Re: c++/6874: deriving from zero-sized objects causes extraneous padding

Re: c++/6874: deriving from zero-sized objects causes extraneous padding

[Charlie Skilbeck]

The following reply was made to PR c++/6874; it has been noted by GNATS.

From: "Charlie Skilbeck" <charlie@skilbeck.com>
To: <lerdsuwa@gcc.gnu.org>,
	<gcc-bugs@gcc.gnu.org>,
	<gcc-prs@gcc.gnu.org>,
	<gnubug@skilbeck.com>,
	<nobody@gcc.gnu.org>,
	<gcc-gnats@gcc.gnu.org>
Cc:  
Subject: Re: c++/6874: deriving from zero-sized objects causes extraneous padding
Date: Fri, 7 Jun 2002 19:04:10 -0700

 Sadly, upgrading to the the beta 3.0 compiler is not an option at this stage
 of our project (the mips version is unstable) - can someone point me at the
 relevant source file, and I'll fix it myself...
 
 Cheers,
 Charlie.
 
 ----- Original Message -----
 From: <lerdsuwa@gcc.gnu.org>
 To: <gcc-bugs@gcc.gnu.org>; <gcc-prs@gcc.gnu.org>; <gnubug@skilbeck.com>;
 <nobody@gcc.gnu.org>
 Sent: Fri, Jun 07, 2002 7:25 AM
 Subject: Re: c++/6874: deriving from zero-sized objects causes extraneous
 padding
 
 
 > Synopsis: deriving from zero-sized objects causes extraneous padding
 >
 > State-Changed-From-To: open->closed
 > State-Changed-By: lerdsuwa
 > State-Changed-When: Fri Jun  7 07:25:37 2002
 > State-Changed-Why:
 >     GCC 3.0 and later (with the new V3 ABI) behave like
 >     the suggested idea.
 >
 >
 http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view%20audit-trail&database=gcc&p
 r=6874
 >
 >
 

Re: c++/6874: deriving from zero-sized objects causes extraneous padding

[lerdsuwa]

Synopsis: deriving from zero-sized objects causes extraneous padding

State-Changed-From-To: open->closed
State-Changed-By: lerdsuwa
State-Changed-When: Fri Jun  7 07:25:37 2002
State-Changed-Why:
    GCC 3.0 and later (with the new V3 ABI) behave like 
    the suggested idea.

http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view%20audit-trail&database=gcc&pr=6874

c++/6874: deriving from zero-sized objects causes extraneous padding

[gnubug]

>Number:         6874
>Category:       c++
>Synopsis:       deriving from zero-sized objects causes extraneous padding
>Confidential:   no
>Severity:       critical
>Priority:       medium
>Responsible:    unassigned
>State:          open
>Class:          change-request
>Submitter-Id:   net
>Arrival-Date:   Thu May 30 13:36:00 PDT 2002
>Closed-Date:
>Last-Modified:
>Originator:     gnubug@skilbeck.com
>Release:        2.95.??
>Organization:
>Environment:
mips
>Description:
when deriving from a zero-sized struct, can we get the dummy single byte overlaid by the data members of the derived struct?

>How-To-Repeat:
struct Bob
{
  void *operator new(size_t s);
  void operator delete(void *p);
};

struct Bill : Bob
{
  int Jack;
};

...

sizeof(Bob)  == 1 (Fine)
sizeof(Bill) == 8 (sizeof(int) would be nice, like other compilers)
>Fix:
er... hack the gcc!?
>Release-Note:
>Audit-Trail:
>Unformatted: