Re: java/5941: incorrect "Unreachable statement" error

[Tom Tromey <tromey@redhat.com>]

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

From: Tom Tromey <tromey@redhat.com>
To: shroff@transeda.com
Cc: gcc-gnats@gcc.gnu.org, "Eric B. Blake" <ebb9@email.byu.edu>,
        Per Bothner <per@bothner.com>
Subject: Re: java/5941: incorrect "Unreachable statement" error
Date: 25 Mar 2002 14:51:58 -0700

 >>>>> "Saurin" == Saurin B Shroff <shroff@transeda.com> writes:
 
 Hi.  I looked at this PR a little more today.
 
 Saurin> Following is a simplified code that shows this behavior:
 
 In your original code the loop didn't appear to always complete
 abnormally.  So this code looks different.  We might be seeing two
 different problems.
 
 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> 	return 12;
 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.
 
 I think what gcj does is reasonable.  This might simply be a bug in
 the language spec.  However, I'm not certain.  Perhaps there is a
 subtle reason for this omission.
 
 Eric, Per, what do you think?
 
 Saurin> What I would suggest that "Unreachable statement" should be a
 Saurin> warning rather than error since it stops the compilation
 
 The language specification requires an error for unreachable code.
 
 Tom