Avoid unexpected behavior if move/copy is incorrectly implemented #577
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ChaiScript 6 always used a shared_ptr to wrap C++ objects created in ChaiScript. Newer versions avoid this by only wrapping objects that cannot be copied. This has the side effect that ChaiScript depends on correctly implemented C++ copy and move constructors in unexpected locations. I don't think the reduced overhead (by avoiding the shared_ptr) justifies the new behavior in every case. Therefore, I suggest we temporarily only perform this optimization if the class is trivially destructible, until unexpected copies and moves in ChaiScript are fixed (if this is even possible), or there is a sanitizer/compiler warning that can detect these cases. Before the change the following code will call the ctor once, move once, and the dtor twice: auto obj = MoveableObject(); After this change it will only call the ctor once and the dtor once.
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ChaiScript 6 always used a shared_ptr to wrap C++ objects created in
ChaiScript. Newer versions avoid this by only wrapping objects that cannot
be copied. This has the side effect that ChaiScript depends on correctly
implemented C++ copy and move constructors in unexpected locations.
I don't think the reduced overhead (by avoiding the shared_ptr) justifies
the new behavior in every case.
Therefore, I suggest we temporarily only perform this optimization if the class
is trivially destructible, until unexpected copies and moves in ChaiScript
are fixed (if this is even possible), or there is a sanitizer/compiler warning
that can detect these cases.
Before the change the following code will call the ctor once, move once,
and the dtor twice:
auto obj = MoveableObject();
After this change it will only call the ctor once and the dtor once.