Add C++ WebAssembly ABI (mono#1711)

* Minor code refactorings.

* Fix debug assert issue with vtable methods.

* Add support for WebAssembly C++ ABI to parser and AST converter.

(cherry picked from commit 9b06e7b)

Author: tritao

src/AST/ASTContext.cs

@@ -11,7 +11,8 @@ public enum CppAbi
         Microsoft,
         ARM,
         iOS,
-        iOS64
+        iOS64,
+        WebAssembly
     }
 
     /// <summary>

src/AST/ClassLayout.cs

@@ -31,14 +31,7 @@ public struct VTableComponent
         public Declaration Declaration;
 
         /// Method declaration (if Kind == FunctionPointer).
-        public Method Method
-        {
-            get
-            {
-                Debug.Assert(Kind == VTableComponentKind.FunctionPointer);
-                return Declaration as Method;
-            }
-        }
+        public Method Method => Declaration as Method;
     }
 
     /// <summary>

src/CLI/CLI.cs

@@ -288,7 +288,7 @@ static void Main(string[] args)
 
             Generator gen = new Generator(options);
 
-            bool validOptions = gen.ValidateOptions(errorMessages);
+            var validOptions = gen.ValidateOptions(errorMessages);
             PrintErrorMessages(errorMessages);
 
             if (errorMessages.Any() || !validOptions)

src/CLI/Generator.cs

@@ -13,30 +13,13 @@ namespace CppSharp
 {
     class Generator : ILibrary
     {
-        private Options options = null;
+        private readonly Options options;
         private string triple = "";
         private CppAbi abi = CppAbi.Microsoft;
 
         public Generator(Options options)
         {
-            if (options == null)
-                throw new ArgumentNullException(nameof(options));
-
-            this.options = options;
-        }
-
-        static TargetPlatform GetCurrentPlatform()
-        {
-            if (Platform.IsWindows)
-                return TargetPlatform.Windows;
-
-            if (Platform.IsMacOS)
-                return TargetPlatform.MacOS;
-
-            if (Platform.IsLinux)
-                return TargetPlatform.Linux;
-
-            throw new System.NotImplementedException("Unknown host platform");
+            this.options = options ?? throw new ArgumentNullException(nameof(options));
         }
 
         void SetupTargetTriple()
@@ -78,8 +61,7 @@ public bool ValidateOptions(List<string> messages)
                 return false;
             }
 
-            if (!options.Platform.HasValue)
-                options.Platform = GetCurrentPlatform();
+            options.Platform ??= Platform.Host;
 
             if (string.IsNullOrEmpty(options.OutputDir))
             {
@@ -189,7 +171,7 @@ public void Postprocess(Driver driver, ASTContext ctx)
 
         public void Run()
         {
-            StringBuilder messageBuilder = new StringBuilder();
+            var messageBuilder = new StringBuilder();
             messageBuilder.Append($"Generating {GetGeneratorKindName(options.Kind)}");
             messageBuilder.Append($" bindings for {GetPlatformName(options.Platform)} {options.Architecture}");
 

src/CppParser/Bindings/CLI/Decl.h

@@ -256,7 +256,8 @@ namespace CppSharp
                 Microsoft = 1,
                 ARM = 2,
                 iOS = 3,
-                iOS64 = 4
+                iOS64 = 4,
+                WebAssembly = 5
             };
 
             public enum class RecordArgABI

src/CppParser/Bindings/CSharp/i686-apple-darwin12.4.0/CppSharp.CppParser.cs

@@ -6301,7 +6301,8 @@ public enum CppAbi
                 Microsoft = 1,
                 ARM = 2,
                 iOS = 3,
-                iOS64 = 4
+                iOS64 = 4,
+                WebAssembly = 5
             }
 
             public enum RecordArgABI

src/CppParser/Bindings/CSharp/i686-pc-win32-msvc/CppSharp.CppParser.cs

@@ -6301,7 +6301,8 @@ public enum CppAbi
                 Microsoft = 1,
                 ARM = 2,
                 iOS = 3,
-                iOS64 = 4
+                iOS64 = 4,
+                WebAssembly = 5
             }
 
             public enum RecordArgABI

src/CppParser/Bindings/CSharp/x86_64-apple-darwin12.4.0/CppSharp.CppParser.cs

@@ -6301,7 +6301,8 @@ public enum CppAbi
                 Microsoft = 1,
                 ARM = 2,
                 iOS = 3,
-                iOS64 = 4
+                iOS64 = 4,
+                WebAssembly = 5
             }
 
             public enum RecordArgABI

src/CppParser/Bindings/CSharp/x86_64-linux-gnu-cxx11abi/CppSharp.CppParser.cs

@@ -6301,7 +6301,8 @@ public enum CppAbi
                 Microsoft = 1,
                 ARM = 2,
                 iOS = 3,
-                iOS64 = 4
+                iOS64 = 4,
+                WebAssembly = 5
             }
 
             public enum RecordArgABI

src/CppParser/Bindings/CSharp/x86_64-linux-gnu/CppSharp.CppParser.cs

@@ -6301,7 +6301,8 @@ public enum CppAbi
                 Microsoft = 1,
                 ARM = 2,
                 iOS = 3,
-                iOS64 = 4
+                iOS64 = 4,
+                WebAssembly = 5
             }
 
             public enum RecordArgABI