This PR closes a subtle race condition bug that could potentially happen anywhere that for-loops are spawned with go func - the for loop operates on a reference which changes faster than the function call can potentially happen, causing a function to use the wrong parameter when referenced.
The solution is very simple, make a local copy of the variable and pass the resulting function by copy, rather than by reference - then there's no way the for loop can accidentally reference the wrong data.
Testing and Verifying
This change is hard to test, so we're not going to write a unit test to simulate it explicitly. The performance implicaitons of doing a pass-by-copy are trivial, therefore there is no reason to not do the safer thing. Our existing test suite should test that the change does not have correctness implications.
What is the purpose of the change
This PR closes a subtle race condition bug that could potentially happen anywhere that for-loops are spawned with
go func- the for loop operates on a reference which changes faster than the function call can potentially happen, causing a function to use the wrong parameter when referenced.The solution is very simple, make a local copy of the variable and pass the resulting function by copy, rather than by reference - then there's no way the for loop can accidentally reference the wrong data.
Testing and Verifying
This change is hard to test, so we're not going to write a unit test to simulate it explicitly. The performance implicaitons of doing a pass-by-copy are trivial, therefore there is no reason to not do the safer thing. Our existing test suite should test that the change does not have correctness implications.
Documentation and Release Note
This PR has no implications for documentation.