Added a new pass to check for ABI-specific parameters.

src/Generator/Driver.cs

@@ -102,6 +102,9 @@ namespace Cxxi
             passes.CheckTypeReferences();
             passes.CheckFlagEnums();
 
+            if (Options.GeneratorKind == LanguageGeneratorKind.CSharp)
+                passes.CheckAbiParameters(Options);
+
             if (Transform != null)
                 Transform.SetupPasses(this, passes);
 

src/Generator/Passes/CheckAbiParameters.cs

@@ -0,0 +1,60 @@
+namespace Cxxi.Passes
+{
+    public class CheckAbiParameters : TranslationUnitPass
+    {
+        private readonly DriverOptions options;
+
+        public CheckAbiParameters(DriverOptions options)
+        {
+            this.options = options;
+        }
+
+        public override bool VisitMethodDecl(Method method)
+        {
+            if (!NeedsHiddenStructParameterReturn(method, options))
+                return true;
+
+            var structParameter = new Parameter()
+                {
+                    Kind = ParameterKind.HiddenStructureReturn,
+                    QualifiedType = new QualifiedType(
+                        new BuiltinType(PrimitiveType.IntPtr)),
+                    Name = "return",
+                    IgnoreFlags = IgnoreFlags.Generation
+                };
+
+            method.Parameters.Insert(0, structParameter);
+
+            return true;
+        }
+
+        public static bool NeedsHiddenStructParameterReturn(Method method, DriverOptions options)
+        {
+            // In both the Microsoft and Itanium ABI, functions returning
+            // structure types by value have an extra parameter 
+            // Itanium ABI reference (3.1.4 Return values):
+            // http://refspecs.linux-foundation.org/cxxabi-1.83.html#calls
+            // Microsoft ABI reference:
+            // http://blog.aaronballman.com/2012/02/describing-the-msvc-abi-for-structure-return-types/
+
+            Class retClass;
+            if (!method.ReturnType.IsTagDecl(out retClass))
+                return false;
+
+            // TODO: Add the various combinations for that need hidden parameter
+            var needsMSHiddenPtr = options.IsMicrosoftAbi && method.IsThisCall;
+
+            return needsMSHiddenPtr || options.IsItaniumAbi;
+        }
+    }
+
+    public static class CheckAbiParametersExtensions
+    {
+        public static void CheckAbiParameters(this PassBuilder builder,
+            DriverOptions options)
+        {
+            var pass = new CheckAbiParameters(options);
+            builder.AddPass(pass);
+        }
+    }
+}