Skip to main content

C++ object layout implementation


There are several cool implementation techniques of C++ object layout, especially when multiple inheritance, virtual functions and virtual inheritance is involved. Understanding the consequences of these rather advanced concepts in the language on the implementation of the language is quite interesting. There are several "gotchas" involved. Example, it is highly recommended to invoke the virtual base class's constructor in the derived most class when there is a diamond shape inheritance hierarchy. It is a pretty eloborate subject so I won't duplicate the same thing here. I would just assemble some really good articles on the topic. Lippman's book "Inside The C++ Object Model" talks about it at length.

Please see:

C++ Object layout in multiple inheritance
Adjustor thunks
Multiple inheritance in C++ (Stroustrup)

Comments

Anonymous said…
So what does "thunk" mean?
Why is this term used?
Sun Mar 12, 08:37:00 AM PST
Sumant said…
Please see the following post.
Sun Mar 12, 09:52:00 AM PST
marry said…
Blogs are so informative where we get lots of information on any topic. Nice job keep it up!!
_____________________________

Dissertation Editing
Fri Dec 04, 02:26:00 AM PST
Post a Comment

Popular Content

Multi-dimensional arrays in C++11

What new can be said about multi-dimensional arrays in C++? As it turns out, quite a bit! With the advent of C++11, we get new standard library class std::array. We also get new language features, such as template aliases and variadic templates. So I'll talk about interesting ways in which they come together.

It all started with a simple question of how to define a multi-dimensional std::array. It is a great example of deceptively simple things. Are the following the two arrays identical except that one is native and the other one is std::array?

int native[3][4];
std::array<std::array<int, 3>, 4> arr;

No! They are not. In fact, arr is more like an int[4][3]. Note the difference in the array subscripts. The native array is an array of 3 elements where every element is itself an array of 4 integers. 3 rows and 4 columns. If you want a std::array with the same layout, what you really need is:

std::array<std::array<int, 4>, 3> arr;

That's quite annoying for two r…
25 comments
Read more

Covariance and Contravariance in C++ Standard Library

Covariance and Contravariance are concepts that come up often as you go deeper into generic programming. While designing a language that supports parametric polymorphism (e.g., templates in C++, generics in Java, C#), the language designer has a choice between Invariance, Covariance, and Contravariance when dealing with generic types. C++'s choice is "invariance". Let's look at an example.
struct Vehicle {}; struct Car : Vehicle {}; std::vector<Vehicle *> vehicles; std::vector<Car *> cars; vehicles = cars; // Does not compile The above program does not compile because C++ templates are invariant. Of course, each time a C++ template is instantiated, the compiler creates a brand new type that uniquely represents that instantiation. Any other type to the same template creates another unique type that has nothing to do with the earlier one. Any two unrelated user-defined types in C++ can't be assigned to each-other by default. You have to provide a c…
17 comments
Read more

Unit Testing C++ Templates and Mock Injection Using Traits

Unit testing your template code comes up from time to time. (You test your templates, right?) Some templates are easy to test. No others. Sometimes it's not clear how to about injecting mock code into the template code that's under test. I've seen several reasons why code injection becomes challenging.

Here I've outlined some examples below with roughly increasing code injection difficulty. Template accepts a type argument and an object of the same type by reference in constructorTemplate accepts a type argument. Makes a copy of the constructor argument or simply does not take oneTemplate accepts a type argument and instantiates multiple interrelated templates without virtual functions Lets start with the easy ones.
Template accepts a type argument and an object of the same type by reference in constructor This one appears straight-forward because the unit test simply instantiates the template under test with a mock type. Some assertion might be tested in the mock c…
Post a Comment
Read more