakeSpan for (lvalue) references, supporting mutable output. */
+// For the temporaries/rvalue references constructor, only supporting const output.
-template <typename V> constexpr auto MakeSpan(V& v SPAN_ATTR_LIFETIMEBOUND) -> Span<typename std::remove_pointer<decltype(v.data())>::type> { return v; }
+template <typename T> Span(T&&) -> Span<std::enable_if_t<!std::is_lvalue_reference_v<T>, const std::remove_pointer_t<decltype(std::declval<T&&>().data())>>>;
+// For (lvalue) references, supporting mutable output.
+template <typename T> Span(T&) -> Span<std::remove_pointer_t<decltype(std::declval<T&>().data())>>;
 
 /** Pop the last element off a span, and return a reference to that element. */
 template <typename T>
@@ -256,12 +258,12 @@ Span<std::byte> AsWritableBytes(Span<T> s) noexcept
 template <typename V>
 Span<const std::byte> MakeByteSpan(V&& v) noexcept
 {
-    return AsBytes(MakeSpan(std::forward<V>(v)));
+    return AsBytes(Span{std::forward<V>(v)});
 }
 template <typename V>
 Span<std::byte> MakeWritableByteSpan(V&& v) noexcept
 {
-    return AsWritableBytes(MakeSpan(std::forward<V>(v)));
+    return AsWritableBytes(Span{std::forward<V>(v)});
 }
 
 // Helper functions to safely cast to unsigned char pointers.
@@ -274,7 +276,7 @@ inline const unsigned char* UCharCast(const std::byte* c) { return reinterpret_c
 // Helper function to safely convert a Span to a Span<[const] unsigned char>.
 template <typename T> constexpr auto UCharSpanCast(Span<T> s) -> Span<typename std::remove_pointer<decltype(UCharCast(s.data()))>::type> { return {UCharCast(s.data()), s.size()}; }
 
-/** Like MakeSpan, but for (const) unsigned char member types only. Only works for (un)signed char containers. */
+/** Like the Span constructor, but for (const) unsigned char member types only. Only works for (un)signed char containers. */
-template <typename V> constexpr auto MakeUCharSpan(V&& v) -> decltype(UCharSpanCast(MakeSpan(std::forward<V>(v)))) { return UCharSpanCast(MakeSpan(std::forward<V>(v))); }
+template <typename V> constexpr auto MakeUCharSpan(V&& v) -> decltype(UCharSpanCast(Span{std::forward<V>(v)})) { return UCharSpanCast(Span{std::forward<V>(v)}); }
 
 #endif // BITCOIN_SPAN_H

src/test/crypto_tests.cpp

@@ -770,8 +770,8 @@ static void TestSHA3_256(const std::string& input, const std::string& output)
     int s1 = InsecureRandRange(in_bytes.size() + 1);
     int s2 = InsecureRandRange(in_bytes.size() + 1 - s1);
     int s3 = in_bytes.size() - s1 - s2;
-    sha.Write(MakeSpan(in_bytes).first(s1)).Write(MakeSpan(in_bytes).subspan(s1, s2));
+    sha.Write(Span{in_bytes}.first(s1)).Write(Span{in_bytes}.subspan(s1, s2));
-    sha.Write(MakeSpan(in_bytes).last(s3)).Finalize(out);
+    sha.Write(Span{in_bytes}.last(s3)).Finalize(out);
     BOOST_CHECK(std::equal(std::begin(out_bytes), std::end(out_bytes), out));
 }
 

src/test/fuzz/asmap.cpp

@@ -49,7 +49,7 @@ FUZZ_TARGET(asmap)
     CNetAddr net_addr;
     if (ipv6) {
         assert(addr_size == ADDR_IPV6_SIZE);
-        net_addr.SetLegacyIPv6(Span<const uint8_t>(addr_data, addr_size));
+        net_addr.SetLegacyIPv6({addr_data, addr_size});
     } else {
         assert(addr_size == ADDR_IPV4_SIZE);
         in_addr ipv4;

src/test/fuzz/utxo_snapshot.cpp

@@ -38,7 +38,7 @@ FUZZ_TARGET_INIT(utxo_snapshot, initialize_chain)
     {
         CAutoFile outfile{fsbridge::fopen(snapshot_path, "wb"), SER_DISK, CLIENT_VERSION};
         const auto file_data{ConsumeRandomLengthByteVector(fuzzed_data_provider)};
-        outfile << Span<const uint8_t>{file_data};
+        outfile << Span{file_data};
     }
 
     const auto ActivateFuzzedSnapshot{[&] {

src/test/key_io_tests.cpp

@@ -46,7 +46,7 @@ BOOST_AUTO_TEST_CASE(key_io_valid_parse)
             privkey = DecodeSecret(exp_base58string);
             BOOST_CHECK_MESSAGE(privkey.IsValid(), "!IsValid:" + strTest);
             BOOST_CHECK_MESSAGE(privkey.IsCompressed() == isCompressed, "compressed mismatch:" + strTest);
-            BOOST_CHECK_MESSAGE(Span<const uint8_t>{privkey} == Span<const uint8_t>{exp_payload}, "key mismatch:" + strTest);
+            BOOST_CHECK_MESSAGE(Span{privkey} == Span{exp_payload}, "key mismatch:" + strTest);
 
             // Private key must be invalid public key
             destination = DecodeDestination(exp_base58string);

src/test/net_tests.cpp

@@ -386,9 +386,9 @@ BOOST_AUTO_TEST_CASE(cnetaddr_unserialize_v2)
     s.SetVersion(s.GetVersion() | ADDRV2_FORMAT);
 
     // Valid IPv4.
-    s << MakeSpan(ParseHex("01"          // network type (IPv4)
+    s << Span{ParseHex("01"          // network type (IPv4)
-                           "04"          // address length
+                       "04"          // address length
-                           "01020304")); // address
+                       "01020304")}; // address
     s >> addr;
     BOOST_CHECK(addr.IsValid());
     BOOST_CHECK(addr.IsIPv4());
@@ -397,35 +397,35 @@ BOOST_AUTO_TEST_CASE(cnetaddr_unserialize_v2)
     BOOST_REQUIRE(s.empty());
 
     // Invalid IPv4, valid length but address itself is shorter.
-    s << MakeSpan(ParseHex("01"      // network type (IPv4)
+    s << Span{ParseHex("01"      // network type (IPv4)
-                           "04"      // address length
+                       "04"      // address length
-                           "0102")); // address
+                       "0102")}; // address
     BOOST_CHECK_EXCEPTION(s >> addr, std::ios_base::failure, HasReason("end of data"));
     BOOST_REQUIRE(!s.empty()); // The stream is not consumed on invalid input.
     s.clear();
 
     // Invalid IPv4, with bogus length.
-    s << MakeSpan(ParseHex("01"          // network type (IPv4)
+    s << Span{ParseHex("01"          // network type (IPv4)
-                           "05"          // address length
+                       "05"          // address length
-                           "01020304")); // address
+                       "01020304")}; // address
     BOOST_CHECK_EXCEPTION(s >> addr, std::ios_base::failure,
                           HasReason("BIP155 IPv4 address with length 5 (should be 4)"));
     BOOST_REQUIRE(!s.empty()); // The stream is not consumed on invalid input.
     s.clear();
 
     // Invalid IPv4, with extreme length.
-    s << MakeSpan(ParseHex("01"          // network type (IPv4)
+    s << Span{ParseHex("01"          // network type (IPv4)
-                           "fd0102"      // address length (513 as CompactSize)
+                       "fd0102"      // address length (513 as CompactSize)
-                           "01020304")); // address
+                       "01020304")}; // address
     BOOST_CHECK_EXCEPTION(s >> addr, std::ios_base::failure,
                           HasReason("Address too long: 513 > 512"));
     BOOST_REQUIRE(!s.empty()); // The stream is not consumed on invalid input.
     s.clear();
 
     // Valid IPv6.
-    s << MakeSpan(ParseHex("02"                                  // network type (IPv6)
+    s << Span{ParseHex("02"                                  // network type (IPv6)
-                           "10"                                  // address length
+                       "10"                                  // address length
-                           "0102030405060708090a0b0c0d0e0f10")); // address
+                       "0102030405060708090a0b0c0d0e0f10")}; // address
     s >> addr;
     BOOST_CHECK(addr.IsValid());
     BOOST_CHECK(addr.IsIPv6());
@@ -434,10 +434,10 @@ BOOST_AUTO_TEST_CASE(cnetaddr_unserialize_v2)
     BOOST_REQUIRE(s.empty());
 
     // Valid IPv6, contains embedded "internal".
-    s << MakeSpan(ParseHex(
+    s << Span{ParseHex(
         "02"                                  // network type (IPv6)
         "10"                                  // address length
-        "fd6b88c08724ca978112ca1bbdcafac2")); // address: 0xfd + sha256("bitcoin")[0:5] +
+        "fd6b88c08724ca978112ca1bbdcafac2")}; // address: 0xfd + sha256("bitcoin")[0:5] +
                                               // sha256(name)[0:10]
     s >> addr;
     BOOST_CHECK(addr.IsInternal());
@@ -446,44 +446,44 @@ BOOST_AUTO_TEST_CASE(cnetaddr_unserialize_v2)
     BOOST_REQUIRE(s.empty());
 
     // Invalid IPv6, with bogus length.
-    s << MakeSpan(ParseHex("02"    // network type (IPv6)
+    s << Span{ParseHex("02"    // network type (IPv6)
-                           "04"    // address length
+                       "04"    // address length
-                           "00")); // address
+                       "00")}; // address
     BOOST_CHECK_EXCEPTION(s >> addr, std::ios_base::failure,
                           HasReason("BIP155 IPv6 address with length 4 (should be 16)"));
     BOOST_REQUIRE(!s.empty()); // The stream is not consumed on invalid input.
     s.clear();
 
     // Invalid IPv6, contains embedded IPv4.
-    s << MakeSpan(ParseHex("02"                                  // network type (IPv6)
+    s << Span{ParseHex("02"                                  // network type (IPv6)
-                           "10"                                  // address length
+                       "10"                                  // address length
-                           "00000000000000000000ffff01020304")); // address
+                       "00000000000000000000ffff01020304")}; // address
     s >> addr;
     BOOST_CHECK(!addr.IsValid());
     BOOST_REQUIRE(s.empty());
 
     // Invalid IPv6, contains embedded TORv2.
-    s << MakeSpan(ParseHex("02"                                  // network type (IPv6)
+    s << Span{ParseHex("02"                                  // network type (IPv6)
-                           "10"                                  // address length
+                       "10"                                  // address length
-                           "fd87d87eeb430102030405060708090a")); // address
+                       "fd87d87eeb430102030405060708090a")}; // address
     s >> addr;
     BOOST_CHECK(!addr.IsValid());
     BOOST_REQUIRE(s.empty());
 
     // TORv2, no longer supported.
-    s << MakeSpan(ParseHex("03"                      // network type (TORv2)
+    s << Span{ParseHex("03"                      // network type (TORv2)
-                           "0a"                      // address length
+                       "0a"                      // address length
-                           "f1f2f3f4f5f6f7f8f9fa")); // address
+                       "f1f2f3f4f5f6f7f8f9fa")}; // address
     s >> addr;
     BOOST_CHECK(!addr.IsValid());
     BOOST_REQUIRE(s.empty());
 
     // Valid TORv3.
-    s << MakeSpan(ParseHex("04"                               // network type (TORv3)
+    s << Span{ParseHex("04"                               // network type (TORv3)
-                           "20"                               // address length
+                       "20"                               // address length
-                           "79bcc625184b05194975c28b66b66b04" // address
+                       "79bcc625184b05194975c28b66b66b04" // address
-                           "69f7f6556fb1ac3189a79b40dda32f1f"
+                       "69f7f6556fb1ac3189a79b40dda32f1f"
-                           ));
+                       )};
     s >> addr;
     BOOST_CHECK(addr.IsValid());
     BOOST_CHECK(addr.IsTor());
@@ -493,20 +493,20 @@ BOOST_AUTO_TEST_CASE(cnetaddr_unserialize_v2)
     BOOST_REQUIRE(s.empty());
 
     // Invalid TORv3, with bogus length.
-    s << MakeSpan(ParseHex("04" // network type (TORv3)
+    s << Span{ParseHex("04" // network type (TORv3)
-                           "00" // address length
+                       "00" // address length
-                           "00" // address
+                       "00" // address
-                           ));
+                       )};
     BOOST_CHECK_EXCEPTION(s >> addr, std::ios_base::failure,
                           HasReason("BIP155 TORv3 address with length 0 (should be 32)"));
     BOOST_REQUIRE(!s.empty()); // The stream is not consumed on invalid input.
     s.clear();
 
     // Valid I2P.
-    s << MakeSpan(ParseHex("05"                               // network type (I2P)
+    s << Span{ParseHex("05"                               // network type (I2P)
-                           "20"                               // address length
+                       "20"                               // address length
-                           "a2894dabaec08c0051a481a6dac88b64" // address
+                       "a2894dabaec08c0051a481a6dac88b64" // address
-                           "f98232ae42d4b6fd2fa81952dfe36a87"));
+                       "f98232ae42d4b6fd2fa81952dfe36a87")};
     s >> addr;
     BOOST_CHECK(addr.IsValid());
     BOOST_CHECK(addr.IsI2P());
@@ -516,20 +516,20 @@ BOOST_AUTO_TEST_CASE(cnetaddr_unserialize_v2)
     BOOST_REQUIRE(s.empty());
 
     // Invalid I2P, with bogus length.
-    s << MakeSpan(ParseHex("05" // network type (I2P)
+    s << Span{ParseHex("05" // network type (I2P)
-                           "03" // address length
+                       "03" // address length
-                           "00" // address
+                       "00" // address
-                           ));
+                       )};
     BOOST_CHECK_EXCEPTION(s >> addr, std::ios_base::failure,
                           HasReason("BIP155 I2P address with length 3 (should be 32)"));
     BOOST_REQUIRE(!s.empty()); // The stream is not consumed on invalid input.
     s.clear();
 
     // Valid CJDNS.
-    s << MakeSpan(ParseHex("06"                               // network type (CJDNS)
+    s << Span{ParseHex("06"                               // network type (CJDNS)
-                           "10"                               // address length
+                       "10"                               // address length
-                           "fc000001000200030004000500060007" // address
+                       "fc000001000200030004000500060007" // address
-                           ));
+                       )};
     s >> addr;
     BOOST_CHECK(addr.IsValid());
     BOOST_CHECK(addr.IsCJDNS());
@@ -538,49 +538,49 @@ BOOST_AUTO_TEST_CASE(cnetaddr_unserialize_v2)
     BOOST_REQUIRE(s.empty());
 
     // Invalid CJDNS, wrong prefix.
-    s << MakeSpan(ParseHex("06"                               // network type (CJDNS)
+    s << Span{ParseHex("06"                               // network type (CJDNS)
-                           "10"                               // address length
+                       "10"                               // address length
-                           "aa000001000200030004000500060007" // address
+                       "aa000001000200030004000500060007" // address
-                           ));
+                       )};
     s >> addr;
     BOOST_CHECK(addr.IsCJDNS());
     BOOST_CHECK(!addr.IsValid());
     BOOST_REQUIRE(s.empty());
 
     // Invalid CJDNS, with bogus length.
-    s << MakeSpan(ParseHex("06" // network type (CJDNS)
+    s << Span{ParseHex("06" // network type (CJDNS)
-                           "01" // address length
+                       "01" // address length
-                           "00" // address
+                       "00" // address
-                           ));
+                       )};
     BOOST_CHECK_EXCEPTION(s >> addr, std::ios_base::failure,
                           HasReason("BIP155 CJDNS address with length 1 (should be 16)"));
     BOOST_REQUIRE(!s.empty()); // The stream is not consumed on invalid input.
     s.clear();
 
     // Unknown, with extreme length.
-    s << MakeSpan(ParseHex("aa"             // network type (unknown)
+    s << Span{ParseHex("aa"             // network type (unknown)
-                           "fe00000002"     // address length (CompactSize's MAX_SIZE)
+                       "fe00000002"     // address length (CompactSize's MAX_SIZE)
-                           "01020304050607" // address
+                       "01020304050607" // address
-                           ));
+                       )};
     BOOST_CHECK_EXCEPTION(s >> addr, std::ios_base::failure,
                           HasReason("Address too long: 33554432 > 512"));
     BOOST_REQUIRE(!s.empty()); // The stream is not consumed on invalid input.
     s.clear();
 
     // Unknown, with reasonable length.
-    s << MakeSpan(ParseHex("aa"       // network type (unknown)
+    s << Span{ParseHex("aa"       // network type (unknown)
-                           "04"       // address length
+                       "04"       // address length
-                           "01020304" // address
+                       "01020304" // address
-                           ));
+                       )};
     s >> addr;
     BOOST_CHECK(!addr.IsValid());
     BOOST_REQUIRE(s.empty());
 
     // Unknown, with zero length.
-    s << MakeSpan(ParseHex("aa" // network type (unknown)
+    s << Span{ParseHex("aa" // network type (unknown)
-                           "00" // address length
+                       "00" // address length
-                           ""   // address
+                       ""   // address
-                           ));
+                       )};
     s >> addr;
     BOOST_CHECK(!addr.IsValid());
     BOOST_REQUIRE(s.empty());

src/test/script_tests.cpp

@@ -284,7 +284,7 @@ public:
         CScript scriptPubKey = script;
         if (wm == WitnessMode::PKH) {
             uint160 hash;
-            CHash160().Write(MakeSpan(script).subspan(1)).Finalize(hash);
+            CHash160().Write(Span{script}.subspan(1)).Finalize(hash);
             script = CScript() << OP_DUP << OP_HASH160 << ToByteVector(hash) << OP_EQUALVERIFY << OP_CHECKSIG;
             scriptPubKey = CScript() << witnessversion << ToByteVector(hash);
         } else if (wm == WitnessMode::SH) {
@@ -1812,7 +1812,7 @@ BOOST_AUTO_TEST_CASE(bip341_keypath_test_vectors)
             BOOST_CHECK_EQUAL(HexStr(sighash), input["intermediary"]["sigHash"].get_str());
 
             // To verify the sigmsg, hash the expected sigmsg, and compare it with the (expected) sighash.
-            BOOST_CHECK_EQUAL(HexStr((CHashWriter(HASHER_TAPSIGHASH) << MakeSpan(ParseHex(input["intermediary"]["sigMsg"].get_str()))).GetSHA256()), input["intermediary"]["sigHash"].get_str());
+            BOOST_CHECK_EQUAL(HexStr((CHashWriter(HASHER_TAPSIGHASH) << Span{ParseHex(input["intermediary"]["sigMsg"].get_str())}).GetSHA256()), input["intermediary"]["sigHash"].get_str());
         }
 
     }

src/test/util_tests.cpp

@@ -142,13 +142,11 @@ BOOST_AUTO_TEST_CASE(util_HexStr)
         "04678afdb0fe5548271967f1a67130b7105cd6a828e03909a67962e0ea1f61deb649f6bc3f4cef38c4f35504e51ec112de5c384df7ba0b8d578a4c702b6bf11d5f");
 
     BOOST_CHECK_EQUAL(
-        HexStr(Span<const unsigned char>(
+        HexStr(Span{ParseHex_expected}.last(0)),
-               ParseHex_expected + sizeof(ParseHex_expected),
-               ParseHex_expected + sizeof(ParseHex_expected))),
         "");
 
     BOOST_CHECK_EQUAL(
-        HexStr(Span<const unsigned char>(ParseHex_expected, ParseHex_expected)),
+        HexStr(Span{ParseHex_expected}.first(0)),
         "");
 
     {

src/wallet/rpc/backup.cpp

@@ -35,7 +35,7 @@ std::string static EncodeDumpString(const std::string &str) {
     std::stringstream ret;
     for (const unsigned char c : str) {
         if (c <= 32 || c >= 128 || c == '%') {
-            ret << '%' << HexStr(Span<const unsigned char>(&c, 1));
+            ret << '%' << HexStr({&c, 1});
         } else {
             ret << c;
         }

src/wallet/rpcwallet.cpp

@@ -4413,5 +4413,5 @@ static const CRPCCommand commands[] =
     { "wallet",             &walletprocesspsbt,              },
 };
 // clang-format on
-    return MakeSpan(commands);
+    return commands;
 }