Implement ComWrappers API for AOT/Trim compatibility

[PhantomGamers]

Built-in COM support is required for WmiLight but is not trim compatible.

I know this was discussed in #7, though despite the OP of that issue saying that enabling BuiltInComInteropSupport allowed their app to work with full trimming, in my app I'm getting the following exception:

Exception Info: System.AccessViolationException: Attempted to read or write protected memory. This is often an indication that other memory is corrupt.
Stack:
   at WmiLight.Wbem.IWbemServices.ExecQuery(System.String, System.String, WmiLight.Wbem.WbemClassObjectEnumeratorBehaviorOption, WmiLight.Wbem.IWbemContext, WmiLight.Wbem.IWbemClassObjectEnumerator ByRef)
   at WmiLight.Wbem.IWbemServices.ExecQuery(System.String, System.String, WmiLight.Wbem.WbemClassObjectEnumeratorBehaviorOption, WmiLight.Wbem.IWbemContext, WmiLight.Wbem.IWbemClassObjectEnumerator ByRef)
   at WmiLight.Wbem.IWbemServicesExtensions.ExecQuery(WmiLight.Wbem.IWbemServices, System.String, WmiLight.Wbem.WbemClassObjectEnumeratorBehaviorOption, WmiLight.Wbem.IWbemContext)
   at WmiLight.WmiConnection.InternalExecuteQuery(WmiLight.WmiQuery)
   at WmiLight.WmiConnection.ExecuteQuery(WmiLight.WmiQuery)

and when compiling I get the warning:

ILLink : Trim analysis warning IL2026: Internal.Runtime.InteropServices.ComActivator.GetClassFactoryForTypeInternal(ComActivationContextInternal*): Using member 'Internal.Runtime.InteropServices.ComActivator.GetClassFactoryForType(ComActivationContext)' which has 'RequiresUnreferencedCodeAttribute' can break functionality when trimming application code. Built-in COM support is not trim compatible. https://aka.ms/dotnet-illink/com

It does work fine with TrimMode set to partial, however this is not ideal.

At the link given in the trim warning, there is a link to this page which discusses using the ComWrappers api which is Trimming/AOT friendly.

I may try to implement this myself, but I see in #9 that a version 4.0 is in the works so I will wait for that before investigating further.

[MartinKuschnik]

Implementing a custom COM Wraper does not seams to be easy. Also because WmiLight targets .Net Standard and ComWrappers is a .NET 5+ runtime feature.

Can you please add the following to your project file and give it a try?

PS: I had to clear the publish dir by hand. Otherwise i got the same error.

<Target Name="ConfigureTrimming" BeforeTargets="PrepareForILLink">
  <ItemGroup>
	<ManagedAssemblyToLink Condition="'%(Filename)' == 'WmiLight'">
            <IsTrimmable>false</IsTrimmable>
	</ManagedAssemblyToLink>

	<ManagedAssemblyToLink Condition="'%(Filename)' == 'netstandard'">
	     <IsTrimmable>false</IsTrimmable>
	</ManagedAssemblyToLink>
  </ItemGroup>
</Target>

[PhantomGamers]

Implementing a custom COM Wraper does not seams to be easy.

Yeah it seems very annoying. It's in Microsoft's plans to implement a source generator to greatly streamline the process dotnet/runtime#66674, but at this point I doubt it'll be implemented any time soon.

Also because WmiLight targets .Net Standard and ComWrappers is a .NET 5+ runtime feature.

Yes, if I implemented this I would multitarget .net standard and .net 5 (or 6/7, probably just net standard and 6 since 5 is no longer supported and 6 is lts), so that existing apps that depend on WmiLight do not break.

Can you please add the following to your project file and give it a try?

Hm, this did not seem to work for me, I'm getting the same error even after clearing out my publish directory, along with all of the bin/ and obj/ directories. You are saying that you were getting the exact same AccessViolationException from my original post, and that target group fixed it?

[MartinKuschnik]

I created a simple .Net 7 Test App: WmiTrimTestApp.zip

Im getting following issue:

...\WmiTrimTestApp\bin\Release\net7.0\publish\win-x64>WmiTrimTestApp.exe
Fatal error. System.AccessViolationException: Attempted to read or write protected memory. This is often an indication that other memory is corrupt.
Repeat 2 times:
--------------------------------
   at WmiLight.Wbem.IWbemServices.ExecQuery(System.String, System.String, WmiLight.Wbem.WbemClassObjectEnumeratorBehaviorOption, WmiLight.Wbem.IWbemContext, WmiLight.Wbem.IWbemClassObjectEnumerator ByRef)
--------------------------------
   at WmiLight.Wbem.IWbemServicesExtensions.ExecQuery(WmiLight.Wbem.IWbemServices, System.String, WmiLight.Wbem.WbemClassObjectEnumeratorBehaviorOption, WmiLight.Wbem.IWbemContext)
   at WmiLight.WmiConnection.InternalExecuteQuery(WmiLight.WmiQuery)
   at WmiLight.WmiConnection.ExecuteQuery(WmiLight.WmiQuery)
   at WmiLight.WmiQuery.GetEnumerator()
   at Program.Main(System.String[])

After editing the Project file it works.

[PhantomGamers]

The code you posted didn't work for me, though now I'm thinking it was because I was putting it in the project file of my library which uses WmiLight but I should have actually put it in my application project where the trimming occurs. That did give me an idea though and I just tested this and it appears to work:

<ItemGroup>
  <TrimmerRootAssembly Include="WmiLight" />
</ItemGroup>

Of course this only sidesteps the issue by preventing trimming on this, but it's a good enough solution for me until the aforementioned code generator is implemented by MS. I'll have to do more testing after I track down the other trimming issues in my app though.

Thanks for your help!

[MartinKuschnik]

dotnet/linker#2991 could fix the issue.

[MartinKuschnik]

@PhantomGamers Have a look to the version v5.0.0-pre. Native AOT should work with this version.

Feedback would be nice.