null string concatenation

Hi,

With reference to the bug:
   http://www.kaffe.org/pipermail/kaffe/2003-November/044458.html

I suggest the following patch:

--- kopi-2.1B/src/kjc/JCompoundAssignmentExpression.java        2002-07-16 
03:53:32.000000000 +0900
+++ test/JCompoundAssignmentExpression.java     2003-11-25 19:26:58.000000000 
+0900
@@ -239,6 +239,13 @@
 
     if (oper == OPE_PLUS && 
type.equals(factory.createReferenceType(TypeFactory.RFT_STRING))) {
       //      left.genCode(context, false);
+      /* Isn't it stupid to call String.valueOf(String) ?
+       * But we must do this because it may be null.
+       */
+      code.plantMethodRefInstruction(opc_invokestatic,
+                              "java/lang/String",
+                              "valueOf",
+                              "(Ljava/lang/Object;)Ljava/lang/String;");
       right.genCode(context, false);
       if (!right.getType(factory).isReference()) {
        code.plantMethodRefInstruction(opc_invokestatic,


By the way, the bytecode which JCompoundAssignmentExpression.java generates
looks quite different from the bytecode produced by gcj or Sun's javac. The
former uses String.concat and the latter uses StringBuffer for string
concatenation.  Which is better?