* [Bug c++/17386] libstdc++ iostreams miscompilation
2004-09-09 23:53 [Bug c++/17386] New: libstdc++ iostreams miscompilation rth at gcc dot gnu dot org
@ 2004-09-10 0:06 ` rth at gcc dot gnu dot org
2004-09-10 0:41 ` [Bug c++/17386] [4.0 Regression] " pinskia at gcc dot gnu dot org
` (5 subsequent siblings)
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From: rth at gcc dot gnu dot org @ 2004-09-10 0:06 UTC (permalink / raw)
To: gcc-bugs
------- Additional Comments From rth at gcc dot gnu dot org 2004-09-10 00:06 -------
The problem is that locale_init.cc is miscompiled. Specifically, the
initialization of _ZN14__gnu_internal9num_put_cE in _ZNSt6locale5_ImplC2Ej
has two initializations of its vptr (fine), and the stores get interchanged
by the scheduler (not fine), because alias analysis sez that the stores do
not conflict.
A minimal test case is
struct A
{
virtual void a();
int x;
};
struct C : public A
{
virtual void a();
};
inline void* operator new(__SIZE_TYPE__, void* __p) throw() { return __p; }
extern C obj;
void foo()
{
new(&obj) C;
}
Examining the assembly at -O2 -fomit-frame-pointer we see
movl $_ZTV1A+8, obj
movl $_ZTV1C+8, obj
ret
If alias analysis were working properly, we'd expect the first store to
be eliminated as dead. By the rtl optimizer, at least, since we don't
do any field-level dead store elimination at the tree level at the moment.
The problem, I believe, is in the front end. Looking at the last tree dump,
obj.<D1575>._vptr.A = &_ZTV1A[2];
obj._vptr.A = &_ZTV1C[2];
Obviously, the vptr field is at the same location in the base class as it
is in the derived class. Yet we are accessing the field different ways.
I have not yet determined class C has a separate FIELD_DECL for this vptr,
or if we're simply applying the FIELD_DECL from class A to an object of
class C.
--
What |Removed |Added
----------------------------------------------------------------------------
CC| |jason at gcc dot gnu dot org
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=17386
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* [Bug c++/17386] [4.0 Regression] libstdc++ iostreams miscompilation
2004-09-09 23:53 [Bug c++/17386] New: libstdc++ iostreams miscompilation rth at gcc dot gnu dot org
2004-09-10 0:06 ` [Bug c++/17386] " rth at gcc dot gnu dot org
@ 2004-09-10 0:41 ` pinskia at gcc dot gnu dot org
2004-09-10 0:47 ` rth at gcc dot gnu dot org
` (4 subsequent siblings)
6 siblings, 0 replies; 8+ messages in thread
From: pinskia at gcc dot gnu dot org @ 2004-09-10 0:41 UTC (permalink / raw)
To: gcc-bugs
------- Additional Comments From pinskia at gcc dot gnu dot org 2004-09-10 00:41 -------
Confirmed.
--
What |Removed |Added
----------------------------------------------------------------------------
CC|apinski at apple dot com |pinskia at gcc dot gnu dot
| |org
Severity|normal |critical
Status|UNCONFIRMED |NEW
Ever Confirmed| |1
Last reconfirmed|0000-00-00 00:00:00 |2004-09-10 00:41:28
date| |
Summary|libstdc++ iostreams |[4.0 Regression] libstdc++
|miscompilation |iostreams miscompilation
Target Milestone|--- |4.0.0
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=17386
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* [Bug c++/17386] [4.0 Regression] libstdc++ iostreams miscompilation
2004-09-09 23:53 [Bug c++/17386] New: libstdc++ iostreams miscompilation rth at gcc dot gnu dot org
2004-09-10 0:06 ` [Bug c++/17386] " rth at gcc dot gnu dot org
2004-09-10 0:41 ` [Bug c++/17386] [4.0 Regression] " pinskia at gcc dot gnu dot org
@ 2004-09-10 0:47 ` rth at gcc dot gnu dot org
2004-09-10 0:48 ` pinskia at gcc dot gnu dot org
` (3 subsequent siblings)
6 siblings, 0 replies; 8+ messages in thread
From: rth at gcc dot gnu dot org @ 2004-09-10 0:47 UTC (permalink / raw)
To: gcc-bugs
--
What |Removed |Added
----------------------------------------------------------------------------
Severity|critical |normal
Status|NEW |ASSIGNED
Last reconfirmed|2004-09-10 00:41:28 |2004-09-10 00:47:21
date| |
Target Milestone|4.0.0 |---
Version|4.0.0 |2.95
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=17386
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* [Bug c++/17386] [4.0 Regression] libstdc++ iostreams miscompilation
2004-09-09 23:53 [Bug c++/17386] New: libstdc++ iostreams miscompilation rth at gcc dot gnu dot org
` (2 preceding siblings ...)
2004-09-10 0:47 ` rth at gcc dot gnu dot org
@ 2004-09-10 0:48 ` pinskia at gcc dot gnu dot org
2004-09-10 21:42 ` cvs-commit at gcc dot gnu dot org
` (2 subsequent siblings)
6 siblings, 0 replies; 8+ messages in thread
From: pinskia at gcc dot gnu dot org @ 2004-09-10 0:48 UTC (permalink / raw)
To: gcc-bugs
--
What |Removed |Added
----------------------------------------------------------------------------
Target Milestone|--- |4.0.0
Version|2.95 |4.0.0
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=17386
^ permalink raw reply [flat|nested] 8+ messages in thread
* [Bug c++/17386] [4.0 Regression] libstdc++ iostreams miscompilation
2004-09-09 23:53 [Bug c++/17386] New: libstdc++ iostreams miscompilation rth at gcc dot gnu dot org
` (3 preceding siblings ...)
2004-09-10 0:48 ` pinskia at gcc dot gnu dot org
@ 2004-09-10 21:42 ` cvs-commit at gcc dot gnu dot org
2004-09-10 21:44 ` rth at gcc dot gnu dot org
2004-09-11 22:11 ` pinskia at gcc dot gnu dot org
6 siblings, 0 replies; 8+ messages in thread
From: cvs-commit at gcc dot gnu dot org @ 2004-09-10 21:42 UTC (permalink / raw)
To: gcc-bugs
------- Additional Comments From cvs-commit at gcc dot gnu dot org 2004-09-10 21:42 -------
Subject: Bug 17386
CVSROOT: /cvs/gcc
Module name: gcc
Changes by: rth@gcc.gnu.org 2004-09-10 21:42:01
Modified files:
gcc/cp : ChangeLog call.c class.c typeck.c
Log message:
PR c++/17386
* call.c (build_vfield_ref): Move...
* class.c (build_vfield_ref): ... here. Convert datum to the
primary base containing the vptr.
(make_new_vtable): Simplify build_primary_vtable arguments.
(finish_struct_1): Do not duplicate TYPE_VFIELD.
* typeck.c (build_class_member_access_expr): Don't warn for
null object access to base fields.
Patches:
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/cp/ChangeLog.diff?cvsroot=gcc&r1=1.4343&r2=1.4344
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/cp/call.c.diff?cvsroot=gcc&r1=1.504&r2=1.505
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/cp/class.c.diff?cvsroot=gcc&r1=1.669&r2=1.670
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/cp/typeck.c.diff?cvsroot=gcc&r1=1.574&r2=1.575
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=17386
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* [Bug c++/17386] [4.0 Regression] libstdc++ iostreams miscompilation
2004-09-09 23:53 [Bug c++/17386] New: libstdc++ iostreams miscompilation rth at gcc dot gnu dot org
` (4 preceding siblings ...)
2004-09-10 21:42 ` cvs-commit at gcc dot gnu dot org
@ 2004-09-10 21:44 ` rth at gcc dot gnu dot org
2004-09-11 22:11 ` pinskia at gcc dot gnu dot org
6 siblings, 0 replies; 8+ messages in thread
From: rth at gcc dot gnu dot org @ 2004-09-10 21:44 UTC (permalink / raw)
To: gcc-bugs
------- Additional Comments From rth at gcc dot gnu dot org 2004-09-10 21:44 -------
http://gcc.gnu.org/ml/gcc-patches/2004-09/msg01018.html
--
What |Removed |Added
----------------------------------------------------------------------------
Status|ASSIGNED |RESOLVED
Resolution| |FIXED
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=17386
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* [Bug c++/17386] [4.0 Regression] libstdc++ iostreams miscompilation
2004-09-09 23:53 [Bug c++/17386] New: libstdc++ iostreams miscompilation rth at gcc dot gnu dot org
` (5 preceding siblings ...)
2004-09-10 21:44 ` rth at gcc dot gnu dot org
@ 2004-09-11 22:11 ` pinskia at gcc dot gnu dot org
6 siblings, 0 replies; 8+ messages in thread
From: pinskia at gcc dot gnu dot org @ 2004-09-11 22:11 UTC (permalink / raw)
To: gcc-bugs
------- Additional Comments From pinskia at gcc dot gnu dot org 2004-09-11 22:11 -------
*** Bug 17420 has been marked as a duplicate of this bug. ***
--
What |Removed |Added
----------------------------------------------------------------------------
CC| |rearnsha at gcc dot gnu dot
| |org
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=17386
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