Merge bitcoin/bitcoin#31519: refactor: Use std::span over Span

ffff4a293a bench: Update span-serialize comment (MarcoFalke)
fa4d6ec97b refactor: Avoid false-positive gcc warning (MarcoFalke)
fa942332b4 scripted-diff: Bump copyright headers after std::span changes (MarcoFalke)
fa0c6b7179 refactor: Remove unused Span alias (MarcoFalke)
fade0b5e5e scripted-diff: Use std::span over Span (MarcoFalke)
fadccc26c0 refactor: Make Span an alias of std::span (MarcoFalke)
fa27e36717 test: Fix broken span_tests (MarcoFalke)
fadf02ef8b refactor: Return std::span from MakeUCharSpan (MarcoFalke)
fa720b94be refactor: Return std::span from MakeByteSpan (MarcoFalke)

Pull request description:

  `Span` has some issues:

  * It does not support fixed-size spans, which are available through `std::span`.
  * It is confusing to have it available and in use at the same time with `std::span`.
  * It does not obey the standard library iterator build hardening flags. See https://github.com/bitcoin/bitcoin/issues/31272 for a discussion. For example, this allows to catch issues like the one fixed in commit fabeca3458.

  Both types are type-safe and can even implicitly convert into each other in most contexts.

  However, exclusively using `std::span` seems less confusing, so do it here with a scripted-diff.

ACKs for top commit:
  l0rinc:
    reACK ffff4a293a
  theuni:
    ACK ffff4a293a.

Tree-SHA512: 9cc2f1f43551e2c07cc09f38b1f27d11e57e9e9bc0c6138c8fddd0cef54b91acd8b14711205ff949be874294a121910d0aceffe0e8914c4cff07f1e0e87ad5b8

src/wallet/test/db_tests.cpp

@@ -1,4 +1,4 @@
-// Copyright (c) 2018-2022 The Bitcoin Core developers
+// Copyright (c) 2018-present The Bitcoin Core developers
 // Distributed under the MIT software license, see the accompanying
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
@@ -24,7 +24,7 @@
 
 inline std::ostream& operator<<(std::ostream& os, const std::pair<const SerializeData, SerializeData>& kv)
 {
-    Span key{kv.first}, value{kv.second};
+    std::span key{kv.first}, value{kv.second};
     os << "(\"" << std::string_view{reinterpret_cast<const char*>(key.data()), key.size()} << "\", \""
        << std::string_view{reinterpret_cast<const char*>(value.data()), value.size()} << "\")";
     return os;
@@ -43,7 +43,7 @@ static SerializeData StringData(std::string_view str)
     return SerializeData{bytes.begin(), bytes.end()};
 }
 
-static void CheckPrefix(DatabaseBatch& batch, Span<const std::byte> prefix, MockableData expected)
+static void CheckPrefix(DatabaseBatch& batch, std::span<const std::byte> prefix, MockableData expected)
 {
     std::unique_ptr<DatabaseCursor> cursor = batch.GetNewPrefixCursor(prefix);
     MockableData actual;
@@ -212,7 +212,7 @@ BOOST_AUTO_TEST_CASE(db_cursor_prefix_byte_test)
         } else {
             // Write elements to it if not berkeleyro
             for (const auto& [k, v] : {e, p, ps, f, fs, ff, ffs}) {
-                batch->Write(Span{k}, Span{v});
+                batch->Write(std::span{k}, std::span{v});
             }
         }
 

src/wallet/test/fuzz/wallet_bdb_parser.cpp

@@ -44,7 +44,7 @@ FUZZ_TARGET(wallet_bdb_parser, .init = initialize_wallet_bdb_parser)
 
     {
         AutoFile outfile{fsbridge::fopen(wallet_path, "wb")};
-        outfile << Span{buffer};
+        outfile << std::span{buffer};
     }
 
     const DatabaseOptions options{};

src/wallet/test/util.cpp

@@ -1,4 +1,4 @@
-// Copyright (c) 2021-2022 The Bitcoin Core developers
+// Copyright (c) 2021-present The Bitcoin Core developers
 // Distributed under the MIT software license, see the accompanying
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
@@ -94,7 +94,7 @@ CTxDestination getNewDestination(CWallet& w, OutputType output_type)
     return *Assert(w.GetNewDestination(output_type, ""));
 }
 
-MockableCursor::MockableCursor(const MockableData& records, bool pass, Span<const std::byte> prefix)
+MockableCursor::MockableCursor(const MockableData& records, bool pass, std::span<const std::byte> prefix)
 {
     m_pass = pass;
     std::tie(m_cursor, m_cursor_end) = records.equal_range(BytePrefix{prefix});
@@ -166,7 +166,7 @@ bool MockableBatch::HasKey(DataStream&& key)
     return m_records.count(key_data) > 0;
 }
 
-bool MockableBatch::ErasePrefix(Span<const std::byte> prefix)
+bool MockableBatch::ErasePrefix(std::span<const std::byte> prefix)
 {
     if (!m_pass) {
         return false;

src/wallet/test/util.h

@@ -1,4 +1,4 @@
-// Copyright (c) 2021-2022 The Bitcoin Core developers
+// Copyright (c) 2021-present The Bitcoin Core developers
 // Distributed under the MIT software license, see the accompanying
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
@@ -59,7 +59,7 @@ public:
     bool m_pass;
 
     explicit MockableCursor(const MockableData& records, bool pass) : m_cursor(records.begin()), m_cursor_end(records.end()), m_pass(pass) {}
-    MockableCursor(const MockableData& records, bool pass, Span<const std::byte> prefix);
+    MockableCursor(const MockableData& records, bool pass, std::span<const std::byte> prefix);
     ~MockableCursor() = default;
 
     Status Next(DataStream& key, DataStream& value) override;
@@ -75,7 +75,7 @@ private:
     bool WriteKey(DataStream&& key, DataStream&& value, bool overwrite=true) override;
     bool EraseKey(DataStream&& key) override;
     bool HasKey(DataStream&& key) override;
-    bool ErasePrefix(Span<const std::byte> prefix) override;
+    bool ErasePrefix(std::span<const std::byte> prefix) override;
 
 public:
     explicit MockableBatch(MockableData& records, bool pass) : m_records(records), m_pass(pass) {}
@@ -88,7 +88,7 @@ public:
     {
         return std::make_unique<MockableCursor>(m_records, m_pass);
     }
-    std::unique_ptr<DatabaseCursor> GetNewPrefixCursor(Span<const std::byte> prefix) override {
+    std::unique_ptr<DatabaseCursor> GetNewPrefixCursor(std::span<const std::byte> prefix) override {
         return std::make_unique<MockableCursor>(m_records, m_pass, prefix);
     }
     bool TxnBegin() override { return m_pass; }