Merge bitcoin/bitcoin#30406: refactor: modernize-use-equals-default

3333bae tidy: modernize-use-equals-default (MarcoFalke)

Pull request description:

  Prior to C++20, `modernize-use-equals-default` could have been problematic because it could turn a non-aggregate into an aggregate. The risk would be that aggregate initialization would be enabled where the author did not intend to enable it.

  With C++20, aggregate for those is forbidden either way. (https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2018/p1008r1.pdf)

  So enabled it for code clarity, consistency, and possibly unlocking compiler optimizations. See https://clang.llvm.org/extra/clang-tidy/checks/modernize/use-equals-default.html

ACKs for top commit:
  stickies-v:
    ACK 3333bae

Tree-SHA512: ab42ff01be7ca7e7d8b4c6a485e68426f59627d83dd827cf292304829562348dc17a52ee009f5f6f3c1c2081d7166ffac4baef23197ebeba8de7767c6ddfe255

Author: fanquake

src/.clang-tidy

@@ -10,6 +10,7 @@ misc-unused-using-decls,
 misc-no-recursion,
 modernize-use-default-member-init,
 modernize-use-emplace,
+modernize-use-equals-default,
 modernize-use-noexcept,
 modernize-use-nullptr,
 performance-*,

src/arith_uint256.h

@@ -240,7 +240,7 @@ class base_uint
 /** 256-bit unsigned big integer. */
 class arith_uint256 : public base_uint<256> {
 public:
-    arith_uint256() {}
+    arith_uint256() = default;
     arith_uint256(const base_uint<256>& b) : base_uint<256>(b) {}
     arith_uint256(uint64_t b) : base_uint<256>(b) {}
 

src/blockencodings.h

@@ -59,7 +59,7 @@ class BlockTransactions {
     uint256 blockhash;
     std::vector<CTransactionRef> txn;
 
-    BlockTransactions() {}
+    BlockTransactions() = default;
     explicit BlockTransactions(const BlockTransactionsRequest& req) :
         blockhash(req.blockhash), txn(req.indexes.size()) {}
 
@@ -109,7 +109,7 @@ class CBlockHeaderAndShortTxIDs {
     /**
      * Dummy for deserialization
      */
-    CBlockHeaderAndShortTxIDs() {}
+    CBlockHeaderAndShortTxIDs() = default;
 
     /**
      * @param[in]  nonce  This should be randomly generated, and is used for the siphash secret key

src/chain.h

@@ -66,7 +66,7 @@ class CBlockFileInfo
         READWRITE(VARINT(obj.nTimeLast));
     }
 
-    CBlockFileInfo() {}
+    CBlockFileInfo() = default;
 
     std::string ToString() const;
 

src/coins.h

@@ -154,7 +154,7 @@ class CCoinsViewCursor
 {
 public:
     CCoinsViewCursor(const uint256 &hashBlockIn): hashBlock(hashBlockIn) {}
-    virtual ~CCoinsViewCursor() {}
+    virtual ~CCoinsViewCursor() = default;
 
     virtual bool GetKey(COutPoint &key) const = 0;
     virtual bool GetValue(Coin &coin) const = 0;
@@ -198,7 +198,7 @@ class CCoinsView
     virtual std::unique_ptr<CCoinsViewCursor> Cursor() const;
 
     //! As we use CCoinsViews polymorphically, have a virtual destructor
-    virtual ~CCoinsView() {}
+    virtual ~CCoinsView() = default;
 
     //! Estimate database size (0 if not implemented)
     virtual size_t EstimateSize() const { return 0; }

src/crypto/muhash.h

@@ -97,7 +97,7 @@ class MuHash3072
 
 public:
     /* The empty set. */
-    MuHash3072() noexcept {};
+    MuHash3072() noexcept = default;
 
     /* A singleton with variable sized data in it. */
     explicit MuHash3072(Span<const unsigned char> in) noexcept;

src/crypto/sha3.h

@@ -32,7 +32,7 @@ class SHA3_256
 public:
     static constexpr size_t OUTPUT_SIZE = 32;
 
-    SHA3_256() {}
+    SHA3_256() = default;
     SHA3_256& Write(Span<const unsigned char> data);
     SHA3_256& Finalize(Span<unsigned char> output);
     SHA3_256& Reset();

src/flatfile.h

@@ -18,7 +18,7 @@ struct FlatFilePos
 
     SERIALIZE_METHODS(FlatFilePos, obj) { READWRITE(VARINT_MODE(obj.nFile, VarIntMode::NONNEGATIVE_SIGNED), VARINT(obj.nPos)); }
 
-    FlatFilePos() {}
+    FlatFilePos() = default;
 
     FlatFilePos(int nFileIn, unsigned int nPosIn) :
         nFile(nFileIn),

src/headerssync.h

@@ -100,7 +100,7 @@ struct CompressedHeader {
 
 class HeadersSyncState {
 public:
-    ~HeadersSyncState() {}
+    ~HeadersSyncState() = default;
 
     enum class State {
         /** PRESYNC means the peer has not yet demonstrated their chain has

src/httpserver.h

@@ -156,7 +156,7 @@ class HTTPClosure
 {
 public:
     virtual void operator()() = 0;
-    virtual ~HTTPClosure() {}
+    virtual ~HTTPClosure() = default;
 };
 
 /** Event class. This can be used either as a cross-thread trigger or as a timer.