[PATCH 10 of 10] rust-cpython: add safe way to map PyLeakedRef<&T> to PyLeakedRef<U>

Raphaël Gomès raphael.gomes at octobus.net
Thu Oct 10 15:21:25 EDT 2019


Indeed, I don't think there is a way to prevent this. We might get 
additional feedback when upstreaming to rust-cpython though.

Rest of the series looks good to me. This is all a needed improvement.

On 10/10/19 4:34 PM, Yuya Nishihara wrote:
> On Thu, 10 Oct 2019 13:53:54 +0200, Raphaël Gomès wrote:
>> Is it not possible to just take a `fn` type? It forces a non-capturing fn.
> Interesting idea, but still fn() would allow mutating a static variable.
> IIRC, mutation of static variable can be safely written by using lazy_static
> and Mutex.
>
>> On 10/8/19 7:16 PM, Yuya Nishihara wrote:
>>> +    pub fn map<U>(
>>> +        mut self,
>>> +        py: Python,
>>> +        f: impl FnOnce(T) -> U,
>>> +    ) -> PyLeakedRef<U> {
>>> +        PyLeakedRef {
>>> +            inner: self.inner.clone_ref(py),
>>> +            data: Some(f(self.data.take().unwrap())),
>>> +            py_shared_state: self.py_shared_state,
>>> +        }
>>> +    }
> I'm feeling that it's good to leave leaked_ref.map() unsafe. The new API
> should be less error-prone, and its safety requirement, "don't leak the
> static reference", can be easily guaranteed.
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