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by Rusky
480 days ago
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> - You can't export a reference to the thing you are dropping. You can do that in C++. This prevents "re-animation", where something destroyed comes back to life or is accessed beyond death. Microsoft Managed C++ (early 2000s), supported re-animation and gave it workable semantics. Bad idea, now dead. > > - This is part of why Rust destructors cannot run more than once. ... This is a very backwards way to describe this, I think. Managed C++ only supported re-animation for garbage collected objects, where it is still today a fairly normal thing for a language to support. This is why these "destructors" typically go by a different name, "finalizers." Some languages allow finalizers to run more than once, even concurrently, but this is again due to their GC design and not a natural thing to expect of a "destructor." The design of Drop and unmanaged C++ destructors is that they are (by default) deterministically executed before the object is deallocated. Often this deallocation is not by `delete` or `free`, which could perhaps in principle be cancelled, but by a function return popping a stack frame, or some larger object being freed, which it simply does not make sense to cancel. |
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