consensus: Store transaction nVersion as uin32_t

Given that the use of a transaction's nVersion is always as an unsigned
int, it doesn't make sense to store it as signed and then cast it to
unsigned.

src/core_write.cpp

@@ -176,7 +176,7 @@ void TxToUniv(const CTransaction& tx, const uint256& block_hash, UniValue& entry
     entry.pushKV("hash", tx.GetWitnessHash().GetHex());
     // Transaction version is actually unsigned in consensus checks, just signed in memory,
     // so cast to unsigned before giving it to the user.
-    entry.pushKV("version", static_cast<int64_t>(static_cast<uint32_t>(tx.nVersion)));
+    entry.pushKV("version", static_cast<int64_t>(tx.nVersion));
     entry.pushKV("size", tx.GetTotalSize());
     entry.pushKV("vsize", (GetTransactionWeight(tx) + WITNESS_SCALE_FACTOR - 1) / WITNESS_SCALE_FACTOR);
     entry.pushKV("weight", GetTransactionWeight(tx));

src/primitives/transaction.h

@@ -197,13 +197,13 @@ static constexpr TransactionSerParams TX_NO_WITNESS{.allow_witness = false};
 
 /**
  * Basic transaction serialization format:
- * - int32_t nVersion
+ * - uint32_t nVersion
  * - std::vector<CTxIn> vin
  * - std::vector<CTxOut> vout
  * - uint32_t nLockTime
  *
  * Extended transaction serialization format:
- * - int32_t nVersion
+ * - uint32_t nVersion
  * - unsigned char dummy = 0x00
  * - unsigned char flags (!= 0)
  * - std::vector<CTxIn> vin
@@ -305,7 +305,7 @@ class CTransaction
     // structure, including the hash.
     const std::vector<CTxIn> vin;
     const std::vector<CTxOut> vout;
-    const int32_t nVersion;
+    const uint32_t nVersion;
     const uint32_t nLockTime;
 
 private:
@@ -378,7 +378,7 @@ struct CMutableTransaction
 {
     std::vector<CTxIn> vin;
     std::vector<CTxOut> vout;
-    int32_t nVersion;
+    uint32_t nVersion;
     uint32_t nLockTime;
 
     explicit CMutableTransaction();

src/script/interpreter.cpp

@@ -1743,7 +1743,7 @@ bool GenericTransactionSignatureChecker<T>::CheckSequence(const CScriptNum& nSeq
 
     // Fail if the transaction's version number is not set high
     // enough to trigger BIP 68 rules.
-    if (static_cast<uint32_t>(txTo->nVersion) < 2)
+    if (txTo->nVersion < 2)
         return false;
 
     // Sequence numbers with their most significant bit set are not

test/functional/test_framework/messages.py

@@ -575,7 +575,7 @@ def __init__(self, tx=None):
             self.wit = copy.deepcopy(tx.wit)
 
     def deserialize(self, f):
-        self.nVersion = struct.unpack("<i", f.read(4))[0]
+        self.nVersion = struct.unpack("<I", f.read(4))[0]
         self.vin = deser_vector(f, CTxIn)
         flags = 0
         if len(self.vin) == 0:
@@ -598,7 +598,7 @@ def deserialize(self, f):
 
     def serialize_without_witness(self):
         r = b""
-        r += struct.pack("<i", self.nVersion)
+        r += struct.pack("<I", self.nVersion)
         r += ser_vector(self.vin)
         r += ser_vector(self.vout)
         r += struct.pack("<I", self.nLockTime)
@@ -610,7 +610,7 @@ def serialize_with_witness(self):
         if not self.wit.is_null():
             flags |= 1
         r = b""
-        r += struct.pack("<i", self.nVersion)
+        r += struct.pack("<I", self.nVersion)
         if flags:
             dummy = []
             r += ser_vector(dummy)