33 lines
1.4 KiB
Markdown
33 lines
1.4 KiB
Markdown
---
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uid: collections-known-issues
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---
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# Known issues
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All containers allocated with `Allocator.Temp` on the same thread use a shared `AtomicSafetyHandle` instance rather than each having their own. Most of the time, this isn't an issue because you can't pass `Temp` allocated collections into a job.
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However, when you use `Native*HashMap`, `NativeParallelMultiHashMap`, `Native*HashSet`, and `NativeList` together with their secondary safety handle, this shared `AtomicSafetyHandle` instance is a problem.
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A secondary safety handle ensures that a `NativeArray` which aliases a `NativeList` is invalidated when the `NativeList` is reallocated due to resizing.
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Operations that invalidate an enumerator for these collection types, or invalidate the `NativeArray` that `NativeList.AsArray` returns also invalidates all other previously acquired enumerators. For example, the following throws an error when safety checks are enabled:
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```c#
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var list = new NativeList<int>(Allocator.Temp);
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list.Add(1);
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// This array uses the secondary safety handle of the list, which is
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// shared between all Allocator.Temp allocations.
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var array = list.AsArray();
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var list2 = new NativeHashSet<int>(Allocator.Temp);
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// This invalidates the secondary safety handle, which is also used
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// by the list above.
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list2.TryAdd(1);
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// This throws an InvalidOperationException because the shared safety
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// handle was invalidated.
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var x = array[0];
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```
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