Merge bitcoin/bitcoin#23769: Disallow copies of CChain

faf2614 style: Use 4 spaces for indendation, not 5 (MarcoFalke)
fada66f 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:

  * bitcoin/bitcoin#22677 (comment)

  Fix this by disallowing it.

ACKs for top commit:
  jamesob:
    ACK faf2614 ([`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 faf2614, nice.
  prusnak:
    utACK faf2614

Tree-SHA512: 27b908c78842e4700e118adb876c09c3d1ec04662310e983309e2cd6fa8ad38c9359ff45f36a804359b9f117e351c4739e651b3e6754c14e6c6fcd7ae5e68342

Author: MarcoFalke

src/chain.h

@@ -59,37 +59,40 @@ class CBlockFileInfo
         READWRITE(VARINT(obj.nTimeLast));
     }
 
-     void SetNull() {
-         nBlocks = 0;
-         nSize = 0;
-         nUndoSize = 0;
-         nHeightFirst = 0;
-         nHeightLast = 0;
-         nTimeFirst = 0;
-         nTimeLast = 0;
-     }
-
-     CBlockFileInfo() {
-         SetNull();
-     }
-
-     std::string ToString() const;
-
-     /** update statistics (does not update nSize) */
-     void AddBlock(unsigned int nHeightIn, uint64_t nTimeIn) {
-         if (nBlocks==0 || nHeightFirst > nHeightIn)
-             nHeightFirst = nHeightIn;
-         if (nBlocks==0 || nTimeFirst > nTimeIn)
-             nTimeFirst = nTimeIn;
-         nBlocks++;
-         if (nHeightIn > nHeightLast)
-             nHeightLast = nHeightIn;
-         if (nTimeIn > nTimeLast)
-             nTimeLast = nTimeIn;
-     }
+    void SetNull()
+    {
+        nBlocks = 0;
+        nSize = 0;
+        nUndoSize = 0;
+        nHeightFirst = 0;
+        nHeightLast = 0;
+        nTimeFirst = 0;
+        nTimeLast = 0;
+    }
+
+    CBlockFileInfo()
+    {
+        SetNull();
+    }
+
+    std::string ToString() const;
+
+    /** update statistics (does not update nSize) */
+    void AddBlock(unsigned int nHeightIn, uint64_t nTimeIn)
+    {
+        if (nBlocks == 0 || nHeightFirst > nHeightIn)
+            nHeightFirst = nHeightIn;
+        if (nBlocks == 0 || nTimeFirst > nTimeIn)
+            nTimeFirst = nTimeIn;
+        nBlocks++;
+        if (nHeightIn > nHeightLast)
+            nHeightLast = nHeightIn;
+        if (nTimeIn > nTimeLast)
+            nTimeLast = nTimeIn;
+    }
 };
 
-enum BlockStatus: uint32_t {
+enum BlockStatus : uint32_t {
     //! Unused.
     BLOCK_VALID_UNKNOWN      =    0,
 
@@ -220,34 +223,36 @@ class CBlockIndex
     {
     }
 
-    FlatFilePos GetBlockPos() const {
+    FlatFilePos GetBlockPos() const
+    {
         FlatFilePos ret;
         if (nStatus & BLOCK_HAVE_DATA) {
             ret.nFile = nFile;
-            ret.nPos  = nDataPos;
+            ret.nPos = nDataPos;
         }
         return ret;
     }
 
-    FlatFilePos GetUndoPos() const {
+    FlatFilePos GetUndoPos() const
+    {
         FlatFilePos ret;
         if (nStatus & BLOCK_HAVE_UNDO) {
             ret.nFile = nFile;
-            ret.nPos  = nUndoPos;
+            ret.nPos = nUndoPos;
         }
         return ret;
     }
 
     CBlockHeader GetBlockHeader() const
     {
         CBlockHeader block;
-        block.nVersion       = nVersion;
+        block.nVersion = nVersion;
         if (pprev)
             block.hashPrevBlock = pprev->GetBlockHash();
         block.hashMerkleRoot = hashMerkleRoot;
-        block.nTime          = nTime;
-        block.nBits          = nBits;
-        block.nNonce         = nNonce;
+        block.nTime = nTime;
+        block.nBits = nBits;
+        block.nNonce = nNonce;
         return block;
     }
 
@@ -288,7 +293,7 @@ class CBlockIndex
             *(--pbegin) = pindex->GetBlockTime();
 
         std::sort(pbegin, pend);
-        return pbegin[(pend - pbegin)/2];
+        return pbegin[(pend - pbegin) / 2];
     }
 
     std::string ToString() const
@@ -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());
     }
 
@@ -385,12 +392,12 @@ class CDiskBlockIndex : public CBlockIndex
     uint256 GetBlockHash() const
     {
         CBlockHeader block;
-        block.nVersion        = nVersion;
-        block.hashPrevBlock   = hashPrev;
-        block.hashMerkleRoot  = hashMerkleRoot;
-        block.nTime           = nTime;
-        block.nBits           = nBits;
-        block.nNonce          = nNonce;
+        block.nVersion = nVersion;
+        block.hashPrevBlock = hashPrev;
+        block.hashMerkleRoot = hashMerkleRoot;
+        block.nTime = nTime;
+        block.nBits = nBits;
+        block.nNonce = nNonce;
         return block.GetHash();
     }
 
@@ -407,54 +414,65 @@ class CDiskBlockIndex : public CBlockIndex
 };
 
 /** 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
             return nullptr;
     }
 
     /** 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;
     }
 
     /** Set/initialize a chain with a given tip. */
-    void SetTip(CBlockIndex *pindex);
+    void SetTip(CBlockIndex* pindex);
 
     /** Return a CBlockLocator that refers to a block in this chain (by default the tip). */
-    CBlockLocator GetLocator(const CBlockIndex *pindex = nullptr) const;
+    CBlockLocator GetLocator(const CBlockIndex* pindex = nullptr) const;
 
     /** Find the last common block between this chain and a block index entry. */
-    const CBlockIndex *FindFork(const CBlockIndex *pindex) const;
+    const CBlockIndex* FindFork(const CBlockIndex* pindex) const;
 
     /** Find the earliest block with timestamp equal or greater than the given time and height equal or greater than the given height. */
     CBlockIndex* FindEarliestAtLeast(int64_t nTime, int height) const;