From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <gcc-prs-return-16556-listarch-gcc-prs=gcc.gnu.org@gcc.gnu.org>
Received: (qmail 26012 invoked by alias); 2 Apr 2002 00:46:03 -0000
Mailing-List: contact gcc-prs-help@gcc.gnu.org; run by ezmlm
Precedence: bulk
List-Archive: <http://gcc.gnu.org/ml/gcc-prs/>
List-Post: <mailto:gcc-prs@gcc.gnu.org>
List-Help: <mailto:gcc-prs-help@gcc.gnu.org>
Sender: gcc-prs-owner@gcc.gnu.org
Received: (qmail 25947 invoked by uid 71); 2 Apr 2002 00:46:01 -0000
Date: Mon, 01 Apr 2002 16:46:00 -0000
Message-ID: <20020402004601.25946.qmail@sources.redhat.com>
To: nobody@gcc.gnu.org
Cc: gcc-prs@gcc.gnu.org,
From: Eric Blake <ebb9@email.byu.edu>
Subject: Re: java/5941: incorrect "Unreachable statement" error
Reply-To: Eric Blake <ebb9@email.byu.edu>
X-SW-Source: 2002-04/txt/msg00019.txt.bz2
List-Id: <gcc-prs.sourceware.org>

The following reply was made to PR java/5941; it has been noted by GNATS.

From: Eric Blake <ebb9@email.byu.edu>
To: tromey@redhat.com
Cc: shroff@transeda.com, gcc-gnats@gcc.gnu.org,
 	Per Bothner <per@bothner.com>
Subject: Re: java/5941: incorrect "Unreachable statement" error
Date: Mon, 01 Apr 2002 17:42:18 -0700

 I finally received a reply from Neal Gafter, one of Sun's engineers,
 offline.  To summarize his position (as I don't think I am allowed to
 quote it):
 
 for (int i = 0; ; i++) break;
 
 is legal, even though i++ will never be executed, because i++ is not a
 complete statement and is therefore not subject to the rules of JLS
 14.20.
 
 In fact, this next program should be legal as well, based on the
 definite assignment rules for For statements in JLS chapter 16. Note
 that Sun's JDK 1.3 and 1.4 does not compile it, it has been recorded as
 Sun bug 4660984; Jikes also fails this example, jikes bug 2780:
 
 class C
 {
   void bar()
   {
     for (final int i; 0 < (i = 1); i = i + 1)
       break;
   }
 }
 
 
 Tom Tromey wrote:
 > 
 > 
 > Saurin> public class bug2 {
 > Saurin>     public static int showBug2 () {
 > Saurin>         for (int i=0; i <= 10; i++) {
 > Saurin>             if ( i > 3 ) {
 > Saurin>                 return 10;
 > Saurin>             } else {
 > Saurin>                 return 11;
 > Saurin>             }
 > Saurin>         }
 > Saurin>     }
 > Saurin> }
 > 
 > Saurin> As you will notice that loop is exited after first iteration,
 > Saurin> and so the loop incrementer "i++" will never be executed.
 > 
 > Yes.  It looks like the language spec is unclear on this issue.
 > 
 > I'm looking at The Java Language Specification, 2nd Edition.  Section
 > 14.20 deals with unreachable statements.  The subsection on the `for'
 > statement doesn't mention conditions under which the update expression
 > is considered unreachable.
 > 
 > The Sun JDK 1.2 and 1.4 `javac' compilers don't give an error here,
 > which is suggestive but not authoritative.
 
 -- 
 This signature intentionally left boring.
 
 Eric Blake             ebb9@email.byu.edu
   BYU student, free software programmer