Removed the managed calls to destructors of std::strings passed by value.

The native code calls the destructors itself.

Signed-off-by: Dimitar Dobrev <dpldobrev@protonmail.com>

src/Generator/Generators/CSharp/CSharpSources.cs

@@ -1601,7 +1601,7 @@ namespace CppSharp.Generators.CSharp
         {
             if (method.IsDestructor)
             {
-                WriteLine("{0}.Dispose(false);", Helpers.TargetIdentifier);
+                WriteLine("{0}.Dispose(true);", Helpers.TargetIdentifier);
                 return;
             }
 
@@ -1930,15 +1930,9 @@ namespace CppSharp.Generators.CSharp
 
             // Generate Dispose(bool) method
             PushBlock(CSharpBlockKind.Method);
-            if (@class.IsValueType)
-            {
-                Write("private ");
-            }
-            else
-            {
-                Write("protected ");
+            Write("public ");
+            if (!@class.IsValueType)
                 Write(hasBaseClass ? "override " : "virtual ");
-            }
 
             WriteLine("void Dispose(bool disposing)");
             WriteStartBraceIndent();
@@ -1978,8 +1972,10 @@ namespace CppSharp.Generators.CSharp
                 if (!Options.CheckSymbols ||
                     Driver.Symbols.FindLibraryBySymbol(dtor.Mangled, out library))
                 {
+                    WriteLine("if (disposing)");
                     if (dtor.IsVirtual)
                     {
+                        WriteStartBraceIndent();
                         GenerateVirtualFunctionCall(dtor, @class, true);
                         if (@class.IsAbstract)
                         {
@@ -1987,11 +1983,16 @@ namespace CppSharp.Generators.CSharp
                             WriteLine("else");
                             PushIndent();
                             GenerateInternalFunctionCall(dtor);
-                            PopIndent();   
+                            PopIndent();
                         }
+                        WriteCloseBraceIndent();
                     }
                     else
+                    {
+                        PushIndent();
                         GenerateInternalFunctionCall(dtor);
+                        PopIndent();
+                    }
                 }
             }
 

src/Generator/Types/Std/Stdlib.cs

@@ -78,14 +78,15 @@ namespace CppSharp.Types.Std
             {
                 string varAllocator = "__allocator" + ctx.ParameterIndex;
                 string varBasicString = "__basicString" + ctx.ParameterIndex;
-                ctx.SupportBefore.WriteLine("using (var {0} = new {1}())",
+                ctx.SupportBefore.WriteLine("var {0} = new {1}();",
                     varAllocator, allocator.Visit(typePrinter));
-                ctx.SupportBefore.WriteLine("using (var {0} = new {1}({2}, {3}))",
+                ctx.SupportBefore.WriteLine("var {0} = new {1}({2}, {3});",
                     varBasicString, basicString.Visit(typePrinter),
                     ctx.Parameter.Name, varAllocator);
-                ctx.SupportBefore.WriteStartBraceIndent();
                 ctx.Return.Write("{0}.{1}", varBasicString, Helpers.InstanceIdentifier);
-                ctx.HasCodeBlock = true;
+                ctx.Cleanup.WriteLine("{0}.Dispose({1});", varBasicString,
+                    type.IsPointer() ? "true" : "false");
+                ctx.Cleanup.WriteLine("{0}.Dispose();", varAllocator);
             }
         }
 

tests/Common/Common.Tests.cs

@@ -636,11 +636,20 @@ public class CommonTests : GeneratorTestFixture
     [Test, Ignore("We need symbols for std::string to invoke and auto-compilation of exported templates is not added yet.")]
     public void TestStdString()
     {
+        // when C++ memory is deleted, it's only marked as free but not immediadely freed
+        // this can hide memory bugs while marshalling
+        // so let's use a long string to increase the chance of a crash right away
+        const string t = @"This is a very long string. This is a very long string. This is a very long string. This is a very long string. This is a very long string. This is a very long string. This is a very long string. This is a very long string. 
+This is a very long string. This is a very long string. This is a very long string. This is a very long string. This is a very long string. This is a very long string. This is a very long string. This is a very long string. This is a very long string.
+This is a very long string. This is a very long string. This is a very long string. This is a very long string. This is a very long string. This is a very long string. This is a very long string. This is a very long string. This is a very long string.
+This is a very long string. This is a very long string. This is a very long string. This is a very long string. This is a very long string. This is a very long string. This is a very long string. This is a very long string. This is a very long string.
+This is a very long string. This is a very long string. This is a very long string. This is a very long string. This is a very long string. This is a very long string. This is a very long string. This is a very long string. This is a very long string.
+This is a very long string. This is a very long string. This is a very long string. This is a very long string. This is a very long string. This is a very long string. This is a very long string. This is a very long string. This is a very long string.";
         using (var hasStdString = new HasStdString())
         {
-            Assert.That(hasStdString.testStdString("test"), Is.EqualTo("test_test"));
-            hasStdString.s = "test";
-            Assert.That(hasStdString.s, Is.EqualTo("test"));
+            Assert.That(hasStdString.testStdString(t), Is.EqualTo(t + "_test"));
+            hasStdString.s = t;
+            Assert.That(hasStdString.s, Is.EqualTo(t));
         }
     }