Handle SetLastError=true

DllImportGenerator/Ancillary.Interop/Ancillary.Interop.csproj

@@ -5,6 +5,7 @@
     <LangVersion>8.0</LangVersion>
     <RootNamespace>System.Runtime.InteropServices</RootNamespace>
     <Nullable>enable</Nullable>
+    <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
   </PropertyGroup>
 
 </Project>

DllImportGenerator/Ancillary.Interop/MarshalEx.cs

@@ -39,5 +39,79 @@ public static void SetHandle(SafeHandle safeHandle, IntPtr handle)
         {            
             typeof(SafeHandle).GetMethod("SetHandle", BindingFlags.NonPublic | BindingFlags.Instance)!.Invoke(safeHandle, new object[] { handle });
         }
+
+        /// <summary>
+        /// Set the last platform invoke error on the thread 
+        /// </summary>
+        public static void SetLastWin32Error(int error)
+        {
+            typeof(Marshal).GetMethod("SetLastWin32Error", BindingFlags.NonPublic | BindingFlags.Static)!.Invoke(null, new object[] { error });
+        }
+
+        /// <summary>
+        /// Get the last system error on the current thread (errno on Unix, GetLastError on Windows)
+        /// </summary>
+        public static unsafe int GetLastSystemError()
+        {
+            // Would be internal call that handles getting the last error for the thread using the PAL
+
+            if (OperatingSystem.IsWindows())
+            {
+                return Kernel32.GetLastError();
+            }
+            else if (OperatingSystem.IsMacOS())
+            {
+                return *libc.__error();
+            }
+            else if (OperatingSystem.IsLinux())
+            {
+                return *libc.__errno_location();
+            }
+
+            throw new NotImplementedException();
+        }
+
+        /// <summary>
+        /// Set the last system error on the current thread (errno on Unix, SetLastError on Windows)
+        /// </summary>
+        public static unsafe void SetLastSystemError(int error)
+        {
+            // Would be internal call that handles setting the last error for the thread using the PAL
+
+            if (OperatingSystem.IsWindows())
+            {
+                Kernel32.SetLastError(error);
+            }
+            else if (OperatingSystem.IsMacOS())
+            {
+                *libc.__error() = error;
+            }
+            else if (OperatingSystem.IsLinux())
+            {
+                *libc.__errno_location() = error;
+            }
+            else
+            {
+                throw new NotImplementedException();
+            }
+        }
+
+        private class Kernel32
+        {
+            [DllImport(nameof(Kernel32))]
+            public static extern void SetLastError(int error);
+
+            [DllImport(nameof(Kernel32))]
+            public static extern int GetLastError();
+        }
+
+        private class libc
+        {
+            [DllImport(nameof(libc))]
+            internal static unsafe extern int* __errno_location();
+
+            [DllImport(nameof(libc))]
+            internal static unsafe extern int* __error();
+        }
     }
 }

DllImportGenerator/DllImportGenerator.IntegrationTests/SetLastErrorTests.cs

@@ -0,0 +1,94 @@
+using System;
+using System.Runtime.InteropServices;
+
+using Xunit;
+
+namespace DllImportGenerator.IntegrationTests
+{
+    [BlittableType]
+    public struct SetLastErrorMarshaller
+    {
+        public int val;
+
+        public SetLastErrorMarshaller(int i)
+        {
+            val = i;
+        }
+
+        public int ToManaged()
+        {
+            // Explicity set the last error to something else on unmarshalling
+            MarshalEx.SetLastWin32Error(val * 2);
+            return val;
+        }
+    }
+
+    partial class NativeExportsNE
+    {
+        public partial class SetLastError
+        {
+            [GeneratedDllImport(nameof(NativeExportsNE), EntryPoint = "set_error", SetLastError = true)]
+            public static partial int SetError(int error, byte shouldSetError);
+
+            [GeneratedDllImport(nameof(NativeExportsNE), EntryPoint = "set_error_return_string", SetLastError = true)]
+            [return: MarshalUsing(typeof(SetLastErrorMarshaller))]
+            public static partial int SetError_CustomMarshallingSetsError(int error, byte shouldSetError);
+
+            [GeneratedDllImport(nameof(NativeExportsNE), EntryPoint = "set_error_return_string", SetLastError = true)]
+            [return: MarshalAs(UnmanagedType.LPWStr)]
+            public static partial string SetError_NonBlittableSignature(int error, [MarshalAs(UnmanagedType.U1)] bool shouldSetError, [MarshalAs(UnmanagedType.LPWStr)] string errorString);
+        }
+    }
+
+    public class SetLastErrorTests
+    {
+        [Theory]
+        [InlineData(0)]
+        [InlineData(2)]
+        [InlineData(-5)]
+        public void LastWin32Error_HasExpectedValue(int error)
+        {
+            string errorString = error.ToString();
+            string ret = NativeExportsNE.SetLastError.SetError_NonBlittableSignature(error, shouldSetError: true, errorString);
+            Assert.Equal(error, Marshal.GetLastWin32Error());
+            Assert.Equal(errorString, ret);
+
+            // Clear the last error
+            MarshalEx.SetLastWin32Error(0);
+
+            NativeExportsNE.SetLastError.SetError(error, shouldSetError: 1);
+            Assert.Equal(error, Marshal.GetLastWin32Error());
+
+            MarshalEx.SetLastWin32Error(0);
+
+            // Custom marshalling sets the last error on unmarshalling.
+            // Last error should reflect error from native call, not unmarshalling.
+            NativeExportsNE.SetLastError.SetError_CustomMarshallingSetsError(error, shouldSetError: 1);
+            Assert.Equal(error, Marshal.GetLastWin32Error());
+        }
+
+        [Fact]
+        public void ClearPreviousError()
+        {
+            int error = 100;
+            MarshalEx.SetLastWin32Error(error);
+
+            // Don't actually set the error in the native call. SetLastError=true should clear any existing error.
+            string errorString = error.ToString();
+            string ret = NativeExportsNE.SetLastError.SetError_NonBlittableSignature(error, shouldSetError: false, errorString);
+            Assert.Equal(0, Marshal.GetLastWin32Error());
+            Assert.Equal(errorString, ret);
+
+            MarshalEx.SetLastWin32Error(error);
+
+            // Don't actually set the error in the native call. SetLastError=true should clear any existing error.
+            NativeExportsNE.SetLastError.SetError(error, shouldSetError: 0);
+            Assert.Equal(0, Marshal.GetLastWin32Error());
+
+            // Don't actually set the error in the native call. Custom marshalling still sets the last error.
+            // SetLastError=true should clear any existing error and ignore error set by custom marshalling.
+            NativeExportsNE.SetLastError.SetError_CustomMarshallingSetsError(error, shouldSetError: 0);
+            Assert.Equal(0, Marshal.GetLastWin32Error());
+        }
+    }
+}

DllImportGenerator/DllImportGenerator.UnitTests/CompileFails.cs

@@ -41,8 +41,7 @@ public static IEnumerable<object[]> CodeSnippetsToCompile()
 
             // Unsupported named arguments
             //  * BestFitMapping, ThrowOnUnmappableChar
-            // [TODO]: Expected diagnostic count should be 2 once we support SetLastError
-            yield return new object[] { CodeSnippets.AllDllImportNamedArguments, 3, 0 };
+            yield return new object[] { CodeSnippets.AllDllImportNamedArguments, 2, 0 };
 
             // LCIDConversion
             yield return new object[] { CodeSnippets.LCIDConversionAttribute, 1, 0 };

DllImportGenerator/DllImportGenerator.UnitTests/Compiles.cs

@@ -9,15 +9,15 @@ namespace DllImportGenerator.UnitTests
 {
     public class Compiles
     {
-        public static IEnumerable<object[]> CodeSnippetsToCompile_NoDiagnostics()
+        public static IEnumerable<object[]> CodeSnippetsToCompile()
         {
             yield return new[] { CodeSnippets.TrivialClassDeclarations };
             yield return new[] { CodeSnippets.TrivialStructDeclarations };
             yield return new[] { CodeSnippets.MultipleAttributes };
             yield return new[] { CodeSnippets.NestedNamespace };
             yield return new[] { CodeSnippets.NestedTypes };
             yield return new[] { CodeSnippets.UserDefinedEntryPoint };
-            //yield return new[] { CodeSnippets.AllSupportedDllImportNamedArguments };
+            yield return new[] { CodeSnippets.AllSupportedDllImportNamedArguments };
             yield return new[] { CodeSnippets.DefaultParameters };
             yield return new[] { CodeSnippets.UseCSharpFeaturesForConstants };
 
@@ -161,14 +161,9 @@ public static IEnumerable<object[]> CodeSnippetsToCompile_NoDiagnostics()
             yield return new[] { CodeSnippets.CustomStructMarshallingMarshalUsingParametersAndModifiers };
         }
 
-        public static IEnumerable<object[]> CodeSnippetsToCompile_WithDiagnostics()
-        {
-            yield return new[] { CodeSnippets.AllSupportedDllImportNamedArguments };
-        }
-
         [Theory]
-        [MemberData(nameof(CodeSnippetsToCompile_NoDiagnostics))]
-        public async Task ValidateSnippets_NoDiagnostics(string source)
+        [MemberData(nameof(CodeSnippetsToCompile))]
+        public async Task ValidateSnippets(string source)
         {
             Compilation comp = await TestUtils.CreateCompilation(source);
             TestUtils.AssertPreSourceGeneratorCompilation(comp);
@@ -179,20 +174,5 @@ public async Task ValidateSnippets_NoDiagnostics(string source)
             var newCompDiags = newComp.GetDiagnostics();
             Assert.Empty(newCompDiags);
         }
-
-        [Theory]
-        [MemberData(nameof(CodeSnippetsToCompile_WithDiagnostics))]
-        public async Task ValidateSnippets_WithDiagnostics(string source)
-        {
-            Compilation comp = await TestUtils.CreateCompilation(source);
-            TestUtils.AssertPreSourceGeneratorCompilation(comp);
-
-            var newComp = TestUtils.RunGenerators(comp, out var generatorDiags, new Microsoft.Interop.DllImportGenerator());
-            Assert.NotEmpty(generatorDiags);
-            Assert.All(generatorDiags, d => Assert.StartsWith(Microsoft.Interop.GeneratorDiagnostics.Ids.Prefix, d.Id));
-
-            var newCompDiags = newComp.GetDiagnostics();
-            Assert.Empty(newCompDiags);
-        }
     }
 }

DllImportGenerator/DllImportGenerator/DllImportGenerator.cs

@@ -103,12 +103,6 @@ public void Execute(GeneratorExecutionContext context)
                     generatorDiagnostics.ReportConfigurationNotSupported(generatedDllImportAttr, nameof(DllImportStub.GeneratedDllImportData.ThrowOnUnmappableChar));
                 }
 
-                // [TODO] Remove once we support SetLastError=true
-                if (dllImportData.SetLastError)
-                {
-                    generatorDiagnostics.ReportConfigurationNotSupported(generatedDllImportAttr, nameof(DllImportStub.GeneratedDllImportData.SetLastError), "true");
-                }
-
                 if (lcidConversionAttr != null)
                 {
                     // Using LCIDConversion with GeneratedDllImport is not supported

DllImportGenerator/DllImportGenerator/StubCodeGenerator.cs

@@ -30,6 +30,10 @@ internal sealed class StubCodeGenerator : StubCodeContext
         public string ReturnNativeIdentifier { get; private set; } = ReturnIdentifier;
 
         private const string InvokeReturnIdentifier = "__invokeRetVal";
+        private const string LastErrorIdentifier = "__lastError";
+
+        // Error code representing success. This maps to S_OK for Windows HRESULT semantics and 0 for POSIX errno semantics.
+        private const int SuccessErrorCode = 0;
 
         private static readonly Stage[] Stages = new Stage[]
         {
@@ -170,6 +174,14 @@ public override (string managed, string native) GetIdentifiers(TypePositionInfo
                 AppendVariableDeclations(setupStatements, retMarshaller.TypeInfo, retMarshaller.Generator);
             }
 
+            if (this.dllImportData.SetLastError)
+            {
+                // Declare variable for last error
+                setupStatements.Add(MarshallerHelpers.DeclareWithDefault(
+                    PredefinedType(Token(SyntaxKind.IntKeyword)),
+                    LastErrorIdentifier));
+            }
+
             var tryStatements = new List<StatementSyntax>();
             var finallyStatements = new List<StatementSyntax>();
             var invoke = InvocationExpression(IdentifierName(dllImportName));
@@ -235,11 +247,37 @@ public override (string managed, string native) GetIdentifiers(TypePositionInfo
                                 invoke));
                     }
 
+                    if (this.dllImportData.SetLastError)
+                    {
+                        // Marshal.SetLastSystemError(0);
+                        var clearLastError = ExpressionStatement(
+                            InvocationExpression(
+                                MemberAccessExpression(
+                                    SyntaxKind.SimpleMemberAccessExpression,
+                                    ParseName(TypeNames.System_Runtime_InteropServices_MarshalEx),
+                                    IdentifierName("SetLastSystemError")),
+                                ArgumentList(SingletonSeparatedList(
+                                    Argument(LiteralExpression(SyntaxKind.NumericLiteralExpression, Literal(SuccessErrorCode)))))));
+
+                        // <lastError> = Marshal.GetLastSystemError();
+                        var getLastError = ExpressionStatement(
+                            AssignmentExpression(
+                                SyntaxKind.SimpleAssignmentExpression,
+                                IdentifierName(LastErrorIdentifier),
+                                InvocationExpression(
+                                    MemberAccessExpression(
+                                    SyntaxKind.SimpleMemberAccessExpression,
+                                    ParseName(TypeNames.System_Runtime_InteropServices_MarshalEx),
+                                    IdentifierName("GetLastSystemError")))));
+
+                        invokeStatement = Block(clearLastError, invokeStatement, getLastError);
+                    }
+
                     // Nest invocation in fixed statements
                     if (fixedStatements.Any())
                     {
                         fixedStatements.Reverse();
-                        invokeStatement = fixedStatements.First().WithStatement(Block(invokeStatement));
+                        invokeStatement = fixedStatements.First().WithStatement(invokeStatement);
                         foreach (var fixedStatement in fixedStatements.Skip(1))
                         {
                             invokeStatement = fixedStatement.WithStatement(Block(invokeStatement));
@@ -274,6 +312,19 @@ public override (string managed, string native) GetIdentifiers(TypePositionInfo
                 allStatements.AddRange(tryStatements);
             }
 
+            if (this.dllImportData.SetLastError)
+            {
+                // Marshal.SetLastWin32Error(<lastError>);
+                allStatements.Add(ExpressionStatement(
+                    InvocationExpression(
+                        MemberAccessExpression(
+                            SyntaxKind.SimpleMemberAccessExpression,
+                            ParseName(TypeNames.System_Runtime_InteropServices_MarshalEx),
+                            IdentifierName("SetLastWin32Error")),
+                        ArgumentList(SingletonSeparatedList(
+                            Argument(IdentifierName(LastErrorIdentifier)))))));
+            }
+
             // Return
             if (!stubReturnsVoid)
                 allStatements.Add(ReturnStatement(IdentifierName(ReturnIdentifier)));