Stan Lippman on Supporting Direct Handles to Boxed Value Types


If you haven't read Stan's blog, start from the bottom and read all the entries. They are consistently insightful and fascinating. Today Stan answers a reader question about boxing:

Yes, the need to box occurs only when the source of the assignment to an Object^ is a value type. A Value type, recall, maintains its state within each associated object [what in C++ is created when we write T t]. A Reference type is a duple in which the named instance is a handle holding either null or the address of an unnamed object allocated on the managed heap. When we initialize the Object^ second parameter of Console::WriteLine with a Value type, there is a hiccup in the unified type system because there is no way to represent the Value type directly within the handle of a Reference type. The solution is to create a shadowed Reference to the Value type on the managed heap and pass in the address of that object.

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