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The thing here is making PyArray::resize unsafe as it may reallocate the array in-place thereby invalidate all existing pointers into its interior. The safe replacement is PyReadwriteArray::resize which will release and re-acquire an exclusive borrow of the array.

Does anybody now of other "destructive" methods which would need the same treatment?

I think was arguably unsound for the previous PyReadonlyArray as well as the following appears to work:

use numpy::{npyffi::NPY_ARRAY_WRITEABLE, PyArray};
use pyo3::Python;

Python::with_gil(|py| {
    let pyarray = PyArray::arange(py, 0, 10, 1);
    assert_eq!(pyarray.len(), 10);

    unsafe {
        (*pyarray.as_array_ptr()).flags &= !NPY_ARRAY_WRITEABLE;
        pyarray.resize(100).unwrap();
    }
    assert_eq!(pyarray.len(), 100);
});

@adamreichold adamreichold force-pushed the borrow-checking-redux branch 2 times, most recently from b81fbe5 to 30aaaa8 Compare March 21, 2022 11:09
@adamreichold adamreichold force-pushed the borrow-checking-redux branch from 30aaaa8 to a013e7b Compare March 22, 2022 07:05
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@kngwyu kngwyu left a comment

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Thanks, sounds reasonable. I feel it a bit of shame for me to remain this as is.

Does anybody now of other "destructive" methods which would need the same treatment?

No, I found no other API.

@adamreichold adamreichold merged commit fff48b8 into main Mar 22, 2022
@adamreichold adamreichold deleted the borrow-checking-redux branch March 22, 2022 10:15
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2 participants