fix a bug if the min fee is 0 for FeeFilterRounder

Author: morcos

src/policy/fees.cpp

@@ -299,6 +299,7 @@ void CBlockPolicyEstimator::removeTx(uint256 hash)
 CBlockPolicyEstimator::CBlockPolicyEstimator(const CFeeRate& _minRelayFee)
     : nBestSeenHeight(0)
 {
+    static_assert(MIN_FEERATE > 0, "Min feerate must be nonzero");
     minTrackedFee = _minRelayFee < CFeeRate(MIN_FEERATE) ? CFeeRate(MIN_FEERATE) : _minRelayFee;
     std::vector<double> vfeelist;
     for (double bucketBoundary = minTrackedFee.GetFeePerK(); bucketBoundary <= MAX_FEERATE; bucketBoundary *= FEE_SPACING) {
@@ -485,7 +486,7 @@ void CBlockPolicyEstimator::Read(CAutoFile& filein, int nFileVersion)
 
 FeeFilterRounder::FeeFilterRounder(const CFeeRate& minIncrementalFee)
 {
-    CAmount minFeeLimit = minIncrementalFee.GetFeePerK() / 2;
+    CAmount minFeeLimit = std::max(CAmount(1), minIncrementalFee.GetFeePerK() / 2);
     feeset.insert(0);
     for (double bucketBoundary = minFeeLimit; bucketBoundary <= MAX_FEERATE; bucketBoundary *= FEE_SPACING) {
         feeset.insert(bucketBoundary);

src/policy/fees.h

@@ -179,7 +179,7 @@ static const double MIN_SUCCESS_PCT = .95;
 static const double SUFFICIENT_FEETXS = 1;
 
 // Minimum and Maximum values for tracking feerates
-static const double MIN_FEERATE = 10;
+static constexpr double MIN_FEERATE = 10;
 static const double MAX_FEERATE = 1e7;
 static const double INF_FEERATE = MAX_MONEY;
 static const double INF_PRIORITY = 1e9 * MAX_MONEY;