validation: make CChainState::m_mempool optional

Since we now have multiple chainstate objects, only one of them is active at any given
time. An active chainstate has a mempool, but there's no point to others having one.

This change will simplify proposed assumeutxo semantics. See the discussion here:
https://github.com/bitcoin/bitcoin/pull/15606#pullrequestreview-692965905

Co-authored-by: Russell Yanofsky <russ@yanofsky.org>

4 files changed, 7 insertions, 7 deletions

diff --git a/src/test/util/setup_common.cpp b/src/test/util/setup_common.cpp
index 748272bb1d..d9d236be1d 100644
--- a/src/test/util/setup_common.cpp
+++ b/src/test/util/setup_common.cpp
@@ -180,7 +180,7 @@ TestingSetup::TestingSetup(const std::string& chainName, const std::vector<const
     // instead of unit tests, but for now we need these here.
     RegisterAllCoreRPCCommands(tableRPC);
 
-    m_node.chainman->InitializeChainstate(*m_node.mempool);
+    m_node.chainman->InitializeChainstate(m_node.mempool.get());
     m_node.chainman->ActiveChainstate().InitCoinsDB(
         /* cache_size_bytes */ 1 << 23, /* in_memory */ true, /* should_wipe */ false);
     assert(!m_node.chainman->ActiveChainstate().CanFlushToDisk());
diff --git a/src/test/validation_chainstate_tests.cpp b/src/test/validation_chainstate_tests.cpp
index 92d8cf2e7d..2893b412fb 100644
--- a/src/test/validation_chainstate_tests.cpp
+++ b/src/test/validation_chainstate_tests.cpp
@@ -35,7 +35,7 @@ BOOST_AUTO_TEST_CASE(validation_chainstate_resize_caches)
         return outp;
     };
 
-    CChainState& c1 = WITH_LOCK(cs_main, return manager.InitializeChainstate(mempool));
+    CChainState& c1 = WITH_LOCK(cs_main, return manager.InitializeChainstate(&mempool));
     c1.InitCoinsDB(
         /* cache_size_bytes */ 1 << 23, /* in_memory */ true, /* should_wipe */ false);
     WITH_LOCK(::cs_main, c1.InitCoinsCache(1 << 23));
diff --git a/src/test/validation_chainstatemanager_tests.cpp b/src/test/validation_chainstatemanager_tests.cpp
index 7c1db9d4b9..0bd378631b 100644
--- a/src/test/validation_chainstatemanager_tests.cpp
+++ b/src/test/validation_chainstatemanager_tests.cpp
@@ -36,7 +36,7 @@ BOOST_AUTO_TEST_CASE(chainstatemanager)
 
     // Create a legacy (IBD) chainstate.
     //
-    CChainState& c1 = WITH_LOCK(::cs_main, return manager.InitializeChainstate(mempool));
+    CChainState& c1 = WITH_LOCK(::cs_main, return manager.InitializeChainstate(&mempool));
     chainstates.push_back(&c1);
     c1.InitCoinsDB(
         /* cache_size_bytes */ 1 << 23, /* in_memory */ true, /* should_wipe */ false);
@@ -66,7 +66,7 @@ BOOST_AUTO_TEST_CASE(chainstatemanager)
     //
     const uint256 snapshot_blockhash = GetRandHash();
     CChainState& c2 = WITH_LOCK(::cs_main, return manager.InitializeChainstate(
-        mempool, snapshot_blockhash));
+        &mempool, snapshot_blockhash));
     chainstates.push_back(&c2);
 
     BOOST_CHECK_EQUAL(manager.SnapshotBlockhash().value(), snapshot_blockhash);
@@ -129,7 +129,7 @@ BOOST_AUTO_TEST_CASE(chainstatemanager_rebalance_caches)
 
     // Create a legacy (IBD) chainstate.
     //
-    CChainState& c1 = WITH_LOCK(cs_main, return manager.InitializeChainstate(mempool));
+    CChainState& c1 = WITH_LOCK(cs_main, return manager.InitializeChainstate(&mempool));
     chainstates.push_back(&c1);
     c1.InitCoinsDB(
         /* cache_size_bytes */ 1 << 23, /* in_memory */ true, /* should_wipe */ false);
@@ -147,7 +147,7 @@ BOOST_AUTO_TEST_CASE(chainstatemanager_rebalance_caches)
 
     // Create a snapshot-based chainstate.
     //
-    CChainState& c2 = WITH_LOCK(cs_main, return manager.InitializeChainstate(mempool, GetRandHash()));
+    CChainState& c2 = WITH_LOCK(cs_main, return manager.InitializeChainstate(&mempool, GetRandHash()));
     chainstates.push_back(&c2);
     c2.InitCoinsDB(
         /* cache_size_bytes */ 1 << 23, /* in_memory */ true, /* should_wipe */ false);
diff --git a/src/test/validation_flush_tests.cpp b/src/test/validation_flush_tests.cpp
index a3b344d2c9..2572e2025b 100644
--- a/src/test/validation_flush_tests.cpp
+++ b/src/test/validation_flush_tests.cpp
@@ -20,7 +20,7 @@ BOOST_AUTO_TEST_CASE(getcoinscachesizestate)
 {
     CTxMemPool mempool;
     BlockManager blockman{};
-    CChainState chainstate{mempool, blockman};
+    CChainState chainstate{&mempool, blockman};
     chainstate.InitCoinsDB(/*cache_size_bytes*/ 1 << 10, /*in_memory*/ true, /*should_wipe*/ false);
     WITH_LOCK(::cs_main, chainstate.InitCoinsCache(1 << 10));
     CTxMemPool tx_pool{};