Re: Mauve - the remainder

[Mark Wielaard <mark@klomp.org>]

Hi,

On Thu, 2002-04-18 at 00:02, Mark Wielaard wrote:
> 
> FAIL: gnu.testlet.java.lang.StringBuffer.plus (number 1)
> 
> The following program returns false, but should return true:
> 
> public class SN
> {
>         public static void main(String[] args)
>         {
>                 System.out.println("null".equals(n(0) + ""));
>         }
> 
>         static String n(int i)
>         {
>                 if (i==0) return null; else return "x";
>         }
> }
> 
> The problem is that the String concatenation gets optimized away and
> since n(0) returns null it does not generate the string "null" but it
> generates the value null. The problem disappears when the return type of
> n() is changed to Object.

OK, the following optimization seems to be the problem:

diff -u -r1.353.2.17 parse.y
--- gcc/java/parse.y    15 Apr 2002 09:28:53 -0000      1.353.2.17
+++ gcc/java/parse.y    17 Apr 2002 22:50:38 -0000
@@ -13756,8 +13756,8 @@
     op2 = patch_string_cst (op2);
 
   /* If either one of the constant is null and the other non null
-     operand is a String object, return it. */
-  if (JSTRING_TYPE_P (TREE_TYPE (op1)) && !op2)
+     operand is a String constant, return it. */
+  if ((TREE_CODE (op1) == STRING_CST) && !op2)
     return op1;
 
   /* If OP1 isn't already a StringBuffer, create and

Or does this look to conservative?

Good night,

Mark