refactor: Introduce XRPL_ASSERT_IF for amendment-gated assertions (#7378)

Co-authored-by: xrplf-ai-reviewer[bot] <266832837+xrplf-ai-reviewer[bot]@users.noreply.github.com>

include/xrpl/beast/utility/instrumentation.h

@@ -11,6 +11,8 @@
 // Macros below are copied from antithesis_sdk.h and slightly simplified
 // The duplication is because Visual Studio 2019 cannot compile that header
 // even with the option -Zc:__cplusplus added.
+// NOTE: cond must not contain bare commas outside () or []. Commas inside {}
+// are not protected by the preprocessor and would be parsed as extra arguments.
 #define ALWAYS(cond, message, ...) assert((message) && (cond))
 #define ALWAYS_OR_UNREACHABLE(cond, message) assert((message) && (cond))
 #define SOMETIMES(cond, message, ...)
@@ -22,6 +24,8 @@
 #define XRPL_ASSERT_PARTS(cond, function, description, ...) \
     XRPL_ASSERT(cond, function " : " description)
 
+#define XRPL_ASSERT_IF(guard, cond, message) XRPL_ASSERT(!(guard) || (cond), message)
+
 // How to use the instrumentation macros:
 //
 // * XRPL_ASSERT if cond must be true but the line might not be reached during
@@ -29,6 +33,14 @@
 // * XRPL_ASSERT_PARTS is for convenience, and works like XRPL_ASSERT, but
 //   splits the message param into "function" and "description", then joins
 //   them with " : " before passing to XRPL_ASSERT.
+// * XRPL_ASSERT_IF(guard, cond, message) asserts the implication
+//   `guard => cond`: it can only fail when guard is true (e.g. an amendment
+//   is enabled) and cond is false. Unlike `if (guard) XRPL_ASSERT(...)`, the
+//   assertion site is always evaluated, so the fuzzer registers it
+//   unconditionally; cond itself is short-circuited and only evaluated when
+//   guard is true. NOTE: do not rely on side effects in guard — in release
+//   builds the assertion body is stripped, and the compiler may optimize away
+//   a side-effect-free guard entirely.
 // * ALWAYS if cond must be true _and_ the line must be reached during fuzzing.
 //   Same like `assert` in normal use.
 // * REACHABLE if the line must be reached during fuzzing

src/libxrpl/ledger/helpers/LendingHelpers.cpp

@@ -798,44 +798,44 @@ doOverpayment(
     // (P * factor) / factor round-trip can leave the new principal one
     // scale-unit high, so these equalities do not hold on the pre-amendment
     // code path and must be gated to match the fix they verify.
-    if (rules.enabled(fixCleanup3_2_0))
-    {
-        // The valueChange returned by tryOverpayment satisfies
-        //   valueChange = (newInterestDue - oldInterestDue) + untrackedInterest.
-        // Using the loan-state identity v = p + i + m and the adjacent
-        // `principal change agrees` assertion (dp = oldP - newP), this
-        // rearranges into three independently-computable terms:
-        //
-        //   1. TVO change beyond what principal repayment alone explains:
-        //        newTVO - (oldTVO - dp)
-        //   2. Management fee released by re-amortization (positive when
-        //      mfee decreased; zero when managementFeeRate == 0):
-        //        oldMfee - newMfee
-        //   3. The overpayment's penalty interest part (= untrackedInterest
-        //      for the overpayment path; see computeOverpaymentComponents):
-        //        trackedInterestPart()
-        [[maybe_unused]] Number const tvoChange = newRoundedLoanState.valueOutstanding -
-            (totalValueOutstandingProxy - overpaymentComponents.trackedPrincipalDelta);
-        [[maybe_unused]] Number const managementFeeReleased =
-            managementFeeOutstandingProxy - newRoundedLoanState.managementFeeDue;
-        [[maybe_unused]] Number const interestPart = overpaymentComponents.trackedInterestPart();
+    //
+    // The valueChange returned by tryOverpayment satisfies
+    //   valueChange = (newInterestDue - oldInterestDue) + untrackedInterest.
+    // Using the loan-state identity v = p + i + m and the adjacent
+    // `principal change agrees` assertion (dp = oldP - newP), this
+    // rearranges into three independently-computable terms:
+    //
+    //   1. TVO change beyond what principal repayment alone explains:
+    //        newTVO - (oldTVO - dp)
+    //   2. Management fee released by re-amortization (positive when
+    //      mfee decreased; zero when managementFeeRate == 0):
+    //        oldMfee - newMfee
+    //   3. The overpayment's penalty interest part (= untrackedInterest
+    //      for the overpayment path; see computeOverpaymentComponents):
+    //        trackedInterestPart()
+    bool const fix320Enabled = rules.enabled(fixCleanup3_2_0);
+    XRPL_ASSERT_IF(
+        fix320Enabled,
+        overpaymentComponents.trackedPrincipalDelta ==
+            principalOutstandingProxy - newRoundedLoanState.principalOutstanding,
+        "xrpl::detail::doOverpayment : principal change agrees");
 
-        XRPL_ASSERT_PARTS(
-            overpaymentComponents.trackedPrincipalDelta ==
-                principalOutstandingProxy - newRoundedLoanState.principalOutstanding,
-            "xrpl::detail::doOverpayment",
-            "principal change agrees");
+    XRPL_ASSERT_IF(
+        fix320Enabled,
+        [&] {
+            Number const tvoChange = newRoundedLoanState.valueOutstanding -
+                (totalValueOutstandingProxy - overpaymentComponents.trackedPrincipalDelta);
+            Number const managementFeeReleased =
+                managementFeeOutstandingProxy - newRoundedLoanState.managementFeeDue;
+            Number const interestPart = overpaymentComponents.trackedInterestPart();
+            return loanPaymentParts.valueChange == tvoChange + managementFeeReleased + interestPart;
+        }(),
+        "xrpl::detail::doOverpayment : interest paid agrees");
 
-        XRPL_ASSERT_PARTS(
-            loanPaymentParts.valueChange == tvoChange + managementFeeReleased + interestPart,
-            "xrpl::detail::doOverpayment",
-            "interest paid agrees");
-
-        XRPL_ASSERT_PARTS(
-            overpaymentComponents.trackedPrincipalDelta == loanPaymentParts.principalPaid,
-            "xrpl::detail::doOverpayment",
-            "principal payment matches");
-    }
+    XRPL_ASSERT_IF(
+        fix320Enabled,
+        overpaymentComponents.trackedPrincipalDelta == loanPaymentParts.principalPaid,
+        "xrpl::detail::doOverpayment : principal payment matches");
 
     // All validations passed, so update the proxy objects (which will
     // modify the actual Loan ledger object)
@@ -1326,13 +1326,11 @@ computeOverpaymentComponents(
     TenthBips32 const overpaymentFeeRate,
     TenthBips16 const managementFeeRate)
 {
-    if (rules.enabled(fixCleanup3_2_0))
-    {
-        XRPL_ASSERT(
-            overpayment > 0 && isRounded(asset, overpayment, loanScale),
-            "xrpl::detail::computeOverpaymentComponents : valid overpayment "
-            "amount");
-    }
+    XRPL_ASSERT_IF(
+        rules.enabled(fixCleanup3_2_0),
+        overpayment > 0 && isRounded(asset, overpayment, loanScale),
+        "xrpl::detail::computeOverpaymentComponents : valid overpayment "
+        "amount");
 
     // First, deduct the fixed overpayment fee from the total amount.
     // This reduces the effective payment that will be applied to the loan.

src/libxrpl/ledger/helpers/MPTokenHelpers.cpp

@@ -736,10 +736,10 @@ unlockEscrowMPT(
     STAmount const& grossAmount,
     beast::Journal j)
 {
-    if (!view.rules().enabled(fixTokenEscrowV1))
-    {
-        XRPL_ASSERT(netAmount == grossAmount, "xrpl::unlockEscrowMPT : netAmount == grossAmount");
-    }
+    XRPL_ASSERT_IF(
+        !view.rules().enabled(fixTokenEscrowV1),
+        netAmount == grossAmount,
+        "xrpl::unlockEscrowMPT : netAmount == grossAmount");
 
     auto const& issuer = netAmount.getIssuer();
     auto const& mptIssue = netAmount.get<MPTIssue>();