New function pointer APIs by jgh07 · Pull Request #123819 · dotnet/runtime

jgh07 · 2026-01-30T22:34:50Z

This implements #75348.

MakeFunctionPointerType is only implemented for CoreCLR, a Mono implementation will follow.

…, ILGeneratorImpl.EmitCalli(Type)

dotnet-policy-service · 2026-01-30T22:35:57Z

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jgh07 · 2026-01-30T22:36:15Z

src/libraries/System.Private.CoreLib/src/System/Reflection/Emit/ILGenerator.cs

        public abstract void EmitCalli(OpCode opcode, CallingConvention unmanagedCallConv, Type? returnType, Type[]? parameterTypes);

+        /// <summary>
+        /// Puts a <see cref="OpCodes.Calli"/> instruction onto the Microsoft intermediate language (MSIL) stream,


I kept this description largely the same as the existing overloads. I think it might make more sense to update it though, since as far as I'm concerned the term MSIL was dropped in favor of CIL.

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

Copilot

Pull request overview

This PR implements new function pointer APIs as proposed in issue #75348, enabling better support for function pointer types in IL generation and reflection scenarios.

Changes:

Adds Type.MakeFunctionPointerSignatureType and Type.MakeModifiedSignatureType static factory methods for creating signature types
Implements ILGenerator.EmitCalli(Type functionPointerType) overload in ILGeneratorImpl for modern function pointer calling conventions
Adds new internal SignatureFunctionPointerType and SignatureModifiedType classes to represent these signature types

Reviewed changes

Copilot reviewed 16 out of 16 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
System.Runtime.cs	Adds public API surface for new function pointer and modified signature type factory methods
Type.cs	Implements MakeFunctionPointerSignatureType and MakeModifiedSignatureType factory methods with XML documentation
SignatureFunctionPointerType.cs	New internal class representing function pointer signature types with support for calling conventions
SignatureModifiedType.cs	New internal class representing types with required/optional custom modifiers
SignatureType.cs	Changes UnderlyingSystemType from sealed to virtual to allow SignatureModifiedType to override it
ILGenerator.cs	Adds new EmitCalli overload accepting function pointer Type with XML documentation
ILGeneratorImpl.cs	Implements the new EmitCalli overload with stack tracking and signature token generation
SignatureHelper.cs	Makes WriteSignatureForFunctionPointerType internal and adds logic to unwrap SignatureTypes
ModuleBuilderImpl.cs	Adds GetFunctionPointerSignatureToken method to generate standalone signatures for calli instructions
DynamicILGenerator.cs	Adds stub TODO implementation for EmitCalli - not yet functional
System.Reflection.Emit.ILGeneration.cs	Adds public API surface for new EmitCalli overload
Strings.resx	Adds error message for invalid function pointer type arguments
System.Private.CoreLib.Shared.projitems	Adds new SignatureFunctionPointerType and SignatureModifiedType to project, plus unrelated whitespace fix
SignatureTypes.cs	Adds tests for the new MakeFunctionPointerSignatureType and MakeModifiedSignatureType methods
AssemblySaveILGeneratorTests.cs	Adds end-to-end test for EmitCalli with function pointer types
Utilities.cs	Adds ClassWithFunctionPointer test helper class

Comments suppressed due to low confidence (1)

src/libraries/System.Reflection.Emit/src/System/Reflection/Emit/SignatureHelper.cs:6

This using directive appears to be unused. There are no references to System.IO types in this file. Consider removing it to keep the code clean.

using System.Reflection.Metadata;

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

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

src/coreclr/System.Private.CoreLib/src/System/Reflection/Emit/DynamicILGenerator.cs

src/libraries/System.Private.CoreLib/src/System.Private.CoreLib.Shared.projitems

src/libraries/System.Private.CoreLib/src/System/Type.cs

src/coreclr/System.Private.CoreLib/src/System/RuntimeHandles.cs

src/coreclr/vm/runtimehandles.cpp

Copilot

Pull request overview

Copilot reviewed 21 out of 21 changed files in this pull request and generated 7 comments.

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

src/libraries/System.Private.CoreLib/src/System/Type.cs

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

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

src/coreclr/System.Private.CoreLib/src/System/RuntimeType.CoreCLR.cs

src/libraries/System.Private.CoreLib/src/System/Type.cs

…ointerSignatureType

Copilot

Pull request overview

Copilot reviewed 24 out of 24 changed files in this pull request and generated 3 comments.

src/libraries/System.Reflection.Emit.ILGeneration/tests/ILGenerator/Emit4Tests.cs

src/libraries/System.Private.CoreLib/src/System/Type.cs

src/libraries/System.Runtime/tests/System.Runtime.Tests/System/Reflection/SignatureTypes.cs

src/libraries/System.Private.CoreLib/src/System/Type.cs

MichalStrehovsky · 2026-02-12T04:33:27Z

.../nativeaot/System.Private.CoreLib/src/System/Reflection/Runtime/TypeInfos/RuntimeTypeInfo.cs

+
+            for (int i = 0; i < parameterTypes.Length; i++)
+            {
+                ArgumentNullException.ThrowIfNull(parameterTypes[i], nameof(parameterTypes));


Do we want to allow void as parameter type?

(Or uninstantiated generic type definitions.)

Probably not, I'll add checks for those.

jkotas · 2026-02-12T07:28:53Z

src/coreclr/System.Private.CoreLib/src/System/Reflection/Emit/SignatureHelper.cs

+        {
+            Debug.Assert(type != null);
+
+            if (type.IsFunctionPointer)


I do not see why we are special casing function pointer here. Should it be handled by AddOneArgTypeHelper instead?

If there is a non-obvious reason for this special case, comment would be nice.

I moved it to AddOneArgTypeHelper.

jkotas · 2026-02-14T22:25:30Z

src/coreclr/System.Private.CoreLib/src/System/Reflection/Emit/SignatureHelper.cs

+                    if (t.ContainsGenericParameters)
+                        throw new ArgumentException(SR.Argument_GenericsInvalid, nameof(requiredCustomModifiers));
+
+                    AddElementType((CorElementType)0x22); // ELEMENT_TYPE_CMOD_INTERNAL


Is there a reason why we cannot use the ELEMENT_TYPE_CMOD_OPT/ELEMENT_TYPE_CMOD_REQD encoding that's used for arguments in AddDynamicArgument? It looks odd that argument types and return types use different encoding.

Only reason was that at the start I wanted to avoid adding a DynamicScope parameter. I've cleaned it up now.

jkotas · 2026-02-14T22:31:47Z

src/coreclr/System.Private.CoreLib/src/System/Reflection/Emit/SignatureHelper.cs

                }
            }
+            else if (clsArgument.IsFunctionPointer && scope != null)
+            {


Should we throw NotSupportedException for scope == null? It is better to throw than produce bad binary silently.

I assume that it can be hit with (non-persistent) Reflection.Emit. Is that right? We may want to add a test that validates it is throwing (and not crashing or producing bad output).

I assume that it can be hit with (non-persistent) Reflection.Emit. Is that right?

Yes, or by just invoking SignatureHelper manually. I added an exception.

src/coreclr/System.Private.CoreLib/src/System/Reflection/Emit/SignatureHelper.cs

Copilot

Pull request overview

Copilot reviewed 30 out of 30 changed files in this pull request and generated no new comments.

Copilot

Pull request overview

Copilot reviewed 30 out of 30 changed files in this pull request and generated 3 comments.

src/coreclr/System.Private.CoreLib/src/System/Reflection/Emit/SignatureHelper.cs

src/libraries/System.Private.CoreLib/src/System.Private.CoreLib.Shared.projitems

src/libraries/System.Private.CoreLib/src/System/Type.cs

Copilot

Pull request overview

Copilot reviewed 30 out of 30 changed files in this pull request and generated 1 comment.

src/libraries/System.Runtime/tests/System.Runtime.Tests/System/Reflection/SignatureTypes.cs

jgh07 · 2026-02-16T19:28:08Z

src/libraries/System.Private.CoreLib/src/System/Reflection/Emit/TypeBuilder.cs


+        public override Type MakeFunctionPointerType(Type[]? parameterTypes, bool isUnmanaged = false)
+        {
+            return Type.MakeFunctionPointerSignatureType(this, parameterTypes, isUnmanaged);


Is a signature type sufficient here?

jgh07 added 2 commits January 30, 2026 21:21

Implement MakeFunctionPointerSignatureType, MakeModifiedSignatureType…

12c00b0

…, ILGeneratorImpl.EmitCalli(Type)

Override UnderlyingSystemType in SignatureModifiedType

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Remove unused using

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[WIP] Implement remaining APIs for runtime issue 123819 jgh07/runtime#1

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jgh07 mentioned this pull request Jan 31, 2026

[API Proposal]: IL Emit support for FunctionPointer #75348

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Implement RuntimeType.MakeFunctionPointerType

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This was referenced Feb 1, 2026

iOS.Device test WorkItemExecutions #122874

Open

XHarness package install failure on iOS due to devicectl NSPOSIXErrorDomain error 49 #123796

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Clone arrays; Remove unbounded stackalloc

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Add more checks, defensive clones

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src/libraries/System.Private.CoreLib/src/System/Type.cs Outdated Show resolved Hide resolved

Implement DynamicILGenerator.EmitCalli; Fix issues with MakeFunctionP…

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…ointerSignatureType

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Clone before null checks

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MichalStrehovsky reviewed Feb 12, 2026

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build-analysis bot mentioned this pull request Feb 12, 2026

System.Security.Cryptography.CryptographicException : m_safeCertContext is an invalid handle. #124279

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jkotas reviewed Feb 12, 2026

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Remove AddFunctionPointer helper

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src/coreclr/System.Private.CoreLib/src/System/Reflection/Emit/SignatureHelper.cs Show resolved Hide resolved

More improvements and cleanup

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jgh07 and others added 2 commits February 15, 2026 19:42

Merge branch 'main' into issue-75348

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Remove unused parameter

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jgh07 and others added 2 commits February 15, 2026 19:57

Remove items that were accidentally added in merge

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Handle non-RuntimeTypes in MakeFunctionPointerType

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Implement MakeFunctionPointerType on TypeBuilder, EnumBuilder

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jgh07 commented Feb 16, 2026

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jgh07 commented Jan 30, 2026 •

edited

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