Do not call GetHashCode() on enums#5639
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Forgind merged 2 commits intodotnet:masterfrom Aug 14, 2020
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Closing to reopen and trigger a CI build. See #5646. |
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| hashCode = hashCode * -1521134295 + EqualityComparer<string>.Default.GetHashCode(obj.ElementName); | ||
| hashCode = hashCode * -1521134295 + EqualityComparer<string>.Default.GetHashCode(obj.ElementDescription); | ||
| hashCode = hashCode * -1521134295 + obj.Kind.GetHashCode(); | ||
| hashCode = hashCode * -1521134295 + EqualityComparer<EvaluationLocationKind>.Default.GetHashCode(obj.Kind); |
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I wasn't familiar with this idiom, and when I tried putting it into sharplab, it seemed to do the same thing. What did I do wrong?
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One super hacky way to quickly check if a piece of code allocates is simply running it in a tight while (true) loop in a trivial console app and checking the VS diagnostics window.
Seeing small yellow markers appear regularly means that GC is collecting something and that something has to be allocations performed in the loop.
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benvillalobos
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cdmihai
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Calling
GetHashCode()on an enum results in boxing (i.e. a GC allocation) when running on .NET Framework. This has been addressed in .NET Core (dotnet/coreclr#7895) but we want to fix it on our side still because it's showing in Visual Studio profiles:https://devdiv.visualstudio.com/DevDiv/_workitems/edit/1166715
This PR is also removing the calls to
base.GetHashCode()which are pointless in structures that calculate the hashcode out of all their fields.