Using UnsafeAccessorAttribute throws BadImageFormatException on .NET9-preview6

[czd890]

Description

Using UnsafeAccessorAttribute throws BadImageFormatException on .NET9-preview6.
used the test code is copied from https://learn.microsoft.com/en-us/dotnet/api/system.runtime.compilerservices.unsafeaccessorattribute?view=net-8.0#examples.

Reproduction Steps

// .csproj
<TargetFramework>net9</TargetFramework>

// Program.cs
Accessors<object>.GetSetPrivateField(new Class<object>());

public class Class<T>
{
    private T _field;
    private void M(T t) { }
    private void GM<U>(U u) { }
    private void GMWithConstraints<U, V>(U u, V v) where U : V, IEquatable<U> { }
}

class Accessors<V>
{
    [UnsafeAccessor(UnsafeAccessorKind.Field, Name = "_field")]
    public extern static ref V GetSetPrivateField(Class<V> c);

    [UnsafeAccessor(UnsafeAccessorKind.Method, Name = "M")]
    public extern static void CallM(Class<V> c, V v);

    [UnsafeAccessor(UnsafeAccessorKind.Method, Name = "GM")]
    public extern static void CallGM<X>(Class<V> c, X x);

    [UnsafeAccessor(UnsafeAccessorKind.Method, Name = "GMWithConstraints")]
    public extern static void CallGMWithConstraints<X, Y>(Class<V> c, X x, Y y) where X : Y, IEquatable<X>;
}

Expected behavior

no exception

Actual behavior

Unhandled exception. System.BadImageFormatException: Invalid usage of UnsafeAccessorAttribute.

Regression?

No response

Known Workarounds

No response

Configuration

Host:
Version: 9.0.0-preview.6.24327.7
Architecture: x64
Commit: static

.NET SDKs installed:
6.0.406 [C:\Program Files\dotnet\sdk]
8.0.100 [C:\Program Files\dotnet\sdk]
8.0.204 [C:\Program Files\dotnet\sdk]
9.0.100-preview.6.24328.19 [C:\Program Files\dotnet\sdk]

.NET runtimes installed:
Microsoft.AspNetCore.All 2.1.30 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All]
Microsoft.AspNetCore.App 2.1.30 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 3.1.32 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 6.0.14 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 6.0.29 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 7.0.18 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 8.0.0 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 8.0.4 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 9.0.0-preview.6.24328.4 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.NETCore.App 2.1.30 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 3.1.32 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 6.0.14 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 6.0.29 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 7.0.18 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 8.0.0 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 8.0.4 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 9.0.0-preview.6.24327.7 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.WindowsDesktop.App 3.1.32 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
Microsoft.WindowsDesktop.App 6.0.14 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
Microsoft.WindowsDesktop.App 6.0.29 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
Microsoft.WindowsDesktop.App 7.0.18 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
Microsoft.WindowsDesktop.App 8.0.0 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
Microsoft.WindowsDesktop.App 8.0.4 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
Microsoft.WindowsDesktop.App 9.0.0-preview.6.24327.6 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]

Other information

No response

[jkotas]

cc @AaronRobinsonMSFT

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[lambdageek]

Doesn't repro for me (tried win-x64 and osx-arm64). @czd890 do you build the project in visual studio or using the dotnet CLI? If you're using the CLI, could you delete the bin and obj folders and do dotnet build -bl and upload the msbuild.binlog file?

[dotnet-policy-service]

This issue has been marked needs-author-action and may be missing some important information.

[AaronRobinsonMSFT]

This also doesn't repo in main out of dotnet/runtime. I will try to pull down .NET 9 Preview 6 and verify with that version.

[AaronRobinsonMSFT]

Confirmed this works for me as well. Output below.

...\tmp\Test>dotnet run
...\tmp\Test\Program.cs(16,15): warning CS8618: Non-nullable field '_field' must contain a non-null value when exiting constructor. Consider adding the 'required' modifier or declaring the field as nullable.
...\tmp\Test\Program.cs(16,15): warning CS0169: The field 'Class<T>._field' is never used
OSArchitecture: X64
OSDescription: Microsoft Windows 10.0.22631
FrameworkDescription: .NET 9.0.0-preview.6.24327.7

Before
After

using System.Runtime.CompilerServices;
using System.Runtime.InteropServices;

// OS and .NET information
Console.WriteLine($"{nameof(RuntimeInformation.OSArchitecture)}: {RuntimeInformation.OSArchitecture}");
Console.WriteLine($"{nameof(RuntimeInformation.OSDescription)}: {RuntimeInformation.OSDescription}");
Console.WriteLine($"{nameof(RuntimeInformation.FrameworkDescription)}: {RuntimeInformation.FrameworkDescription}");
Console.WriteLine();

Console.WriteLine("Before");
Accessors<object>.GetSetPrivateField(new Class<object>());
Console.WriteLine("After");

public class Class<T>
{
    private T _field;
    private void M(T t) { }
    private void GM<U>(U u) { }
    private void GMWithConstraints<U, V>(U u, V v) where U : V, IEquatable<U> { }
}

class Accessors<V>
{
    [UnsafeAccessor(UnsafeAccessorKind.Field, Name = "_field")]
    public extern static ref V GetSetPrivateField(Class<V> c);

    [UnsafeAccessor(UnsafeAccessorKind.Method, Name = "M")]
    public extern static void CallM(Class<V> c, V v);

    [UnsafeAccessor(UnsafeAccessorKind.Method, Name = "GM")]
    public extern static void CallGM<X>(Class<V> c, X x);

    [UnsafeAccessor(UnsafeAccessorKind.Method, Name = "GMWithConstraints")]
    public extern static void CallGMWithConstraints<X, Y>(Class<V> c, X x, Y y) where X : Y, IEquatable<X>;
}

[czd890]

Hi @AaronRobinsonMSFT so sorry! The Accessors.GetSetPrivateField works after the deleted bin and obj folders.