[release/11.0-preview6] Fix async resumption stub with byref parameters#130022
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svick merged 3 commits intoJul 1, 2026
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It is not valid IL to initialize a byref local with `initobj`. Just load the value of these directly. We had a test for byref parameters, but it did not suspend and did not result in creation of a resumption stub. The test case requires suspension + NoInlining to guarantee a suspension point is created.
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/ba-g all known issues. |
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@svick, it is ready to merge. |
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Backport of #129999 to release/11.0-preview6
/cc @jakobbotsch
Customer Impact
A Task-returning method
Awith a byref parameter may cause the runtime to throw anInvalidProgramExceptionif directly returning the result of another Task-returning methodB(), the task returned byBsuspends and also one of the following is true:Ais marked with[MethodImpl(MethodImplOptions.NoInlining)]BreturnsTask<T>andAreturnsTaskIn these cases the runtime produces an internal IL stub with invalid IL. The invalid IL tries to zero a byref local using
initobj, which is not legal IL. Reported by ASP.NET in #129990.Regression
This issue exists since runtime async was introduced, but #128384 made it possible to hit this issue from C# code.
Testing
Unit test introduced.
Risk
Low. Adjust IL emission to load a
byrefzero withoutinitobj.