Skip to content

Unmarshaled COM 'interface' struct trimmability #706

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
merged 2 commits into from
Oct 4, 2022
Merged

Unmarshaled COM 'interface' struct trimmability #706

Changes from all commits
Commits
Show all changes
2 commits
Select commit Hold shift + click to select a range
da0665e
Expose vtbl struct for access by the consuming project
AArnott Oct 4, 2022
fef79ae
Generate more trimmable COM "interface" structs
AArnott Oct 4, 2022
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
26 changes: 17 additions & 9 deletions src/Microsoft.Windows.CsWin32/Generator.cs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -3441,6 +3441,7 @@ private TypeDeclarationSyntax DeclareInterfaceAsStruct(TypeDefinitionHandle type
QualifiedMethodDefinition methodDefinition = methodDefHandle.Resolve();
string methodName = methodDefinition.Reader.GetString(methodDefinition.Method.Name);
IdentifierNameSyntax innerMethodName = IdentifierName($"{methodName}_{methodCounter}");
LiteralExpressionSyntax methodOffset = LiteralExpression(SyntaxKind.NumericLiteralExpression, Literal(methodCounter - 1));

MethodSignature<TypeHandleInfo> signature = methodDefinition.Method.DecodeSignature(SignatureHandleProvider.Instance, null);
CustomAttributeHandleCollection? returnTypeAttributes = methodDefinition.Generator.GetReturnTypeCustomAttributes(methodDefinition.Method);
Expand All @@ -3452,18 +3453,24 @@ private TypeDeclarationSyntax DeclareInterfaceAsStruct(TypeDefinitionHandle type
.AddParameters(parameterList.Parameters.Select(p => FunctionPointerParameter(p.Type!).WithModifiers(p.Modifiers)).ToArray())
.AddParameters(FunctionPointerParameter(returnType.Type));

TypeSyntax unmanagedDelegateType = FunctionPointerType().WithCallingConvention(
FunctionPointerCallingConvention(TokenWithSpace(SyntaxKind.UnmanagedKeyword))
.WithUnmanagedCallingConventionList(FunctionPointerUnmanagedCallingConventionList(
SingletonSeparatedList(FunctionPointerUnmanagedCallingConvention(Identifier("Stdcall"))))))
.WithParameterList(funcPtrParameters);
FieldDeclarationSyntax vtblFunctionPtr = FieldDeclaration(
VariableDeclaration(
FunctionPointerType().WithCallingConvention(FunctionPointerCallingConvention(TokenWithSpace(SyntaxKind.UnmanagedKeyword))
.WithUnmanagedCallingConventionList(FunctionPointerUnmanagedCallingConventionList(
SingletonSeparatedList(FunctionPointerUnmanagedCallingConvention(Identifier("Stdcall"))))))
.WithParameterList(funcPtrParameters))
VariableDeclaration(unmanagedDelegateType)
.WithVariables(SingletonSeparatedList(VariableDeclarator(innerMethodName.Identifier))))
.WithModifiers(TokenList(TokenWithSpace(SyntaxKind.InternalKeyword)));
vtblMembers.Add(vtblFunctionPtr);

// Build up an unmanaged delegate cast directly from the vtbl pointer and invoke it.
// By doing this, we make the emitted code more trimmable by not referencing the full virtual method table and its full set of types
// when the app may only invoke a subset of the methods.
IdentifierNameSyntax pThisLocal = IdentifierName("pThis");
InvocationExpressionSyntax vtblInvocation = InvocationExpression(MemberAccessExpression(SyntaxKind.PointerMemberAccessExpression, vtblFieldName, innerMethodName))
ExpressionSyntax vtblIndexingExpression = ParenthesizedExpression(
CastExpression(unmanagedDelegateType, ElementAccessExpression(vtblFieldName).AddArgumentListArguments(Argument(methodOffset))));
InvocationExpressionSyntax vtblInvocation = InvocationExpression(vtblIndexingExpression)
.WithArgumentList(FixTrivia(ArgumentList()
.AddArguments(Argument(pThisLocal))
.AddArguments(parameterList.Parameters.Select(p => Argument(IdentifierName(p.Identifier.ValueText)).WithRefKindKeyword(p.Modifiers.Count > 0 ? p.Modifiers[0] : default)).ToArray())));
Expand Down Expand Up @@ -3506,13 +3513,14 @@ private TypeDeclarationSyntax DeclareInterfaceAsStruct(TypeDefinitionHandle type
members.Add(methodDeclaration);
}

// We expose the vtbl struct, not because we expect folks to use it directly, but because some folks may use it to manually generate CCWs.
StructDeclarationSyntax? vtblStruct = StructDeclaration(Identifier("Vtbl"))
.AddMembers(vtblMembers.ToArray())
.AddModifiers(TokenWithSpace(SyntaxKind.PrivateKeyword));
.AddModifiers(TokenWithSpace(this.Visibility));
members.Add(vtblStruct);

// private Vtbl* lpVtbl;
members.Add(FieldDeclaration(VariableDeclaration(PointerType(IdentifierName(vtblStruct.Identifier))).AddVariables(VariableDeclarator(vtblFieldName.Identifier))).AddModifiers(TokenWithSpace(SyntaxKind.PrivateKeyword)));
// private void** lpVtbl; // Vtbl* (but we avoid strong typing to enable trimming the entire vtbl struct away)
members.Add(FieldDeclaration(VariableDeclaration(PointerType(PointerType(PredefinedType(Token(SyntaxKind.VoidKeyword))))).AddVariables(VariableDeclarator(vtblFieldName.Identifier))).AddModifiers(TokenWithSpace(SyntaxKind.PrivateKeyword)));

StructDeclarationSyntax iface = StructDeclaration(ifaceName.Identifier)
.AddModifiers(TokenWithSpace(this.Visibility), TokenWithSpace(SyntaxKind.UnsafeKeyword))
Expand Down