Merge bitcoin/bitcoin#23769: Disallow copies of CChain

faf2614f60 style: Use 4 spaces for indendation, not 5 (MarcoFalke)
fada66fc2c Disallow copies of CChain (MarcoFalke)

Pull request description:

  Creating a copy of the chain is not a valid use case in normal operation. Also, it massively degrades performance.

  However, it seems to be a mistake that no one looks out for during review:

  * https://github.com/bitcoin/bitcoin/pull/22677#discussion_r760400537

  Fix this by disallowing it.

ACKs for top commit:
  jamesob:
    ACK faf2614f60 ([`jamesob/ackr/23769.1.MarcoFalke.disallow_copies_of_cchai`](https://github.com/jamesob/bitcoin/tree/ackr/23769.1.MarcoFalke.disallow_copies_of_cchai))
  glozow:
    utACK faf2614f60, nice.
  prusnak:
    utACK faf2614

Tree-SHA512: 27b908c78842e4700e118adb876c09c3d1ec04662310e983309e2cd6fa8ad38c9359ff45f36a804359b9f117e351c4739e651b3e6754c14e6c6fcd7ae5e68342

src/chain.h

@@ -59,7 +59,8 @@ public:
         READWRITE(VARINT(obj.nTimeLast));
     }
 
-     void SetNull() {
+    void SetNull()
+    {
         nBlocks = 0;
         nSize = 0;
         nUndoSize = 0;
@@ -69,14 +70,16 @@ public:
         nTimeLast = 0;
     }
 
-     CBlockFileInfo() {
+    CBlockFileInfo()
+    {
         SetNull();
     }
 
     std::string ToString() const;
 
     /** update statistics (does not update nSize) */
-     void AddBlock(unsigned int nHeightIn, uint64_t nTimeIn) {
+    void AddBlock(unsigned int nHeightIn, uint64_t nTimeIn)
+    {
         if (nBlocks == 0 || nHeightFirst > nHeightIn)
             nHeightFirst = nHeightIn;
         if (nBlocks == 0 || nTimeFirst > nTimeIn)
@@ -220,7 +223,8 @@ public:
     {
     }
 
-    FlatFilePos GetBlockPos() const {
+    FlatFilePos GetBlockPos() const
+    {
         FlatFilePos ret;
         if (nStatus & BLOCK_HAVE_DATA) {
             ret.nFile = nFile;
@@ -229,7 +233,8 @@ public:
         return ret;
     }
 
-    FlatFilePos GetUndoPos() const {
+    FlatFilePos GetUndoPos() const
+    {
         FlatFilePos ret;
         if (nStatus & BLOCK_HAVE_UNDO) {
             ret.nFile = nFile;
@@ -353,11 +358,13 @@ class CDiskBlockIndex : public CBlockIndex
 public:
     uint256 hashPrev;
 
-    CDiskBlockIndex() {
+    CDiskBlockIndex()
+    {
         hashPrev = uint256();
     }
 
-    explicit CDiskBlockIndex(const CBlockIndex* pindex) : CBlockIndex(*pindex) {
+    explicit CDiskBlockIndex(const CBlockIndex* pindex) : CBlockIndex(*pindex)
+    {
         hashPrev = (pprev ? pprev->GetBlockHash() : uint256());
     }
 
@@ -407,35 +414,45 @@ public:
 };
 
 /** An in-memory indexed chain of blocks. */
-class CChain {
+class CChain
+{
 private:
     std::vector<CBlockIndex*> vChain;
 
 public:
+    CChain() = default;
+    CChain(const CChain&) = delete;
+    CChain& operator=(const CChain&) = delete;
+
     /** Returns the index entry for the genesis block of this chain, or nullptr if none. */
-    CBlockIndex *Genesis() const {
+    CBlockIndex* Genesis() const
+    {
         return vChain.size() > 0 ? vChain[0] : nullptr;
     }
 
     /** Returns the index entry for the tip of this chain, or nullptr if none. */
-    CBlockIndex *Tip() const {
+    CBlockIndex* Tip() const
+    {
         return vChain.size() > 0 ? vChain[vChain.size() - 1] : nullptr;
     }
 
     /** Returns the index entry at a particular height in this chain, or nullptr if no such height exists. */
-    CBlockIndex *operator[](int nHeight) const {
+    CBlockIndex* operator[](int nHeight) const
+    {
         if (nHeight < 0 || nHeight >= (int)vChain.size())
             return nullptr;
         return vChain[nHeight];
     }
 
     /** Efficiently check whether a block is present in this chain. */
-    bool Contains(const CBlockIndex *pindex) const {
+    bool Contains(const CBlockIndex* pindex) const
+    {
         return (*this)[pindex->nHeight] == pindex;
     }
 
     /** Find the successor of a block in this chain, or nullptr if the given index is not found or is the tip. */
-    CBlockIndex *Next(const CBlockIndex *pindex) const {
+    CBlockIndex* Next(const CBlockIndex* pindex) const
+    {
         if (Contains(pindex))
             return (*this)[pindex->nHeight + 1];
         else
@@ -443,7 +460,8 @@ public:
     }
 
     /** Return the maximal height in the chain. Is equal to chain.Tip() ? chain.Tip()->nHeight : -1. */
-    int Height() const {
+    int Height() const
+    {
         return vChain.size() - 1;
     }