fix: Check Fee-Free Division by Zero in AMMWithdraw singleWithdrawEPrice (#6989)

src/test/app/AMM_test.cpp

@@ -2229,6 +2229,31 @@ private:
             ammAlice.withdraw(alice_, XRPAmount{9'999'999'999});
             BEAST_EXPECT(ammAlice.expectBalances(XRPAmount{1}, USD(10'000), IOUAmount{100}));
         });
+
+        // singleWithdrawEPrice: crafted ePrice = lptAMMBalance*f/amountBalance
+        // makes the denominator (T*f - A*E) exactly zero.
+        // Pre-fixCleanup3_3_0: std::overflow_error escapes to the
+        // transactor backstop and is returned as tefEXCEPTION.
+        // Post-fixCleanup3_3_0: denominator check returns tecAMM_FAILED.
+        //
+        // Pool: USD(100)/EUR(100), baseFee=1000 (1%).
+        // Alice is the creator so her discounted fee is 100 (0.1%), f=0.001.
+        // ePrice = lptAMMBalance(100) * f(0.001) / amountBalance(100) = 0.001
+        testAMM(
+            [&](AMM& ammAlice, Env& env) {
+                auto const err =
+                    env.enabled(fixCleanup3_3_0) ? Ter(tecAMM_FAILED) : Ter(tefEXCEPTION);
+                ammAlice.withdraw(
+                    WithdrawArg{
+                        .account = alice_,
+                        .asset1Out = USD(0),
+                        .maxEP = IOUAmount{1, -3},  // ePrice=0.001 → denom=0
+                        .err = err});
+            },
+            {{USD(100), EUR(100)}},
+            1000,
+            std::nullopt,
+            {all - fixCleanup3_3_0, all});
     }
 
     void