Ipicture vtable all instances code#
Code to initialize this pointer with the right value will be added to the constructor. Each instance of such a type is given an additional member called a vptr that points to the correct vtable for that object. The compiler cannot know this ahead of time, so how does it call the right function? The answer is that for each type having a virtual function, the compiler inserts a table of function pointers called a vtable into the resulting binary. Of course whether m is a Cat or Dog depends on the output of rand. So, let’s start by looking at how the compiler implements virtual functions. I’m assuming that you are familiar with writing C++ but maybe not with its implementation. In later parts we will focus on narrowing down the possibilities. Instead, the goal of this exercise will be to determine which function might be being called at a particular point. The information needed to do that is just not present until runtime. In most cases, we cannot hope to “devirtualize” a virtual function call. So in general, the binaries we’re looking at have been compiled with g++ -m32 -fno-rtti -fnoexceptions -O1 file.cpp and then stripped with strip. For this reason, we’re going to focus on the behavior of GCC. Most virtual function implementation details are not standardized and can vary from compiler to compiler.I’m using 32bit x86 as the example platform.The code was compiled without RTTI (RTTI will be discussed later) and without exceptions.If you are already familiar with virtual function reversing, then you my want to proceed directly to part 2. But before that I’m going to go through some more simple cases. These can often include thousands of classes and massive type hierarchies, so I think it is worth describing some techniques for reversing them. However, I wanted to take some time to write about dealing with virtual functions in large, ‘enterprisy’ code-bases.
There are a few posts in various parts of the internet discussing reverse engineering C++, and these often address virtual functions to a large or small extent. The IDTExtensibility2 dispinterface is defined in the MSADDin Designer typelibrary (MSADDNDR.dll/MSADDNDR.tlb) file usually present at the location /Program Files/Common Files/Designer.Menu Reversing C++ Virtual Functions: Part 1 17 December 2016 Typically such addins are housed in ActiveX dlls(inproc server) and can be dynamically loaded and unloaded by the user through the main application.Īn Office COM addin must implement the IDTExtensibility2 interface. Microsoft Office 2000 and later support a new, uniform design architecture for building such application add-ins. To build and test the addin, you must have MS Office 2000 installed on your system, or at least Outlook2K.The project code has been built with VC++ 6.0 sp3+/AT元.0 and tested on Win2K with Office 2000 installed.Īn Office addin is a COM Automation component that dynamically extends/enhances and controls any Office suite of applications. I'm assuming that you are a VC++ COM programmer, and have had some experience with ATL based component development and OLE/Automation, although this is not strictly necessary. Except a couple of minor things like registry keys, for instance, the fundamentals remain the same. Along the way we'll see the relevant registry keys and also take a look at useful features of the ATL Wizards and learn to use them effectively Although we'll be writing an Outlook2000 COM addin, COM addins for other Office2000 applications like Word,Access etc can be built very similarly. Next we'll add our own propertysheet for the addin to Outlook's Tools->Options.
Ipicture vtable all instances how to#
Then I'll show you how to add standard UI elements like toolbars and menu items to Outlook and how to respond to their events. We'll startout by writing a basic functional COM addin. Through this article/tutorial, we will learn how to program an Outlook2000/2K+ COM addin using a pure ATL COM object. If you like this article or found it interesting read, I'd be glad if you could give me a good rating and mail me your comments.:) Thanks. Since I took quite sometime to write this, despite my best efforts, in case of any errors or omissions, kindly drop me a mail. The code in this article is not optimized and the general approach has been kept simple for the reader to follow. While coding the project, I thought this would make a good topic for an article especially since most of the Office related stuff I found on the Internet were VB/VBA related and almost none with ATL. Recently, I wrote an Outlook2000 COM addin as a part of a project to build a CRM tool.
A FAQ is now included at the bottom of this article.
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