[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/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