[WIP] Checkpoint

src/libxrpl/basics/Number.cpp

@@ -222,9 +222,12 @@ Number::Guard::bringIntoRange(
     {
         mantissa *= 10;
         --exponent;
+        std::cout << "bringIntoRange. mantissa*=10: " << mantissa << ", exponent: " << exponent
+                  << std::endl;
     }
     if (exponent < minExponent)
     {
+        std::cout << "bringIntoRange. zero\n";
         constexpr Number zero = Number{};
 
         negative = zero.negative_;
@@ -246,13 +249,50 @@ Number::Guard::doRoundUp(
     auto r = round();
     if (r == 1 || (r == 0 && (mantissa & 1) == 1))
     {
-        ++mantissa;
-        // Ensure mantissa after incrementing fits within both the
-        // min/maxMantissa range and is a valid "rep".
-        if (mantissa > maxMantissa || mantissa > maxRep)
+        std::cout << "doRoundUp. r: " << r << std::endl;
+        if (isFeatureEnabled(fixCleanup3_2_0) || !getCurrentTransactionRules())
         {
-            mantissa /= 10;
-            ++exponent;
+            // Ensure mantissa after incrementing fits within both the
+            // min/maxMantissa range and is a valid "rep".
+            if (mantissa < maxMantissa && mantissa < maxRep)
+            {
+                // Nothing unusual here, just increment the mantissa
+                ++mantissa;
+                std::cout << "\tmantissa++: " << mantissa << std::endl;
+            }
+            else
+            {
+                // Incrementing the mantissa will require dividing, which will require rounding. So
+                // _don't_ increment the mantissa. Instead, divide and round recursively. It should
+                // be impossible to recurse more than once, because once the mantissa is divided by
+                // 10, it will be _well_ under maxMantissa and maxRep, so adding 1 will have no
+                // change of bringing it back over.
+                push(mantissa % 10);
+                mantissa /= 10;
+                ++exponent;
+                XRPL_ASSERT_PARTS(
+                    mantissa < maxMantissa && mantissa < maxRep,
+                    "xrpl::Number::Guard::doRoundUp",
+                    "can't recurse more than once");
+                std::cout << "\tmantissa/=10: " << mantissa << ", exponent: " << exponent
+                          << std::endl;
+                // Here be dragons
+                doRoundUp(negative, mantissa, exponent, minMantissa, maxMantissa, location);
+                return;
+            }
+        }
+        else
+        {
+            // Need to preserve the incorrect behavior until the fix amendment can be retired,
+            // because otherwise would risk an unplanned ledger fork.
+            ++mantissa;
+            // Ensure mantissa after incrementing fits within both the
+            // min/maxMantissa range and is a valid "rep".
+            if (mantissa > maxMantissa || mantissa > maxRep)
+            {
+                mantissa /= 10;
+                ++exponent;
+            }
         }
     }
     bringIntoRange(negative, mantissa, exponent, minMantissa);
@@ -667,6 +707,8 @@ Number::operator*=(Number const& y)
     auto const& minMantissa = range.min;
     auto const& maxMantissa = range.max;
 
+    std::cout << "zn: " << zn << ", zm: " << zm << ", ze: " << ze << std::endl;
+
     while (zm > maxMantissa || zm > maxRep)
     {
         // The following is optimization for:
@@ -675,6 +717,9 @@ Number::operator*=(Number const& y)
         g.push(divu10(zm));
         ++ze;
     }
+
+    std::cout << "zn: " << zn << ", zm: " << zm << ", ze: " << ze << std::endl;
+
     xm = static_cast<internalrep>(zm);
     xe = ze;
     g.doRoundUp(
@@ -787,8 +832,7 @@ Number::operator/=(Number const& y)
     return *this;
 }
 
-Number::
-operator rep() const
+Number::operator rep() const
 {
     rep drops = mantissa();
     int offset = exponent();

src/libxrpl/ledger/helpers/LendingHelpers.cpp

@@ -1857,18 +1857,8 @@ loanMakePayment(
 
     // -------------------------------------------------------------
     // overpayment handling
-    //
-    // If the "fixSecurity3_1_3" amendment is enabled, truncate "amount",
-    // at the loan scale. If the raw value is used, the overpayment
-    // amount could be meaningless dust. Trying to process such a small
-    // amount will, at best, waste time when all the result values round
-    // to zero. At worst, it can cause logical errors with tiny amounts
-    // of interest that don't add up correctly.
-    auto const roundedAmount = view.rules().enabled(fixSecurity3_1_3)
-        ? roundToAsset(asset, amount, loanScale, Number::towards_zero)
-        : amount;
     if (paymentType == LoanPaymentType::overpayment && loan->isFlag(lsfLoanOverpayment) &&
-        paymentRemainingProxy > 0 && totalPaid < roundedAmount &&
+        paymentRemainingProxy > 0 && totalPaid < amount &&
         numPayments < loanMaximumPaymentsPerTransaction)
     {
         TenthBips32 const overpaymentInterestRate{loan->at(sfOverpaymentInterestRate)};
@@ -1877,7 +1867,7 @@ loanMakePayment(
         // It shouldn't be possible for the overpayment to be greater than
         // totalValueOutstanding, because that would have been processed as
         // another normal payment. But cap it just in case.
-        Number const overpayment = std::min(roundedAmount - totalPaid, *totalValueOutstandingProxy);
+        Number const overpayment = std::min(amount - totalPaid, *totalValueOutstandingProxy);
 
         detail::ExtendedPaymentComponents const overpaymentComponents =
             detail::computeOverpaymentComponents(

src/libxrpl/tx/transactors/lending/LoanPay.cpp

@@ -30,7 +30,6 @@
 #include <bit>
 #include <cstdint>
 #include <memory>
-#include <vector>
 
 namespace xrpl {
 
@@ -144,7 +143,6 @@ LoanPay::calculateBaseFee(ReadView const& view, STTx const& tx)
     Number const numPaymentEstimate = static_cast<std::int64_t>(amount / regularPayment);
 
     // Charge one base fee per paymentsPerFeeIncrement payments, rounding up.
-    // This set round is safe because there's a mode guard just above
     Number::setround(Number::upward);
     auto const feeIncrements = std::max(
         std::int64_t(1),
@@ -442,10 +440,9 @@ LoanPay::doApply()
     // Vault object state changes
     view.update(vaultSle);
 
-    Number const assetsAvailableBefore = *assetsAvailableProxy;
-    Number const assetsTotalBefore = *assetsTotalProxy;
 #if !NDEBUG
     {
+        Number const assetsAvailableBefore = *assetsAvailableProxy;
         Number const pseudoAccountBalanceBefore = accountHolds(
             view,
             vaultPseudoAccount,
@@ -469,6 +466,16 @@ LoanPay::doApply()
         "xrpl::LoanPay::doApply",
         "assets available must not be greater than assets outstanding");
 
+    if (*assetsAvailableProxy > *assetsTotalProxy)
+    {
+        // LCOV_EXCL_START
+        JLOG(j_.fatal()) << "Vault assets available must not be greater "
+                            "than assets outstanding. Available: "
+                         << *assetsAvailableProxy << ", Total: " << *assetsTotalProxy;
+        return tecINTERNAL;
+        // LCOV_EXCL_STOP
+    }
+
     JLOG(j_.debug()) << "total paid to vault raw: " << totalPaidToVaultRaw
                      << ", total paid to vault rounded: " << totalPaidToVaultRounded
                      << ", total paid to broker: " << totalPaidToBroker
@@ -494,68 +501,12 @@ LoanPay::doApply()
     associateAsset(*vaultSle, asset);
 
     // Duplicate some checks after rounding
-    Number const assetsAvailableAfter = *assetsAvailableProxy;
-    Number const assetsTotalAfter = *assetsTotalProxy;
-
     XRPL_ASSERT_PARTS(
-        assetsAvailableAfter <= assetsTotalAfter,
+        *assetsAvailableProxy <= *assetsTotalProxy,
         "xrpl::LoanPay::doApply",
         "assets available must not be greater than assets outstanding");
-    if (assetsAvailableAfter == assetsAvailableBefore)
-    {
-        // An unchanged assetsAvailable indicates that the amount paid to the
-        // vault was zero, or rounded to zero. That should be impossible, but I
-        // can't rule it out for extreme edge cases, so fail gracefully if it
-        // happens.
-        //
-        // LCOV_EXCL_START
-        JLOG(j_.warn()) << "LoanPay: Vault assets available unchanged after rounding: "  //
-                        << "Before: " << assetsAvailableBefore                           //
-                        << ", After: " << assetsAvailableAfter;
-        return tecPRECISION_LOSS;
-        // LCOV_EXCL_STOP
-    }
-    if (paymentParts->valueChange != beast::zero && assetsTotalAfter == assetsTotalBefore)
-    {
-        // Non-zero valueChange with an unchanged assetsTotal indicates that the
-        // actual value change rounded to zero. That should be impossible, but I
-        // can't rule it out for extreme edge cases, so fail gracefully if it
-        // happens.
-        //
-        // LCOV_EXCL_START
-        JLOG(j_.warn())
-            << "LoanPay: Vault assets expected change, but unchanged after rounding: "  //
-            << "Before: " << assetsTotalBefore                                          //
-            << ", After: " << assetsTotalAfter                                          //
-            << ", ValueChange: " << paymentParts->valueChange;
-        return tecPRECISION_LOSS;
-        // LCOV_EXCL_STOP
-    }
-    if (paymentParts->valueChange == beast::zero && assetsTotalAfter != assetsTotalBefore)
-    {
-        // A change in assetsTotal when there was no valueChange indicates that
-        // something really weird happened. That should be flat out impossible.
-        //
-        // LCOV_EXCL_START
-        JLOG(j_.fatal()) << "LoanPay: Vault assets changed unexpectedly after rounding: "  //
-                         << "Before: " << assetsTotalBefore                                //
-                         << ", After: " << assetsTotalAfter                                //
-                         << ", ValueChange: " << paymentParts->valueChange;
-        return tecINTERNAL;
-        // LCOV_EXCL_STOP
-    }
-    if (assetsAvailableAfter > assetsTotalAfter)
-    {
-        // Assets available are not allowed to be larger than assets total.
-        // LCOV_EXCL_START
-        JLOG(j_.fatal()) << "LoanPay: Vault assets available must not be greater "
-                            "than assets outstanding. Available: "
-                         << assetsAvailableAfter << ", Total: " << assetsTotalAfter;
-        return tecINTERNAL;
-        // LCOV_EXCL_STOP
-    }
 
-    // These three values are used to check that funds are conserved after the transfers
+#if !NDEBUG
     auto const accountBalanceBefore = accountHolds(
         view,
         account_,
@@ -584,6 +535,7 @@ LoanPay::doApply()
               ahIGNORE_AUTH,
               j_,
               SpendableHandling::shFULL_BALANCE);
+#endif
 
     if (totalPaidToVaultRounded != beast::zero)
     {
@@ -619,22 +571,19 @@ LoanPay::doApply()
         return ter;
 
 #if !NDEBUG
-    {
-        Number const pseudoAccountBalanceAfter = accountHolds(
-            view,
-            vaultPseudoAccount,
-            asset,
-            FreezeHandling::fhIGNORE_FREEZE,
-            AuthHandling::ahIGNORE_AUTH,
-            j_);
-        XRPL_ASSERT_PARTS(
-            assetsAvailableAfter == pseudoAccountBalanceAfter,
-            "xrpl::LoanPay::doApply",
-            "vault pseudo balance agrees after");
-    }
-#endif
+    Number const assetsAvailableAfter = *assetsAvailableProxy;
+    Number const pseudoAccountBalanceAfter = accountHolds(
+        view,
+        vaultPseudoAccount,
+        asset,
+        FreezeHandling::fhIGNORE_FREEZE,
+        AuthHandling::ahIGNORE_AUTH,
+        j_);
+    XRPL_ASSERT_PARTS(
+        assetsAvailableAfter == pseudoAccountBalanceAfter,
+        "xrpl::LoanPay::doApply",
+        "vault pseudo balance agrees after");
 
-    // Check that funds are conserved
     auto const accountBalanceAfter = accountHolds(
         view,
         account_,
@@ -663,121 +612,14 @@ LoanPay::doApply()
               ahIGNORE_AUTH,
               j_,
               SpendableHandling::shFULL_BALANCE);
-    auto const balanceScale = [&]() {
-        // Find a reasonable scale to use for the balance comparisons.
-        //
-        // First find the minimum and maximum exponent of all the non-zero balances, before and
-        // after. If min and max are equal, use that value. If they are not, use "max + 1" to reduce
-        // rounding discrepancies without making the result meaningless. Cap the scale at
-        // STAmount::cMaxOffset, just in case the numbers are all very large.
-        std::vector<int> exponents;
 
-        for (auto const& a : {
-                 accountBalanceBefore,
-                 vaultBalanceBefore,
-                 brokerBalanceBefore,
-                 accountBalanceAfter,
-                 vaultBalanceAfter,
-                 brokerBalanceAfter,
-             })
-        {
-            // Exclude zeroes
-            if (a != beast::zero)
-                exponents.push_back(a.exponent());
-        }
-        if (exponents.empty())
-        {
-            UNREACHABLE("xrpl::LoanPay::doApply : all zeroes");
-            return 0;
-        }
-        auto const [minItr, maxItr] = std::ranges::minmax_element(exponents);
-        auto const min = *minItr;
-        auto const max = *maxItr;
-        JLOG(j_.trace()) << "Min scale: " << min << ", max scale: " << max;
-        // IOU rounding can be interesting. We want all the balance checks to agree, but don't want
-        // to round to such an extreme that it becomes meaningless.  e.g. Everything rounds to one
-        // digit. So add 1 to the max (reducing the number of digits after the decimal point by 1)
-        // if the scales are not already all the same.
-        return std::min(min == max ? max : max + 1, STAmount::cMaxOffset);
-    }();
-
-    // No object changes are made below this point
     XRPL_ASSERT_PARTS(
-        Number::getround() == Number::to_nearest,
-        "xrpl::LoanPay::doApply",
-        "Number rounding to_nearest");
-    NumberRoundModeGuard const mg(Number::to_nearest);
-
-    auto const accountBalanceBeforeRounded = roundToScale(accountBalanceBefore, balanceScale);
-    auto const vaultBalanceBeforeRounded = roundToScale(vaultBalanceBefore, balanceScale);
-    auto const brokerBalanceBeforeRounded = roundToScale(brokerBalanceBefore, balanceScale);
-
-    auto const totalBalanceBefore = accountBalanceBefore + vaultBalanceBefore + brokerBalanceBefore;
-    auto const totalBalanceBeforeRounded = roundToScale(totalBalanceBefore, balanceScale);
-
-    JLOG(j_.trace()) << "Before: "  //
-                     << "account " << Number(accountBalanceBeforeRounded) << " ("
-                     << Number(accountBalanceBefore) << ")"
-                     << ", vault " << Number(vaultBalanceBeforeRounded) << " ("
-                     << Number(vaultBalanceBefore) << ")"
-                     << ", broker " << Number(brokerBalanceBeforeRounded) << " ("
-                     << Number(brokerBalanceBefore) << ")"
-                     << ", total " << Number(totalBalanceBeforeRounded) << " ("
-                     << Number(totalBalanceBefore) << ")";
-
-    auto const accountBalanceAfterRounded = roundToScale(accountBalanceAfter, balanceScale);
-    auto const vaultBalanceAfterRounded = roundToScale(vaultBalanceAfter, balanceScale);
-    auto const brokerBalanceAfterRounded = roundToScale(brokerBalanceAfter, balanceScale);
-
-    auto const totalBalanceAfter = accountBalanceAfter + vaultBalanceAfter + brokerBalanceAfter;
-    auto const totalBalanceAfterRounded = roundToScale(totalBalanceAfter, balanceScale);
-
-    JLOG(j_.trace()) << "After: "  //
-                     << "account " << Number(accountBalanceAfterRounded) << " ("
-                     << Number(accountBalanceAfter) << ")"
-                     << ", vault " << Number(vaultBalanceAfterRounded) << " ("
-                     << Number(vaultBalanceAfter) << ")"
-                     << ", broker " << Number(brokerBalanceAfterRounded) << " ("
-                     << Number(brokerBalanceAfter) << ")"
-                     << ", total " << Number(totalBalanceAfterRounded) << " ("
-                     << Number(totalBalanceAfter) << ")";
-
-    auto const accountBalanceChange = accountBalanceAfter - accountBalanceBefore;
-    auto const vaultBalanceChange = vaultBalanceAfter - vaultBalanceBefore;
-    auto const brokerBalanceChange = brokerBalanceAfter - brokerBalanceBefore;
-
-    auto const totalBalanceChange = accountBalanceChange + vaultBalanceChange + brokerBalanceChange;
-    auto const totalBalanceChangeRounded = roundToScale(totalBalanceChange, balanceScale);
-
-    JLOG(j_.trace()) << "Changes: "                                    //
-                     << "account " << to_string(accountBalanceChange)  //
-                     << ", vault " << to_string(vaultBalanceChange)    //
-                     << ", broker " << to_string(brokerBalanceChange)  //
-                     << ", total " << to_string(totalBalanceChangeRounded) << " ("
-                     << Number(totalBalanceChange) << ")";
-
-    if (totalBalanceBeforeRounded != totalBalanceAfterRounded)
-    {
-        JLOG(j_.warn()) << "Total rounded balances don't match"
-                        << (totalBalanceChangeRounded == beast::zero ? ", but total changes do"
-                                                                     : "");
-    }
-    if (totalBalanceChangeRounded != beast::zero)
-    {
-        JLOG(j_.warn()) << "Total balance changes don't match"
-                        << (totalBalanceBeforeRounded == totalBalanceAfterRounded
-                                ? ", but total balances do"
-                                : "");
-    }
-
-    // Rounding for IOUs can be weird, so check a few different ways to show
-    // that funds are conserved.
-    XRPL_ASSERT_PARTS(
-        totalBalanceBeforeRounded == totalBalanceAfterRounded ||
-            totalBalanceChangeRounded == beast::zero,
+        accountBalanceBefore + vaultBalanceBefore + brokerBalanceBefore ==
+            accountBalanceAfter + vaultBalanceAfter + brokerBalanceAfter,
         "xrpl::LoanPay::doApply",
         "funds are conserved (with rounding)");
-
+    XRPL_ASSERT_PARTS(
+        accountBalanceAfter >= beast::zero, "xrpl::LoanPay::doApply", "positive account balance");
     XRPL_ASSERT_PARTS(
         accountBalanceAfter < accountBalanceBefore || account_ == asset.getIssuer(),
         "xrpl::LoanPay::doApply",
@@ -798,6 +640,7 @@ LoanPay::doApply()
         vaultBalanceAfter > vaultBalanceBefore || brokerBalanceAfter > brokerBalanceBefore,
         "xrpl::LoanPay::doApply",
         "vault and/or broker balance increased");
+#endif
 
     return tesSUCCESS;
 }

src/test/app/Loan_test.cpp

@@ -370,11 +370,16 @@ protected:
                         env.balance(vaultPseudo, broker.asset).number());
                     if (ownerCount == 0)
                     {
-                        // The Vault must be perfectly balanced if there
-                        // are no loans outstanding
+                        // Allow some slop for rounding IOUs
+
+                        // TODO: This needs to be an exact match once all the
+                        // other rounding issues are worked out.
                         auto const total = vaultSle->at(sfAssetsTotal);
                         auto const available = vaultSle->at(sfAssetsAvailable);
-                        env.test.BEAST_EXPECT(total == available);
+                        env.test.BEAST_EXPECT(
+                            total == available ||
+                            (!broker.asset.integral() && available != 0 &&
+                             ((total - available) / available < Number(1, -6))));
                         env.test.BEAST_EXPECT(vaultSle->at(sfLossUnrealized) == 0);
                     }
                 }
@@ -7063,140 +7068,6 @@ protected:
         BEAST_EXPECT(afterSecondCoverAvailable == 0);
     }
 
-    void
-    testYieldTheftRounding(std::uint32_t flags)
-    {
-        testcase("Rounding manipulation does not permit yield theft");
-        using namespace jtx;
-        using namespace loan;
-
-        // 1. Setup Environment
-        Env env(*this, all);
-        Account const issuer{"issuer"};
-        Account const lender{"lender"};
-        Account const borrower{"borrower"};
-
-        env.fund(XRP(1000), issuer, lender, borrower);
-        env.close();
-
-        // 2. Asset Selection
-        PrettyAsset const iou = issuer["USD"];
-        env(trust(lender, iou(100'000'000)));
-        env(trust(borrower, iou(100'000'000)));
-        env(pay(issuer, lender, iou(100'000'000)));
-        env(pay(issuer, borrower, iou(100'000'000)));
-        env.close();
-
-        // 3. Create Vault and Broker with High Debt Limit (100M)
-        auto const brokerInfo = createVaultAndBroker(
-            env,
-            iou,
-            lender,
-            {
-                .vaultDeposit = 5'000'000,
-                .debtMax = Number{100'000'000},
-                .coverDeposit = 500'000,
-            });
-        auto const [currentSeq, vaultKeylet] = [&]() {
-            auto const brokerSle = env.le(keylet::loanbroker(brokerInfo.brokerID));
-            auto const currentSeq = brokerSle->at(sfLoanSequence);
-            auto const vaultKeylet = keylet::vault(brokerSle->at(sfVaultID));
-            return std::make_tuple(currentSeq, vaultKeylet);
-        }();
-
-        // 4. Loan Parameters (Attack Vector)
-        Number const principal = 1'000'000;
-        TenthBips32 const interestRate = TenthBips32{1};  // 0.001%
-        std::uint32_t const paymentInterval = 86400;
-        std::uint32_t const paymentTotal = 3650;
-
-        auto const loanSetFee = fee(env.current()->fees().base * 2);
-        env(set(borrower, brokerInfo.brokerID, iou(principal).value(), flags),
-            sig(sfCounterpartySignature, lender),
-            loan::interestRate(interestRate),
-            loan::paymentInterval(paymentInterval),
-            loan::paymentTotal(paymentTotal),
-            fee(loanSetFee));
-        env.close();
-
-        // --- RETRIEVE OBJECTS & SETUP ATTACK ---
-
-        auto borrowerBalance = [&]() { return env.balance(borrower, iou); };
-        auto const borrowerScale = static_cast<STAmount const&>(borrowerBalance()).exponent();
-
-        auto const loanKeylet = keylet::loan(brokerInfo.brokerID, currentSeq);
-        auto const maybePeriodicPayment = [&]() -> std::optional<STAmount> {
-            auto const loanSle = env.le(loanKeylet);
-            if (!BEAST_EXPECT(loanSle))
-                return std::nullopt;
-            // Construct Payment
-            return STAmount{iou, loanSle->at(sfPeriodicPayment)};
-        }();
-        if (!maybePeriodicPayment)
-            return;
-        auto const periodicPayment = *maybePeriodicPayment;
-        auto const roundedPayment = roundToScale(periodicPayment, borrowerScale, Number::upward);
-
-        // ATTACK: Add dust buffer (1e-9) to force 'excess' logic execution
-        STAmount const paymentBuffer{iou, Number(1, -9)};
-        STAmount const attackPayment = periodicPayment + paymentBuffer;
-
-        auto const maybeInitialVaultAssets = [&]() -> std::optional<Number> {
-            auto const vault = env.le(vaultKeylet);
-            if (!BEAST_EXPECT(vault))
-                return std::nullopt;
-            return vault->at(sfAssetsTotal);
-        }();
-        if (!maybeInitialVaultAssets)
-            return;
-        auto const initialVaultAssets = *maybeInitialVaultAssets;
-
-        // 5. Execution Loop
-        int yieldTheftCount = 0;
-        auto previousAssetsTotal = initialVaultAssets;
-
-        for (int i = 0; i < 100; ++i)
-        {
-            auto const balanceBefore = borrowerBalance();
-            env(pay(borrower, loanKeylet.key, attackPayment, flags));
-            env.close();
-            auto const borrowerDelta = balanceBefore - borrowerBalance();
-            BEAST_EXPECT(borrowerDelta.signum() == roundedPayment.signum());
-
-            auto const loanSle = env.le(loanKeylet);
-            if (!BEAST_EXPECT(loanSle))
-                break;
-            auto const updatedPayment = STAmount{iou, loanSle->at(sfPeriodicPayment)};
-            BEAST_EXPECT(
-                (roundToScale(updatedPayment, borrowerScale, Number::upward) == roundedPayment));
-            BEAST_EXPECT(
-                (updatedPayment == periodicPayment) ||
-                (flags == tfLoanOverpayment && i >= 2 && updatedPayment < periodicPayment));
-
-            auto const currentVaultSle = env.le(vaultKeylet);
-            if (!BEAST_EXPECT(currentVaultSle))
-                break;
-
-            auto const currentAssetsTotal = currentVaultSle->at(sfAssetsTotal);
-            auto const delta = currentAssetsTotal - previousAssetsTotal;
-
-            BEAST_EXPECT(
-                (delta == beast::zero && borrowerDelta <= roundedPayment) ||
-                (delta > beast::zero && borrowerDelta > roundedPayment));
-
-            // If tx succeeded but Assets Total didn't change, interest was
-            // stolen.
-            if (delta == beast::zero && borrowerDelta > roundedPayment)
-            {
-                yieldTheftCount++;
-            }
-
-            previousAssetsTotal = currentAssetsTotal;
-        }
-
-        BEAST_EXPECTS(yieldTheftCount == 0, std::to_string(yieldTheftCount));
-    }
-
     // Tests that vault withdrawals work correctly when the vault has unrealized
     // loss from an impaired loan, ensuring the invariant check properly
     // accounts for the loss.
@@ -7335,11 +7206,6 @@ public:
         testLoanPayLateFullPaymentBypassesPenalties();
         testLoanCoverMinimumRoundingExploit();
 #endif
-        for (auto const flags : {0u, tfLoanOverpayment})
-        {
-            testYieldTheftRounding(flags);
-        }
-
         testWithdrawReflectsUnrealizedLoss();
         testInvalidLoanSet();
 

src/test/basics/Number_test.cpp

@@ -1584,3 +1584,101 @@ public:
 BEAST_DEFINE_TESTSUITE(Number, basics, xrpl);
 
 }  // namespace xrpl
+#include <xrpl/basics/Number.h>
+#include <xrpl/beast/unit_test.h>
+#include <xrpl/protocol/AccountID.h>
+#include <xrpl/protocol/MPTIssue.h>
+#include <xrpl/protocol/STAmount.h>
+
+#include <boost/multiprecision/cpp_int.hpp>
+
+#include <cstdint>
+#include <limits>
+#include <sstream>
+#include <string>
+
+namespace xrpl {
+
+class NumberUpwardWrongDirection_test : public beast::unit_test::suite
+{
+    using BigInt = boost::multiprecision::cpp_int;
+
+    static std::string
+    fmt(BigInt const& value)
+    {
+        std::ostringstream os;
+        os << value;
+        auto s = os.str();
+        std::string out;
+        int count = 0;
+        for (auto it = s.rbegin(); it != s.rend(); ++it)
+        {
+            if (count && count % 3 == 0)
+                out.insert(out.begin(), '_');
+            out.insert(out.begin(), *it);
+            ++count;
+        }
+        return out;
+    }
+
+public:
+    void
+    testUpwardRoundsDown()
+    {
+        testcase << "upward rounding produces a value below exact at maxRep cusp";
+
+        auto const origScale = Number::getMantissaScale();
+        auto const origRound = Number::setround(Number::upward);
+        Number::setMantissaScale(MantissaRange::large);
+
+        constexpr std::int64_t aValue = 1'000'000'000'000'049'863LL;
+        constexpr std::int64_t bValue = 9'223'372'036'854'315'903LL;
+
+        // JSON -> STAmount -> Number
+        AccountID const dummyIssuer = AccountID{42u};
+        MPTIssue const issue(/*sequence=*/1u, dummyIssuer);
+
+        STAmount const amountA{MPTAmount{aValue}, issue};
+        STAmount const amountB{MPTAmount{bValue}, issue};
+
+        // Public conversion operator: STAmount::operator Number() const.
+        Number const a = amountA;
+        Number const b = amountB;
+        Number const product = a * b;
+
+        // Exact reference in BigInt.
+        BigInt const exactProduct = BigInt(aValue) * BigInt(bValue);
+
+        // What Number actually stored.
+        BigInt storedValue = BigInt(product.mantissa());
+        for (int i = 0; i < product.exponent(); ++i)
+            storedValue *= 10;
+
+        BigInt const signedDifference = storedValue - exactProduct;
+
+        log << "\n"
+            << "  a              = " << fmt(BigInt(aValue)) << "\n"
+            << "  b              = " << fmt(BigInt(bValue)) << "\n"
+            << "  exact a*b      = " << fmt(exactProduct) << "\n"
+            << "  stored         = " << fmt(storedValue) << "\n"
+            << "  stored - exact = " << fmt(signedDifference) << "\n"
+            << "  upward         = " << (signedDifference >= 0 ? "held" : "VIOLATED") << "\n";
+
+        BEAST_EXPECT(signedDifference >= 0);
+        BEAST_EXPECT(product.mantissa() == (std::numeric_limits<std::int64_t>::max() /10) + 1);
+        BEAST_EXPECT(product.exponent() == 19);
+
+        Number::setround(origRound);
+        Number::setMantissaScale(origScale);
+    }
+
+    void
+    run() override
+    {
+        testUpwardRoundsDown();
+    }
+};
+
+BEAST_DEFINE_TESTSUITE(NumberUpwardWrongDirection, basics, ripple);
+
+}  // namespace xrpl