Remove GeneratedDllImportAttribute.PreserveSig

src/coreclr/System.Private.CoreLib/src/System/Runtime/InteropServices/Marshal.CoreCLR.cs

@@ -731,12 +731,12 @@ public static object BindToMoniker(string monikerName)
 
         [UnconditionalSuppressMessage("ReflectionAnalysis", "IL2050:UnrecognizedReflectionPattern",
             Justification = "The calling method is annotated with RequiresUnreferencedCode")]
-        [GeneratedDllImport(Interop.Libraries.Ole32, PreserveSig = false)]
+        [GeneratedDllImport(Interop.Libraries.Ole32)]
         private static partial int MkParseDisplayName(IntPtr pbc, [MarshalAs(UnmanagedType.LPWStr)] string szUserName, out uint pchEaten, out IntPtr ppmk);
 
         [UnconditionalSuppressMessage("ReflectionAnalysis", "IL2050:UnrecognizedReflectionPattern",
             Justification = "The calling method is annotated with RequiresUnreferencedCode")]
-        [GeneratedDllImport(Interop.Libraries.Ole32, PreserveSig = false)]
+        [GeneratedDllImport(Interop.Libraries.Ole32)]
         private static partial int BindMoniker(IntPtr pmk, uint grfOpt, ref Guid iidResult, out IntPtr ppvResult);
 
         [SupportedOSPlatform("windows")]

src/libraries/Common/src/Interop/Windows/Kernel32/Interop.GetUserDefaultLCID.cs

@@ -7,7 +7,7 @@ internal static partial class Interop
 {
     internal static partial class Kernel32
     {
-        [GeneratedDllImport(Interop.Libraries.Kernel32, CharSet = CharSet.Unicode, PreserveSig = true)]
+        [GeneratedDllImport(Interop.Libraries.Kernel32, CharSet = CharSet.Unicode)]
         internal static partial int GetUserDefaultLCID();
     }
 }

src/libraries/Common/src/System/Runtime/InteropServices/GeneratedDllImportAttribute.cs

@@ -22,14 +22,13 @@ sealed class GeneratedDllImportAttribute : Attribute
         public CharSet CharSet { get; set; }
         public string? EntryPoint { get; set; }
         public bool ExactSpelling { get; set; }
-        public bool PreserveSig { get; set; }
         public bool SetLastError { get; set; }
 
         public GeneratedDllImportAttribute(string dllName)
         {
-            this.Value = dllName;
+            LibraryName = dllName;
         }
 
-        public string Value { get; private set; }
+        public string LibraryName { get; private set; }
     }
 }

src/libraries/System.Runtime.InteropServices/gen/DllImportGenerator/DllImportGenerator.cs

@@ -21,9 +21,6 @@ namespace Microsoft.Interop
     [Generator]
     public sealed class DllImportGenerator : IIncrementalGenerator
     {
-        private const string GeneratedDllImport = nameof(GeneratedDllImport);
-        private const string GeneratedDllImportAttribute = nameof(GeneratedDllImportAttribute);
-
         internal sealed record IncrementalStubGenerationContext(
             StubEnvironment Environment,
             DllImportStubContext StubContext,
@@ -351,7 +348,6 @@ private static GeneratedDllImportData ProcessGeneratedDllImportAttribute(Attribu
             CharSet charSet = CharSet.Ansi;
             string? entryPoint = null;
             bool exactSpelling = false; // VB has different and unusual default behavior here.
-            bool preserveSig = true;
             bool setLastError = false;
 
             // All other data on attribute is defined as NamedArguments.
@@ -360,7 +356,7 @@ private static GeneratedDllImportData ProcessGeneratedDllImportAttribute(Attribu
                 switch (namedArg.Key)
                 {
                     default:
-                        Debug.Fail($"An unknown member was found on {GeneratedDllImport}");
+                        Debug.Fail($"An unknown member was found on {attrData.AttributeClass}");
                         continue;
                     case nameof(GeneratedDllImportData.CharSet):
                         userDefinedValues |= DllImportMember.CharSet;
@@ -374,10 +370,6 @@ private static GeneratedDllImportData ProcessGeneratedDllImportAttribute(Attribu
                         userDefinedValues |= DllImportMember.ExactSpelling;
                         exactSpelling = (bool)namedArg.Value.Value!;
                         break;
-                    case nameof(GeneratedDllImportData.PreserveSig):
-                        userDefinedValues |= DllImportMember.PreserveSig;
-                        preserveSig = (bool)namedArg.Value.Value!;
-                        break;
                     case nameof(GeneratedDllImportData.SetLastError):
                         userDefinedValues |= DllImportMember.SetLastError;
                         setLastError = (bool)namedArg.Value.Value!;
@@ -391,7 +383,6 @@ private static GeneratedDllImportData ProcessGeneratedDllImportAttribute(Attribu
                 CharSet = charSet,
                 EntryPoint = entryPoint,
                 ExactSpelling = exactSpelling,
-                PreserveSig = preserveSig,
                 SetLastError = setLastError,
             };
         }
@@ -584,12 +575,6 @@ private static AttributeSyntax CreateDllImportAttributeForTarget(GeneratedDllImp
                 ExpressionSyntax value = CreateBoolExpressionSyntax(targetDllImportData.ExactSpelling);
                 newAttributeArgs.Add(AttributeArgument(name, null, value));
             }
-            if (targetDllImportData.IsUserDefined.HasFlag(DllImportMember.PreserveSig))
-            {
-                NameEqualsSyntax name = NameEquals(nameof(DllImportAttribute.PreserveSig));
-                ExpressionSyntax value = CreateBoolExpressionSyntax(targetDllImportData.PreserveSig);
-                newAttributeArgs.Add(AttributeArgument(name, null, value));
-            }
             if (targetDllImportData.IsUserDefined.HasFlag(DllImportMember.SetLastError))
             {
                 NameEqualsSyntax name = NameEquals(nameof(DllImportAttribute.SetLastError));
@@ -629,9 +614,6 @@ static ExpressionSyntax CreateEnumExpressionSyntax<T>(T value) where T : Enum
         private static GeneratedDllImportData GetTargetDllImportDataFromStubData(GeneratedDllImportData dllImportData, string originalMethodName, bool forwardAll)
         {
             DllImportMember membersToForward = DllImportMember.All
-                               // https://docs.microsoft.com/dotnet/api/system.runtime.interopservices.dllimportattribute.preservesig
-                               // If PreserveSig=false (default is true), the P/Invoke stub checks/converts a returned HRESULT to an exception.
-                               & ~DllImportMember.PreserveSig
                                // https://docs.microsoft.com/dotnet/api/system.runtime.interopservices.dllimportattribute.setlasterror
                                // If SetLastError=true (default is false), the P/Invoke stub gets/caches the last error after invoking the native function.
                                & ~DllImportMember.SetLastError;
@@ -646,7 +628,6 @@ private static GeneratedDllImportData GetTargetDllImportDataFromStubData(Generat
                 EntryPoint = dllImportData.EntryPoint,
                 ExactSpelling = dllImportData.ExactSpelling,
                 SetLastError = dllImportData.SetLastError,
-                PreserveSig = dllImportData.PreserveSig,
                 IsUserDefined = dllImportData.IsUserDefined & membersToForward
             };
 

src/libraries/System.Runtime.InteropServices/gen/DllImportGenerator/DllImportStubContext.cs

@@ -218,35 +218,8 @@ private static (ImmutableArray<TypePositionInfo>, IMarshallingGeneratorFactory)
 
                 IMarshallingGeneratorFactory elementFactory = new AttributedMarshallingModelGeneratorFactory(generatorFactory, new AttributedMarshallingModelOptions(options, runtimeMarshallingDisabled));
                 // We don't need to include the later generator factories for collection elements
-                // as the later generator factories only apply to parameters or to the synthetic return value for PreserveSig support.
+                // as the later generator factories only apply to parameters.
                 generatorFactory = new AttributedMarshallingModelGeneratorFactory(generatorFactory, elementFactory, new AttributedMarshallingModelOptions(options, runtimeMarshallingDisabled));
-                if (!dllImportData.PreserveSig)
-                {
-                    // Create type info for native out param
-                    if (!method.ReturnsVoid)
-                    {
-                        // Transform the managed return type info into an out parameter and add it as the last param
-                        TypePositionInfo nativeOutInfo = retTypeInfo with
-                        {
-                            InstanceIdentifier = PInvokeStubCodeGenerator.ReturnIdentifier,
-                            RefKind = RefKind.Out,
-                            RefKindSyntax = SyntaxKind.OutKeyword,
-                            ManagedIndex = TypePositionInfo.ReturnIndex,
-                            NativeIndex = typeInfos.Count
-                        };
-                        typeInfos.Add(nativeOutInfo);
-                    }
-
-                    // Use a marshalling generator that supports the HRESULT return->exception marshalling.
-                    generatorFactory = new NoPreserveSigMarshallingGeneratorFactory(generatorFactory);
-
-                    // Create type info for native HRESULT return
-                    retTypeInfo = new TypePositionInfo(SpecialTypeInfo.Int32, NoMarshallingInfo.Instance);
-                    retTypeInfo = retTypeInfo with
-                    {
-                        NativeIndex = TypePositionInfo.ReturnIndex
-                    };
-                }
 
                 generatorFactory = new ByValueContentsMarshalKindValidator(generatorFactory);
             }

src/libraries/System.Runtime.InteropServices/gen/DllImportGenerator/GeneratedDllImportData.cs

@@ -18,8 +18,7 @@ public enum DllImportMember
         CharSet = 1 << 0,
         EntryPoint = 1 << 1,
         ExactSpelling = 1 << 2,
-        PreserveSig = 1 << 3,
-        SetLastError = 1 << 4,
+        SetLastError = 1 << 3,
         All = ~None
     }
 
@@ -39,7 +38,6 @@ public sealed record GeneratedDllImportData(string ModuleName)
         public CharSet CharSet { get; init; }
         public string? EntryPoint { get; init; }
         public bool ExactSpelling { get; init; }
-        public bool PreserveSig { get; init; }
         public bool SetLastError { get; init; }
     }
 }