[Fwd: Re: [aspectj-users] capturing implicit toString() function call (f

["Benjamin Mesing" <benjamin.mesing@xxxxxxxxxxxxxxx>]

Forwarded because of a bounce of the original message.

---------- Forwarded message ----------
Date: Thu, 11 Nov 2004 08:02:37 -0500 (EST)
From: Prof. Laurie HENDREN <hendren@xxxxxxxxxxxxxxx>
To: aspectj-users@xxxxxxxxxxx
Subject: Re: [aspectj-users] capturing implicit toString() function call

Hi Ben,

I tried to reply to the list, but it was bounced.  My original reply
was not quite right.

The problem is that the weaver looks at the generated bytecode and
compilers can actually generate lots of different things to handle
strcat and toString().

If you look at the key bits of the bytecode produced by javac for your
println you see that your explicit toString shows up as a toString, but
the second one is implicit in the second append to StringBuffer,  and then
the last toString in the generated code corresponds to conversion of
a StringBuffer to a String.

Cheers, Laurie


public static void main(java.lang.String[]);
  Code:
   0:   new     #2; //class HelloWorld
   3:   dup
   4:   invokespecial   #3; //Method "<init>":()V
   7:   astore_1
   8:   getstatic       #4; //Field 
java/lang/System.out:Ljava/io/PrintStream;
   11:  new     #5; //class StringBuffer
   14:  dup
   15:  invokespecial   #6; //Method java/lang/StringBuffer."<init>":()V
   18:  aload_1
   19:  invokevirtual   #7; //Method toString:()Ljava/lang/String;
   22:  invokevirtual   #8; //Method 
java/lang/StringBuffer.append:(Ljava/lang/S
tring;)Ljava/lang/StringBuffer;
   25:  aload_1
   26:  invokevirtual   #9; //Method 
java/lang/StringBuffer.append:(Ljava/lang/O
bject;)Ljava/lang/StringBuffer;
   29:  invokevirtual   #10; //Method 
java/lang/StringBuffer.toString:()Ljava/la
ng/String;
   32:  invokevirtual   #11; //Method 
java/io/PrintStream.println:(Ljava/lang/St
ring;)V
   35:  return


+-------------------------------------------------------------+
| Laurie Hendren, Professor, School of Computer Science       |
| McGill University                                           |
| 318 McConnell Engineering Building      tel: (514) 398-7391 |
| 3480 University Street                  fax: (514) 398-3883 |
| Montreal, Quebec H3A 2A7               hendren@xxxxxxxxxxxx |
| CANADA                  http://www.sable.mcgill.ca/~hendren |
+-------------------------------------------------------------+

On Thu, 11 Nov 2004, Benjamin Mesing wrote:

> Hello,
>
> I have stumbled over a problem. When specifying a pointcut, implicit
> calls of toString functions will not be captured. Consider the following
> example, wher "jpt hit" will be printed only once.
> Is there anything I can do about it?
>
> public class HelloWorld {
>
> 	public static void main(String[] args) {
> 		HelloWorld hw = new HelloWorld();
> 		// here occurs an explicit and an implicit call of
> 		// toString()
> 		System.out.println(hw.toString() + hw);
> 	}
> 	public String toString()
> 	{
> 		return "Hello World ";
> 	}
> }
>
> public aspect TestAspect
> {
> 	before() : call (String HelloWorld.toString())
> 	{
> 		System.out.println("jpt hit");
> 	}
> }
>
> Greetings Ben
> _______________________________________________
> aspectj-users mailing list
> aspectj-users@xxxxxxxxxxx
> http://dev.eclipse.org/mailman/listinfo/aspectj-users