[Mono-list] Mono embedding - null pointer access violation on ves_icall_System_Reflection_Assembly_GetExecutingAssembly

Jean-Michel.Perraud at csiro.au Jean-Michel.Perraud at csiro.au
Thu Apr 25 22:30:09 UTC 2013

Hi Rodrigo,

I get the same behaviour whether I attach before or after loading the mono runtime, and 32 or 64 bit process.
I cannot figure out what I changed so much to end up in this pickle. But I could certainly do with a code review from someone more seasoned with mono embedding. My MS.NET embedding side is getting very usable, but visibly the Mono side has bugs I am not on top of.
Happy to provide further information as needed.


From: Rodrigo Kumpera [mailto:kumpera at gmail.com]
Sent: Tuesday, 23 April 2013 12:50 AM
To: Perraud, Jean-Michel (CLW, Black Mountain)
Cc: Mono List
Subject: Re: [Mono-list] Mono embedding - null pointer access violation on ves_icall_System_Reflection_Assembly_GetExecutingAssembly

Did you attach the thread before calling into the mono runtime?

On Fri, Apr 12, 2013 at 8:00 PM, <Jean-Michel.Perraud at csiro.au<mailto:Jean-Michel.Perraud at csiro.au>> wrote:

I am trying to flush out bugs in an application with Mono (3.0.6) embedded. Improving on the Linux front, an issue on Windows is now baffling me. The issue seems deep in JIT exec code but has got to be because of my code.
I tried to condense the diagnosis with the (visual studio) native stack trace (I could not get the managed part from MonoDevelop yet). I'd highly appreciate the informed guess of a guru to suggest where to look to fix it.


The high level call (in the R language) is like:
        callStaticMethod( "SomeNamespace.AClassName", "TheStaticMethod", "SomeString", "AnotherString" )

The main C code for preparing the CLR method call
        MonoMethod * methodCallStaticMethod = rclr_mono_get_method( spTypeClrFacade, "CallStaticMethodMono", 3);
        void** static_mparams = (void**)malloc(3*sizeof(void*));
        MonoArray* methParams = create_array_object(params, paramCount);
        static_mparams[0] = create_mono_string(ns_qualified_typename);
        static_mparams[1] = create_mono_string(methodName);
        static_mparams[2] = methParams;
        result = mono_runtime_invoke (methodCallStaticMethod, NULL, static_mparams, &exception);
        // calling the C# method:
        // public static object CallStaticMethodMono(string typename, string methodName, object[] arguments)

further in the stack strace, in:
        icall.c : ves_icall_System_Reflection_Assembly_GetExecutingAssembly (void)
the following line returns dest as a NULL pointer, which looks like a very unexpected condition hence the crash.
        mono_stack_walk_no_il (get_executing, &dest);
It seems that the root cause is in the function:
                        while (MONO_CONTEXT_GET_SP (&ctx) < jit_tls->end_of_stack)
which is already false at the first iteration, hence 'dest' remains NULL.

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