[ILLink]: Using InternalsVisibleTo in System.Private.CoreLib breaks a runtime build

[arturek]

Description

When the InternalsVisibleTo attribute is used in the System.Private.CoreLib project (where it is also defined), ILLink crashes (because of NullReferenceException) and prints ILLink : error IL1012: IL Trimmer has encountered an unexpected error.

I found this problem while working on adding tests to #92534.

Reproduction Steps

1. apply the commit arturek/runtime@677f9c2
2. run build.cmd clr+libs -c Debug in the x64 console (Release mode fails the same way)

Expected behavior

The runtime and libraries are successfully built.

Actual behavior

The following error is printed:

  sfx -> Trimming win-x64 shared framework assemblies with ILLinker...
ILLink : error IL1012: IL Trimmer has encountered an unexpected error. Please report the issue at https://aka.ms/report-illink [C:\r\gh
\dotnet\rt2\runtime\src\libraries\sfx.proj]
  Fatal error in IL Linker
  Unhandled exception. System.NullReferenceException: Object reference not set to an instance of an object.
     at Mono.Linker.UnconditionalSuppressMessageAttributeState.GetModuleFromProvider(ICustomAttributeProvider provider) in C:\r\gh\dotn
  et\rt2\runtime\src\tools\illink\src\linker\Linker\UnconditionalSuppressMessageAttributeState.cs:line 252
     at Mono.Linker.UnconditionalSuppressMessageAttributeState.TryGetSuppressionsForProvider(ICustomAttributeProvider provider, Diction
  ary`2& suppressions) in C:\r\gh\dotnet\rt2\runtime\src\tools\illink\src\linker\Linker\UnconditionalSuppressMessageAttributeState.cs:l
  ine 175
     at Mono.Linker.UnconditionalSuppressMessageAttributeState.IsSuppressedOnElement(Int32 id, ICustomAttributeProvider provider, Suppr
  essMessageInfo& info) in C:\r\gh\dotnet\rt2\runtime\src\tools\illink\src\linker\Linker\UnconditionalSuppressMessageAttributeState.cs:
  line 146
     at Mono.Linker.UnconditionalSuppressMessageAttributeState.IsSuppressed(Int32 id, ICustomAttributeProvider warningOrigin, SuppressM
  essageInfo& info) in C:\r\gh\dotnet\rt2\runtime\src\tools\illink\src\linker\Linker\UnconditionalSuppressMessageAttributeState.cs:line
   111
     at Mono.Linker.UnconditionalSuppressMessageAttributeState.IsSuppressed(Int32 id, MessageOrigin warningOrigin, SuppressMessageInfo&
   info) in C:\r\gh\dotnet\rt2\runtime\src\tools\illink\src\linker\Linker\UnconditionalSuppressMessageAttributeState.cs:line 82
     at Mono.Linker.LinkContext.IsWarningSuppressed(Int32 warningCode, String subcategory, MessageOrigin origin) in C:\r\gh\dotnet\rt2\
  runtime\src\tools\illink\src\linker\Linker\LinkContext.cs:line 744
     at Mono.Linker.MessageContainer.CreateWarningMessageContainer(LinkContext context, MessageOrigin origin, DiagnosticId id, WarnVers
  ion version, String subcategory, String[] args) in C:\r\gh\dotnet\rt2\runtime\src\tools\illink\src\linker\Linker\MessageContainer.cs:
  line 185
     at Mono.Linker.MessageContainer.CreateWarningMessage(LinkContext context, MessageOrigin origin, DiagnosticId id, WarnVersion versi
  on, String[] args) in C:\r\gh\dotnet\rt2\runtime\src\tools\illink\src\linker\Linker\MessageContainer.cs:line 132
     at Mono.Linker.LinkContext.LogWarning(MessageOrigin origin, DiagnosticId id, String[] args) in C:\r\gh\dotnet\rt2\runtime\src\tool
  s\illink\src\linker\Linker\LinkContext.cs:line 595
     at Mono.Linker.Steps.CheckSuppressionsDispatcher.Process(LinkContext context) in C:\r\gh\dotnet\rt2\runtime\src\tools\illink\src\l
  inker\Linker.Steps\CheckSuppressionsDispatcher.cs:line 33
     at Mono.Linker.Pipeline.ProcessStep(LinkContext context, IStep step) in C:\r\gh\dotnet\rt2\runtime\src\tools\illink\src\linker\Lin
  ker\Pipeline.cs:line 178
     at Mono.Linker.Pipeline.Process(LinkContext context) in C:\r\gh\dotnet\rt2\runtime\src\tools\illink\src\linker\Linker\Pipeline.cs:
  line 167
     at Mono.Linker.Driver.Run(ILogger customLogger) in C:\r\gh\dotnet\rt2\runtime\src\tools\illink\src\linker\Linker\Driver.cs:line 81
  4
     at Mono.Linker.Driver.Main(String[] args) in C:\r\gh\dotnet\rt2\runtime\src\tools\illink\src\linker\Linker\Driver.cs:line 68

Build FAILED.

ILLink : error IL1012: IL Trimmer has encountered an unexpected error. Please report the issue at https://aka.ms/report-illink [C:\r\gh
\dotnet\rt2\runtime\src\libraries\sfx.proj]
    0 Warning(s)
    1 Error(s)

Regression?

Probably not a regression, as this functionality was never used there.

Known Workarounds

no workarounds found

Configuration

.Net SDK 8.0.100-rc.1.23455.8 (x64)
Windows 11 Home 22H2
x64

Other information

The error happens because the DeclaringType property of the Mono.Cecil.MethodDefinition instance (representing the System.Int32 GetClassFactoryForTypeInContext(Internal.Runtime.InteropServices.ComActivationContextInternal*,System.IntPtr) method) is null. When this instance is created its DeclaringType is correct, but later it becomes null. I don't know when.

Tagging subscribers to this area: @vitek-karas, @agocke, @VSadov
See info in area-owners.md if you want to be subscribed.

Issue Details

---

Description

When the InternalsVisibleTo attribute is used in the System.Private.CoreLib project (where it is also defined), ILLink crashes (because of NullReferenceException) and prints ILLink : error IL1012: IL Trimmer has encountered an unexpected error.

I found this problem while working on adding tests to #92534.

Reproduction Steps

1. apply the commit arturek/runtime@677f9c2
2. run build.cmd clr+libs -c Debug in the x64 console (Release mode fails the same way)

Expected behavior

The runtime and libraries are successfully built.

Actual behavior

The following error is printed:

  sfx -> Trimming win-x64 shared framework assemblies with ILLinker...
ILLink : error IL1012: IL Trimmer has encountered an unexpected error. Please report the issue at https://aka.ms/report-illink [C:\r\gh
\dotnet\rt2\runtime\src\libraries\sfx.proj]
  Fatal error in IL Linker
  Unhandled exception. System.NullReferenceException: Object reference not set to an instance of an object.
     at Mono.Linker.UnconditionalSuppressMessageAttributeState.GetModuleFromProvider(ICustomAttributeProvider provider) in C:\r\gh\dotn
  et\rt2\runtime\src\tools\illink\src\linker\Linker\UnconditionalSuppressMessageAttributeState.cs:line 252
     at Mono.Linker.UnconditionalSuppressMessageAttributeState.TryGetSuppressionsForProvider(ICustomAttributeProvider provider, Diction
  ary`2& suppressions) in C:\r\gh\dotnet\rt2\runtime\src\tools\illink\src\linker\Linker\UnconditionalSuppressMessageAttributeState.cs:l
  ine 175
     at Mono.Linker.UnconditionalSuppressMessageAttributeState.IsSuppressedOnElement(Int32 id, ICustomAttributeProvider provider, Suppr
  essMessageInfo& info) in C:\r\gh\dotnet\rt2\runtime\src\tools\illink\src\linker\Linker\UnconditionalSuppressMessageAttributeState.cs:
  line 146
     at Mono.Linker.UnconditionalSuppressMessageAttributeState.IsSuppressed(Int32 id, ICustomAttributeProvider warningOrigin, SuppressM
  essageInfo& info) in C:\r\gh\dotnet\rt2\runtime\src\tools\illink\src\linker\Linker\UnconditionalSuppressMessageAttributeState.cs:line
   111
     at Mono.Linker.UnconditionalSuppressMessageAttributeState.IsSuppressed(Int32 id, MessageOrigin warningOrigin, SuppressMessageInfo&
   info) in C:\r\gh\dotnet\rt2\runtime\src\tools\illink\src\linker\Linker\UnconditionalSuppressMessageAttributeState.cs:line 82
     at Mono.Linker.LinkContext.IsWarningSuppressed(Int32 warningCode, String subcategory, MessageOrigin origin) in C:\r\gh\dotnet\rt2\
  runtime\src\tools\illink\src\linker\Linker\LinkContext.cs:line 744
     at Mono.Linker.MessageContainer.CreateWarningMessageContainer(LinkContext context, MessageOrigin origin, DiagnosticId id, WarnVers
  ion version, String subcategory, String[] args) in C:\r\gh\dotnet\rt2\runtime\src\tools\illink\src\linker\Linker\MessageContainer.cs:
  line 185
     at Mono.Linker.MessageContainer.CreateWarningMessage(LinkContext context, MessageOrigin origin, DiagnosticId id, WarnVersion versi
  on, String[] args) in C:\r\gh\dotnet\rt2\runtime\src\tools\illink\src\linker\Linker\MessageContainer.cs:line 132
     at Mono.Linker.LinkContext.LogWarning(MessageOrigin origin, DiagnosticId id, String[] args) in C:\r\gh\dotnet\rt2\runtime\src\tool
  s\illink\src\linker\Linker\LinkContext.cs:line 595
     at Mono.Linker.Steps.CheckSuppressionsDispatcher.Process(LinkContext context) in C:\r\gh\dotnet\rt2\runtime\src\tools\illink\src\l
  inker\Linker.Steps\CheckSuppressionsDispatcher.cs:line 33
     at Mono.Linker.Pipeline.ProcessStep(LinkContext context, IStep step) in C:\r\gh\dotnet\rt2\runtime\src\tools\illink\src\linker\Lin
  ker\Pipeline.cs:line 178
     at Mono.Linker.Pipeline.Process(LinkContext context) in C:\r\gh\dotnet\rt2\runtime\src\tools\illink\src\linker\Linker\Pipeline.cs:
  line 167
     at Mono.Linker.Driver.Run(ILogger customLogger) in C:\r\gh\dotnet\rt2\runtime\src\tools\illink\src\linker\Linker\Driver.cs:line 81
  4
     at Mono.Linker.Driver.Main(String[] args) in C:\r\gh\dotnet\rt2\runtime\src\tools\illink\src\linker\Linker\Driver.cs:line 68

Build FAILED.

ILLink : error IL1012: IL Trimmer has encountered an unexpected error. Please report the issue at https://aka.ms/report-illink [C:\r\gh
\dotnet\rt2\runtime\src\libraries\sfx.proj]
    0 Warning(s)
    1 Error(s)

Regression?

Probably not a regression, as this functionality was never used there.

Known Workarounds

no workarounds found

Configuration

.Net SDK 8.0.100-rc.1.23455.8 (x64)
Windows 11 Home 22H2
x64

Other information

The error happens because the DeclaringType property of the Mono.Cecil.MethodDefinition instance (representing the System.Int32 GetClassFactoryForTypeInContext(Internal.Runtime.InteropServices.ComActivationContextInternal*,System.IntPtr) method) is null. When this instance is created its DeclaringType is correct, but later it becomes null. I don't know when.

Author:	arturek
Assignees:	-
Labels:	area-AssemblyLoader-coreclr, untriaged
Milestone:	-

Tagging subscribers to this area: @agocke, @sbomer, @vitek-karas
See info in area-owners.md if you want to be subscribed.

Issue Details

---

Description

When the InternalsVisibleTo attribute is used in the System.Private.CoreLib project (where it is also defined), ILLink crashes (because of NullReferenceException) and prints ILLink : error IL1012: IL Trimmer has encountered an unexpected error.

I found this problem while working on adding tests to #92534.

Reproduction Steps

1. apply the commit arturek/runtime@677f9c2
2. run build.cmd clr+libs -c Debug in the x64 console (Release mode fails the same way)

Expected behavior

The runtime and libraries are successfully built.

Actual behavior

The following error is printed:

  sfx -> Trimming win-x64 shared framework assemblies with ILLinker...
ILLink : error IL1012: IL Trimmer has encountered an unexpected error. Please report the issue at https://aka.ms/report-illink [C:\r\gh
\dotnet\rt2\runtime\src\libraries\sfx.proj]
  Fatal error in IL Linker
  Unhandled exception. System.NullReferenceException: Object reference not set to an instance of an object.
     at Mono.Linker.UnconditionalSuppressMessageAttributeState.GetModuleFromProvider(ICustomAttributeProvider provider) in C:\r\gh\dotn
  et\rt2\runtime\src\tools\illink\src\linker\Linker\UnconditionalSuppressMessageAttributeState.cs:line 252
     at Mono.Linker.UnconditionalSuppressMessageAttributeState.TryGetSuppressionsForProvider(ICustomAttributeProvider provider, Diction
  ary`2& suppressions) in C:\r\gh\dotnet\rt2\runtime\src\tools\illink\src\linker\Linker\UnconditionalSuppressMessageAttributeState.cs:l
  ine 175
     at Mono.Linker.UnconditionalSuppressMessageAttributeState.IsSuppressedOnElement(Int32 id, ICustomAttributeProvider provider, Suppr
  essMessageInfo& info) in C:\r\gh\dotnet\rt2\runtime\src\tools\illink\src\linker\Linker\UnconditionalSuppressMessageAttributeState.cs:
  line 146
     at Mono.Linker.UnconditionalSuppressMessageAttributeState.IsSuppressed(Int32 id, ICustomAttributeProvider warningOrigin, SuppressM
  essageInfo& info) in C:\r\gh\dotnet\rt2\runtime\src\tools\illink\src\linker\Linker\UnconditionalSuppressMessageAttributeState.cs:line
   111
     at Mono.Linker.UnconditionalSuppressMessageAttributeState.IsSuppressed(Int32 id, MessageOrigin warningOrigin, SuppressMessageInfo&
   info) in C:\r\gh\dotnet\rt2\runtime\src\tools\illink\src\linker\Linker\UnconditionalSuppressMessageAttributeState.cs:line 82
     at Mono.Linker.LinkContext.IsWarningSuppressed(Int32 warningCode, String subcategory, MessageOrigin origin) in C:\r\gh\dotnet\rt2\
  runtime\src\tools\illink\src\linker\Linker\LinkContext.cs:line 744
     at Mono.Linker.MessageContainer.CreateWarningMessageContainer(LinkContext context, MessageOrigin origin, DiagnosticId id, WarnVers
  ion version, String subcategory, String[] args) in C:\r\gh\dotnet\rt2\runtime\src\tools\illink\src\linker\Linker\MessageContainer.cs:
  line 185
     at Mono.Linker.MessageContainer.CreateWarningMessage(LinkContext context, MessageOrigin origin, DiagnosticId id, WarnVersion versi
  on, String[] args) in C:\r\gh\dotnet\rt2\runtime\src\tools\illink\src\linker\Linker\MessageContainer.cs:line 132
     at Mono.Linker.LinkContext.LogWarning(MessageOrigin origin, DiagnosticId id, String[] args) in C:\r\gh\dotnet\rt2\runtime\src\tool
  s\illink\src\linker\Linker\LinkContext.cs:line 595
     at Mono.Linker.Steps.CheckSuppressionsDispatcher.Process(LinkContext context) in C:\r\gh\dotnet\rt2\runtime\src\tools\illink\src\l
  inker\Linker.Steps\CheckSuppressionsDispatcher.cs:line 33
     at Mono.Linker.Pipeline.ProcessStep(LinkContext context, IStep step) in C:\r\gh\dotnet\rt2\runtime\src\tools\illink\src\linker\Lin
  ker\Pipeline.cs:line 178
     at Mono.Linker.Pipeline.Process(LinkContext context) in C:\r\gh\dotnet\rt2\runtime\src\tools\illink\src\linker\Linker\Pipeline.cs:
  line 167
     at Mono.Linker.Driver.Run(ILogger customLogger) in C:\r\gh\dotnet\rt2\runtime\src\tools\illink\src\linker\Linker\Driver.cs:line 81
  4
     at Mono.Linker.Driver.Main(String[] args) in C:\r\gh\dotnet\rt2\runtime\src\tools\illink\src\linker\Linker\Driver.cs:line 68

Build FAILED.

ILLink : error IL1012: IL Trimmer has encountered an unexpected error. Please report the issue at https://aka.ms/report-illink [C:\r\gh
\dotnet\rt2\runtime\src\libraries\sfx.proj]
    0 Warning(s)
    1 Error(s)

Regression?

Probably not a regression, as this functionality was never used there.

Known Workarounds

no workarounds found

Configuration

.Net SDK 8.0.100-rc.1.23455.8 (x64)
Windows 11 Home 22H2
x64

Other information

The error happens because the DeclaringType property of the Mono.Cecil.MethodDefinition instance (representing the System.Int32 GetClassFactoryForTypeInContext(Internal.Runtime.InteropServices.ComActivationContextInternal*,System.IntPtr) method) is null. When this instance is created its DeclaringType is correct, but later it becomes null. I don't know when.

Author:	arturek
Assignees:	-
Labels:	area-AssemblyLoader-coreclr, untriaged, area-Tools-ILLink
Milestone:	-

[jkotas]

I found this problem while working on adding tests to #92534.

We do not use InternalsVisible in core runtime assemblies. Even if this bug is fixed, we would not want to add InternalsVisible in CoreLib.

[danmoseley]

Consider code sharing instead. We do that in several test assemblies.

[arturek]

@jkotas Thank you for this information.
@danmoseley I used sharing in other places and thought about it initially. Unfortunately, the way how the DebuggerDisplay and DebuggerTypeProxy attributes are tested do not work well with sharing. The test method looks for equality of classes used internally to implement the debug view functionality. I started to investigate a solution with InternalsVisibleTo because I planned to create my instances of internal debug type proxy for this equality check.

IMO using a library that returns a simplified debug view model for a given object (similar to the way VS debugger does it internally) would be a much better solution. No references to internal classes would be needed and verification could also cover other aspects of using these attributes, including the way how all names, values and types are formatted. If you know any solution or a library which can provide such functionality and can be used in this project to test debug views, please let me know. Otherwise, I'll try to find some other way to solve this testing problem.

[jkotas]

We use reflection to test internal types like debugger proxies.

[vitek-karas]

For this specific crash, it's actually a bug in basically the design of IL2121 (detection of redundant suppressions).

What happens here is:

• Method Internal.Runtime.InteropServices.ComActivator.GetClassFactoryForTypeInContext is UnmanagedCallersOnly and is not rooted. This is basically a bug in the sfx project - it runs the trimmer without any feature switches, so we don't check code which is hidden behind some feature switch - even that code should not produce warnings internally, it should all be annotated as necessary. It should be rooted by a descriptor.
• This method is private, so we don't keep it in the library mode (which keeps everything public/internal)
• It calls a local function, which get translated into <GetClassFactoryForTypeInContext>g__GetClassFactoryForTypeLocal|5_0. This method is internal! So the library mode roots it. No idea why Roslyn generates a local function for a private method as internal, that feels wrong.
• In OutputStep the trimmer removes the UCO method and only leaves the local function.
• We generate IL2121 for the local function - I don't know yet why this happens, the suppressions there seem to be correct, but it's pretty complicated with some suppressions added via XMLs.
• Now we try to determine if IL2121 is itself suppressed on the local function - for this we walk the "scope" stack, so we look at the UCO method as that is the owning scope for the local function. And then we try to go to the owning type of the UCO - but that fails as that reference is null. The UCO has been removed from its parent's type as it's been trimmed - so it has no parent type.

The design flaw is that this is technically a valid situation to get into - the trimmer may be forced into keeping compiler generated methods for some reason, without keeping their respective scopes (user defined methods). Such configuration should always produce warnings, but those may be suppressed or ignored, it should not crash the trimmer.

The simplest fix is probably to make the IsWarningSuppressed robust to nulls (again, not having Cecil null annotated bites us). It can play it safe and if it can't find the owner type, just assume the warning is not suppressed there - it's unlikely to happy in otherwise warning free scenarios (I can't think of a case where this should happen without warnings).