miner: Avoid stack-use-after-return in validationinterface

This is achieved by switching to a shared_ptr.

Also, switch the validationinterfaces in the tests to use shared_ptrs
for the same reason.

Author: MarcoFalke

src/rpc/mining.cpp

@@ -874,7 +874,7 @@ static UniValue getblocktemplate(const JSONRPCRequest& request)
     return result;
 }
 
-class submitblock_StateCatcher : public CValidationInterface
+class submitblock_StateCatcher final : public CValidationInterface
 {
 public:
     uint256 hash;
@@ -942,17 +942,17 @@ static UniValue submitblock(const JSONRPCRequest& request)
     }
 
     bool new_block;
-    submitblock_StateCatcher sc(block.GetHash());
-    RegisterValidationInterface(&sc);
+    auto sc = std::make_shared<submitblock_StateCatcher>(block.GetHash());
+    RegisterSharedValidationInterface(sc);
     bool accepted = ProcessNewBlock(Params(), blockptr, /* fForceProcessing */ true, /* fNewBlock */ &new_block);
-    UnregisterValidationInterface(&sc);
+    UnregisterSharedValidationInterface(sc);
     if (!new_block && accepted) {
         return "duplicate";
     }
-    if (!sc.found) {
+    if (!sc->found) {
         return "inconclusive";
     }
-    return BIP22ValidationResult(sc.state);
+    return BIP22ValidationResult(sc->state);
 }
 
 static UniValue submitheader(const JSONRPCRequest& request)

src/test/validation_block_tests.cpp

@@ -32,7 +32,7 @@ struct MinerTestingSetup : public RegTestingSetup {
 
 BOOST_FIXTURE_TEST_SUITE(validation_block_tests, MinerTestingSetup)
 
-struct TestSubscriber : public CValidationInterface {
+struct TestSubscriber final : public CValidationInterface {
     uint256 m_expected_tip;
 
     explicit TestSubscriber(uint256 tip) : m_expected_tip(tip) {}
@@ -175,8 +175,8 @@ BOOST_AUTO_TEST_CASE(processnewblock_signals_ordering)
         LOCK(cs_main);
         initial_tip = ::ChainActive().Tip();
     }
-    TestSubscriber sub(initial_tip->GetBlockHash());
-    RegisterValidationInterface(&sub);
+    auto sub = std::make_shared<TestSubscriber>(initial_tip->GetBlockHash());
+    RegisterSharedValidationInterface(sub);
 
     // create a bunch of threads that repeatedly process a block generated above at random
     // this will create parallelism and randomness inside validation - the ValidationInterface
@@ -206,10 +206,10 @@ BOOST_AUTO_TEST_CASE(processnewblock_signals_ordering)
     }
     SyncWithValidationInterfaceQueue();
 
-    UnregisterValidationInterface(&sub);
+    UnregisterSharedValidationInterface(sub);
 
     LOCK(cs_main);
-    BOOST_CHECK_EQUAL(sub.m_expected_tip, ::ChainActive().Tip()->GetBlockHash());
+    BOOST_CHECK_EQUAL(sub->m_expected_tip, ::ChainActive().Tip()->GetBlockHash());
 }
 
 /**

src/test/validationinterface_tests.cpp

@@ -12,7 +12,6 @@
 
 BOOST_FIXTURE_TEST_SUITE(validationinterface_tests, TestingSetup)
 
-/**
 struct TestSubscriberNoop final : public CValidationInterface {
     void BlockChecked(const CBlock&, const BlockValidationState&) override {}
 };
@@ -34,9 +33,9 @@ BOOST_AUTO_TEST_CASE(unregister_validation_interface_race)
     std::thread sub{[&] {
         // keep going for about 1 sec, which is 250k iterations
         for (int i = 0; i < 250000; i++) {
-            TestSubscriberNoop sub{};
-            RegisterValidationInterface(&sub);
-            UnregisterValidationInterface(&sub);
+            auto sub = std::make_shared<TestSubscriberNoop>();
+            RegisterSharedValidationInterface(sub);
+            UnregisterSharedValidationInterface(sub);
         }
         // tell the other thread we are done
         generate = false;
@@ -46,7 +45,6 @@ BOOST_AUTO_TEST_CASE(unregister_validation_interface_race)
     sub.join();
     BOOST_CHECK(!generate);
 }
-*/
 
 class TestInterface : public CValidationInterface
 {