Re: java/5794: gcj fails to verify .class file generated by Sun JDK 1.4 compiler

[Tom Tromey <tromey at redhat dot com>]

The following reply was made to PR java/5794; it has been noted by GNATS.

From: Tom Tromey <tromey@redhat.com>
To: adam@medovina.org
Cc: gcc-gnats@gcc.gnu.org
Subject: Re: java/5794: gcj fails to verify .class file generated by Sun JDK 1.4 compiler
Date: 28 Feb 2002 17:47:43 -0700

 >>>>> "Adam" == adam  <adam@medovina.org> writes:
 
 Adam> Number:         5794
 Adam> Synopsis:       gcj fails to verify .class file generated by Sun JDK 1.4 compiler
 
 Could you upload the resulting .class file?
 Just reply to this email and attach it, keeping gcc-gnats on the CC
 line.
 
 Adam> When Sun's Java compiler in JDK 1.4 compiles a try...finally
 Adam> block, it emits a (useless and unused) exception table entry
 Adam> whose target is within the range of protected instructions.
 Adam> There is nothing inherently unsafe with this, but we check for
 Adam> this case and reject it in verify.c.
 
 It seems to me that this must be invalid.
 
 Adam> I tried that and then gcj complained about a stack overflow in
 Adam> the same .class file.
 
 Yeah.  Suppose the VM encounters an internal error and throws an
 exception after it has set the PC to the start of the exception
 handler but before the first instruction of the handler (probably a
 pop or an astore) is executed.  This leads inexorably to a stack
 overflow.  I imagine the gij verifier will die on this too.
 
 I'd like to see the class file though.  It's possible there are
 obscure extenuating circumstances.  Or perhaps they've tightened the
 verification spec and I don't yet know about it.
 
 Tom