Change gas & related fields to unsigned integer type (#2839)

* Change gas & related fields to unsigned integer type
* Implement AddUint64Overflow

types/context.go

@@ -203,8 +203,10 @@ func (c Context) WithConsensusParams(params *abci.ConsensusParams) Context {
 	if params == nil {
 		return c
 	}
+
+	// TODO: Do we need to handle invalid MaxGas values?
 	return c.withValue(contextKeyConsensusParams, params).
-		WithGasMeter(NewGasMeter(params.BlockSize.MaxGas))
+		WithGasMeter(NewGasMeter(uint64(params.BlockSize.MaxGas)))
 }
 
 func (c Context) WithChainID(chainID string) Context { return c.withValue(contextKeyChainID, chainID) }

types/gas.go

@@ -18,13 +18,19 @@ var (
 )
 
 // Gas measured by the SDK
-type Gas = int64
+type Gas = uint64
 
 // ErrorOutOfGas defines an error thrown when an action results in out of gas.
 type ErrorOutOfGas struct {
 	Descriptor string
 }
 
+// ErrorGasOverflow defines an error thrown when an action results gas consumption
+// unsigned integer overflow.
+type ErrorGasOverflow struct {
+	Descriptor string
+}
+
 // GasMeter interface to track gas consumption
 type GasMeter interface {
 	GasConsumed() Gas
@@ -49,7 +55,14 @@ func (g *basicGasMeter) GasConsumed() Gas {
 }
 
 func (g *basicGasMeter) ConsumeGas(amount Gas, descriptor string) {
-	g.consumed += amount
+	var overflow bool
+
+	// TODO: Should we set the consumed field after overflow checking?
+	g.consumed, overflow = AddUint64Overflow(g.consumed, amount)
+	if overflow {
+		panic(ErrorGasOverflow{descriptor})
+	}
+
 	if g.consumed > g.limit {
 		panic(ErrorOutOfGas{descriptor})
 	}
@@ -71,7 +84,13 @@ func (g *infiniteGasMeter) GasConsumed() Gas {
 }
 
 func (g *infiniteGasMeter) ConsumeGas(amount Gas, descriptor string) {
-	g.consumed += amount
+	var overflow bool
+
+	// TODO: Should we set the consumed field after overflow checking?
+	g.consumed, overflow = AddUint64Overflow(g.consumed, amount)
+	if overflow {
+		panic(ErrorGasOverflow{descriptor})
+	}
 }
 
 // GasConfig defines gas cost for each operation on KVStores

types/gas_test.go

@@ -21,7 +21,7 @@ func TestGasMeter(t *testing.T) {
 
 	for tcnum, tc := range cases {
 		meter := NewGasMeter(tc.limit)
-		used := int64(0)
+		used := uint64(0)
 
 		for unum, usage := range tc.usage {
 			used += usage

types/int.go

@@ -2,6 +2,7 @@ package types
 
 import (
 	"encoding/json"
+	"math"
 	"testing"
 
 	"math/big"
@@ -529,6 +530,16 @@ func (i *Uint) UnmarshalJSON(bz []byte) error {
 
 //__________________________________________________________________________
 
+// AddUint64Overflow performs the addition operation on two uint64 integers and
+// returns a boolean on whether or not the result overflows.
+func AddUint64Overflow(a, b uint64) (uint64, bool) {
+	if math.MaxUint64-a < b {
+		return 0, true
+	}
+
+	return a + b, false
+}
+
 // intended to be used with require/assert:  require.True(IntEq(...))
 func IntEq(t *testing.T, exp, got Int) (*testing.T, bool, string, string, string) {
 	return t, exp.Equal(got), "expected:\t%v\ngot:\t\t%v", exp.String(), got.String()

types/int_test.go

@@ -590,3 +590,28 @@ func TestEncodingTableUint(t *testing.T) {
 		require.Equal(t, tc.i, i, "Unmarshaled value is different from expected. tc #%d", tcnum)
 	}
 }
+
+func TestAddUint64Overflow(t *testing.T) {
+	testCases := []struct {
+		a, b     uint64
+		result   uint64
+		overflow bool
+	}{
+		{0, 0, 0, false},
+		{100, 100, 200, false},
+		{math.MaxUint64 / 2, math.MaxUint64/2 + 1, math.MaxUint64, false},
+		{math.MaxUint64 / 2, math.MaxUint64/2 + 2, 0, true},
+	}
+
+	for i, tc := range testCases {
+		res, overflow := AddUint64Overflow(tc.a, tc.b)
+		require.Equal(
+			t, tc.overflow, overflow,
+			"invalid overflow result; tc: #%d, a: %d, b: %d", i, tc.a, tc.b,
+		)
+		require.Equal(
+			t, tc.result, res,
+			"invalid uint64 result; tc: #%d, a: %d, b: %d", i, tc.a, tc.b,
+		)
+	}
+}

types/result.go

@@ -16,10 +16,10 @@ type Result struct {
 	Log string
 
 	// GasWanted is the maximum units of work we allow this tx to perform.
-	GasWanted int64
+	GasWanted uint64
 
 	// GasUsed is the amount of gas actually consumed. NOTE: unimplemented
-	GasUsed int64
+	GasUsed uint64
 
 	// Tx fee amount and denom.
 	FeeAmount int64