From 795928af79215670c9ee17733ef8c119ff0f805f Mon Sep 17 00:00:00 2001
From: Olek <115580134+oleks-rip@users.noreply.github.com>
Date: Fri, 21 Nov 2025 17:20:45 -0500
Subject: [PATCH] Fix: nullptr resolving without db config (#6029)

If the config disables SQL db usage, such as a validator:

```
[ledger_tx_tables]
use_tx_tables = 0
```

then the pointer to DB engine is null, but it was still resolved during startup. Although it didn't crash in Release mode, possibly due to the compiler optimizing it away, it did crash in Debug mode. This change explicitly checks for the validity of the pointer and generates a runtime error if not set.
---
 src/xrpld/app/rdb/backend/detail/Node.cpp           | 12 ++++++++++--
 src/xrpld/app/rdb/backend/detail/Node.h             |  2 +-
 src/xrpld/app/rdb/backend/detail/SQLiteDatabase.cpp |  3 +--
 3 files changed, 12 insertions(+), 5 deletions(-)

diff --git a/src/xrpld/app/rdb/backend/detail/Node.cpp b/src/xrpld/app/rdb/backend/detail/Node.cpp
index 88f11a272b..6e62d5ba6e 100644
--- a/src/xrpld/app/rdb/backend/detail/Node.cpp
+++ b/src/xrpld/app/rdb/backend/detail/Node.cpp
@@ -190,7 +190,7 @@ getRowsMinMax(soci::session& session, TableType type)
 bool
 saveValidatedLedger(
     DatabaseCon& ldgDB,
-    DatabaseCon& txnDB,
+    std::unique_ptr<DatabaseCon> const& txnDB,
     Application& app,
     std::shared_ptr<Ledger const> const& ledger,
     bool current)
@@ -273,7 +273,15 @@ saveValidatedLedger(
 
         if (app.config().useTxTables())
         {
-            auto db = txnDB.checkoutDb();
+            if (!txnDB)
+            {
+                // LCOV_EXCL_START
+                JLOG(j.fatal()) << "TxTables db isn't available";
+                Throw<std::runtime_error>("TxTables db isn't available");
+                // LCOV_EXCL_STOP
+            }
+
+            auto db = txnDB->checkoutDb();
 
             soci::transaction tr(*db);
 
diff --git a/src/xrpld/app/rdb/backend/detail/Node.h b/src/xrpld/app/rdb/backend/detail/Node.h
index 0e8c678be5..39bd2b563d 100644
--- a/src/xrpld/app/rdb/backend/detail/Node.h
+++ b/src/xrpld/app/rdb/backend/detail/Node.h
@@ -130,7 +130,7 @@ getRowsMinMax(soci::session& session, TableType type);
 bool
 saveValidatedLedger(
     DatabaseCon& ldgDB,
-    DatabaseCon& txnDB,
+    std::unique_ptr<DatabaseCon> const& txnDB,
     Application& app,
     std::shared_ptr<Ledger const> const& ledger,
     bool current);
diff --git a/src/xrpld/app/rdb/backend/detail/SQLiteDatabase.cpp b/src/xrpld/app/rdb/backend/detail/SQLiteDatabase.cpp
index edd1fb2174..8d44665569 100644
--- a/src/xrpld/app/rdb/backend/detail/SQLiteDatabase.cpp
+++ b/src/xrpld/app/rdb/backend/detail/SQLiteDatabase.cpp
@@ -411,8 +411,7 @@ SQLiteDatabaseImp::saveValidatedLedger(
 {
     if (existsLedger())
     {
-        if (!detail::saveValidatedLedger(
-                *lgrdb_, *txdb_, app_, ledger, current))
+        if (!detail::saveValidatedLedger(*lgrdb_, txdb_, app_, ledger, current))
             return false;
     }