c/4104: structure misalignment problem causing kernel failures

[Paul Clements]

The following reply was made to PR c/4104; it has been noted by GNATS.

From: Paul Clements <Paul.Clements@SteelEye.com>
To: rodrigc@gcc.gnu.org
Cc: gcc-bugs@gcc.gnu.org, gcc-prs@gcc.gnu.org, nobody@gcc.gnu.org
Subject: Re: c/4104: structure misalignment problem causing kernel failures
Date: Mon, 15 Oct 2001 09:29:06 -0400

 rodrigc@gcc.gnu.org wrote:
 > 
 > Synopsis: structure misalignment problem causing kernel failures
 > 
 > State-Changed-From-To: open->feedback
 > State-Changed-By: rodrigc
 > State-Changed-When: Sat Oct 13 20:52:01 2001
 > State-Changed-Why:
 >     Please review the bug submission guidelines at
 >     http://gcc.gnu.org/bugs.html and submit preprocessed source
 >     with your bug report.
 > 
 >     Also, since you are using the Redhat version of gcc,
 >     please report your bug to Red Hat's bug reporting
 >     system at:
 >     http://bugzilla.redhat.com/bugzilla/
 > 
 > http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view&pr=4104&database=gcc
 
 
 more info:
 ----------------------
 
 Subject: [Bug 52451] Changed - structure misalignment problem in gcc
 2.96-81
 Date: Thu, 23 Aug 2001 16:59:12 -0400
 From: bugzilla@redhat.com
 To: jakub@redhat.com, paul.clements@steeleye.com, dlt@redhat.com
 
 Please do not reply directly to this email. All additional
 comments should be made in the comments box of this bug
 report.
 
 https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=52451
 
 --- shadow/52451	Thu Aug 23 16:37:00 2001
 +++ shadow/52451.tmp.10269	Thu Aug 23 16:59:12 2001
 @@ -3,7 +3,7 @@
  Version: 7.1
  Platform: i386
  OS/Version: Linux
 -Status: NEEDINFO   
 +Status: ASSIGNED   
  Resolution: 
  Severity: high
  Priority: normal
 @@ -139,3 +139,24 @@
  Created an attachment (id=29274)
  pre-processed source file, which demonstrates misalignment problem
  
 +
 +------- Additional comments from jakub@redhat.com 2001-08-23 16:59:38
 -------
 +Simplified testcase
 +typedef struct x { int a; int b; } __attribute__((aligned(32))) X;
 +typedef struct y { X x[32]; int c; } Y;
 +
 +Y y[3];
 +
 +int main(void)
 +{
 +  if (sizeof (y) != 3168)
 +    abort ();
 +  exit (0);
 +}
 +(the X in array is important, changing it to
 +typedef struct y { X x; X y[31]; int c; } Y;
 +fixes it).
 +This testcase works on gcc < 2.96-RH or on 2.96-RH+ (incl. 3.0, 3.0.1,
 3.1)
 +on non-IA-32 architectures (tested alpha, IA-64, sparc).
 +Fails on IA-32 with 2.96-RH, 3.0, 3.0.1, 3.1.
 +Apparently some config/i386 alignment issue, will debug this tomorrow.