From ad04d1cb35b9612d36078c62213bdbb13f56d73d Mon Sep 17 00:00:00 2001
From: Pieter Wuille <pieter.wuille@gmail.com>
Date: Fri, 18 Nov 2016 12:15:01 -0800
Subject: [PATCH] Always add default_witness_commitment with GBT client support

---
 src/main.cpp             | 9 +--------
 src/rpc/mining.cpp       | 4 +++-
 src/test/miner_tests.cpp | 1 +
 3 files changed, 5 insertions(+), 9 deletions(-)

diff --git a/src/main.cpp b/src/main.cpp
index 4293a6beb..56a510384 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -3531,15 +3531,8 @@ std::vector<unsigned char> GenerateCoinbaseCommitment(CBlock& block, const CBloc
 {
     std::vector<unsigned char> commitment;
     int commitpos = GetWitnessCommitmentIndex(block);
-    bool fHaveWitness = false;
-    for (size_t t = 1; t < block.vtx.size(); t++) {
-        if (!block.vtx[t]->wit.IsNull()) {
-            fHaveWitness = true;
-            break;
-        }
-    }
     std::vector<unsigned char> ret(32, 0x00);
-    if (fHaveWitness && IsWitnessEnabled(pindexPrev, consensusParams)) {
+    if (consensusParams.vDeployments[Consensus::DEPLOYMENT_SEGWIT].nTimeout != 0) {
         if (commitpos == -1) {
             uint256 witnessroot = BlockWitnessMerkleRoot(block, NULL);
             CHash256().Write(witnessroot.begin(), 32).Write(&ret[0], 32).Finalize(witnessroot.begin());
diff --git a/src/rpc/mining.cpp b/src/rpc/mining.cpp
index 6b0e52a30..f3cd1fbf0 100644
--- a/src/rpc/mining.cpp
+++ b/src/rpc/mining.cpp
@@ -680,7 +680,9 @@ UniValue getblocktemplate(const JSONRPCRequest& request)
     result.push_back(Pair("curtime", pblock->GetBlockTime()));
     result.push_back(Pair("bits", strprintf("%08x", pblock->nBits)));
     result.push_back(Pair("height", (int64_t)(pindexPrev->nHeight+1)));
-    if (!pblocktemplate->vchCoinbaseCommitment.empty()) {
+
+    const struct BIP9DeploymentInfo& segwit_info = VersionBitsDeploymentInfo[Consensus::DEPLOYMENT_SEGWIT];
+    if (!pblocktemplate->vchCoinbaseCommitment.empty() && setClientRules.find(segwit_info.name) != setClientRules.end()) {
         result.push_back(Pair("default_witness_commitment", HexStr(pblocktemplate->vchCoinbaseCommitment.begin(), pblocktemplate->vchCoinbaseCommitment.end())));
     }
 
diff --git a/src/test/miner_tests.cpp b/src/test/miner_tests.cpp
index aea892093..85a2e907c 100644
--- a/src/test/miner_tests.cpp
+++ b/src/test/miner_tests.cpp
@@ -214,6 +214,7 @@ BOOST_AUTO_TEST_CASE(CreateNewBlock_validity)
         txCoinbase.vin[0].scriptSig = CScript();
         txCoinbase.vin[0].scriptSig.push_back(blockinfo[i].extranonce);
         txCoinbase.vin[0].scriptSig.push_back(chainActive.Height());
+        txCoinbase.vout.resize(1); // Ignore the (optional) segwit commitment added by CreateNewBlock (as the hardcoded nonces don't account for this)
         txCoinbase.vout[0].scriptPubKey = CScript();
         pblock->vtx[0] = MakeTransactionRef(std::move(txCoinbase));
         if (txFirst.size() == 0)