Merge #13063: Use shared pointer to retain wallet instance

80b4910f7d87983f50047074c3c2397b0a5c4e92 wallet: Use shared pointer to retain wallet instance (João Barbosa)

Pull request description:

  Currently there are 3 places where it makes sense to retain a wallet shared pointer:
   - `vpwallets`;
   - `interfaces::Wallet` interface instance - used by the UI;
   - wallet RPC functions - given by `GetWalletForJSONRPCRequest`.

  The way it is now it is possible to have, for instance, listunspent RPC and in parallel unload the wallet (once #13111 is merged) without blocking. Once the RPC finishes, the shared pointer will release the wallet.

  It is also possible to get all existing wallets without blocking because the caller keeps a local list of shared pointers.

  This is mostly relevant for wallet unloading.

  This PR replaces #11402.

Tree-SHA512: b7e37c7e1ab56626085afe2d40b1628e8d4f0dbda08df01b7e618ecd2d894ce9b83d4219443f444ba889096286eff002f163cb0a48f37063b62e9ba4ccfa6cce

3 files changed, 7 insertions, 6 deletions

diff --git a/src/interfaces/node.cpp b/src/interfaces/node.cpp
index 73657d4f5..927035117 100644
--- a/src/interfaces/node.cpp
+++ b/src/interfaces/node.cpp
@@ -222,8 +222,8 @@ class NodeImpl : public Node
     {
 #ifdef ENABLE_WALLET
         std::vector<std::unique_ptr<Wallet>> wallets;
-        for (CWallet* wallet : GetWallets()) {
-            wallets.emplace_back(MakeWallet(*wallet));
+        for (const std::shared_ptr<CWallet>& wallet : GetWallets()) {
+            wallets.emplace_back(MakeWallet(wallet));
         }
         return wallets;
 #else
@@ -249,7 +249,7 @@ class NodeImpl : public Node
     std::unique_ptr<Handler> handleLoadWallet(LoadWalletFn fn) override
     {
         CHECK_WALLET(
-            return MakeHandler(::uiInterface.LoadWallet.connect([fn](CWallet* wallet) { fn(MakeWallet(*wallet)); })));
+            return MakeHandler(::uiInterface.LoadWallet.connect([fn](std::shared_ptr<CWallet> wallet) { fn(MakeWallet(wallet)); })));
     }
     std::unique_ptr<Handler> handleNotifyNumConnectionsChanged(NotifyNumConnectionsChangedFn fn) override
     {
diff --git a/src/interfaces/wallet.cpp b/src/interfaces/wallet.cpp
index 63b9d80a9..3029dbe8e 100644
--- a/src/interfaces/wallet.cpp
+++ b/src/interfaces/wallet.cpp
@@ -118,7 +118,7 @@ WalletTxOut MakeWalletTxOut(CWallet& wallet, const CWalletTx& wtx, int n, int de
 class WalletImpl : public Wallet
 {
 public:
-    WalletImpl(CWallet& wallet) : m_wallet(wallet) {}
+    WalletImpl(const std::shared_ptr<CWallet>& wallet) : m_shared_wallet(wallet), m_wallet(*wallet.get()) {}
 
     bool encryptWallet(const SecureString& wallet_passphrase) override
     {
@@ -453,11 +453,12 @@ public:
         return MakeHandler(m_wallet.NotifyWatchonlyChanged.connect(fn));
     }
 
+    std::shared_ptr<CWallet> m_shared_wallet;
     CWallet& m_wallet;
 };
 
 } // namespace
 
-std::unique_ptr<Wallet> MakeWallet(CWallet& wallet) { return MakeUnique<WalletImpl>(wallet); }
+std::unique_ptr<Wallet> MakeWallet(const std::shared_ptr<CWallet>& wallet) { return MakeUnique<WalletImpl>(wallet); }
 
 } // namespace interfaces
diff --git a/src/interfaces/wallet.h b/src/interfaces/wallet.h
index ff779cd0a..82ae0b14b 100644
--- a/src/interfaces/wallet.h
+++ b/src/interfaces/wallet.h
@@ -363,7 +363,7 @@ struct WalletTxOut
 
 //! Return implementation of Wallet interface. This function will be undefined
 //! in builds where ENABLE_WALLET is false.
-std::unique_ptr<Wallet> MakeWallet(CWallet& wallet);
+std::unique_ptr<Wallet> MakeWallet(const std::shared_ptr<CWallet>& wallet);
 
 } // namespace interfaces