class Exn {

  Object myMethod() {
    Object retVal=null;
    try {
      System.out.println("try");
    } catch (Exception e) {
      System.out.println("catch");
    } finally {
      System.out.println("finally");
      return retVal;
    }
  }

}

javac 1.2.2 generates the following:

Method myMethod:"()Ljava/lang/Object;"
stack 2 locals 2
{
aconst_null;
astore_1;
try t13, t25;
getstatic Field java/lang/System.out:"Ljava/io/PrintStream;";
ldc String "try";
invokevirtual Method java/io/PrintStream.println:"(Ljava/lang/String;)V";
endtry t13;
goto L26;
catch t13 java/lang/Exception;
pop;
getstatic Field java/lang/System.out:"Ljava/io/PrintStream;";
ldc String "catch";
invokevirtual Method java/io/PrintStream.println:"(Ljava/lang/String;)V";
goto L26;
endtry t25;
catch t25 #0;
pop;
L26: getstatic Field java/lang/System.out:"Ljava/io/PrintStream;";
ldc String "finally";
invokevirtual Method java/io/PrintStream.println:"(Ljava/lang/String;)V";
aload_1;
areturn;
}

javac 1.3 generates jsr instructions to a subroutine that can
never complete normally (could use goto instead), and leaves
a spurious unreachable return at the end.

Method myMethod:"()Ljava/lang/Object;"
stack 2 locals 5
{
aconst_null;
astore_1;
try t16, t31;
getstatic Field java/lang/System.out:"Ljava/io/PrintStream;";
ldc String "try";
invokevirtual Method java/io/PrintStream.println:"(Ljava/lang/String;)V";
endtry t16;
jsr L37;
goto L49;
catch t16 java/lang/Exception;
astore_2;
getstatic Field java/lang/System.out:"Ljava/io/PrintStream;";
ldc String "catch";
invokevirtual Method java/io/PrintStream.println:"(Ljava/lang/String;)V";
jsr L37;
goto L49;
endtry t31;
catch t31 #0;
astore_3;
jsr L37;
aload_3;
athrow;
L37: astore 4;
getstatic Field java/lang/System.out:"Ljava/io/PrintStream;";
ldc String "finally";
invokevirtual Method java/io/PrintStream.println:"(Ljava/lang/String;)V";
aload_1;
areturn;
L49: return;
}

javac 1.4 adopts a different scheme for compiling try-finally in order
to eliminate a bug in the handling of asynchronous exceptions, however,
the spurious return remains:

Method myMethod:"()Ljava/lang/Object;"
stack 2 locals 5
{
aconst_null;
astore_1;
try t16, t31;
getstatic Field java/lang/System.out:"Ljava/io/PrintStream;";
ldc String "try";
invokevirtual Method java/io/PrintStream.println:"(Ljava/lang/String;)V";
endtry t16;
jsr L37;
endtry t31;
goto L49;
catch t16 java/lang/Exception;
try t31;
astore_2;
getstatic Field java/lang/System.out:"Ljava/io/PrintStream;";
ldc String "catch";
invokevirtual Method java/io/PrintStream.println:"(Ljava/lang/String;)V";
jsr L37;
endtry t31;
goto L49;
catch t31 #0;
catch t31 #0;
catch t31 #0;
try t31;
astore_3;
jsr L37;
endtry t31;
aload_3;
athrow;
L37: astore 4;
getstatic Field java/lang/System.out:"Ljava/io/PrintStream;";
ldc String "finally";
invokevirtual Method java/io/PrintStream.println:"(Ljava/lang/String;)V";
aload_1;
areturn;
L49: return;
}

william.maddox@Eng 2000-08-10