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* c++/7470: Vtable: virtual function pointers not in declaration order
@ 2002-08-02 2:36 grigory
0 siblings, 0 replies; 4+ messages in thread
From: grigory @ 2002-08-02 2:36 UTC (permalink / raw)
To: gcc-gnats
>Number: 7470
>Category: c++
>Synopsis: Vtable: virtual function pointers not in declaration order
>Confidential: no
>Severity: serious
>Priority: medium
>Responsible: unassigned
>State: open
>Class: sw-bug
>Submitter-Id: net
>Arrival-Date: Fri Aug 02 02:36:01 PDT 2002
>Closed-Date:
>Last-Modified:
>Originator: Grigory Zagorodnev
>Release: 3.1.1
>Organization:
>Environment:
Red Hat Linux release 7.1 (Seawolf)
Kernel 2.4.2-2smp on a 2-processor i686
gcc version 3.1.1
Configured with: ./configure --prefix=/usr/local --program-suffix=-3.1.1 --enable-threads
Thread model: posix
>Description:
The C++ ABI defines order of virtual function pointers in such way:
"2.5.2 Virtual Table Components and Order
The order of the virtual function pointers in a virtual table is the order of declaration of the corresponding member functions in the class. There is an entry for any virtual function declared in a class, whether it is a new function or overrides a base class function, unless it overrides a function from the primary base, and conversion between their return types does not require an adjustment."
*** G++ 3.1.1 compiler violates given rules ***
Let's consider the example.
--- fail.cpp ----------------------
struct base
{
short b;
virtual int foo() {}
};
struct derived: virtual base
{
int d;
virtual int foo() {}
virtual int bar() {}
};
-----------------------------------
Note that function declaration order is "foo, bar" and 'base' is not the primary base class for 'derived', since it's not nearly empty class.
New we check the virtual table for 'derived' class using "g++-3.1.1 -c -fdump-class-hierarchy fail.cpp".
The virtual table is:
Vtable for derived
derived::_ZTV7derived: 9 entries
0 8
4 0
8 &_ZTI7derived
12 derived::bar()
16 derived::foo()
20 0fffffff8
24 0fffffff8
28 &_ZTI7derived
32 derived::_ZTv0_n12_N7derived3fooEv()
We see that virtual functions appear in the order "bar, foo" which is wrong. It's expected to have functions in the declaration order as spcified by the ABI.
>How-To-Repeat:
1. Compile given testcase
g++-3.1.1 -c -fdump-class-hierarchy fail.cpp
2. Look for 'derived' virtual table in the produced fail.cpp.class file
>Fix:
>Release-Note:
>Audit-Trail:
>Unformatted:
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: c++/7470: Vtable: virtual function pointers not in declaration order
@ 2002-09-13 16:52 nathan
0 siblings, 0 replies; 4+ messages in thread
From: nathan @ 2002-09-13 16:52 UTC (permalink / raw)
To: gcc-bugs, gcc-prs, grigory, nathan
Synopsis: Vtable: virtual function pointers not in declaration order
State-Changed-From-To: analyzed->closed
State-Changed-By: nathan
State-Changed-When: Fri Sep 13 16:52:40 2002
State-Changed-Why:
now fixed
http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view%20audit-trail&database=gcc&pr=7470
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: c++/7470: Vtable: virtual function pointers not in declaration order
@ 2002-08-02 8:04 nathan
0 siblings, 0 replies; 4+ messages in thread
From: nathan @ 2002-08-02 8:04 UTC (permalink / raw)
To: gcc-bugs, gcc-prs, grigory, nathan, nobody
Synopsis: Vtable: virtual function pointers not in declaration order
Responsible-Changed-From-To: unassigned->nathan
Responsible-Changed-By: nathan
Responsible-Changed-When: Fri Aug 2 08:04:24 2002
Responsible-Changed-Why:
patching
http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view%20audit-trail&database=gcc&pr=7470
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: c++/7470: Vtable: virtual function pointers not in declaration order
@ 2002-08-02 3:54 nathan
0 siblings, 0 replies; 4+ messages in thread
From: nathan @ 2002-08-02 3:54 UTC (permalink / raw)
To: gcc-bugs, gcc-prs, grigory, nobody
Synopsis: Vtable: virtual function pointers not in declaration order
State-Changed-From-To: open->analyzed
State-Changed-By: nathan
State-Changed-When: Fri Aug 2 03:54:24 2002
State-Changed-Why:
confirmed. an ABI bug
http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view%20audit-trail&database=gcc&pr=7470
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2002-09-13 23:52 UTC | newest]
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2002-08-02 2:36 c++/7470: Vtable: virtual function pointers not in declaration order grigory
2002-08-02 3:54 nathan
2002-08-02 8:04 nathan
2002-09-13 16:52 nathan
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