coinstats: Return purely out-param CCoinsStats

In previous commits in this patchset, we removed all in-param members of
CCoinsStats. Now that that's done, we can modify GetUTXOStats to return
an optional CCoinsStats instead of a status bool. Callers are modified
accordingly.

In rpc/blockchain.cpp, we discover that GetUTXOStats' status bool when
getting UTXO stats for pprev was not checked for error. We fix this as
well.

1 files changed, 4 insertions, 4 deletions

diff --git a/src/validation.cpp b/src/validation.cpp
index 5fdf0398df..40c2618db9 100644
--- a/src/validation.cpp
+++ b/src/validation.cpp
@@ -5095,22 +5095,22 @@ bool ChainstateManager::PopulateAndValidateSnapshot(
 
     assert(coins_cache.GetBestBlock() == base_blockhash);
 
-    CCoinsStats stats{};
     auto breakpoint_fnc = [] { /* TODO insert breakpoint here? */ };
 
     // As above, okay to immediately release cs_main here since no other context knows
     // about the snapshot_chainstate.
     CCoinsViewDB* snapshot_coinsdb = WITH_LOCK(::cs_main, return &snapshot_chainstate.CoinsDB());
 
-    if (!GetUTXOStats(snapshot_coinsdb, m_blockman, stats, CoinStatsHashType::HASH_SERIALIZED, breakpoint_fnc)) {
+    const std::optional<CCoinsStats> maybe_stats = GetUTXOStats(snapshot_coinsdb, m_blockman, CoinStatsHashType::HASH_SERIALIZED, breakpoint_fnc);
+    if (!maybe_stats.has_value()) {
         LogPrintf("[snapshot] failed to generate coins stats\n");
         return false;
     }
 
     // Assert that the deserialized chainstate contents match the expected assumeutxo value.
-    if (AssumeutxoHash{stats.hashSerialized} != au_data.hash_serialized) {
+    if (AssumeutxoHash{maybe_stats->hashSerialized} != au_data.hash_serialized) {
         LogPrintf("[snapshot] bad snapshot content hash: expected %s, got %s\n",
-            au_data.hash_serialized.ToString(), stats.hashSerialized.ToString());
+            au_data.hash_serialized.ToString(), maybe_stats->hashSerialized.ToString());
         return false;
     }