Add static_assert to prevent VARINT(<signed value>)

Using VARINT with signed types is dangerous because negative values will appear
to serialize correctly, but then deserialize as positive values mod 128.

This commit changes the VARINT macro to trigger an error by default if called
with an signed value, and updates broken uses of VARINT to pass a special flag
that lets them keep working with no change in behavior.

1 files changed, 3 insertions, 3 deletions

diff --git a/src/rpc/blockchain.cpp b/src/rpc/blockchain.cpp
index 2077723af5..3f66c0c536 100644
--- a/src/rpc/blockchain.cpp
+++ b/src/rpc/blockchain.cpp
@@ -834,18 +834,18 @@ static void ApplyStats(CCoinsStats &stats, CHashWriter& ss, const uint256& hash,
 {
     assert(!outputs.empty());
     ss << hash;
-    ss << VARINT(outputs.begin()->second.nHeight * 2 + outputs.begin()->second.fCoinBase);
+    ss << VARINT(outputs.begin()->second.nHeight * 2 + outputs.begin()->second.fCoinBase, VarIntMode::NONNEGATIVE_SIGNED);
     stats.nTransactions++;
     for (const auto output : outputs) {
         ss << VARINT(output.first + 1);
         ss << output.second.out.scriptPubKey;
-        ss << VARINT(output.second.out.nValue);
+        ss << VARINT(output.second.out.nValue, VarIntMode::NONNEGATIVE_SIGNED);
         stats.nTransactionOutputs++;
         stats.nTotalAmount += output.second.out.nValue;
         stats.nBogoSize += 32 /* txid */ + 4 /* vout index */ + 4 /* height + coinbase */ + 8 /* amount */ +
                            2 /* scriptPubKey len */ + output.second.out.scriptPubKey.size() /* scriptPubKey */;
     }
-    ss << VARINT(0);
+    ss << VARINT(0u);
 }
 
 //! Calculate statistics about the unspent transaction output set