Update GeneratedDllImportAttribute CharSet -> StringMarshalling

docs/design/libraries/DllImportGenerator/Compatibility.md

@@ -12,9 +12,9 @@ In the event a marshaller would generate code that has a specific target framewo
 
 ### Semantic changes compared to `DllImportAttribute`
 
-The default value of [`CharSet`](https://docs.microsoft.com/dotnet/api/system.runtime.interopservices.dllimportattribute.charset) is runtime/language-defined. In the built-in system, the default value of the `CharSet` property is `CharSet.Ansi`. The P/Invoke source generator makes no assumptions about the `CharSet` if it is not explicitly set on `GeneratedDllImportAttribute`. Marshalling of `char` or `string` requires explicitly specifying marshalling information.
+[`CharSet`](https://docs.microsoft.com/dotnet/api/system.runtime.interopservices.dllimportattribute.charset) has been replaced with a new `StringMarshalling` enumeration. `Ansi` and `Auto` are no longer supported as first-class options and `Utf8` has been added.
 
-The built-in system treats `CharSet.None` as `CharSet.Ansi`. The P/Invoke source generator will treat `CharSet.None` as if the `CharSet` was not set.
+With `DllImportAttribute`, the default value of [`CharSet`](https://docs.microsoft.com/dotnet/api/system.runtime.interopservices.dllimportattribute.charset) is runtime/language-defined. In the built-in system, the default value of the `CharSet` property is `CharSet.Ansi`. The P/Invoke source generator makes no assumptions about `StringMarshalling` if it is not explicitly set on `GeneratedDllImportAttribute`. Marshalling of `char` or `string` requires explicitly specifying marshalling information.
 
 [`BestFitMapping`](https://docs.microsoft.com/dotnet/api/system.runtime.interopservices.dllimportattribute.bestfitmapping) and [`ThrowOnUnmappableChar`](https://docs.microsoft.com/dotnet/api/system.runtime.interopservices.dllimportattribute.throwonunmappablechar) will not be supported for `GeneratedDllImportAttribute`. These values only have meaning on Windows when marshalling string data (`char`, `string`, `StringBuilder`) as [ANSI](https://docs.microsoft.com/windows/win32/intl/code-pages). As the general recommendation - including from Windows - is to move away from ANSI, the P/Invoke source generator will not support these fields.
 
@@ -33,31 +33,30 @@ These are all part of `NetCoreApp` and will be referenced by default unless [imp
 
 ### `char` marshalling
 
-Marshalling of `char` will not be supported when configured with any of the following:
-  - [`CharSet.Ansi`, `CharSet.Auto`, or `CharSet.None`](https://docs.microsoft.com/dotnet/api/system.runtime.interopservices.charset) will not be supported.
+Marshalling of `char` will only be supported with `StringMarshalling.Utf16` or as `UnmanagedType.U2` or `UnmanagedType.I2`. It will not be supported when configured with any of the following:
   - [`UnmanagedType.U1` or `UnmanagedType.I1`](https://docs.microsoft.com/dotnet/api/system.runtime.interopservices.unmanagedtype)
-  - No explicit marshalling information - either [`DllImportAttribute.CharSet`](https://docs.microsoft.com/dotnet/api/system.runtime.interopservices.dllimportattribute.charset) or [`MarshalAsAttribute`](https://docs.microsoft.com/dotnet/api/system.runtime.interopservices.marshalasattribute)
+  - `StringMarshalling.Utf8` will not be supported.
+  - No explicit marshalling information - either `GeneratedDllImportAttribute.StringMarshalling` or [`MarshalAsAttribute`](https://docs.microsoft.com/dotnet/api/system.runtime.interopservices.marshalasattribute)
 
-For `CharSet.Ansi` and `CharSet.None`, the built-in system used the [system default Windows ANSI code page](https://docs.microsoft.com/windows/win32/api/stringapiset/nf-stringapiset-widechartomultibyte) when on Windows and took the first byte of the UTF-8 encoding on non-Windows platforms. The above reasoning also applies to marshalling of a `char` as `UnmanagedType.U1` and `UnmanagedType.I1`. All approaches are fundamentally flawed and therefore not supported. If a single-byte character is expected to be marshalled it is left to the caller to convert a .NET `char` into a single `byte` prior to calling the native function.
+In the built-in system, marshalling with `CharSet.Ansi` and `CharSet.None` used the [system default Windows ANSI code page](https://docs.microsoft.com/windows/win32/api/stringapiset/nf-stringapiset-widechartomultibyte) when on Windows and took the first byte of the UTF-8 encoding on non-Windows platforms. The above reasoning also applies to marshalling of a `char` as `UnmanagedType.U1` and `UnmanagedType.I1`. All approaches are fundamentally flawed and therefore not supported. If a single-byte character is expected to be marshalled it is left to the caller to convert a .NET `char` into a single `byte` prior to calling the native function.
 
 For `CharSet.Auto`, the built-in system relied upon detection at runtime of the platform when determining the targeted encoding. Performing this check in generated code violates the "pay-for-play" principle. Given that there are no scenarios for this feature in `NetCoreApp` it will not be supported.
 
 ### `string` marshalling
 
 Marshalling of `string` will not be supported when configured with any of the following:
-  - [`CharSet.None`](https://docs.microsoft.com/dotnet/api/system.runtime.interopservices.charset)
   - [`UnmanagedType.VBByRefStr`](https://docs.microsoft.com/dotnet/api/system.runtime.interopservices.unmanagedtype)
-  - No explicit marshalling information - either [`DllImportAttribute.CharSet`](https://docs.microsoft.com/dotnet/api/system.runtime.interopservices.dllimportattribute.charset) or [`MarshalAsAttribute`](https://docs.microsoft.com/dotnet/api/system.runtime.interopservices.marshalasattribute)
+  - No explicit marshalling information - either `GeneratedDllImportAttribute.StringMarshalling` or [`MarshalAsAttribute`](https://docs.microsoft.com/dotnet/api/system.runtime.interopservices.marshalasattribute)
 
 When converting from native to managed, the built-in system would throw a [`MarshalDirectiveException`](https://docs.microsoft.com/dotnet/api/system.runtime.interopservices.marshaldirectiveexception) if the string's length is over 0x7ffffff0. The generated marshalling code will no longer perform this check.
 
 In the built-in system, marshalling a `string` contains an optimization for parameters passed by value to allocate on the stack (instead of through [`AllocCoTaskMem`](https://docs.microsoft.com/dotnet/api/system.runtime.interopservices.marshal.alloccotaskmem)) if the string is below a certain length (MAX_PATH). For UTF-16, this optimization was also applied for parameters passed by read-only reference. The generated marshalling code will include this optimization for read-only reference parameters for non-UTF-16 as well.
 
-When marshalling as [ANSI](https://docs.microsoft.com/windows/win32/intl/code-pages) on Windows (using `CharSet.Ansi` or `UnmanagedType.LPStr`):
+When marshalling as [ANSI](https://docs.microsoft.com/windows/win32/intl/code-pages) on Windows (using `UnmanagedType.LPStr`):
   - Best-fit mapping will be disabled and no exception will be thrown for unmappable characters. In the built-in system, this behaviour was configured through [`DllImportAttribute.BestFitMapping`] and [`DllImportAttribute.ThrowOnUnmappableChar`]. The generated marshalling code will have the equivalent behaviour of `BestFitMapping=false` and `ThrowOnUnmappableChar=false`.
   - No optimization for stack allocation will be performed. Marshalling will always allocate through `AllocCoTaskMem`.
 
-On Windows, marshalling using `CharSet.Auto` is treated as UTF-16. When marshalling a string as UTF-16 by value or by read-only reference, the string is pinned and the pointer passed to the P/Invoke. The generated marshalling code will always pin the input string - even on non-Windows.
+The p/invoke source generator does not provide an equivalent to using `CharSet.Auto` in the built-in system. If platform-dependent behaviour is desired, it is left to the user to define different p/invokes with different marshalling configurations.
 
 ### Custom marshaller support
 

eng/generators.targets

@@ -47,6 +47,7 @@
                         and @(EnabledGenerators->AnyHaveMetadataValue('Identity', 'DllImportGenerator'))
                         and '$(IncludeDllImportGeneratorSources)' == 'true'">
     <Compile Include="$(LibrariesProjectRoot)Common\src\System\Runtime\InteropServices\GeneratedDllImportAttribute.cs" />
+    <Compile Include="$(LibrariesProjectRoot)Common\src\System\Runtime\InteropServices\StringMarshalling.cs" />
 
     <!-- Only add the following files if we are on the latest TFM (that is, net7). -->
     <Compile Condition="'$(NetCoreAppCurrentTargetFrameworkMoniker)' == '$(TargetFrameworkMoniker)'" Include="$(LibrariesProjectRoot)Common\src\System\Runtime\InteropServices\GeneratedMarshallingAttribute.cs" />

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

@@ -15,7 +15,7 @@ internal static bool GetBoolValue(string switchName, out bool exist)
             return GetConfigBoolValue(switchName, out exist);
         }
 
-        [GeneratedDllImport(RuntimeHelpers.QCall, EntryPoint = "ClrConfig_GetConfigBoolValue", CharSet = CharSet.Unicode)]
+        [GeneratedDllImport(RuntimeHelpers.QCall, EntryPoint = "ClrConfig_GetConfigBoolValue", StringMarshalling = StringMarshalling.Utf16)]
         private static partial bool GetConfigBoolValue(string configSwitchName, out bool exist);
     }
 }

src/coreclr/System.Private.CoreLib/src/System/Diagnostics/Debugger.cs

@@ -77,7 +77,7 @@ public static extern bool IsAttached
         // report the message depending on its settings.
         public static void Log(int level, string? category, string? message) => LogInternal(level, category, message);
 
-        [GeneratedDllImport(RuntimeHelpers.QCall, EntryPoint = "DebugDebugger_Log", CharSet = CharSet.Unicode)]
+        [GeneratedDllImport(RuntimeHelpers.QCall, EntryPoint = "DebugDebugger_Log", StringMarshalling = StringMarshalling.Utf16)]
         private static partial void LogInternal(int level, string? category, string? message);
 
         // Checks to see if an attached debugger has logging enabled

src/coreclr/System.Private.CoreLib/src/System/Diagnostics/Eventing/EventPipe.CoreCLR.cs

@@ -28,13 +28,13 @@ private static unsafe partial ulong Enable(
         //
         // These PInvokes are used by EventSource to interact with the EventPipe.
         //
-        [GeneratedDllImport(RuntimeHelpers.QCall, EntryPoint = "EventPipeInternal_CreateProvider", CharSet = CharSet.Unicode)]
+        [GeneratedDllImport(RuntimeHelpers.QCall, EntryPoint = "EventPipeInternal_CreateProvider", StringMarshalling = StringMarshalling.Utf16)]
         internal static partial IntPtr CreateProvider(string providerName, Interop.Advapi32.EtwEnableCallback callbackFunc);
 
         [GeneratedDllImport(RuntimeHelpers.QCall, EntryPoint = "EventPipeInternal_DefineEvent")]
         internal static unsafe partial IntPtr DefineEvent(IntPtr provHandle, uint eventID, long keywords, uint eventVersion, uint level, void *pMetadata, uint metadataLength);
 
-        [GeneratedDllImport(RuntimeHelpers.QCall, EntryPoint = "EventPipeInternal_GetProvider", CharSet = CharSet.Unicode)]
+        [GeneratedDllImport(RuntimeHelpers.QCall, EntryPoint = "EventPipeInternal_GetProvider", StringMarshalling = StringMarshalling.Utf16)]
         internal static partial IntPtr GetProvider(string providerName);
 
         [GeneratedDllImport(RuntimeHelpers.QCall, EntryPoint = "EventPipeInternal_DeleteProvider")]

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

@@ -93,7 +93,7 @@ internal void CheckTypeNameConflict(string strTypeName, Type? enclosingType)
             return SymbolType.FormCompoundType(strFormat, baseType, 0);
         }
 
-        [GeneratedDllImport(RuntimeHelpers.QCall, EntryPoint = "ModuleBuilder_GetTypeRef", CharSet = CharSet.Unicode)]
+        [GeneratedDllImport(RuntimeHelpers.QCall, EntryPoint = "ModuleBuilder_GetTypeRef", StringMarshalling = StringMarshalling.Utf16)]
         private static partial int GetTypeRef(QCallModule module, string strFullName, QCallModule refedModule, string? strRefedModuleFileName, int tkResolution);
 
         [GeneratedDllImport(RuntimeHelpers.QCall, EntryPoint = "ModuleBuilder_GetMemberRef")]
@@ -107,7 +107,7 @@ private int GetMemberRef(Module? refedModule, int tr, int defToken)
             return GetMemberRef(new QCallModule(ref thisModule), new QCallModule(ref refedRuntimeModule), tr, defToken);
         }
 
-        [GeneratedDllImport(RuntimeHelpers.QCall, EntryPoint = "ModuleBuilder_GetMemberRefFromSignature", CharSet = CharSet.Unicode)]
+        [GeneratedDllImport(RuntimeHelpers.QCall, EntryPoint = "ModuleBuilder_GetMemberRefFromSignature", StringMarshalling = StringMarshalling.Utf16)]
         private static partial int GetMemberRefFromSignature(QCallModule module, int tr, string methodName, byte[] signature, int length);
 
         private int GetMemberRefFromSignature(int tr, string methodName, byte[] signature, int length)
@@ -159,10 +159,10 @@ private int GetTokenFromTypeSpec(byte[] signature, int length)
             return GetTokenFromTypeSpec(new QCallModule(ref thisModule), signature, length);
         }
 
-        [GeneratedDllImport(RuntimeHelpers.QCall, EntryPoint = "ModuleBuilder_GetArrayMethodToken", CharSet = CharSet.Unicode)]
+        [GeneratedDllImport(RuntimeHelpers.QCall, EntryPoint = "ModuleBuilder_GetArrayMethodToken", StringMarshalling = StringMarshalling.Utf16)]
         private static partial int GetArrayMethodToken(QCallModule module, int tkTypeSpec, string methodName, byte[] signature, int sigLength);
 
-        [GeneratedDllImport(RuntimeHelpers.QCall, EntryPoint = "ModuleBuilder_GetStringConstant", CharSet = CharSet.Unicode)]
+        [GeneratedDllImport(RuntimeHelpers.QCall, EntryPoint = "ModuleBuilder_GetStringConstant", StringMarshalling = StringMarshalling.Utf16)]
         private static partial int GetStringConstant(QCallModule module, string str, int length);
 
         [GeneratedDllImport(RuntimeHelpers.QCall, EntryPoint = "ModuleBuilder_SetFieldRVAContent")]

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

@@ -148,14 +148,14 @@ public static FieldInfo GetField(Type type, FieldInfo field)
         #endregion
 
         #region Internal Static FCalls
-        [GeneratedDllImport(RuntimeHelpers.QCall, EntryPoint = "TypeBuilder_DefineMethod", CharSet = CharSet.Unicode)]
+        [GeneratedDllImport(RuntimeHelpers.QCall, EntryPoint = "TypeBuilder_DefineMethod", StringMarshalling = StringMarshalling.Utf16)]
         internal static partial int DefineMethod(QCallModule module, int tkParent, string name, byte[] signature, int sigLength,
             MethodAttributes attributes);
 
         [GeneratedDllImport(RuntimeHelpers.QCall, EntryPoint = "TypeBuilder_DefineMethodSpec")]
         internal static partial int DefineMethodSpec(QCallModule module, int tkParent, byte[] signature, int sigLength);
 
-        [GeneratedDllImport(RuntimeHelpers.QCall, EntryPoint = "TypeBuilder_DefineField", CharSet = CharSet.Unicode)]
+        [GeneratedDllImport(RuntimeHelpers.QCall, EntryPoint = "TypeBuilder_DefineField", StringMarshalling = StringMarshalling.Utf16)]
         internal static partial int DefineField(QCallModule module, int tkParent, string name, byte[] signature, int sigLength,
             FieldAttributes attributes);
 
@@ -186,11 +186,11 @@ internal static void DefineCustomAttribute(ModuleBuilder module, int tkAssociate
                 localAttr, (localAttr != null) ? localAttr.Length : 0);
         }
 
-        [GeneratedDllImport(RuntimeHelpers.QCall, EntryPoint = "TypeBuilder_DefineProperty", CharSet = CharSet.Unicode)]
+        [GeneratedDllImport(RuntimeHelpers.QCall, EntryPoint = "TypeBuilder_DefineProperty", StringMarshalling = StringMarshalling.Utf16)]
         internal static partial int DefineProperty(QCallModule module, int tkParent, string name, PropertyAttributes attributes,
             byte[] signature, int sigLength);
 
-        [GeneratedDllImport(RuntimeHelpers.QCall, EntryPoint = "TypeBuilder_DefineEvent", CharSet = CharSet.Unicode)]
+        [GeneratedDllImport(RuntimeHelpers.QCall, EntryPoint = "TypeBuilder_DefineEvent", StringMarshalling = StringMarshalling.Utf16)]
         internal static partial int DefineEvent(QCallModule module, int tkParent, string name, EventAttributes attributes, int tkEventType);
 
         [GeneratedDllImport(RuntimeHelpers.QCall, EntryPoint = "TypeBuilder_DefineMethodSemantics")]
@@ -203,7 +203,7 @@ internal static partial void DefineMethodSemantics(QCallModule module, int tkAss
         [GeneratedDllImport(RuntimeHelpers.QCall, EntryPoint = "TypeBuilder_SetMethodImpl")]
         internal static partial void SetMethodImpl(QCallModule module, int tkMethod, MethodImplAttributes MethodImplAttributes);
 
-        [GeneratedDllImport(RuntimeHelpers.QCall, EntryPoint = "TypeBuilder_SetParamInfo", CharSet = CharSet.Unicode)]
+        [GeneratedDllImport(RuntimeHelpers.QCall, EntryPoint = "TypeBuilder_SetParamInfo", StringMarshalling = StringMarshalling.Utf16)]
         internal static partial int SetParamInfo(QCallModule module, int tkMethod, int iSequence,
             ParameterAttributes iParamAttributes, string? strParamName);
 
@@ -219,7 +219,7 @@ internal static partial int SetParamInfo(QCallModule module, int tkMethod, int i
         [GeneratedDllImport(RuntimeHelpers.QCall, EntryPoint = "TypeBuilder_SetConstantValue")]
         private static unsafe partial void SetConstantValue(QCallModule module, int tk, int corType, void* pValue);
 
-        [GeneratedDllImport(RuntimeHelpers.QCall, EntryPoint = "TypeBuilder_SetPInvokeData", CharSet = CharSet.Unicode)]
+        [GeneratedDllImport(RuntimeHelpers.QCall, EntryPoint = "TypeBuilder_SetPInvokeData", StringMarshalling = StringMarshalling.Utf16)]
         private static partial void SetPInvokeData(QCallModule module, string DllName, string name, int token, int linkFlags);
 
         #endregion
@@ -635,11 +635,11 @@ public bool IsCreated()
         #endregion
 
         #region FCalls
-        [GeneratedDllImport(RuntimeHelpers.QCall, EntryPoint = "TypeBuilder_DefineType", CharSet = CharSet.Unicode)]
+        [GeneratedDllImport(RuntimeHelpers.QCall, EntryPoint = "TypeBuilder_DefineType", StringMarshalling = StringMarshalling.Utf16)]
         private static partial int DefineType(QCallModule module,
             string fullname, int tkParent, TypeAttributes attributes, int tkEnclosingType, int[] interfaceTokens);
 
-        [GeneratedDllImport(RuntimeHelpers.QCall, EntryPoint = "TypeBuilder_DefineGenericParam", CharSet = CharSet.Unicode)]
+        [GeneratedDllImport(RuntimeHelpers.QCall, EntryPoint = "TypeBuilder_DefineGenericParam", StringMarshalling = StringMarshalling.Utf16)]
         private static partial int DefineGenericParam(QCallModule module,
             string name, int tkParent, GenericParameterAttributes attributes, int position, int[] constraints);