C++ Class Layout Using MSVC

The article is originally inspired by this one: http://www.openrce.org/articles/full_view/23. The undocumented parameters in MSVC++ compiler are: /d1reportSingleClassLayout<classname> and /d1reportAllClassLayout.

A simple example:

The dumped layout:

You see: When using virtual inheritance, an additional vbptr is added into class layout. There is also a separated section containing the virtual base class, with vbptr pointing to it. So, the object size of virtual inheritance is bigger than non-virtual inheritance.

Now, here is a complex example:

The dumped layout:

The layout of CDerive class is so complicated. First, it has 3 base classes, 1 field and 1 virtual base section. The the first 2 base classes(CBase2, CBase3) have their vbptr pointed to the address of the virtual base section.

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