virtual-multiple inheritance. what an extra dword is for?

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Hello All,

I've fount that if I compile the same program using gcc and vc 2003 =
the same class E (see complete source bellow) has different size (on vc =
it is 4 bytes bigger). Digging into this I've found that vc is reserving =
a dword in the E class right before storage for virtual base class. In =
my tests value of this dword always was 0. I did not see any code =
referencing this memory.=20

Anybody has any idea what this dword is for?

Vladimir.

/*

Compile:
cl -EHsc -Zi t11.cpp

Classes hierarchy
A
/ \
| |
| |
B D C
| | |
| | |
\ | /
E

Output: My Interpritation:

ma=3Dff1, sizeof(A)=3D8 sizeof(vtable) + sizeof(ma_)
mb=3Dff2, sizeof(B)=3D20 sizeof(vtable) + sizeof(mb_) + =
1*sizeof(DWORD) + sizeof(A)
mc=3Dff3, sizeof(C)=3D20 sizeof(vtable) + sizeof(mb_) + =
1*sizeof(DWORD) + sizeof(A)
md=3Dff4, sizeof(D)=3D8 sizeof(vtable) + sizeof(md_)
me=3Dff5, sizeof(E)=3D40 =20
&before - &after =3D 13

Layout of the stack in the "main" function:

Nr Address Value Points to My Interpritation
01 0012feb0 00000fe2 << veriable "after"

02 0012feb4 0041f178 t11!E::`vftable' << veriable e, start of E, =
start of E::D
03 0012feb8 00000ff4 << e.md_
04 0012febc 0041f188 t11!E::`vbtable' << start of E::B
05 0012fec0 00000ff2 << e.mb_
06 0012fec4 0041f17c t11!E::`vbtable' << start of E::C
07 0012fec8 00000ff3 << e.mc_
08 0012fecc 00000ff5 << e.me_
09 0012fed0 00000000 << ???WHAT ARE THIS FOR???
10 0012fed4 0041f174 t11!E::`vftable' << start of E::A
11 0012fed8 00000ff1 << e.ma_, end of E
12 0012fedc 0000000c << veriable "distance"

13 0012fee0 00000fe1 << veriable "before"

*/

#include<iostream>

using namespace std;

class A {
public:
explicit A(long ma)
: ma_(ma) {
}
virtual void foo();
private:
long ma_;
};

void A::foo() {
cout << hex << "ma=3D" << ma_ << ", sizeof(A)=3D" << dec << =
sizeof(A) << "\n";
}

class B : public virtual A {
public:
explicit B(long mb)
: mb_(mb), A(0) {
}
virtual void foo();
private:
long mb_;
};

void B::foo() {
cout << hex << "mb=3D" << mb_ << ", sizeof(B)=3D" << dec << =
sizeof(B) << "\n";
}

class C : public virtual A {
public:
explicit C(long mc)
: mc_(mc), A(0) {
}
virtual void foo();
private:
long mc_;
};

void C::foo() {
cout << hex << "mc=3D" << mc_ << ", sizeof(C)=3D" << dec << =
sizeof(C) << "\n";
}

class D {
public:
explicit D(long md)
: md_(md) {
}
virtual void foo();
private:
long md_;
};

void D::foo() {
cout << hex << "md=3D" << md_ << ", sizeof(D)=3D" << dec << =
sizeof(D) << "\n";
}

class E : public B, public C, public D {
public:
explicit E(long ma=3D0xFF1, long mb=3D0xFF2, long mc=3D0xFF3, long =
md=3D0xFF4, long me=3D0xFF5)
: A(ma), B(mb), C(mc), D(md), me_(me) {
}
virtual void foo();
private:
long me_;
};

void E::foo() {
A::foo();
B::foo();
C::foo();
D::foo();
cout << hex << "me=3D" << me_ << ", sizeof(E)=3D" << dec << =
sizeof(E) << "\n";
}

int main(int, char **) {
cout << hex;

int distance =3D 0;
int before =3D 0xFE1;

E e;
if(!distance) { //to prevent compiler from rearanging veriables on =
the stack
int after =3D 0xFE2;
distance =3D &before - &after;
}
e.foo();

cout << dec << "&before - &after =3D " << abs(distance) << "\n";

return 0;
}
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<HTML><HEAD>
<META http-equiv=3DContent-Type content=3D"text/html; =
charset=3Diso-8859-1">
<META content=3D"MSHTML 6.00.2800.1400" name=3DGENERATOR>
<STYLE></STYLE>
</HEAD>
<BODY>
<DIV><FONT face=3DCourier size=3D2>Hello All,</FONT></DIV>
<DIV><FONT face=3DCourier size=3D2></FONT> </DIV>
<DIV><FONT face=3DCourier size=3D2>    I've fount that if =
I compile=20
the same program using gcc and vc 2003  the same class E =
(see complete=20
source bellow) has different size (on vc it is 4 bytes bigger). Digging =
into=20
this I've found that vc is reserving a dword in the E class right before =
storage=20
for virtual base class. In my tests value of this dword always was 0. I =
did not=20
see any code referencing this memory. </FONT></DIV>
<DIV><FONT face=3DCourier size=3D2></FONT> </DIV>
<DIV><FONT face=3DCourier size=3D2>    Anybody has any =
idea what this=20
dword is for?</FONT></DIV>
<DIV><FONT face=3DCourier size=3D2></FONT> </DIV>
<DIV><FONT face=3DCourier size=3D2>Vladimir.</FONT></DIV>
<DIV><FONT face=3DCourier size=3D2></FONT> </DIV>
<DIV><FONT face=3DCourier size=3D2></FONT> </DIV>
<DIV><FONT face=3DCourier size=3D2>/*</FONT></DIV>
<DIV><FONT face=3DCourier></FONT> </DIV>
<DIV><FONT face=3DCourier size=3D2>Compile:<BR>    cl =
-EHsc -Zi=20
t11.cpp</FONT></DIV>
<DIV><FONT face=3DCourier></FONT> </DIV>
<DIV><FONT face=3DCourier size=3D2>Classes=20
hierarchy<BR>       =
A<BR>    =20
/   \<BR>    |    =20
|<BR>    |     =
|<BR>   =20
B  D  C<BR>    |  | =20
|<BR>    |  |  |<BR>     \ =
|=20
/<BR>       E</FONT></DIV>
<DIV><FONT face=3DCourier></FONT> </DIV>
<DIV><FONT face=3DCourier=20
size=3D2>Output:         &nb=
sp;           =20
My Interpritation:</FONT></DIV>
<DIV><FONT face=3DCourier></FONT> </DIV>
<DIV><FONT face=3DCourier size=3D2>    ma=3Dff1,=20
sizeof(A)=3D8      sizeof(vtable) +=20
sizeof(ma_)<BR>    mb=3Dff2, =
sizeof(B)=3D20    =20
sizeof(vtable) + sizeof(mb_) + 1*sizeof(DWORD) + =
sizeof(A)<BR>   =20
mc=3Dff3, sizeof(C)=3D20     sizeof(vtable) + =
sizeof(mb_) +=20
1*sizeof(DWORD) + sizeof(A)<BR>    md=3Dff4,=20
sizeof(D)=3D8      sizeof(vtable) +=20
sizeof(md_)<BR>    me=3Dff5, =
sizeof(E)=3D40    =20
<BR>    &before - &after =3D 13</FONT></DIV>
<DIV><FONT face=3DCourier></FONT> </DIV>
<DIV><FONT face=3DCourier size=3D2>Layout of the stack in the "main"=20
function:</FONT></DIV>
<DIV><FONT face=3DCourier></FONT> </DIV>
<DIV><FONT face=3DCourier size=3D2>    Nr =
Address  =20
Value    Points=20
to          My=20
Interpritation<BR>    01 0012feb0 =20
00000fe2          &nbsp=
;        =20
<< veriable "after"</FONT></DIV>
<DIV><FONT face=3DCourier></FONT> </DIV>
<DIV><FONT face=3DCourier size=3D2>    02 0012feb4  =
0041f178=20
t11!E::`vftable'   << veriable e, start of E, start of=20
E::D<BR>    03 0012feb8 =20
00000ff4          &nbsp=
;        =20
<< e.md_<BR>    04 0012febc  0041f188=20
t11!E::`vbtable'   << start of =
E::B<BR>    05=20
0012fec0 =20
00000ff2          &nbsp=
;        =20
<< e.mb_<BR>    06 0012fec4  0041f17c=20
t11!E::`vbtable'   << start of =
E::C<BR>    07=20
0012fec8 =20
00000ff3          &nbsp=
;        =20
<< e.mc_<BR>    08 0012fecc =20
00000ff5          &nbsp=
;        =20
<< e.me_<BR>    09 0012fed0 =20
00000000          &nbsp=
;        =20
<< ???WHAT ARE THIS FOR???<BR>    10 0012fed4  =

0041f174 t11!E::`vftable'   << start of=20
E::A<BR>    11 0012fed8 =20
00000ff1          &nbsp=
;        =20
<< e.ma_, end of E<BR>    12 0012fedc =20
0000000c          &nbsp=
;        =20
<< veriable "distance"</FONT></DIV>
<DIV><FONT face=3DCourier></FONT> </DIV>
<DIV><FONT face=3DCourier size=3D2>    13 0012fee0 =20
00000fe1          &nbsp=
;        =20
<< veriable "before"</FONT></DIV>
<DIV><FONT face=3DCourier></FONT> </DIV>
<DIV><FONT face=3DCourier size=3D2>*/</FONT></DIV>
<DIV><FONT face=3DCourier></FONT> </DIV>
<DIV><FONT face=3DCourier size=3D2>#include<iostream></FONT></DIV>
<DIV><FONT face=3DCourier></FONT> </DIV>
<DIV><FONT face=3DCourier size=3D2>using namespace std;<BR><BR>class A=20
{<BR>public:<BR>    explicit A(long=20
ma)<BR>        : ma_(ma)=20
{<BR>    }<BR>    virtual void=20
foo();<BR>private:<BR>    long ma_;<BR>};</FONT></DIV>
<DIV><FONT face=3DCourier></FONT> </DIV>
<DIV><FONT face=3DCourier size=3D2>void A::foo() {<BR>    =
cout=20
<< hex << "ma=3D" << ma_ << ", sizeof(A)=3D" =
<< dec=20
<< sizeof(A) << "\n";<BR>}</FONT></DIV>
<DIV><FONT face=3DCourier></FONT> </DIV>
<DIV><FONT face=3DCourier size=3D2>class B : public virtual A=20
{<BR>public:<BR>    explicit B(long=20
mb)<BR>        : mb_(mb), A(0)=20
{<BR>    }<BR>    virtual void=20
foo();<BR>private:<BR>    long mb_;<BR>};</FONT></DIV>
<DIV><FONT face=3DCourier></FONT> </DIV>
<DIV><FONT face=3DCourier size=3D2>void B::foo() {<BR>    =
cout=20
<< hex << "mb=3D" << mb_ << ", sizeof(B)=3D" =
<< dec=20
<< sizeof(B) << "\n";<BR>}</FONT></DIV>
<DIV><FONT face=3DCourier></FONT> </DIV>
<DIV><FONT face=3DCourier size=3D2>class C : public virtual A=20
{<BR>public:<BR>    explicit C(long=20
mc)<BR>        : mc_(mc), A(0)=20
{<BR>    }<BR>    virtual void=20
foo();<BR>private:<BR>    long mc_;<BR>};</FONT></DIV>
<DIV><FONT face=3DCourier></FONT> </DIV>
<DIV><FONT face=3DCourier size=3D2>void C::foo() {<BR>    =
cout=20
<< hex << "mc=3D" << mc_ << ", sizeof(C)=3D" =
<< dec=20
<< sizeof(C) << "\n";<BR>}</FONT></DIV>
<DIV><FONT face=3DCourier></FONT> </DIV>
<DIV><FONT face=3DCourier size=3D2>class D =
{<BR>public:<BR>   =20
explicit D(long md)<BR>        : =
md_(md)=20
{<BR>    }<BR>    virtual void=20
foo();<BR>private:<BR>    long md_;<BR>};</FONT></DIV>
<DIV><FONT face=3DCourier></FONT> </DIV>
<DIV><FONT face=3DCourier size=3D2>void D::foo() {<BR>    =
cout=20
<< hex << "md=3D" << md_ << ", sizeof(D)=3D" =
<< dec=20
<< sizeof(D) << "\n";<BR>}</FONT></DIV>
<DIV><FONT face=3DCourier></FONT> </DIV>
<DIV><FONT face=3DCourier size=3D2>class E : public B, public C, public =
D=20
{<BR>public:<BR>    explicit E(long ma=3D0xFF1, long =
mb=3D0xFF2, long=20
mc=3D0xFF3, long md=3D0xFF4, long=20
me=3D0xFF5)<BR>        : A(ma), =
B(mb), C(mc),=20
D(md), me_(me) {<BR>    }<BR>    virtual =
void=20
foo();<BR>private:<BR>    long me_;<BR>};</FONT></DIV>
<DIV><FONT face=3DCourier></FONT> </DIV>
<DIV><FONT face=3DCourier size=3D2>void E::foo() {<BR>    =

A::foo();<BR>    B::foo();<BR>   =20
C::foo();<BR>    D::foo();<BR>    cout =
<<=20
hex << "me=3D" << me_ << ", sizeof(E)=3D" << dec =
<<=20
sizeof(E) << "\n";<BR>}</FONT></DIV>
<DIV><FONT face=3DCourier></FONT> </DIV>
<DIV><FONT face=3DCourier size=3D2>int main(int, char **) =
{<BR>   =20
cout << hex;</FONT></DIV>
<DIV><FONT face=3DCourier></FONT> </DIV>
<DIV><FONT face=3DCourier size=3D2>    int distance =3D=20
0;<BR>    int before =3D 0xFE1;</FONT></DIV>
<DIV><FONT face=3DCourier></FONT> </DIV>
<DIV><FONT face=3DCourier size=3D2>    E =
e;<BR>   =20
if(!distance) { //to prevent compiler from rearanging veriables on the=20
stack<BR>        int after =3D=20
0xFE2;<BR>        distance =3D =
&before -=20
&after;<BR>    }<BR>    =
e.foo();</FONT></DIV>
<DIV><FONT face=3DCourier></FONT> </DIV>
<DIV><FONT face=3DCourier size=3D2>    cout << dec =
<<=20
"&before - &after =3D "  << abs(distance) <<=20
"\n";</FONT></DIV>
<DIV><FONT face=3DCourier></FONT> </DIV>
<DIV><FONT face=3DCourier size=3D2>    return=20
0;<BR>}</FONT></DIV></BODY></HTML>

------=_NextPart_000_002C_01C4577D.73E543F0--

Doug
Mon Jun 21 13:22:39 CDT 2004

Vladimir_petter wrote:

>Hello All,
>
> I've fount that if I compile the same program using gcc and vc 2003 the same class E (see complete source bellow) has different size (on vc it is 4 bytes bigger). Digging into this I've found that vc is reserving a dword in the E class right before storage for virtual base class. In my tests value of this dword always was 0. I did not see any code referencing this memory.
>
> Anybody has any idea what this dword is for?

See if this article helps you figure it out:

C++: Under the Hood
Jan Gray
http://msdn.microsoft.com/archive/default.asp?url=/archive/en-us/dnarvc/html/jangrayhood.asp

--
Doug Harrison
Microsoft MVP - Visual C++

Vladimir_petter
Mon Jun 21 15:37:32 CDT 2004

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Hello Doug,

Thanks for the link. It definetly helped.=20
I am still not 100% sure, but my guess is that this DWORD is a =
reservaton for a future vbtable to store deplacement of A relative to E.
See bellow corrected picture.

Thanks,
Vladimir.

=20
Layout of the stack in the "main" function:
=20
Nr Address Value Points to My Interpritation
01 0012feb0 00000fe2 << veriable "after"
=20
02 0012feb4 0041f178 t11!E::`vftable' << veriable e, start of E, =
start of E::D ---------------
03 0012feb8 00000ff4 << e.md_ =
|
04 0012febc 0041f188 t11!E::`vbtable' << deplacement info for A =
relative to B------------- |
05 0012fec0 00000ff2 << e.mb_, start of E::b =
| |
06 0012fec4 0041f17c t11!E::`vbtable' << deplacement info for A =
relative to C-------- | |
07 0012fec8 00000ff3 << e.mc_ =
| | |
08 0012fecc 00000ff5 << e.me_ =
| | |
09 0012fed0 00000000 << ?is this a reservation =
for future vbtable? | | |
10 0012fed4 0041f174 t11!E::`vftable' << start of =
E::A---------------------------- | | |
11 0012fed8 00000ff1 << e.ma_, end of E =
| | | |
=
| | | |
12 0012fedc 0000000c << veriable "distance" =
| | | |
13 0012fee0 00000fe1 << veriable "before" =
| | | |
=
| | | |
=
| | | |
t11!E::`vftable' at 0041f174 =
<- | | |
0041f174 0040112c =
t11!ILT+295(?fooE$4PPPPPPPMCAAEXXZ)--------------------------- | =
| |
=
| | | |
t11!E::`vftable' at 0041f178: =
| | | |
0041f178 004012f3 =
t11!ILT+750(?fooEUAEXXZ)--------------------------------- | | =
| <-
=
| | | | =20
t11!E::`vbtable' at 0041f17c =
| | <- |
0041f17c 00000000 =
| | |
0041f180 00000010 << decimal 16, 4 dwords from C to A in E =
| | |
0041f184 00000000 =
| | |
=
| | |
t11!E::`vbtable' at 0041f188 =
| | <-
0041f188 00000000 =
| |
0041f18c 00000018 << decimal 24, 6 dwords from B to A in E =
| |
0041f190 00000000 =
| |
=
| |
t11!ILT+295(?fooE$4PPPPPPPMCAAEXXZ): =
| <-
0040112c e98f540000 jmp t11!E::foo (004065c0)-- =
|
| =
|
t11!E::foo: <- =
|
004065c0 2b49fc sub ecx,[ecx-0x4] =
|
004065c3 83e920 sub ecx,0x20 =
|
004065c6 e928adffff jmp t11!ILT+750(?fooEUAEXXZ) =
(004012f3)-- |
=
| |
t11!ILT+750(?fooEUAEXXZ): =
<- <-
004012f3 e9e8040000 jmp t11!E::foo (004017e0)-- =
=20
|
t11!E::foo [t11.cpp @ 117]: <-
004017e0 55 push ebp
004017e1 8bec mov ebp,esp
004017e3 51 push ecx
004017e4 894dfc mov [ebp-0x4],ecx
004017e7 8b45fc mov eax,[ebp-0x4]
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<HTML><HEAD>
<META http-equiv=3DContent-Type content=3D"text/html; =
charset=3Diso-8859-1">
<META content=3D"MSHTML 6.00.2800.1400" name=3DGENERATOR>
<STYLE></STYLE>
</HEAD>
<BODY>
<DIV><FONT face=3DCourier size=3D2></FONT> </DIV>
<DIV>
<DIV><FONT face=3DCourier size=3D2>Hello Doug,</FONT></DIV>
<DIV><FONT face=3DCourier size=3D2></FONT> </DIV>
<DIV><FONT face=3DArial size=3D2><FONT face=3DCourier>Thanks for the =
link. It=20
definetly helped. </FONT></FONT></DIV>
<DIV><FONT face=3DArial size=3D2><FONT face=3DCourier>I am still not =
100% sure, but my=20
guess is that this DWORD is a reservaton for a future vbtable to store=20
deplacement of A relative to E.</FONT></FONT></DIV><FONT face=3DArial =
size=3D2><FONT=20
face=3DCourier></FONT></FONT></DIV>
<DIV><FONT face=3DArial size=3D2><FONT face=3DCourier>See bellow =
corrected=20
picture.</FONT></FONT></DIV>
<DIV><FONT face=3DArial size=3D2><FONT =
face=3DCourier></FONT></FONT> </DIV>
<DIV><FONT face=3DArial size=3D2><FONT =
face=3DCourier>Thanks,</FONT></FONT></DIV>
<DIV><FONT face=3DArial size=3D2><FONT =
face=3DCourier>Vladimir.</FONT></DIV>
<DIV><BR> <BR><FONT face=3DCourier>Layout of the stack in the =
"main"=20
function:<BR> <BR>    Nr Address  =20
Value    Points=20
to          My=20
Interpritation<BR>    01 0012feb0 =20
00000fe2          &nbsp=
;        =20
<< veriable "after"<BR> <BR>    02 =
0012feb4 =20
0041f178 t11!E::`vftable'   << veriable e, start of E, =
start of=20
E::D ---------------<BR>    03 0012feb8 =20
00000ff4          &nbsp=
;        =20
<<=20
e.md_           &n=
bsp;           &nb=
sp;           &nbs=
p;          =20
|<BR>    04 0012febc  0041f188 =
t11!E::`vbtable'  =20
<< deplacement info for A relative to B-------------  =20
|<BR>    05 0012fec0 =20
00000ff2          &nbsp=
;        =20
<< e.mb_, start of=20
E::b           &nb=
sp;           &nbs=
p;   =20
|   |<BR>    06 0012fec4  0041f17c=20
t11!E::`vbtable'   << deplacement info for A relative to =

C--------    |   |<BR>    07=20
0012fec8 =20
00000ff3          &nbsp=
;        =20
<<=20
e.mc_           &n=
bsp;           &nb=
sp;           &nbs=
p; =20
|    |   |<BR>    08 =
0012fecc =20
00000ff5          &nbsp=
;        =20
<<=20
e.me_           &n=
bsp;           &nb=
sp;           &nbs=
p; =20
|    |   |<BR>    09 =
0012fed0 =20
00000000          &nbsp=
;        =20
<< ?is this a reservation for future vbtable? |   =20
|   |<BR>    10 0012fed4  0041f174=20
t11!E::`vftable'   << start of=20
E::A----------------------------  |    |   =

|<BR>    11 0012fed8 =20
00000ff1          &nbsp=
;        =20
<< e.ma_, end of=20
E            =
             =

|  |    |  =20
|<BR>           &n=
bsp;           &nb=
sp;           &nbs=
p;           &nbsp=
;            =
            &=
nbsp;           &n=
bsp;  =20
|  |    |   |<BR>    12=20
0012fedc =20
0000000c          &nbsp=
;        =20
<< veriable=20
"distance"          &nb=
sp;         =20
|  |    |   |<BR>    13=20
0012fee0 =20
00000fe1          &nbsp=
;        =20
<< veriable=20
"before"          &nbsp=
;           =20
|  |    |  =20
|<BR>           &n=
bsp;           &nb=
sp;           &nbs=
p;           &nbsp=
;            =
            &=
nbsp;           &n=
bsp;  =20
|  |    |  =20
|<BR>           &n=
bsp;           &nb=
sp;           &nbs=
p;           &nbsp=
;            =
            &=
nbsp;           &n=
bsp;  =20
|  |    |   |<BR>t11!E::`vftable' at=20
0041f174          &nbsp=
;            =
            &=
nbsp;           &n=
bsp;          =20
<-  |    |   |<BR>   =20
0041f174  0040112c=20
t11!ILT+295(?fooE$4PPPPPPPMCAAEXXZ)--------------------------- &nbsp=
;   =20
|    |  =20
|<BR>           &n=
bsp;           &nb=
sp;           &nbs=
p;           &nbsp=
;            =
            &=
nbsp;          =20
|      |    |  =20
|<BR>t11!E::`vftable' at=20
0041f178:          &nbs=
p;           &nbsp=
;            =
            &=
nbsp;      =20
|      |    |  =20
|<BR>    0041f178  004012f3=20
t11!ILT+750(?fooEUAEXXZ)---------------------------------  &nbs=
p;=20
|      |    | =20
<-<BR>          &nbs=
p;           &nbsp=
;            =
            &=
nbsp;           &n=
bsp;           &nb=
sp;      =20
|    |      |   =20
|   <BR>t11!E::`vbtable' at=20
0041f17c          &nbsp=
;            =
            &=
nbsp;           &n=
bsp;  =20
|    |     <-   =20
|<BR>    0041f17c =20
00000000          &nbsp=
;            =
            &=
nbsp;           &n=
bsp;        =20
|   =20
|          =20
|<BR>    0041f180  00000010 << decimal 16, 4 =
dwords=20
from C to A in=20
E            =
   =20
|   =20
|          =20
|<BR>    0041f184 =20
00000000          &nbsp=
;            =
            &=
nbsp;           &n=
bsp;        =20
|   =20
|          =20
|<BR>           &n=
bsp;           &nb=
sp;           &nbs=
p;           &nbsp=
;            =
            &=
nbsp;     =20
|   =20
|          =20
|<BR>t11!E::`vbtable' at=20
0041f188          &nbsp=
;            =
            &=
nbsp;           &n=
bsp;  =20
|    =
|         =20
<-<BR>    0041f188 =20
00000000          &nbsp=
;            =
            &=
nbsp;           &n=
bsp;        =20
|    |<BR>    0041f18c  00000018 =
<<=20
decimal 24, 6 dwords from B to A in=20
E            =
   =20
|    |<BR>    0041f190 =20
00000000          &nbsp=
;            =
            &=
nbsp;           &n=
bsp;        =20
|   =20
|<BR>           &n=
bsp;           &nb=
sp;           &nbs=
p;           &nbsp=
;            =
            &=
nbsp;     =20
|   =20
|<BR>t11!ILT+295(?fooE$4PPPPPPPMCAAEXXZ):     &n=
bsp;           &nb=
sp;           &nbs=
p;           &nbsp=
;=20
|   <-<BR>    0040112c=20
e98f540000       =
jmp    =20
t11!E::foo=20
(004065c0)--          &=
nbsp;      =20
|<BR>           &n=
bsp;           &nb=
sp;           &nbs=
p;           &nbsp=
;           =20
|            =
     =20
|<BR>t11!E::foo:         &nb=
sp;           &nbs=
p;           &nbsp=
;            =
 =20
<-           &n=
bsp;     =20
|<BR>    004065c0=20
2b49fc          =20
sub    =20
ecx,[ecx-0x4]          =
            &=
nbsp;    =20
|<BR>    004065c3=20
83e920          =20
sub    =20
ecx,0x20          &nbsp=
;            =
         =20
|<BR>    004065c6 =
e928adffff      =20
jmp     t11!ILT+750(?fooEUAEXXZ)=20
(004012f3)--   =20
|<BR>           &n=
bsp;           &nb=
sp;           &nbs=
p;           &nbsp=
;            =
            &=
nbsp;=20
|   =20
|<BR>t11!ILT+750(?fooEUAEXXZ):       &=
nbsp;           &n=
bsp;           &nb=
sp;           &nbs=
p;   =20
<-   <-<BR>    004012f3=20
e9e8040000       =
jmp    =20
t11!E::foo=20
(004017e0)--          &=
nbsp;        =20
<BR>           &nb=
sp;           &nbs=
p;           &nbsp=
;            =
           =20
|<BR>t11!E::foo [t11.cpp @=20
117]:           &n=
bsp;           &nb=
sp;       =20
<-<BR>    004017e0=20
55           &nbsp=
;  =20
push    ebp<BR>    004017e1=20
8bec           &nb=
sp;=20
mov     ebp,esp<BR>    004017e3=20
51           &nbsp=
;  =20
push    ecx<BR>    004017e4=20
894dfc          =20
mov     [ebp-0x4],ecx<BR>    004017e7 =

8b45fc          =20
mov     =
eax,[ebp-0x4]</FONT></FONT></DIV></BODY></HTML>

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virtual-multiple inheritance. what an extra dword is for?

Re: virtual-multiple inheritance. what an extra dword is for? by Doug

Re: virtual-multiple inheritance. what an extra dword is for? by Vladimir_petter