From 748b7b5d0336e1e9a8e76f88a952b63c814465a1 Mon Sep 17 00:00:00 2001
From: Joe Hull <hull@metoliussoftware.com>
Date: Mon, 3 May 2021 01:26:34 -0700
Subject: [PATCH] Add a mechanism to selectively initialize allocated unmanaged
 memory in the default constructor.

* feature: Add a mechanism to selectively initialize unmanaged memory in the default constructor. (C# Only at this point).

* Use the global:: prefix when calling InitBlock
---
 src/Generator/Generators/CSharp/CSharpSources.cs |  3 +++
 src/Generator/Options.cs                         | 12 ++++++++++++
 tests/CSharp/CSharp.Gen.cs                       |  3 +++
 tests/CSharp/CSharp.Tests.cs                     | 13 +++++++++++++
 tests/CSharp/CSharp.h                            |  8 ++++++++
 5 files changed, 39 insertions(+)

diff --git a/src/Generator/Generators/CSharp/CSharpSources.cs b/src/Generator/Generators/CSharp/CSharpSources.cs
index ec779186..93a07c3a 100644
--- a/src/Generator/Generators/CSharp/CSharpSources.cs
+++ b/src/Generator/Generators/CSharp/CSharpSources.cs
@@ -2942,6 +2942,9 @@ internal static{(@new ? " new" : string.Empty)} {printedClass} __GetInstance({Ty
             }
             else
             {
+                if (method.IsDefaultConstructor && Context.Options.ZeroAllocatedMemory(@class))
+                    WriteLine($"global::System.Runtime.CompilerServices.Unsafe.InitBlock((void*){Helpers.InstanceIdentifier}, 0, (uint)sizeof({@internal}));");
+
                 if (!method.IsDefaultConstructor || @class.HasNonTrivialDefaultConstructor)
                     GenerateInternalFunctionCall(method);
             }
diff --git a/src/Generator/Options.cs b/src/Generator/Options.cs
index b980916f..6ea8d067 100644
--- a/src/Generator/Options.cs
+++ b/src/Generator/Options.cs
@@ -119,6 +119,18 @@ namespace CppSharp
         /// </summary>
         public bool GenerateFinalizers;
 
+        /// <summary>
+        /// If <see cref="ZeroAllocatedMemory"/> returns <c>true</c> for a given <see cref="Class"/>,
+        /// unmanaged memory allocated in the class' default constructor will be initialized with
+        /// zeros. The default implementation always returns <c>false</c>. Currently, C# only.
+        /// </summary>
+        /// <remarks>
+        /// If this option returns <c>true</c>, you must take a reference to the nuget package
+        /// System.Runtime.CompilerServices.Unsafe in the project(s) containing the generated file(s) to
+        /// resolve the Unsafe.InitBlock method.
+        /// </remarks>
+        public Func<Class, bool> ZeroAllocatedMemory = (@class) => false;
+
         public string IncludePrefix;
         public Func<TranslationUnit, string> GenerateName;
 
diff --git a/tests/CSharp/CSharp.Gen.cs b/tests/CSharp/CSharp.Gen.cs
index 5347bdde..19ace81e 100644
--- a/tests/CSharp/CSharp.Gen.cs
+++ b/tests/CSharp/CSharp.Gen.cs
@@ -65,6 +65,9 @@ namespace CppSharp.Tests
                     Name = "MacroTest",
                     Namespace = ctx.TranslationUnits.First(u => u.IsValid && !u.IsSystemHeader)
                 };
+
+            // Preserve the original semantics except for our one test class.
+            driver.Options.ZeroAllocatedMemory = (@class) => @class.Name == "ClassZeroAllocatedMemoryTest";
         }
 
         public override void Postprocess(Driver driver, ASTContext ctx)
diff --git a/tests/CSharp/CSharp.Tests.cs b/tests/CSharp/CSharp.Tests.cs
index 25d5adc7..7141037f 100644
--- a/tests/CSharp/CSharp.Tests.cs
+++ b/tests/CSharp/CSharp.Tests.cs
@@ -708,6 +708,19 @@ public unsafe class CSharpTests
         Assert.That(CSharp.HasFreeConstant.AnotherUnit.STD_STRING_CONSTANT, Is.EqualTo("test"));
     }
 
+    [Test]
+    public void TestZeroAllocatedMemoryOption()
+    {
+        // We've arranged in the generator for the ZeroAllocatedMemory option to return true for this one
+        // class.
+        var test = new ClassZeroAllocatedMemoryTest();
+        Assert.That(test.P1, Is.EqualTo(0));
+        Assert.That(test.p2.P2p1, Is.EqualTo(0));
+        Assert.That(test.p2.P2p2, Is.EqualTo(0));
+        Assert.That(test.P3, Is.EqualTo(false));
+        Assert.That(test.P4, Is.EqualTo('\0'));
+    }
+
     [Test]
     public void TestAlignment()
     {
diff --git a/tests/CSharp/CSharp.h b/tests/CSharp/CSharp.h
index 5c501628..4239a0f2 100644
--- a/tests/CSharp/CSharp.h
+++ b/tests/CSharp/CSharp.h
@@ -1487,6 +1487,14 @@ struct TestVariableWithoutType
     static constexpr auto variable = create(n...);
 };
 
+struct DLL_API ClassZeroAllocatedMemoryTest
+{
+    int p1;
+    struct { int p2p1; int p2p2; } p2;
+    bool p3;
+    char p4;
+};
+
 struct DLL_API ConversionFunctions
 {
     ConversionFunctions();