Cannot create a WPF UserControl in a Clr 4.0 self hosting application because of a stackoverflow error

Question

Hi,

I managed to host the CLR 2.0 in a Delphi win32 application that was able to create and host WPF controls inside a Delphi control, something similar to the ElementHost for WinForms applications.

Now, I want to move my solution to the CLR 4.0 and everything works fine except when I try to create a UserControl that has an associated Xaml resource. In that case it causes a stackoverflow error which forces the process to exit! But if I create some WPF controls by code (without reading xaml) then everything works fine!

I managed to step in the framework code until I entered the XamlReader.LoadBaml method, which crashed just after executing the following code:

            // We don't actually use the GeneratedInternalTypeHelper any more.
            // But for v3 compat, don't allow loading of internals in PT unless there is one.
            Type internalTypeHelper = null;
            if (streamInfo.Assembly != null) 
            {
                try 
                { 
                    internalTypeHelper = XamlTypeMapper.GetInternalTypeHelperTypeFromAssembly(parserContext);
                } 
                // This can perform attribute reflection which will fail if the assembly has unresolvable
                // attributes. If that happens, just assume there is no helper.
                catch (Exception e)
                { 
                    if (MS.Internal.CriticalExceptions.IsCriticalException(e))
                    { 
                        throw; 
                    }
                } 
            }

Note that the loaded assemblies use the CLR4 too.

Thanks for your help,

Morgan

Answer 1

I found the issue thanks to another post on Stackoveflow (http://stackoverflow.com/questions/2048540/hosting-clr-in-delphi-with-jcl-example see Important Note).

I had to initialize the fpu with Set8087CW($133F) then the weird stackoverlow stopped!

I still have a weird behaviour though: everything's fine without any debugger, but if i run the app from VS2010, then a black wpf form is displayed preventing me from interacting with the content. However, if i run the app then attach with the debugger then everything's fine!