Merge #16355: refactor: move CCoinsViewErrorCatcher out of init.cpp

4f050b91c7 move-onlyish: move CCoinsViewErrorCatcher out of init.cpp (James O'Beirne)

Pull request description:

  This is part of the [assumeutxo project](https://github.com/bitcoin/bitcoin/projects/11):

  Parent PR: #15606
  Issue: #15605
  Specification: https://github.com/jamesob/assumeutxo-docs/tree/2019-04-proposal/proposal

  ---

  This change moves `CCoinsViewErrorCatcher` out of `init` and into `coins` so that it can later be included in [a `CoinsView` instance](91284964ef (diff-349fbb003d5ae550a2e8fa658e475880R504)) under `CChainState`.

  Instead of hardcoding read failure behavior that has knowledge of qt, it accepts error callbacks via `AddReadErrCallback()`.

ACKs for top commit:
  dongcarl:
    re-ACK 4f050b91c7
  ryanofsky:
    utACK 4f050b91c7. Only change since last review is fixing const.

Tree-SHA512: eaba21606d15d2b8d0e3db7cec57779ce181af953db1ef4af80a0bc1dfb57923d0befde9d61b7be55c32224744f7fb6bd47d4e4c72f3ccfe6eaf0f4ae3765c17

src/init.cpp

@@ -15,6 +15,7 @@
 #include <blockfilter.h>
 #include <chain.h>
 #include <chainparams.h>
+#include <coins.h>
 #include <compat/sanity.h>
 #include <consensus/validation.h>
 #include <fs.h>
@@ -146,31 +147,6 @@ NODISCARD static bool CreatePidFile()
 // shutdown thing.
 //
 
-/**
- * This is a minimally invasive approach to shutdown on LevelDB read errors from the
- * chainstate, while keeping user interface out of the common library, which is shared
- * between bitcoind, and bitcoin-qt and non-server tools.
-*/
-class CCoinsViewErrorCatcher final : public CCoinsViewBacked
-{
-public:
-    explicit CCoinsViewErrorCatcher(CCoinsView* view) : CCoinsViewBacked(view) {}
-    bool GetCoin(const COutPoint &outpoint, Coin &coin) const override {
-        try {
-            return CCoinsViewBacked::GetCoin(outpoint, coin);
-        } catch(const std::runtime_error& e) {
-            uiInterface.ThreadSafeMessageBox(_("Error reading from database, shutting down."), "", CClientUIInterface::MSG_ERROR);
-            LogPrintf("Error reading from database: %s\n", e.what());
-            // Starting the shutdown sequence and returning false to the caller would be
-            // interpreted as 'entry not found' (as opposed to unable to read data), and
-            // could lead to invalid interpretation. Just exit immediately, as we can't
-            // continue anyway, and all writes should be atomic.
-            abort();
-        }
-    }
-    // Writes do not need similar protection, as failure to write is handled by the caller.
-};
-
 static std::unique_ptr<CCoinsViewErrorCatcher> pcoinscatcher;
 static std::unique_ptr<ECCVerifyHandle> globalVerifyHandle;
 
@@ -1544,6 +1520,11 @@ bool AppInitMain(InitInterfaces& interfaces)
 
                 pcoinsdbview.reset(new CCoinsViewDB(nCoinDBCache, false, fReset || fReindexChainState));
                 pcoinscatcher.reset(new CCoinsViewErrorCatcher(pcoinsdbview.get()));
+                pcoinscatcher->AddReadErrCallback([]() {
+                    uiInterface.ThreadSafeMessageBox(
+                        _("Error reading from database, shutting down."),
+                        "", CClientUIInterface::MSG_ERROR);
+                });
 
                 // If necessary, upgrade from older database format.
                 // This is a no-op if we cleared the coinsviewdb with -reindex or -reindex-chainstate