[release/9.0-staging] Ignore modopts/modreqs for UnsafeAccessor field targets by github-actions[bot] · Pull Request #109709 · dotnet/runtime (original) (raw)
Backport of #109694 to release/9.0-staging
Customer Impact
- Customer reported
- Found internally
Customer reported issue: #109665. This was originally found in a MSBuild BinLog reader scenario. The specific issue is fields that are marked as volatile in C# aren't discoverable when using UnsafeAccessors and as such if someone writes the following, it is unable to be accessed.
class A { private volatile int _i; }
This can't be discovered because the volatile in C# is embedded via a modreq and there is no place to describe that using the UnsafeAccessorAttribute.
The general issue is that when discovering the target field member, we currently require a complete match for fields. One could imagine we add some support for this, but given they are generally considered compiler directives, there is little value in considering them in this lookup scenario and so they should be ignored on fields. This is already done in the method case, but the relaxation was missed on field discovery.
Regression
- Yes
- No
Early in the .NET 9 release, the logic for signature comparrison was rewritten and regressed some unsupported issues and has uncovered a regression in a supported scenario.
Testing
Tests for the particular issue were added. I reached out to the Roslyn compiler team and verified the added test case is the only scenario where this occurs.
Risk
Low This is a permissive change on the way fields are looked-up and their types compared. Since C#/VB.NET don't provide other modopts/modreqs it is unlikely this will impact any other scenario.