Fix bug where env.GetUTF8String() would fail when env.PrecalculateSig…

…nature() had been set.

M	jnigi.go
M	jnigi_test.go

jnigi.go

@@ -1881,13 +1881,18 @@ var utf8 *ObjectRef
 // GetUTF8String return global reference to java/lang/String containing "UTF-8"
 func (j *Env) GetUTF8String() *ObjectRef {
 	if utf8 == nil {
+		// make sure we don't use any preCalSig set when we do NewObject
+		savePrecalSig := j.preCalcSig
+		j.preCalcSig = ""
+
 		str, err := j.NewObject("java/lang/String", []byte("UTF-8"))
 		if err != nil {
 			panic(err)
 		}
 		global := j.NewGlobalRef(str)
 		j.DeleteLocalRef(str)
 		utf8 = global
+		j.preCalcSig = savePrecalSig
 	}
 
 	return utf8

jnigi_test.go

@@ -60,6 +60,15 @@ func PTestBasic(t *testing.T) {
 		t.Fatal(err)
 	}
 
+	// test env.GetUTF8String() should be independent of PrecalculateSignature
+	sigStr := "dummy"
+	env.PrecalculateSignature(sigStr)
+	env.GetUTF8String()
+	if !assert.Equal(t, sigStr, env.preCalcSig) {
+		t.Fail()
+	}
+	env.preCalcSig = ""
+
 	// byte array argument, byte array method
 	var testStr string = "hello world"
 	str, err := env.NewObject("java/lang/String", []byte(testStr))