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* [Bug c++/12377] New: Empty base out of class boundaries
@ 2003-09-23 15:57 grigory at stl dot sarov dot ru
2003-09-23 16:02 ` [Bug c++/12377] [ABI] " bangerth at dealii dot org
` (3 more replies)
0 siblings, 4 replies; 5+ messages in thread
From: grigory at stl dot sarov dot ru @ 2003-09-23 15:57 UTC (permalink / raw)
To: gcc-bugs
PLEASE REPLY TO gcc-bugzilla@gcc.gnu.org ONLY, *NOT* gcc-bugs@gcc.gnu.org.
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=12377
Summary: Empty base out of class boundaries
Product: gcc
Version: 3.3.1
Status: UNCONFIRMED
Severity: normal
Priority: P2
Component: c++
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: grigory at stl dot sarov dot ru
CC: gcc-bugs at gcc dot gnu dot org
GCC build triplet: i386-redhat-linux
GCC host triplet: i386-redhat-linux
GCC target triplet: i386-redhat-linux
Using the 3.2-compatable ABI implementation (-fabi_version=1) g++ compiler may
alocate empty virtual base out of class boundaries. That seems to be a bug
rather than a specific implementation.
Let's see: on class hierarchy listed below, g++ 3.3.1 produces class c17 of
size 16 but allocates c17::c10::c0 base at offset 28.
$ cat foo.cpp
struct c0 { };
struct c2 {
unsigned char m1;
};
struct c5 : c0, virtual c2 { };
struct c6 { };
struct c9 : c5, c6 { };
struct c10 :
virtual c2,
virtual c5,
virtual c0,
c9
{
};
struct c17 : virtual c10, c6 { };
$ g++ -c -fdump-class-hierarchy foo.cpp
Class c17
size=16 align=4
c17 (0x4032d400) 0
vptridx=0 vptr=((&c17::_ZTV3c17) + 24)
c10 (0x4032d440) 0 nearly-empty virtual canonical
...
c0 (0x4032d5c0) 28 empty virtual canonical
Of cource an empty base does not take any space there, but the class object
become logically invalid and potentially may lead to run-time problems.
^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug c++/12377] [ABI] Empty base out of class boundaries
2003-09-23 15:57 [Bug c++/12377] New: Empty base out of class boundaries grigory at stl dot sarov dot ru
@ 2003-09-23 16:02 ` bangerth at dealii dot org
2003-09-24 9:13 ` nathan at gcc dot gnu dot org
` (2 subsequent siblings)
3 siblings, 0 replies; 5+ messages in thread
From: bangerth at dealii dot org @ 2003-09-23 16:02 UTC (permalink / raw)
To: gcc-bugs
PLEASE REPLY TO gcc-bugzilla@gcc.gnu.org ONLY, *NOT* gcc-bugs@gcc.gnu.org.
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=12377
bangerth at dealii dot org changed:
What |Removed |Added
----------------------------------------------------------------------------
Summary|Empty base out of class |[ABI] Empty base out of
|boundaries |class boundaries
------- Additional Comments From bangerth at dealii dot org 2003-09-23 14:43 -------
I can confirm this, but I have no clue what is supposed to be
the right value.
What is interesting, though, is that present mainline ICEs while
writing out the class info.
W.
^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug c++/12377] [ABI] Empty base out of class boundaries
2003-09-23 15:57 [Bug c++/12377] New: Empty base out of class boundaries grigory at stl dot sarov dot ru
2003-09-23 16:02 ` [Bug c++/12377] [ABI] " bangerth at dealii dot org
@ 2003-09-24 9:13 ` nathan at gcc dot gnu dot org
2003-09-24 9:40 ` nathan at gcc dot gnu dot org
2003-12-09 18:30 ` dhazeghi at yahoo dot com
3 siblings, 0 replies; 5+ messages in thread
From: nathan at gcc dot gnu dot org @ 2003-09-24 9:13 UTC (permalink / raw)
To: gcc-bugs
PLEASE REPLY TO gcc-bugzilla@gcc.gnu.org ONLY, *NOT* gcc-bugs@gcc.gnu.org.
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=12377
nathan at gcc dot gnu dot org changed:
What |Removed |Added
----------------------------------------------------------------------------
AssignedTo|unassigned at gcc dot gnu |nathan at gcc dot gnu dot
|dot org |org
Status|UNCONFIRMED |ASSIGNED
^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug c++/12377] [ABI] Empty base out of class boundaries
2003-09-23 15:57 [Bug c++/12377] New: Empty base out of class boundaries grigory at stl dot sarov dot ru
2003-09-23 16:02 ` [Bug c++/12377] [ABI] " bangerth at dealii dot org
2003-09-24 9:13 ` nathan at gcc dot gnu dot org
@ 2003-09-24 9:40 ` nathan at gcc dot gnu dot org
2003-12-09 18:30 ` dhazeghi at yahoo dot com
3 siblings, 0 replies; 5+ messages in thread
From: nathan at gcc dot gnu dot org @ 2003-09-24 9:40 UTC (permalink / raw)
To: gcc-bugs
PLEASE REPLY TO gcc-bugzilla@gcc.gnu.org ONLY, *NOT* gcc-bugs@gcc.gnu.org.
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=12377
nathan at gcc dot gnu dot org changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|ASSIGNED |RESOLVED
Resolution| |FIXED
------- Additional Comments From nathan at gcc dot gnu dot org 2003-09-24 09:13 -------
This is fixed in 3.4,
* use -Wabi to warn about it
* use -fabi-version=0 to resolve it
The ICE is now fixed, it was a pretty printer problem
^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug c++/12377] [ABI] Empty base out of class boundaries
2003-09-23 15:57 [Bug c++/12377] New: Empty base out of class boundaries grigory at stl dot sarov dot ru
` (2 preceding siblings ...)
2003-09-24 9:40 ` nathan at gcc dot gnu dot org
@ 2003-12-09 18:30 ` dhazeghi at yahoo dot com
3 siblings, 0 replies; 5+ messages in thread
From: dhazeghi at yahoo dot com @ 2003-12-09 18:30 UTC (permalink / raw)
To: gcc-bugs
--
What |Removed |Added
----------------------------------------------------------------------------
Target Milestone|--- |3.4
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=12377
^ permalink raw reply [flat|nested] 5+ messages in thread
end of thread, other threads:[~2003-12-09 18:30 UTC | newest]
Thread overview: 5+ messages (download: mbox.gz / follow: Atom feed)
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2003-09-23 15:57 [Bug c++/12377] New: Empty base out of class boundaries grigory at stl dot sarov dot ru
2003-09-23 16:02 ` [Bug c++/12377] [ABI] " bangerth at dealii dot org
2003-09-24 9:13 ` nathan at gcc dot gnu dot org
2003-09-24 9:40 ` nathan at gcc dot gnu dot org
2003-12-09 18:30 ` dhazeghi at yahoo dot com
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