Merge bitcoin/bitcoin#21817: refactor: Replace &foo[0] with foo.data()

fac30eec42c486ec1bfd696293040a7aa0f04625 refactor: Replace &foo[0] with foo.data() (MarcoFalke)
faece47c4706783e0460ed977390a44630b2d44c refactor: Avoid &foo[0] on C-Style arrays (MarcoFalke)
face9611093377e8502d91f2ff56f9319a56357c refactor: Use only one temporary buffer in CreateObfuscateKey (MarcoFalke)
fa05dddc42770809fdae4d9c35155f8117960019 refactor: Use CPubKey vector constructor where possible (MarcoFalke)
fabb6dfe6e734eadd91448122f2ce8c1612c39a6 script: Replace address-of idiom with vector data() method (Guido Vranken)

Pull request description:

  The main theme of this refactor is to replace `&foo[0]` with `foo.data()`.

  The first commit is taken from #21781 with the rationale:

  * In CSignatureCache::ComputeEntryECDSA, change the way a vector pointer is resolved to prevent invoking undefined behavior if the vector is empty.

  The other commits aim to remove all `&foo[0]`, where `foo` is any kind of byte representation. The rationale:

  * Sometimes alternative code without any raw data pointers is easier to read (refer to the respective commit message for details)
  * If the raw data pointer is needed, `foo.data()` should be preferred, as pointed out in the developer notes. This addresses the instances that have been missed in commit 592404f03f2b734351d734f0c9ca1fdce997321b, and https://github.com/bitcoin/bitcoin/pull/9804

ACKs for top commit:
  laanwj:
    Code review ACK fac30eec42c486ec1bfd696293040a7aa0f04625
  practicalswift:
    cr ACK fac30eec42c486ec1bfd696293040a7aa0f04625: patch looks correct
  promag:
    Code review ACK fac30eec42c486ec1bfd696293040a7aa0f04625.

Tree-SHA512: e7e73146edbc78911a8e8c728b0a1c6b0ed9a88a008e650aa5dbffe72425bd42c76df70199a9cf7e02637448d7593e0eac52fd0f91f59240283e1390ee21bfa5

23 files changed, 56 insertions, 57 deletions

diff --git a/src/compressor.cpp b/src/compressor.cpp
index ef3135e7a5..a161c42866 100644
--- a/src/compressor.cpp
+++ b/src/compressor.cpp
@@ -124,7 +124,7 @@ bool DecompressScript(CScript& script, unsigned int nSize, const CompressedScrip
         unsigned char vch[33] = {};
         vch[0] = nSize - 2;
         memcpy(&vch[1], in.data(), 32);
-        CPubKey pubkey(&vch[0], &vch[33]);
+        CPubKey pubkey{vch};
         if (!pubkey.Decompress())
             return false;
         assert(pubkey.size() == 65);
diff --git a/src/dbwrapper.cpp b/src/dbwrapper.cpp
index d7694108f5..3a1086bf4c 100644
--- a/src/dbwrapper.cpp
+++ b/src/dbwrapper.cpp
@@ -220,10 +220,9 @@ const unsigned int CDBWrapper::OBFUSCATE_KEY_NUM_BYTES = 8;
  */
 std::vector<unsigned char> CDBWrapper::CreateObfuscateKey() const
 {
-    unsigned char buff[OBFUSCATE_KEY_NUM_BYTES];
-    GetRandBytes(buff, OBFUSCATE_KEY_NUM_BYTES);
-    return std::vector<unsigned char>(&buff[0], &buff[OBFUSCATE_KEY_NUM_BYTES]);
-
+    std::vector<uint8_t> ret(OBFUSCATE_KEY_NUM_BYTES);
+    GetRandBytes(ret.data(), OBFUSCATE_KEY_NUM_BYTES);
+    return ret;
 }
 
 bool CDBWrapper::IsEmpty()
diff --git a/src/key.cpp b/src/key.cpp
index 1e59b301cb..5666adebb8 100644
--- a/src/key.cpp
+++ b/src/key.cpp
@@ -293,7 +293,7 @@ bool CKey::Derive(CKey& keyChild, ChainCode &ccChild, unsigned int nChild, const
 bool CExtKey::Derive(CExtKey &out, unsigned int _nChild) const {
     out.nDepth = nDepth + 1;
     CKeyID id = key.GetPubKey().GetID();
-    memcpy(&out.vchFingerprint[0], &id, 4);
+    memcpy(out.vchFingerprint, &id, 4);
     out.nChild = _nChild;
     return key.Derive(out.key, out.chaincode, _nChild, chaincode);
 }
@@ -312,7 +312,7 @@ void CExtKey::SetSeed(const unsigned char *seed, unsigned int nSeedLen) {
 CExtPubKey CExtKey::Neuter() const {
     CExtPubKey ret;
     ret.nDepth = nDepth;
-    memcpy(&ret.vchFingerprint[0], &vchFingerprint[0], 4);
+    memcpy(ret.vchFingerprint, vchFingerprint, 4);
     ret.nChild = nChild;
     ret.pubkey = key.GetPubKey();
     ret.chaincode = chaincode;
diff --git a/src/key.h b/src/key.h
index 206322956c..3ee49a778b 100644
--- a/src/key.h
+++ b/src/key.h
@@ -151,7 +151,7 @@ struct CExtKey {
     friend bool operator==(const CExtKey& a, const CExtKey& b)
     {
         return a.nDepth == b.nDepth &&
-            memcmp(&a.vchFingerprint[0], &b.vchFingerprint[0], sizeof(vchFingerprint)) == 0 &&
+            memcmp(a.vchFingerprint, b.vchFingerprint, sizeof(vchFingerprint)) == 0 &&
             a.nChild == b.nChild &&
             a.chaincode == b.chaincode &&
             a.key == b.key;
diff --git a/src/pubkey.cpp b/src/pubkey.cpp
index fc1624af25..a89988cc90 100644
--- a/src/pubkey.cpp
+++ b/src/pubkey.cpp
@@ -293,7 +293,7 @@ void CExtPubKey::Decode(const unsigned char code[BIP32_EXTKEY_SIZE]) {
 bool CExtPubKey::Derive(CExtPubKey &out, unsigned int _nChild) const {
     out.nDepth = nDepth + 1;
     CKeyID id = pubkey.GetID();
-    memcpy(&out.vchFingerprint[0], &id, 4);
+    memcpy(out.vchFingerprint, &id, 4);
     out.nChild = _nChild;
     return pubkey.Derive(out.pubkey, out.chaincode, _nChild, chaincode);
 }
diff --git a/src/pubkey.h b/src/pubkey.h
index 12514fc3c9..b653c202fc 100644
--- a/src/pubkey.h
+++ b/src/pubkey.h
@@ -101,7 +101,7 @@ public:
     }
 
     //! Construct a public key from a byte vector.
-    explicit CPubKey(const std::vector<unsigned char>& _vch)
+    explicit CPubKey(Span<const uint8_t> _vch)
     {
         Set(_vch.begin(), _vch.end());
     }
@@ -247,7 +247,7 @@ struct CExtPubKey {
     friend bool operator==(const CExtPubKey &a, const CExtPubKey &b)
     {
         return a.nDepth == b.nDepth &&
-            memcmp(&a.vchFingerprint[0], &b.vchFingerprint[0], sizeof(vchFingerprint)) == 0 &&
+            memcmp(a.vchFingerprint, b.vchFingerprint, sizeof(vchFingerprint)) == 0 &&
             a.nChild == b.nChild &&
             a.chaincode == b.chaincode &&
             a.pubkey == b.pubkey;
diff --git a/src/qt/walletmodel.cpp b/src/qt/walletmodel.cpp
index c6dd0c2ad6..cc6db8d33e 100644
--- a/src/qt/walletmodel.cpp
+++ b/src/qt/walletmodel.cpp
@@ -248,7 +248,7 @@ WalletModel::SendCoinsReturn WalletModel::sendCoins(WalletModelTransaction &tran
 
         CDataStream ssTx(SER_NETWORK, PROTOCOL_VERSION);
         ssTx << *newTx;
-        transaction_array.append((const char*)&(ssTx[0]), ssTx.size());
+        transaction_array.append((const char*)ssTx.data(), ssTx.size());
     }
 
     // Add addresses / update labels that we've sent to the address book,
diff --git a/src/random.cpp b/src/random.cpp
index 9900825abb..174f4cef31 100644
--- a/src/random.cpp
+++ b/src/random.cpp
@@ -628,7 +628,7 @@ std::vector<unsigned char> FastRandomContext::randbytes(size_t len)
     if (requires_seed) RandomSeed();
     std::vector<unsigned char> ret(len);
     if (len > 0) {
-        rng.Keystream(&ret[0], len);
+        rng.Keystream(ret.data(), len);
     }
     return ret;
 }
diff --git a/src/script/descriptor.cpp b/src/script/descriptor.cpp
index e433ed6764..b54ba204f0 100644
--- a/src/script/descriptor.cpp
+++ b/src/script/descriptor.cpp
@@ -1098,7 +1098,7 @@ std::unique_ptr<DescriptorImpl> InferScript(const CScript& script, ParseScriptCo
     TxoutType txntype = Solver(script, data);
 
     if (txntype == TxoutType::PUBKEY) {
-        CPubKey pubkey(data[0].begin(), data[0].end());
+        CPubKey pubkey(data[0]);
         if (pubkey.IsValid()) {
             return std::make_unique<PKDescriptor>(InferPubkey(pubkey, ctx, provider));
         }
@@ -1122,7 +1122,7 @@ std::unique_ptr<DescriptorImpl> InferScript(const CScript& script, ParseScriptCo
     if (txntype == TxoutType::MULTISIG) {
         std::vector<std::unique_ptr<PubkeyProvider>> providers;
         for (size_t i = 1; i + 1 < data.size(); ++i) {
-            CPubKey pubkey(data[i].begin(), data[i].end());
+            CPubKey pubkey(data[i]);
             providers.push_back(InferPubkey(pubkey, ctx, provider));
         }
         return std::make_unique<MultisigDescriptor>((int)data[0][0], std::move(providers));
diff --git a/src/script/interpreter.cpp b/src/script/interpreter.cpp
index 7e119bb3c4..dc0f165be0 100644
--- a/src/script/interpreter.cpp
+++ b/src/script/interpreter.cpp
@@ -1890,7 +1890,7 @@ static bool VerifyWitnessProgram(const CScriptWitness& witness, int witversion,
             const valtype& script_bytes = SpanPopBack(stack);
             exec_script = CScript(script_bytes.begin(), script_bytes.end());
             uint256 hash_exec_script;
-            CSHA256().Write(&exec_script[0], exec_script.size()).Finalize(hash_exec_script.begin());
+            CSHA256().Write(exec_script.data(), exec_script.size()).Finalize(hash_exec_script.begin());
             if (memcmp(hash_exec_script.begin(), program.data(), 32)) {
                 return set_error(serror, SCRIPT_ERR_WITNESS_PROGRAM_MISMATCH);
             }
diff --git a/src/script/sigcache.cpp b/src/script/sigcache.cpp
index c6d898a25a..65867c1c14 100644
--- a/src/script/sigcache.cpp
+++ b/src/script/sigcache.cpp
@@ -53,14 +53,14 @@ public:
     ComputeEntryECDSA(uint256& entry, const uint256 &hash, const std::vector<unsigned char>& vchSig, const CPubKey& pubkey) const
     {
         CSHA256 hasher = m_salted_hasher_ecdsa;
-        hasher.Write(hash.begin(), 32).Write(&pubkey[0], pubkey.size()).Write(&vchSig[0], vchSig.size()).Finalize(entry.begin());
+        hasher.Write(hash.begin(), 32).Write(pubkey.data(), pubkey.size()).Write(vchSig.data(), vchSig.size()).Finalize(entry.begin());
     }
 
     void
     ComputeEntrySchnorr(uint256& entry, const uint256 &hash, Span<const unsigned char> sig, const XOnlyPubKey& pubkey) const
     {
         CSHA256 hasher = m_salted_hasher_schnorr;
-        hasher.Write(hash.begin(), 32).Write(&pubkey[0], pubkey.size()).Write(sig.data(), sig.size()).Finalize(entry.begin());
+        hasher.Write(hash.begin(), 32).Write(pubkey.data(), pubkey.size()).Write(sig.data(), sig.size()).Finalize(entry.begin());
     }
 
     bool
diff --git a/src/script/sign.cpp b/src/script/sign.cpp
index 4d9026427e..da0092f9e3 100644
--- a/src/script/sign.cpp
+++ b/src/script/sign.cpp
@@ -167,7 +167,7 @@ static bool SignStep(const SigningProvider& provider, const BaseSignatureCreator
         return true;
 
     case TxoutType::WITNESS_V0_SCRIPTHASH:
-        CRIPEMD160().Write(&vSolutions[0][0], vSolutions[0].size()).Finalize(h160.begin());
+        CRIPEMD160().Write(vSolutions[0].data(), vSolutions[0].size()).Finalize(h160.begin());
         if (GetCScript(provider, sigdata, CScriptID{h160}, scriptRet)) {
             ret.push_back(std::vector<unsigned char>(scriptRet.begin(), scriptRet.end()));
             return true;
diff --git a/src/test/compress_tests.cpp b/src/test/compress_tests.cpp
index 7b661a0d1d..b7ba46bd30 100644
--- a/src/test/compress_tests.cpp
+++ b/src/test/compress_tests.cpp
@@ -79,7 +79,7 @@ BOOST_AUTO_TEST_CASE(compress_script_to_ckey_id)
     // Check compressed script
     BOOST_CHECK_EQUAL(out.size(), 21U);
     BOOST_CHECK_EQUAL(out[0], 0x00);
-    BOOST_CHECK_EQUAL(memcmp(&out[1], &script[3], 20), 0); // compare the 20 relevant chars of the CKeyId in the script
+    BOOST_CHECK_EQUAL(memcmp(out.data() + 1, script.data() + 3, 20), 0); // compare the 20 relevant chars of the CKeyId in the script
 }
 
 BOOST_AUTO_TEST_CASE(compress_script_to_cscript_id)
@@ -96,7 +96,7 @@ BOOST_AUTO_TEST_CASE(compress_script_to_cscript_id)
     // Check compressed script
     BOOST_CHECK_EQUAL(out.size(), 21U);
     BOOST_CHECK_EQUAL(out[0], 0x01);
-    BOOST_CHECK_EQUAL(memcmp(&out[1], &script[2], 20), 0); // compare the 20 relevant chars of the CScriptId in the script
+    BOOST_CHECK_EQUAL(memcmp(out.data() + 1, script.data() + 2, 20), 0); // compare the 20 relevant chars of the CScriptId in the script
 }
 
 BOOST_AUTO_TEST_CASE(compress_script_to_compressed_pubkey_id)
@@ -113,8 +113,8 @@ BOOST_AUTO_TEST_CASE(compress_script_to_compressed_pubkey_id)
 
     // Check compressed script
     BOOST_CHECK_EQUAL(out.size(), 33U);
-    BOOST_CHECK_EQUAL(memcmp(&out[0], &script[1], 1), 0);
-    BOOST_CHECK_EQUAL(memcmp(&out[1], &script[2], 32), 0); // compare the 32 chars of the compressed CPubKey
+    BOOST_CHECK_EQUAL(memcmp(out.data(), script.data() + 1, 1), 0);
+    BOOST_CHECK_EQUAL(memcmp(out.data() + 1, script.data() + 2, 32), 0); // compare the 32 chars of the compressed CPubKey
 }
 
 BOOST_AUTO_TEST_CASE(compress_script_to_uncompressed_pubkey_id)
@@ -130,7 +130,7 @@ BOOST_AUTO_TEST_CASE(compress_script_to_uncompressed_pubkey_id)
 
     // Check compressed script
     BOOST_CHECK_EQUAL(out.size(), 33U);
-    BOOST_CHECK_EQUAL(memcmp(&out[1], &script[2], 32), 0); // first 32 chars of CPubKey are copied into out[1:]
+    BOOST_CHECK_EQUAL(memcmp(out.data() + 1, script.data() + 2, 32), 0); // first 32 chars of CPubKey are copied into out[1:]
     BOOST_CHECK_EQUAL(out[0], 0x04 | (script[65] & 0x01)); // least significant bit (lsb) of last char of pubkey is mapped into out[0]
 }
 
diff --git a/src/test/crypto_tests.cpp b/src/test/crypto_tests.cpp
index 7358b246b6..edec5f0a31 100644
--- a/src/test/crypto_tests.cpp
+++ b/src/test/crypto_tests.cpp
@@ -33,7 +33,7 @@ static void TestVector(const Hasher &h, const In &in, const Out &out) {
     hash.resize(out.size());
     {
         // Test that writing the whole input string at once works.
-        Hasher(h).Write((unsigned char*)&in[0], in.size()).Finalize(&hash[0]);
+        Hasher(h).Write((const uint8_t*)in.data(), in.size()).Finalize(hash.data());
         BOOST_CHECK(hash == out);
     }
     for (int i=0; i<32; i++) {
@@ -42,15 +42,15 @@ static void TestVector(const Hasher &h, const In &in, const Out &out) {
         size_t pos = 0;
         while (pos < in.size()) {
             size_t len = InsecureRandRange((in.size() - pos + 1) / 2 + 1);
-            hasher.Write((unsigned char*)&in[pos], len);
+            hasher.Write((const uint8_t*)in.data() + pos, len);
             pos += len;
             if (pos > 0 && pos + 2 * out.size() > in.size() && pos < in.size()) {
                 // Test that writing the rest at once to a copy of a hasher works.
-                Hasher(hasher).Write((unsigned char*)&in[pos], in.size() - pos).Finalize(&hash[0]);
+                Hasher(hasher).Write((const uint8_t*)in.data() + pos, in.size() - pos).Finalize(hash.data());
                 BOOST_CHECK(hash == out);
             }
         }
-        hasher.Finalize(&hash[0]);
+        hasher.Finalize(hash.data());
         BOOST_CHECK(hash == out);
     }
 }
diff --git a/src/test/fuzz/util.cpp b/src/test/fuzz/util.cpp
index b8d846a995..7fd7559d72 100644
--- a/src/test/fuzz/util.cpp
+++ b/src/test/fuzz/util.cpp
@@ -273,7 +273,7 @@ CScript ConsumeScript(FuzzedDataProvider& fuzzed_data_provider, const size_t max
     CScript r_script{b.begin(), b.end()};
     if (maybe_p2wsh && fuzzed_data_provider.ConsumeBool()) {
         uint256 script_hash;
-        CSHA256().Write(&r_script[0], r_script.size()).Finalize(script_hash.begin());
+        CSHA256().Write(r_script.data(), r_script.size()).Finalize(script_hash.begin());
         r_script.clear();
         r_script << OP_0 << ToByteVector(script_hash);
     }
diff --git a/src/test/script_standard_tests.cpp b/src/test/script_standard_tests.cpp
index 103a971d98..44fbfa5970 100644
--- a/src/test/script_standard_tests.cpp
+++ b/src/test/script_standard_tests.cpp
@@ -98,7 +98,7 @@ BOOST_AUTO_TEST_CASE(script_standard_Solver_success)
 
     // TxoutType::WITNESS_V0_SCRIPTHASH
     uint256 scriptHash;
-    CSHA256().Write(&redeemScript[0], redeemScript.size())
+    CSHA256().Write(redeemScript.data(), redeemScript.size())
         .Finalize(scriptHash.begin());
 
     s.clear();
@@ -370,7 +370,7 @@ BOOST_AUTO_TEST_CASE(script_standard_GetScriptFor_)
     witnessScript << OP_1 << ToByteVector(pubkeys[0]) << OP_1 << OP_CHECKMULTISIG;
 
     uint256 scriptHash;
-    CSHA256().Write(&witnessScript[0], witnessScript.size())
+    CSHA256().Write(witnessScript.data(), witnessScript.size())
         .Finalize(scriptHash.begin());
 
     expected.clear();
diff --git a/src/test/script_tests.cpp b/src/test/script_tests.cpp
index 14cfadf75d..171234f745 100644
--- a/src/test/script_tests.cpp
+++ b/src/test/script_tests.cpp
@@ -155,10 +155,10 @@ void DoTest(const CScript& scriptPubKey, const CScript& scriptSig, const CScript
     if (libconsensus_flags == flags) {
         int expectedSuccessCode = expect ? 1 : 0;
         if (flags & bitcoinconsensus_SCRIPT_FLAGS_VERIFY_WITNESS) {
-            BOOST_CHECK_MESSAGE(bitcoinconsensus_verify_script_with_amount(scriptPubKey.data(), scriptPubKey.size(), txCredit.vout[0].nValue, (const unsigned char*)&stream[0], stream.size(), 0, libconsensus_flags, nullptr) == expectedSuccessCode, message);
+            BOOST_CHECK_MESSAGE(bitcoinconsensus_verify_script_with_amount(scriptPubKey.data(), scriptPubKey.size(), txCredit.vout[0].nValue, stream.data(), stream.size(), 0, libconsensus_flags, nullptr) == expectedSuccessCode, message);
         } else {
-            BOOST_CHECK_MESSAGE(bitcoinconsensus_verify_script_with_amount(scriptPubKey.data(), scriptPubKey.size(), 0, (const unsigned char*)&stream[0], stream.size(), 0, libconsensus_flags, nullptr) == expectedSuccessCode, message);
-            BOOST_CHECK_MESSAGE(bitcoinconsensus_verify_script(scriptPubKey.data(), scriptPubKey.size(), (const unsigned char*)&stream[0], stream.size(), 0, libconsensus_flags, nullptr) == expectedSuccessCode, message);
+            BOOST_CHECK_MESSAGE(bitcoinconsensus_verify_script_with_amount(scriptPubKey.data(), scriptPubKey.size(), 0, stream.data(), stream.size(), 0, libconsensus_flags, nullptr) == expectedSuccessCode, message);
+            BOOST_CHECK_MESSAGE(bitcoinconsensus_verify_script(scriptPubKey.data(), scriptPubKey.size(), stream.data(), stream.size(), 0, libconsensus_flags, nullptr) == expectedSuccessCode, message);
         }
     }
 #endif
@@ -224,7 +224,7 @@ struct KeyData
         pubkey0 = key0.GetPubKey();
         pubkey0H = key0.GetPubKey();
         pubkey0C = key0C.GetPubKey();
-        *const_cast<unsigned char*>(&pubkey0H[0]) = 0x06 | (pubkey0H[64] & 1);
+        *const_cast<unsigned char*>(pubkey0H.data()) = 0x06 | (pubkey0H[64] & 1);
 
         key1.Set(vchKey1, vchKey1 + 32, false);
         key1C.Set(vchKey1, vchKey1 + 32, true);
@@ -290,7 +290,7 @@ public:
         } else if (wm == WitnessMode::SH) {
             witscript = scriptPubKey;
             uint256 hash;
-            CSHA256().Write(&witscript[0], witscript.size()).Finalize(hash.begin());
+            CSHA256().Write(witscript.data(), witscript.size()).Finalize(hash.begin());
             scriptPubKey = CScript() << witnessversion << ToByteVector(hash);
         }
         if (P2SH) {
@@ -774,7 +774,7 @@ BOOST_AUTO_TEST_CASE(script_build)
     {
         CScript witscript = CScript() << ToByteVector(keys.pubkey0);
         uint256 hash;
-        CSHA256().Write(&witscript[0], witscript.size()).Finalize(hash.begin());
+        CSHA256().Write(witscript.data(), witscript.size()).Finalize(hash.begin());
         std::vector<unsigned char> hashBytes = ToByteVector(hash);
         hashBytes.pop_back();
         tests.push_back(TestBuilder(CScript() << OP_0 << hashBytes,
@@ -1520,7 +1520,7 @@ BOOST_AUTO_TEST_CASE(bitcoinconsensus_verify_script_returns_true)
     stream << spendTx;
 
     bitcoinconsensus_error err;
-    int result = bitcoinconsensus_verify_script(scriptPubKey.data(), scriptPubKey.size(), (const unsigned char*)&stream[0], stream.size(), nIn, libconsensus_flags, &err);
+    int result = bitcoinconsensus_verify_script(scriptPubKey.data(), scriptPubKey.size(), stream.data(), stream.size(), nIn, libconsensus_flags, &err);
     BOOST_CHECK_EQUAL(result, 1);
     BOOST_CHECK_EQUAL(err, bitcoinconsensus_ERR_OK);
 }
@@ -1543,7 +1543,7 @@ BOOST_AUTO_TEST_CASE(bitcoinconsensus_verify_script_tx_index_err)
     stream << spendTx;
 
     bitcoinconsensus_error err;
-    int result = bitcoinconsensus_verify_script(scriptPubKey.data(), scriptPubKey.size(), (const unsigned char*)&stream[0], stream.size(), nIn, libconsensus_flags, &err);
+    int result = bitcoinconsensus_verify_script(scriptPubKey.data(), scriptPubKey.size(), stream.data(), stream.size(), nIn, libconsensus_flags, &err);
     BOOST_CHECK_EQUAL(result, 0);
     BOOST_CHECK_EQUAL(err, bitcoinconsensus_ERR_TX_INDEX);
 }
@@ -1566,7 +1566,7 @@ BOOST_AUTO_TEST_CASE(bitcoinconsensus_verify_script_tx_size)
     stream << spendTx;
 
     bitcoinconsensus_error err;
-    int result = bitcoinconsensus_verify_script(scriptPubKey.data(), scriptPubKey.size(), (const unsigned char*)&stream[0], stream.size() * 2, nIn, libconsensus_flags, &err);
+    int result = bitcoinconsensus_verify_script(scriptPubKey.data(), scriptPubKey.size(), stream.data(), stream.size() * 2, nIn, libconsensus_flags, &err);
     BOOST_CHECK_EQUAL(result, 0);
     BOOST_CHECK_EQUAL(err, bitcoinconsensus_ERR_TX_SIZE_MISMATCH);
 }
@@ -1589,7 +1589,7 @@ BOOST_AUTO_TEST_CASE(bitcoinconsensus_verify_script_tx_serialization)
     stream << 0xffffffff;
 
     bitcoinconsensus_error err;
-    int result = bitcoinconsensus_verify_script(scriptPubKey.data(), scriptPubKey.size(), (const unsigned char*)&stream[0], stream.size(), nIn, libconsensus_flags, &err);
+    int result = bitcoinconsensus_verify_script(scriptPubKey.data(), scriptPubKey.size(), stream.data(), stream.size(), nIn, libconsensus_flags, &err);
     BOOST_CHECK_EQUAL(result, 0);
     BOOST_CHECK_EQUAL(err, bitcoinconsensus_ERR_TX_DESERIALIZE);
 }
@@ -1612,7 +1612,7 @@ BOOST_AUTO_TEST_CASE(bitcoinconsensus_verify_script_amount_required_err)
     stream << spendTx;
 
     bitcoinconsensus_error err;
-    int result = bitcoinconsensus_verify_script(scriptPubKey.data(), scriptPubKey.size(), (const unsigned char*)&stream[0], stream.size(), nIn, libconsensus_flags, &err);
+    int result = bitcoinconsensus_verify_script(scriptPubKey.data(), scriptPubKey.size(), stream.data(), stream.size(), nIn, libconsensus_flags, &err);
     BOOST_CHECK_EQUAL(result, 0);
     BOOST_CHECK_EQUAL(err, bitcoinconsensus_ERR_AMOUNT_REQUIRED);
 }
@@ -1635,7 +1635,7 @@ BOOST_AUTO_TEST_CASE(bitcoinconsensus_verify_script_invalid_flags)
     stream << spendTx;
 
     bitcoinconsensus_error err;
-    int result = bitcoinconsensus_verify_script(scriptPubKey.data(), scriptPubKey.size(), (const unsigned char*)&stream[0], stream.size(), nIn, libconsensus_flags, &err);
+    int result = bitcoinconsensus_verify_script(scriptPubKey.data(), scriptPubKey.size(), stream.data(), stream.size(), nIn, libconsensus_flags, &err);
     BOOST_CHECK_EQUAL(result, 0);
     BOOST_CHECK_EQUAL(err, bitcoinconsensus_ERR_INVALID_FLAGS);
 }
@@ -1733,7 +1733,7 @@ BOOST_AUTO_TEST_CASE(script_assets_test)
     size_t length = file.tellg();
     file.seekg(0, std::ios::beg);
     std::string data(length, '\0');
-    file.read(&data[0], data.size());
+    file.read(data.data(), data.size());
     UniValue tests = read_json(data);
     BOOST_CHECK(tests.isArray());
     BOOST_CHECK(tests.size() > 0);
diff --git a/src/wallet/crypter.cpp b/src/wallet/crypter.cpp
index b50f00e7d1..251778e401 100644
--- a/src/wallet/crypter.cpp
+++ b/src/wallet/crypter.cpp
@@ -78,7 +78,7 @@ bool CCrypter::Encrypt(const CKeyingMaterial& vchPlaintext, std::vector<unsigned
     vchCiphertext.resize(vchPlaintext.size() + AES_BLOCKSIZE);
 
     AES256CBCEncrypt enc(vchKey.data(), vchIV.data(), true);
-    size_t nLen = enc.Encrypt(&vchPlaintext[0], vchPlaintext.size(), vchCiphertext.data());
+    size_t nLen = enc.Encrypt(vchPlaintext.data(), vchPlaintext.size(), vchCiphertext.data());
     if(nLen < vchPlaintext.size())
         return false;
     vchCiphertext.resize(nLen);
@@ -97,7 +97,7 @@ bool CCrypter::Decrypt(const std::vector<unsigned char>& vchCiphertext, CKeyingM
     vchPlaintext.resize(nLen);
 
     AES256CBCDecrypt dec(vchKey.data(), vchIV.data(), true);
-    nLen = dec.Decrypt(vchCiphertext.data(), vchCiphertext.size(), &vchPlaintext[0]);
+    nLen = dec.Decrypt(vchCiphertext.data(), vchCiphertext.size(), vchPlaintext.data());
     if(nLen == 0)
         return false;
     vchPlaintext.resize(nLen);
@@ -121,7 +121,7 @@ bool DecryptSecret(const CKeyingMaterial& vMasterKey, const std::vector<unsigned
     memcpy(chIV.data(), &nIV, WALLET_CRYPTO_IV_SIZE);
     if(!cKeyCrypter.SetKey(vMasterKey, chIV))
         return false;
-    return cKeyCrypter.Decrypt(vchCiphertext, *((CKeyingMaterial*)&vchPlaintext));
+    return cKeyCrypter.Decrypt(vchCiphertext, vchPlaintext);
 }
 
 bool DecryptKey(const CKeyingMaterial& vMasterKey, const std::vector<unsigned char>& vchCryptedSecret, const CPubKey& vchPubKey, CKey& key)
diff --git a/src/wallet/rpcdump.cpp b/src/wallet/rpcdump.cpp
index 653dbdfc1d..a851765c57 100644
--- a/src/wallet/rpcdump.cpp
+++ b/src/wallet/rpcdump.cpp
@@ -469,7 +469,7 @@ RPCHelpMan importpubkey()
     if (!IsHex(request.params[0].get_str()))
         throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "Pubkey must be a hex string");
     std::vector<unsigned char> data(ParseHex(request.params[0].get_str()));
-    CPubKey pubKey(data.begin(), data.end());
+    CPubKey pubKey(data);
     if (!pubKey.IsFullyValid())
         throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "Pubkey is not a valid public key");
 
@@ -871,7 +871,7 @@ static std::string RecurseImportData(const CScript& script, ImportData& import_d
 
     switch (script_type) {
     case TxoutType::PUBKEY: {
-        CPubKey pubkey(solverdata[0].begin(), solverdata[0].end());
+        CPubKey pubkey(solverdata[0]);
         import_data.used_keys.emplace(pubkey.GetID(), false);
         return "";
     }
@@ -893,7 +893,7 @@ static std::string RecurseImportData(const CScript& script, ImportData& import_d
     }
     case TxoutType::MULTISIG: {
         for (size_t i = 1; i + 1< solverdata.size(); ++i) {
-            CPubKey pubkey(solverdata[i].begin(), solverdata[i].end());
+            CPubKey pubkey(solverdata[i]);
             import_data.used_keys.emplace(pubkey.GetID(), false);
         }
         return "";
@@ -997,7 +997,7 @@ static UniValue ProcessImportLegacy(ImportData& import_data, std::map<CKeyID, CP
             throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "Pubkey \"" + str + "\" must be a hex string");
         }
         auto parsed_pubkey = ParseHex(str);
-        CPubKey pubkey(parsed_pubkey.begin(), parsed_pubkey.end());
+        CPubKey pubkey(parsed_pubkey);
         if (!pubkey.IsFullyValid()) {
             throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "Pubkey \"" + str + "\" is not a valid public key");
         }
diff --git a/src/wallet/salvage.cpp b/src/wallet/salvage.cpp
index 6d912be019..ea045eb6d8 100644
--- a/src/wallet/salvage.cpp
+++ b/src/wallet/salvage.cpp
@@ -154,8 +154,8 @@ bool RecoverDatabaseFile(const fs::path& file_path, bilingual_str& error, std::v
             warnings.push_back(strprintf(Untranslated("WARNING: WalletBatch::Recover skipping %s: %s"), strType, strErr));
             continue;
         }
-        Dbt datKey(&row.first[0], row.first.size());
-        Dbt datValue(&row.second[0], row.second.size());
+        Dbt datKey(row.first.data(), row.first.size());
+        Dbt datValue(row.second.data(), row.second.size());
         int ret2 = pdbCopy->put(ptxn, &datKey, &datValue, DB_NOOVERWRITE);
         if (ret2 > 0)
             fSuccess = false;
diff --git a/src/wallet/scriptpubkeyman.cpp b/src/wallet/scriptpubkeyman.cpp
index 149549410c..2eb9ca5c6d 100644
--- a/src/wallet/scriptpubkeyman.cpp
+++ b/src/wallet/scriptpubkeyman.cpp
@@ -162,7 +162,7 @@ IsMineResult IsMineInner(const LegacyScriptPubKeyMan& keystore, const CScript& s
             break;
         }
         uint160 hash;
-        CRIPEMD160().Write(&vSolutions[0][0], vSolutions[0].size()).Finalize(hash.begin());
+        CRIPEMD160().Write(vSolutions[0].data(), vSolutions[0].size()).Finalize(hash.begin());
         CScriptID scriptID = CScriptID(hash);
         CScript subscript;
         if (keystore.GetCScript(scriptID, subscript)) {
diff --git a/src/wallet/wallet.cpp b/src/wallet/wallet.cpp
index f0aaee7e4e..3d0ef9f8c0 100644
--- a/src/wallet/wallet.cpp
+++ b/src/wallet/wallet.cpp
@@ -603,12 +603,12 @@ bool CWallet::EncryptWallet(const SecureString& strWalletPassphrase)
     CKeyingMaterial _vMasterKey;
 
     _vMasterKey.resize(WALLET_CRYPTO_KEY_SIZE);
-    GetStrongRandBytes(&_vMasterKey[0], WALLET_CRYPTO_KEY_SIZE);
+    GetStrongRandBytes(_vMasterKey.data(), WALLET_CRYPTO_KEY_SIZE);
 
     CMasterKey kMasterKey;
 
     kMasterKey.vchSalt.resize(WALLET_CRYPTO_SALT_SIZE);
-    GetStrongRandBytes(&kMasterKey.vchSalt[0], WALLET_CRYPTO_SALT_SIZE);
+    GetStrongRandBytes(kMasterKey.vchSalt.data(), WALLET_CRYPTO_SALT_SIZE);
 
     CCrypter crypter;
     int64_t nStartTime = GetTimeMillis();
diff --git a/src/zmq/zmqpublishnotifier.cpp b/src/zmq/zmqpublishnotifier.cpp
index 25afa94d0f..6ae866cc07 100644
--- a/src/zmq/zmqpublishnotifier.cpp
+++ b/src/zmq/zmqpublishnotifier.cpp
@@ -168,7 +168,7 @@ bool CZMQAbstractPublishNotifier::SendZmqMessage(const char *command, const void
 
     /* send three parts, command & data & a LE 4byte sequence number */
     unsigned char msgseq[sizeof(uint32_t)];
-    WriteLE32(&msgseq[0], nSequence);
+    WriteLE32(msgseq, nSequence);
     int rc = zmq_send_multipart(psocket, command, strlen(command), data, size, msgseq, (size_t)sizeof(uint32_t), nullptr);
     if (rc == -1)
         return false;