Re: c++/6831: Wrong base class alignment (nvalign vs. align)

[Nathan Sidwell <nathan@codesourcery.com>]

The following reply was made to PR c++/6831; it has been noted by GNATS.

From: Nathan Sidwell <nathan@codesourcery.com>
To: Grigory_Zagorodnev@vniief.ims.intel.com, gcc-gnats@gcc.gnu.org,
   gcc-prs@gcc.gnu.org, nathan@gcc.gnu.org, gcc-bugs@gcc.gnu.org
Cc:  
Subject: Re: c++/6831: Wrong base class alignment (nvalign vs. align)
Date: Fri, 05 Jul 2002 13:08:23 +0100

 http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view%20audit-trail&database=gcc&pr=6831
 I do not get the different layout that you describe. I do get a different
 layout to the one you think you should get. The layout I get
 accords to the ABI. Here is the -fdump-class-hierarchy output for E. I have
 marked the important offsets.
 
 this is with a cross compiler configured as --target=ia64-intel-unix
 Class E
    size=48 align=16
 E (0x40090a40) 0 <- offsetof (E)
     vptridx=0 vptr=((&E::_ZTV1E) + 32)
   B (0x40090a80) 0 nearly-empty <- offset of (B)
       primary-for E (0x40090a40)
       subvttidx=8
     A (0x40090ac0) 24 virtual canonical <- offset of A
         vbaseoffset=-24
   D (0x40090b00) 8 <- offset of D
       subvttidx=16 vptridx=24 vptr=((&E::_ZTV1E) + 56)
     C (0x40090b40) 32 virtual canonical <- offset of C
         vbaseoffset=-32
 
 Note D has a dsize of 12, and 4 bytes of tail padding. Because D is a
 non-pod, we can overlay that tail padding with another object. Here
 is the layout we should and do get for ia64
 
 off size name
 0   8 	 E::B::vptr
 8   8    E::D::vptr
 16  4    E::D::d
 20  4    E::e overlayed ontop of D's tail padding
 24  4    E::A
 28  4    alignment padding
 32  16   E::C
 48
 
 nathan
 
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