mine: count sigops while selecting, not only when validating

CheckBlock() caps a block at MAX_BLOCK_SIGOPS and neither assembler counted
against it. Bytes do not bound what a block costs to verify: every OP_CHECKSIG
is an elliptic-curve verification, so a template comfortably inside the size
budget can still be one the network refuses for demanding more work than a
block is allowed to.

Counted with CTransaction::GetSigOpCount -- the same function CheckBlock()
sums, not a second implementation of it -- and seeded from the coinbase,
because CheckBlock() sums over all of vtx. The comparison matches too:
CheckBlock() fails on `> MAX_BLOCK_SIGOPS`, so a block exactly on the limit is
valid and selection accepts it. Assembly and validation differing by one is
the shape of the bug this series started with.

Unlike the size budget this takes no margin. There is no use for headroom in a
sigop count, so assembly holds itself to the consensus number exactly.

Assembly only; MAX_BLOCK_SIGOPS and the CheckBlock() test are unchanged.

1 files changed, 16 insertions, 3 deletions

diff --git a/src/main.cpp b/src/main.cpp
index 64eb290..4d8031d 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -4492,6 +4492,17 @@ bool BitcoinMiner(int nThreadId)
             // coinbase -- because CheckBlock() weighs the whole serialized
             // block and not just the transactions we chose to add to it.
             unsigned int nBlockSize = ::GetSerializeSize(*pblock, SER_DISK);
+            // Sigops are a budget too, and CheckBlock() enforces one that no
+            // assembler here counted against. Bytes do not bound validation
+            // cost: every OP_CHECKSIG is an elliptic-curve verification, so a
+            // template well inside the size limit can still be refused for
+            // demanding more work than a block is allowed to. Counted with
+            // CTransaction::GetSigOpCount, the function CheckBlock() itself
+            // sums, so the two cannot disagree about what a transaction costs.
+            //
+            // Seeded from the coinbase because CheckBlock() sums over all of
+            // vtx, coinbase included.
+            unsigned int nBlockSigOps = pblock->vtx[0].GetSigOpCount();
             while (fFoundSomething && nBlockSize < MAX_BLOCK_SIZE_GEN)
             {
                 fFoundSomething = false;
@@ -4522,8 +4533,9 @@ bool BitcoinMiner(int nThreadId)
                     // transaction would credit the coinbase for a fee no
                     // transaction in the block pays, and the block would be
                     // rejected for a wholly different reason.
-                    unsigned int nTxSize = ::GetSerializeSize(tx, SER_NETWORK);
-                    if (!BlockTemplateFits(nBlockSize, nTxSize))
+                    unsigned int nTxSize   = ::GetSerializeSize(tx, SER_NETWORK);
+                    unsigned int nTxSigOps = tx.GetSigOpCount();
+                    if (!BlockTemplateFits(nBlockSize, nBlockSigOps, nTxSize, nTxSigOps))
                         continue;
 
                     // Transaction fee requirements, mainly only needed for flood control
@@ -4537,7 +4549,8 @@ bool BitcoinMiner(int nThreadId)
                     swap(mapTestPool, mapTestPoolTmp);
 
                     pblock->vtx.push_back(tx);
-                    nBlockSize += nTxSize;
+                    nBlockSize   += nTxSize;
+                    nBlockSigOps += nTxSigOps;
                     vfAlreadyAdded[n] = true;
                     fFoundSomething = true;
                 }