[Mono-dev] Embedded API: .ctor method signature query [mono]

[Jonathan Mitchell]

HI Robert

Thanks for that.
I think you are right.
I call hundreds of methods that take Obj`1<T> arguments with out issue but I see that I have had to construct a number of helper methods to deal with cases of Obj`2<T, K> which failed signature resolution.

I presume that  managed code execution doesn’t involve calls to mono_method_desc_new() - are thunks used instead?
One of the difficulties, I find, of working with the embedded API is trying to visualise just how a particular managed code statement is implemented within the runtime.

I was hoping to be able to call the constructor from C with a pointer to a static (MonoString *)fund(MonoString *).
Not sure if that would even fly.

As a work around I will use an internal call.

Shall I log this as a bug and reference this thread?

Thanks a lot for replying.

Jonathan

> On 3 Mar 2016, at 18:02, Robert Jordan <robertj at gmx.net> wrote:
> 
> On 03.03.2016 14:36, Jonathan Mitchell wrote:
>> HI
>> 
>> I want to call the following constructor via the embedded API:
>> 
>> public CloudClient(Func<string, string> filePathCallback)
>> 
>> All my other embedded method and constructor calls work okay but there is an issue with this one - it is the only place I use a System.Func<T>.
>> The API reports that a method cannot be found for signature .ctor(System.Func`2<string, string>)
>> When I dump out the class method names I see .ctor(System.Func`2<string, string>) listed.
>> 
>> Any ideas on this one?
> 
> It looks like a bug in mono_method_desc_new ():
> 
> https://github.com/mono/mono/blob/master/mono/metadata/debug-helpers.c#L378
> 
> The function is treating
> 
> 	.ctor(System.Func`2<string, string>)
> 
> like a method with 2 arguments:
> 
> arg0 = System.Func`2<string
> arg1 = string>
> 
> This is obviously wrong :)
> 
> The function is then storing the (wrong) argument count
> for optimization purposes, and the comparison of methods
> is starting to fail:
> 
> https://github.com/mono/mono/blob/master/mono/metadata/debug-helpers.c#L447
> 
> Robert
> 
> 
>