[Mono-dev] mono_fntptr_to_delegate

[Bruno Lauze]

Hi, 

 

I am sure someone can help me out. At one point this code did work. I
changed something and/or I just reinstalled latest trunk and it broke.

I am trying to pass C delegate to C#. Everything is working C# is calling
back the method but the parameters seems to be invalid pointers.

The C delegate was returning the delegate object, and the parameters.

 

I did put mono_ftnptr_to_delegate to external removing MONO_INTERNAL and
placing it under MONO_API.

One could use Marshal.GetDelegateFromPointer with mono_runtime_invoke
(Adding that way too at the bottom.)

 

 

Consider the following code:

 

 

DelegateHelper.dll: MyClass.cs:

 

using System;

 

namespace DelegateHelper

{

        public delegate bool TestDelegate(string arg1);

 

        public class MyClass

        {

                public static bool Test(TestDelegate predicate)

                {

                        return predicate("TEST");

                }

        }

}

 

 

main.c:

 

 

#include <stdio.h>

#include <glib.h>

#include <mono/jit/jit.h>

#include <mono/metadata/object.h>

#include <mono/metadata/reflection.h>

#include <mono/metadata/assembly.h>

#include <mono/metadata/threads.h>

#include <mono/metadata/mono-config.h>

 

MONO_API MonoDelegate*

mono_ftnptr_to_delegate (MonoClass *klass, gpointer ftn);

 

MonoBoolean testMethod(MonoObject *arg1, MonoObject *arg2)

{

        printf("Calling delegate!");

        MonoString *str = mono_object_to_string(arg2, NULL); //crash

        return TRUE;

}

 

int main (int argc, char *argv[])

{

        printf ("Delegate Test!\n");

 

        MonoDomain *domain = mono_jit_init_version("DelegateTest",
"v4.0.30319");

        mono_config_parse(NULL);

        void *__parameters__[1];

        MonoAssembly *ass = mono_assembly_open("DelegateHelper.dll", NULL);

        MonoImage *image = mono_assembly_get_image(ass);

        MonoClass *delegateClass = mono_class_from_name(image,
"DelegateHelper", "TestDelegate");

        mono_class_init(delegateClass);

        MonoClass *testClass = mono_class_from_name(image, "DelegateHelper",
"MyClass");

        mono_class_init(testClass);

        gpointer ptr = (gpointer)testMethod;

        MonoDelegate *delegateObj = mono_ftnptr_to_delegate(delegateClass,
ptr); //Short way to call Marshal.GetDelegateFromFunctionPointer()

        MonoMethod *testMethod = mono_class_get_method_from_name(testClass,
"Test", 1);

        __parameters__[0] = delegateObj;

        MonoObject *result = mono_runtime_invoke(testMethod, NULL,
__parameters__, NULL);

        return 0;

}

 

 

Result:

 

Delegate Test!

Calling delegate!

Stacktrace:

 

  at <unknown> <0xffffffff>

  at (wrapper managed-to-native) object.wrapper_native_0x40ea40 ()
<0xffffffff>

  at DelegateHelper.MyClass.Test (System.Func`2<string, bool>) <0x00018>

  at (wrapper runtime-invoke) <Module>.runtime_invoke_bool_object
(object,intptr,intptr,intptr) <0xffffffff>

 

=================================================================

Got a SIGSEGV while executing native code. This usually indicates

a fatal error in the mono runtime or one of the native libraries

used by your application.

=================================================================

 

Abort

 

 

This code could be used instead of mono_ftnptr_to_delegate which is normally
internal

 

        /*

        MonoImage *mscorlib =
mono_assembly_get_image(mono_domain_assembly_open(domain, "mscorlib"));

        MonoClass *marshal = mono_class_from_name(mscorlib,
"System.Runtime.InteropServices", "Marshal");

        MonoMethod *getDelegate = mono_class_get_method_from_name(marshal,
"GetDelegateForFunctionPointer", 2);

        void *marshal_params[2];

        marshal_params[0] = ptr;

        marshal_params[1] = mono_type_get_object(domain,
mono_class_get_type(delegateClass));

        MonoObject *delegateObj = mono_runtime_invoke(getDelegate, NULL,
marshal_params, NULL);

        */

 

 

Please help!!

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