[Mono-bugs] [Bug 487758] New: Marshaling a native function pointer to native function call throws assertion

bugzilla_noreply at novell.com bugzilla_noreply at novell.com
Mon Mar 23 09:54:14 EDT 2009


           Summary: Marshaling a native function pointer to native
                    function call throws assertion
    Classification: Mono
           Product: Mono: Runtime
           Version: 2.2.x
          Platform: 32bit
        OS/Version: All
            Status: NEW
          Severity: Normal
          Priority: P5 - None
         Component: interop
        AssignedTo: mono-bugs at lists.ximian.com
        ReportedBy: bhenderson at ipswitch.com
         QAContact: mono-bugs at lists.ximian.com
          Found By: ---

Created an attachment (id=281198)
 --> (https://bugzilla.novell.com/attachment.cgi?id=281198)
VS2008 project that builds testdll.dll and FunctionPointerInterop.exe

User-Agent:       Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:
Gecko/2008112016 Firefox/3.0.4 Flock/2.0.2

When trying to marshal a native function pointer to a native function call, the
following assertion is thrown:

ERROR:marshal.c:9235:mono_marshal_get_managed_wrapper: assertion failed:
method_signature (method)->pinvoke)

I have been able to work around the issue by providing a Managed delegate as
the parameter, and then calling the un-managed code from the managed delegate. 
But, it would be nice to have support for passing the native pointer rather
than forcing the native to un-managed callback.

I have only tested this on Windows XP, Ubuntu 8.10, and OpenSuse 11 (32-bit),
as these are the only platforms I have up and running at the moment.

Reproducible: Always

Steps to Reproduce:
1. Create a shared library that exports 2 functions.
#include <stdio.h>

extern "C" void TESTDLL_EXPORT foo()

extern "C" void TESTDLL_EXPORT bar(void (*fn)(void))
    if (fn)

2. Implement C# code to import the methods via DllImport, create a delegate
that wraps the native "foo" method, and call the "bar" method with the

        public extern static void foo();

        public extern static void bar(foo_delegate foo);

        public delegate void foo_delegate();

        static foo_delegate my_foo_delegate;

        public static void Start()
            // Create delegate with native pointer
            my_foo_delegate = new foo_delegate(foo);

Actual Results:  

ERROR:marshal.c:9235:mono_marshal_get_managed_wrapper: assertion failed:
method_signature (method)->pinvoke)

Expected Results:  
Expected the native function pointer to be passed, and the output of "foo!" to
the console from the native method.

The attached project is a VS2008 project that builds the native dll
(testdll.dll) and the C# sample application (FunctionPointerInterop.exe) in the
FunctionPointerInterop/bin/debug directory.

The sample contains a Workaround class (the workaround mentioned above), and a
Bug class that demonstrates the defect.

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