Add support for "extended" layouts in the runtimes and add CStruct layout #116082

jkoritzinsky · 2025-05-28T23:39:45Z

Add support for the ExtendedLayout flag, the System.Runtime.InteropServices.ExtendedLayoutAttribute and the CStruct layout from #100896.

Contributes to #100896

Leaving other layouts from #100896 for later PRs to minimize diffs.

dotnet-policy-service · 2025-05-28T23:40:33Z

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Copilot

Pull Request Overview

This PR adds support for an “extended” layout flag in the runtimes, introduces the ExtendedLayoutAttribute and CStruct layout kind, and wires through layout info across types and metadata emitters.

Add IsExtendedLayout and GetExtendedLayoutInfo APIs to core metadata types
Implement ComputeCStructFieldLayout and dispatch in field layout algorithms
Update metadata headers, ILASM grammar, and reflection emit to recognize extended layout

Reviewed Changes

Copilot reviewed 45 out of 45 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
src/coreclr/tools/aot/ILCompiler.Compiler/Compiler/CompilerMetadataFieldLayoutAlgorithm.cs	Dispatch `ComputeExtendedFieldLayout` before explicit layout
src/coreclr/tools/Common/TypeSystem/Interop/IL/PInvokeDelegateWrapper.cs	Stub out `IsExtendedLayout` & `GetExtendedLayoutInfo`
src/coreclr/tools/Common/TypeSystem/Interop/IL/NativeStructType.cs	Override extended layout members and simplify `GetClassLayout`
src/coreclr/tools/Common/TypeSystem/Interop/IL/MarshalUtils.cs	Treat `CStruct` as blittable
src/coreclr/tools/Common/TypeSystem/Interop/IL/InlineArrayType.cs	Stub out `IsExtendedLayout` & `GetExtendedLayoutInfo`
src/coreclr/tools/Common/TypeSystem/Ecma/EcmaType.cs	Parse `ExtendedLayoutAttribute` and implement `IsExtendedLayout`
src/coreclr/tools/Common/TypeSystem/Common/TypeWithRepeatedFields.cs	Forward extended layout members
src/coreclr/tools/Common/TypeSystem/Common/TypeSystemHelpers.cs	Include `IsExtendedLayout` in `HasLayout`
src/coreclr/tools/Common/TypeSystem/Common/MetadataType.cs	Add abstract `IsExtendedLayout`, `GetExtendedLayoutInfo`, and supporting types
src/coreclr/tools/Common/TypeSystem/Common/MetadataFieldLayoutAlgorithm.cs	Implement `ComputeCStructFieldLayout` and `ComputeExtendedFieldLayout`
src/coreclr/tools/Common/TypeSystem/Common/InstantiatedType.Metadata.cs	Override extended layout members
src/coreclr/tools/Common/TypeSystem/Canon/CanonTypes.Metadata.cs	Stub out extended layout members
src/coreclr/nativeaot/Runtime.Base/src/System/Runtime/InteropServices/LayoutKind.cs	Add `LayoutKind.Extended` enum
src/coreclr/md/compiler/custattr_emit.cpp	Handle `tdExtendedLayout` in custom attr emitter
src/coreclr/inc/il_kywd.h	Add IL keyword `extended`
src/coreclr/inc/corhdr.h	Define `tdExtendedLayout` and `IsTdExtendedLayout`
src/coreclr/ilasm/prebuilt/asmparse.grammar	Recognize `extended` in grammar
src/coreclr/ilasm/asmparse.y	Add `EXTENDED_` token and grammar rules
src/coreclr/System.Private.CoreLib/src/System/Reflection/RuntimeCustomAttributeData.cs	Map `ExtendedLayout` to `LayoutKind.Extended`
src/coreclr/System.Private.CoreLib/src/System/Reflection/Emit/RuntimeTypeBuilder.cs	Remove obsolete layout-mask validation

Comments suppressed due to low confidence (1)

src/coreclr/tools/Common/TypeSystem/Common/MetadataFieldLayoutAlgorithm.cs:502

There are no unit tests covering the new CStruct layout path (ComputeCStructFieldLayout and ComputeExtendedFieldLayout). Adding tests for valid field offsets, alignment boundaries, and error conditions will help catch regressions.

private static ComputedInstanceFieldLayout ComputeCStructFieldLayout(MetadataType type, int numInstanceFields)

src/coreclr/tools/Common/TypeSystem/Common/MetadataType.cs

src/coreclr/tools/Common/TypeSystem/Interop/IL/PInvokeDelegateWrapper.cs

src/tests/Loader/classloader/ExtendedLayout/CStruct.cs

src/tests/Loader/classloader/ExtendedLayout/ExtendedLayoutTypes.il

src/tests/Loader/classloader/ExtendedLayout/CStruct.cs

src/libraries/System.Private.CoreLib/src/System/Reflection/TypeAttributes.cs

src/coreclr/tools/Common/TypeSystem/Common/MetadataType.cs

…ds into GetClassLayout

src/coreclr/tools/Common/TypeSystem/Common/MetadataFieldLayoutAlgorithm.cs

src/coreclr/tools/Common/TypeSystem/Common/TypeSystemHelpers.cs

src/coreclr/tools/Common/TypeSystem/Ecma/EcmaType.cs

jkotas · 2025-06-15T00:17:45Z

src/libraries/System.Runtime/ref/System.Runtime.cs

    public partial class ExternalException : System.SystemException
    {
        public ExternalException() { }
        [System.ComponentModel.EditorBrowsableAttribute(System.ComponentModel.EditorBrowsableState.Never)]
-        [System.ObsoleteAttribute("This API supports obsolete formatter-based serialization. It should not be called or extended by application code.", DiagnosticId="SYSLIB0051", UrlFormat="https://aka.ms/dotnet-warnings/{0}")]
+        [System.ObsoleteAttribute("This API supports obsolete formatter-based serialization. It should not be called or extended by application code.", DiagnosticId = "SYSLIB0051", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]


Suggested change

[System.ObsoleteAttribute("This API supports obsolete formatter-based serialization. It should not be called or extended by application code.", DiagnosticId = "SYSLIB0051", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]

[System.ObsoleteAttribute("This API supports obsolete formatter-based serialization. It should not be called or extended by application code.", DiagnosticId="SYSLIB0051", UrlFormat="https://aka.ms/dotnet-warnings/{0}")]

Nit: Canonical formatting generated by genapi tool does not have spaces.

jkotas · 2025-06-15T00:18:32Z

src/libraries/System.Runtime/ref/System.Runtime.cs

@@ -14202,11 +14203,21 @@ protected virtual void Dispose(bool disposing) { }
        protected void SetHandle(System.IntPtr handle) { }
        public void SetHandleAsInvalid() { }
    }
+
+    [System.AttributeUsageAttribute(System.AttributeTargets.Struct, Inherited = false)]


Suggested change

[System.AttributeUsageAttribute(System.AttributeTargets.Struct, Inherited = false)]

[System.AttributeUsageAttribute(System.AttributeTargets.Struct, Inherited=false)]

jkotas · 2025-06-15T00:48:44Z

src/coreclr/tools/aot/ILCompiler.Compiler/Compiler/CompilerMetadataFieldLayoutAlgorithm.cs

-            {
-                return ComputeAutoFieldLayout(type, numInstanceFields);
-            }
+                MetadataLayoutKind.Explicit => ComputeExplicitFieldLayout(type, numInstanceFields),


Pass the result of type.GetClassLayout() to the worked methods to avoid recomputing it? (All except ComputeCStructFieldLayout needs it on some path.) It can be passed around as in since it is likely going grow into a large struct over time.

jkotas · 2025-06-15T01:01:43Z

src/coreclr/tools/Common/TypeSystem/Common/MetadataFieldLayoutAlgorithm.cs

+                // CStruct cannot have zero size.
+                ThrowHelper.ThrowTypeLoadException(ExceptionStringID.ClassLoadBadFormat, type);
+            }
+


Do we need InlineArray handling here?

jkoritzinsky added 12 commits May 28, 2025 08:34

Add TypeAttribute and LayoutKind values

cdfb3d4

Update ilasm

a0b5bfa

Don't block loading extended layout types

37de415

Update SRE support for ExtendedLayout

62289ae

Add support in the managed type system for extended layout

084bc47

Implement CStruct layout support in NAOT

b066bd6

Implement CStruct in CoreCLR

858a9a8

Implement CStruct in Mono

106f590

Add tests for ExtendedLayout(CStruct)

f4c7fc7

Get tests passing on CoreCLR

19c4a60

Fix handling for type without ExtendedLayoutAttribute

0db4b1d

Remove preamble emitted into grammar file

82119fc

jkoritzinsky requested review from davidwrighton, AaronRobinsonMSFT and Copilot May 28, 2025 23:39

jkoritzinsky requested review from thaystg, steveisok, vitek-karas and MichalStrehovsky as code owners May 28, 2025 23:39

jkoritzinsky added the area-System.Runtime.InteropServices label May 28, 2025

dotnet-policy-service bot assigned jkoritzinsky May 28, 2025

Copilot AI reviewed May 28, 2025

View reviewed changes

src/coreclr/tools/Common/TypeSystem/Common/MetadataType.cs Outdated Show resolved Hide resolved

src/coreclr/tools/Common/TypeSystem/Interop/IL/PInvokeDelegateWrapper.cs Show resolved Hide resolved

jkoritzinsky mentioned this pull request May 28, 2025

Implement compiler support for System.Runtime.InteropServices.ExtendedLayoutAttribute dotnet/roslyn#78741

Open

2 tasks

AaronRobinsonMSFT reviewed May 29, 2025

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src/tests/Loader/classloader/ExtendedLayout/CStruct.cs Show resolved Hide resolved

src/tests/Loader/classloader/ExtendedLayout/ExtendedLayoutTypes.il Show resolved Hide resolved

src/tests/Loader/classloader/ExtendedLayout/CStruct.cs Show resolved Hide resolved

jkotas reviewed May 29, 2025

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src/libraries/System.Private.CoreLib/src/System/Reflection/TypeAttributes.cs Show resolved Hide resolved

jkoritzinsky added 3 commits May 29, 2025 10:52

Define ExtendedLayoutAttribute in corelib

62d7083

Add reference to Microsoft.Bcl.Memory for ILVerification.csproj

0e58822

Don't allow empty CStruct types.

a6e5f24

jkotas reviewed May 29, 2025

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src/coreclr/tools/Common/TypeSystem/Common/MetadataType.cs Outdated Show resolved Hide resolved

jkoritzinsky added 2 commits May 30, 2025 14:45

Add missing var

a8bc97e

Collapse together the different "get class layout related info" metho…

5d86388

…ds into GetClassLayout

jkotas reviewed Jun 5, 2025

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src/coreclr/tools/Common/TypeSystem/Common/MetadataFieldLayoutAlgorithm.cs Outdated Show resolved Hide resolved

jkotas reviewed Jun 5, 2025

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src/coreclr/tools/Common/TypeSystem/Common/TypeSystemHelpers.cs Outdated Show resolved Hide resolved

jkotas reviewed Jun 5, 2025

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src/coreclr/tools/Common/TypeSystem/Ecma/EcmaType.cs Outdated Show resolved Hide resolved

PR feedback

d028bea

build-analysis bot mentioned this pull request Jun 11, 2025

RestApiException`1: The response contained an invalid status code 500 Internal Server Error dotnet/dnceng#2298

Open

3 tasks

Add missing impl

05085e3

This was referenced Jun 13, 2025

System.Net.Http.Functional.Tests timeouts #115683

Open

iOS.Device.LibraryMode.Test: failed to determine exit code - RETURN_CODE_NOT_SET #116558

Open

Merge branch 'main' into extended-layout

1cb8206

jkotas reviewed Jun 15, 2025

View reviewed changes

build-analysis bot mentioned this pull request Jun 15, 2025

Test failure: System.Reflection.Metadata.ApplyUpdateTest.TestGenericAddStaticField #115318

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Add support for "extended" layouts in the runtimes and add CStruct layout #116082

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	[System.ObsoleteAttribute("This API supports obsolete formatter-based serialization. It should not be called or extended by application code.", DiagnosticId = "SYSLIB0051", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
	[System.ObsoleteAttribute("This API supports obsolete formatter-based serialization. It should not be called or extended by application code.", DiagnosticId="SYSLIB0051", UrlFormat="https://aka.ms/dotnet-warnings/{0}")]

	[System.AttributeUsageAttribute(System.AttributeTargets.Struct, Inherited = false)]
	[System.AttributeUsageAttribute(System.AttributeTargets.Struct, Inherited=false)]

Add support for "extended" layouts in the runtimes and add CStruct layout #116082

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Pull Request Overview

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