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#define TYPE_CHECK(T, S) \ while (false) { \ *(static_cast<T* volatile*>(0)) = static_cast<S*>(0); \ } I am reading Google v8's code and found the above macro for type check.
However, I do not understand why it works. while(false) never get executed, right? Can someone explain those lines? Thanks
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Quite a fancy hack - the purpose of the macro seems to be to check if the type S is assignable to (i.e., is a subclass of) the type T. If it is not, the pointer cast from S* to T* will produce a compiler error. The while (false) prevents the code from actually having any other effect.
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