Closing the dataset while an async operation is running can end with a segfault

[mmomtchev]

const gdal = require('gdal-next');
const ds = gdal.open('sample.tif');
const band = ds.bands.get(1)
band.pixels.readAsync(0, 0, 10, 10);
ds.close();

This is not expected to work, but the user should be protected against a segfault.

[yocontra]

@mmomtchev I think the correct behavior would be for ds.close() to throw if work is still ongoing, thoughts?

[mmomtchev]

In the next version ds.close() will block until the currently running I/O finishes (it cannot be canceled) and then it will cancel all operations that have not yet started - they will end up rejecting with Dataset closed
Frankly, if I had seen this sooner, I would have probably settled for it 😄
But I already implemented a locking hierarchy on top of Brian Revis excellent PtrManager which manages the lifetime of all datasets