* C++ ABI change since 3.2 with no warning
@ 2002-10-04 17:02 Janis Johnson
2002-10-08 13:09 ` Mark Mitchell
0 siblings, 1 reply; 2+ messages in thread
From: Janis Johnson @ 2002-10-04 17:02 UTC (permalink / raw)
To: gcc
While working on C++ compatibility tests I broke up g++.dg/init/empty1.C
into this set of source files. This test passes when everything is
built with either GCC 3.2 or with the mainline but fails when empty1_x.C
is compiled with GCC 3.2 and the rest is built with the mainline. The
original test is for a PR that was fixed in 3.0.2. The failure is due
to a change in alignment. Is this expected? Should it get a warning
with -Wabi for having changed since GCC 3.2?
Janis
--- empty1.h -----------------------------------------------------------
class EmptyBase0 {};
class EmptyBase1 : public EmptyBase0 {};
class Base1 {
public:
unsigned int t_;
Base1(unsigned int);
};
class PEPE : public Base1, public EmptyBase1 {
public:
PEPE(unsigned int);
};
--- empty1_main.C ------------------------------------------------------
// Copyright (C) 2001 Free Software Foundation, Inc.
// Contributed by Nathan Sidwell 3 Sept 2001 <nathan@codesourcery.com>
// Split into pieces for binary compatibility testing October 2002
// Bug 4203. We were bit copying empty bases including the
// padding. Which clobbers whatever they overlay.
extern void empty1_x (void);
int
main ()
{
empty1_x ();
}
--- empty1_x.C ---------------------------------------------------------
extern "C" void abort (void);
#include "empty1.h"
void
empty1_x ()
{
PEPE pepe(0xff);
if (pepe.t_ != 255)
abort ();
}
--- empty1_y.C ---------------------------------------------------------
#include "empty1.h"
Base1::Base1(unsigned int t) : t_(t) {}
PEPE::PEPE(unsigned int t) : Base1(t), EmptyBase1(EmptyBase1()) {}
------------------------------------------------------------------------
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: C++ ABI change since 3.2 with no warning
2002-10-04 17:02 C++ ABI change since 3.2 with no warning Janis Johnson
@ 2002-10-08 13:09 ` Mark Mitchell
0 siblings, 0 replies; 2+ messages in thread
From: Mark Mitchell @ 2002-10-08 13:09 UTC (permalink / raw)
To: Janis Johnson, gcc
--On Friday, October 04, 2002 04:17:06 PM -0700 Janis Johnson
<janis187@us.ibm.com> wrote:
> While working on C++ compatibility tests I broke up g++.dg/init/empty1.C
> into this set of source files. This test passes when everything is
> built with either GCC 3.2 or with the mainline but fails when empty1_x.C
> is compiled with GCC 3.2 and the rest is built with the mainline. The
> original test is for a PR that was fixed in 3.0.2. The failure is due
> to a change in alignment. Is this expected?
I think so; we intentionally fixed the alignment of certain tiny classes,
in both C and C++ on the mainline recently.
If we're going to warn about it, we should do it in both C and C++.
I'll take a look at it when I get home and make sure that this is what
it is.
--
Mark Mitchell mark@codesourcery.com
CodeSourcery, LLC http://www.codesourcery.com
--- empty1.h -----------------------------------------------------------
class EmptyBase0 {};
class EmptyBase1 : public EmptyBase0 {};
class Base1 {
public:
unsigned int t_;
Base1(unsigned int);
};
class PEPE : public Base1, public EmptyBase1 {
public:
PEPE(unsigned int);
};
--- empty1_main.C ------------------------------------------------------
// Copyright (C) 2001 Free Software Foundation, Inc.
// Contributed by Nathan Sidwell 3 Sept 2001 <nathan@codesourcery.com>
// Split into pieces for binary compatibility testing October 2002
// Bug 4203. We were bit copying empty bases including the
// padding. Which clobbers whatever they overlay.
extern void empty1_x (void);
int
main ()
{
empty1_x ();
}
--- empty1_x.C ---------------------------------------------------------
extern "C" void abort (void);
#include "empty1.h"
void
empty1_x ()
{
PEPE pepe(0xff);
if (pepe.t_ != 255)
abort ();
}
--- empty1_y.C ---------------------------------------------------------
#include "empty1.h"
Base1::Base1(unsigned int t) : t_(t) {}
PEPE::PEPE(unsigned int t) : Base1(t), EmptyBase1(EmptyBase1()) {}
------------------------------------------------------------------------
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