In bug 1193762, there's been work on eliminating the implicit conversion from nsCOMPtr<T> to T*, at least for rvalues, to avoid the safety problem discussed there. The problem is that then you can't pass an nsCOMPtr<T>&& to a function that wants a T*, even though this is perfectly safe: the lifetime of the temporary is guaranteed to outlast the function call. The only solution hitherto devised other than requiring lots of .get() is to invent a new type for refcounted function parameters, which is awkward.
A new language feature could be used to solve this: allow conversion operators to behave differently based on how the variable is declared. For instance, it might convert differently if the source or destination is a local variable, global/static variable, member variable, or function parameter. This would allow our problem to be easily solved by defining something in nsCOMPtr like: operator T* [[parameter]]()&&; while leaving the operator deleted for non-parameters. If this can be declared on any method, or perhaps on the class itself, it could also be used to enforce nsCOMPtr not being used as a global or static variable. Are there other places where this would be useful? I don't know if this makes sense to propose as a language feature, but I thought it would be worth bringing up in case anyone has more compelling use-cases. _______________________________________________ dev-platform mailing list dev-platform@lists.mozilla.org https://lists.mozilla.org/listinfo/dev-platform
