fix: rounding issues: bitcoin/bitcoin#22949

SmartArray · Apr 6, 2022 · 344e306 · 344e306
1 parent 5e3a8f8
commit 344e306
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Showing 4 changed files with 9 additions and 7 deletions.
diff --git a/src/policy/feerate.cpp b/src/policy/feerate.cpp
@@ -7,6 +7,7 @@
 #include <policy/feerate.h>
 
 #include <tinyformat.h>
+#include <cmath>
 
 CFeeRate::CFeeRate(const CAmount& nFeePaid, uint32_t num_bytes)
 {
@@ -23,7 +24,7 @@ CAmount CFeeRate::GetFee(uint32_t num_bytes) const
 {
     const int64_t nSize{num_bytes};
 
-    CAmount nFee = nSatoshisPerK * nSize / 1000;
+    CAmount nFee{static_cast<CAmount>(std::ceil(nSatoshisPerK * nSize / 1000.0))};
 
     if (nFee == 0 && nSize != 0) {
         if (nSatoshisPerK > 0) nFee = CAmount(1);

diff --git a/src/policy/feerate.h b/src/policy/feerate.h
@@ -49,6 +49,7 @@ class CFeeRate
     CFeeRate(const CAmount& nFeePaid, uint32_t num_bytes);
     /**
      * Return the fee in satoshis for the given size in bytes.
+     * If the calculated fee would have fractional satoshis, then the returned fee will always be rounded up to the nearest satoshi.
      */
     CAmount GetFee(uint32_t num_bytes) const;
     /**

diff --git a/src/test/amount_tests.cpp b/src/test/amount_tests.cpp
@@ -52,10 +52,10 @@ BOOST_AUTO_TEST_CASE(GetFeeTest)
     // Truncates the result, if not integer
     BOOST_CHECK_EQUAL(feeRate.GetFee(0), CAmount(0));
     BOOST_CHECK_EQUAL(feeRate.GetFee(8), CAmount(1)); // Special case: returns 1 instead of 0
-    BOOST_CHECK_EQUAL(feeRate.GetFee(9), CAmount(1));
-    BOOST_CHECK_EQUAL(feeRate.GetFee(121), CAmount(14));
-    BOOST_CHECK_EQUAL(feeRate.GetFee(122), CAmount(15));
-    BOOST_CHECK_EQUAL(feeRate.GetFee(999), CAmount(122));
+    BOOST_CHECK_EQUAL(feeRate.GetFee(9), CAmount(2));
+    BOOST_CHECK_EQUAL(feeRate.GetFee(121), CAmount(15));
+    BOOST_CHECK_EQUAL(feeRate.GetFee(122), CAmount(16));
+    BOOST_CHECK_EQUAL(feeRate.GetFee(999), CAmount(123));
     BOOST_CHECK_EQUAL(feeRate.GetFee(1e3), CAmount(123));
     BOOST_CHECK_EQUAL(feeRate.GetFee(9e3), CAmount(1107));
 

diff --git a/src/test/transaction_tests.cpp b/src/test/transaction_tests.cpp
@@ -808,12 +808,12 @@ BOOST_AUTO_TEST_CASE(test_IsStandard)
     // nDustThreshold = 182 * 3702 / 1000
     dustRelayFee = CFeeRate(3702);
     // dust:
-    t.vout[0].nValue = 673 - 1;
+    t.vout[0].nValue = 674 - 1;
     reason.clear();
     BOOST_CHECK(!IsStandardTx(CTransaction(t), reason));
     BOOST_CHECK_EQUAL(reason, "dust");
     // not dust:
-    t.vout[0].nValue = 673;
+    t.vout[0].nValue = 674;
     BOOST_CHECK(IsStandardTx(CTransaction(t), reason));
     dustRelayFee = CFeeRate(DUST_RELAY_TX_FEE);