From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 29366 invoked by alias); 8 Mar 2003 14:16:01 -0000 Mailing-List: contact gcc-prs-help@gcc.gnu.org; run by ezmlm Precedence: bulk List-Archive: List-Post: List-Help: Sender: gcc-prs-owner@gcc.gnu.org Received: (qmail 29348 invoked by uid 71); 8 Mar 2003 14:16:00 -0000 Date: Sat, 08 Mar 2003 14:16:00 -0000 Message-ID: <20030308141600.29347.qmail@sources.redhat.com> To: nobody@gcc.gnu.org Cc: gcc-prs@gcc.gnu.org, From: Nathan Sidwell Subject: Re: c++/9881: What is an address constant expression? Reply-To: Nathan Sidwell X-SW-Source: 2003-03/txt/msg00396.txt.bz2 List-Id: The following reply was made to PR c++/9881; it has been noted by GNATS. From: Nathan Sidwell To: Richard C Bilson Cc: bangerth@ticam.utexas.edu, gcc-bugs@gcc.gnu.org, gcc-gnats@gcc.gnu.org, pabuhr@uwaterloo.ca Subject: Re: c++/9881: What is an address constant expression? Date: Sat, 08 Mar 2003 14:13:17 +0000 Richard C Bilson wrote: > Whether the new behavior is in error is a matter of debate it seems. > I think that 5.19.4 requires the initializer in question to be an > address constant expression and thus be a static initialization. yup, I see you are correct, thanks for the reference. > As far as I can tell, the code to handle &(((T*)0)->x) also works > just fine in the case that the pointer is not null. So I removed the > restriction that the operand of the indirection be a NPC. > > This fixes our example code, solves the real problem that prompted us to > complain in the first place, and doesn't seem to cause any trouble with > the gcc test suite. I can't say whether it would cause a recurrence > of the problems you fixed in the first place, but I do have some SPARC > machines at my disposal if you have an example of the problem for me > to try. I suspect it will break. you need g++.dg/other/packed1.C, I'm curious as to why it didn't fail for you. The real problem is gcc does represents a pointer to a misaligned int as an 'int *' rather than something like 'int __attribute__((misaligned)) *' which would help the dereferencing machinery out. The current mechanmism 'works' only when the field decl is visible. The fold behaviour takes that out. Yuck! nathan -- Nathan Sidwell :: http://www.codesourcery.com :: CodeSourcery LLC The voices in my head said this was stupid too nathan@codesourcery.com : http://www.cs.bris.ac.uk/~nathan/ : nathan@acm.org