C++ :: Virtual Function Table Pointer Misplaced In Object Memory
Jul 29, 2014
I have found that when I dump a C++ object from memory to a file - it seems that there is a misplacement of the last Virtual-Function-Table pointer - in that appears at the beginning. The result is that the gdump information based on this object dump (using green hills) is incorrect. I copied the contents of the gdump information below. The executable is compiled in linux.
Basically MEIO::CameraStatus contains an item that relates to its parent class (line 188). Then it has 18 items that are all Diagnostics::EventsCounter items. Now for each Diagnostics::EventsCounter item there is a Virtual-Function-Table Info Pointer as its last item. All is fine and good except that the last item of MEIO::CameraStatus which is _selfReset is missing its last item of 4 bytes (which is the Virtual-Function-Table Info Pointer ). On the other hand - right before the first Diagnostics::EventsCounter item ("_vidErrors") - there is an extra 4 bytes which happens to be the Virtual-Function-Table Info Pointer. As I said the gdump information file does not see this.
Why the object memory "moves" the last Virtual-Function-Table Info Pointer to the beginning (right before _vidErrors) and is there a way to "fix" this?
///////////////////////////////////////////////////////////////////////////
"MEIO::CameraStatus" val:0x000002f0 ind208,-1) Struct-Begin Info
188: "" offset 0, Parent-Class Private Info C++ Struct ref = 114
189: "_vidErrors" offset 160, Member Info C++ Struct ref = 128
190: "_vdiErrors" offset 480, Member Info C++ Struct ref = 128
[Code] .....
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Apr 22, 2015
Here is an example,
Code:
class A {
public:
virtual void foo(){}
virtual void foo2(){}
virtual void foo3(){}
};
int main() {
A a;
int ret = sizeof(A);
return 0;
}
Basically object a contains a virtual table pointer which is of size 4 bytes. Since class A should have a virtual table which contains three pointers pointing to foo, foo2,foo3 separately. So the virtual table should be of size 12 bytes. I wonder where is virtual table located in memory?
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Let's look at this simplified code, it gives compilation error
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using namespace std;
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public:
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[Code] ....
Without using pointer, how to make this works?
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[Code]....
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[Code] ....
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[code].....
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Code:
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[Code] ...
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[Code] ....
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Code:
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[Code] ...
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Code:
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[Code] .....
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template <typename vecTyp>
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[Code].....
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public:
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Sep 25, 2013
have a look-
class Base
{
private:
{
[Code].....
my question is why we can't directly call the member function of the desired class instead of using virtual function.
***********same program using virtual keyword*******************
class Base
{
private:
{
[Code].....
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Feb 17, 2013
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#ifndef SHAPES_H
#define SHAPES_H
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[Code]....
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