[Mono-dev] minimal setup for embedded application

[Jonathan Shore]

Hi,

So I've been running some embedded apps with mono for a while successfully.   In each case have a full mono installation available locally on the box on which the application is run.

I needed to create a minimal mono environment  so can run the app with embedded mono, but without a full mono installation.   My application just depends on mscorlib.dll, System.Core.dll, and System.Data.dll (4.0).  I am testing on a virgin install of ubuntu 10.4, which for better or worse has an ancient mono installed (2.4.4), but would represent the typical target environment.  

I created a very minimal install and directed the mono VM to find what it needs in the application-local install, with:

   mono_set_dirs (myapp_lib, myapp_etc);

This appears to work as expected.   Was able to load my assembly and start evaluation of a function.   However, ran into a problem when one of the functions attempts to use reflection to find a type.   I called Assembly.GetTypes() on the System.Core assembly, but throws the following exception:

searching assembly: System.Core, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089

exception: System.Reflection.ReflectionTypeLoadException: The classes in the module cannot be loaded.

  at (wrapper managed-to-native) System.Reflection.Assembly:GetTypes (System.Reflection.Assembly,bool)

  at System.Reflection.Assembly.GetTypes () [0x00000] in <filename unknown>:0 

(the "searching" message is a diagnostic from my code).   I believe it successfully located System.Core, but for some reason is failing to load the classes.   Previously I did not have System.Core.dll in the same directory with my application dll and it complained about not finding (so it has definitely found the dll).

Any ideas on what causes the System.Reflection.ReflectionTypeLoadException to be thrown?

My setup is as follows:

$ ls lib

com.gf.core.dll  mono  System.Core.dll  System.Data.dll

$ ls mono

2.0 4.0

$ ls mono/2.0

mscorlib.dll  System.Core.dll  System.Data.dll

$ ls mono/4.0

mscorlib.dll  System.Core.dll  System.Data.dll

In my code, mono_set_dirs (...) is set to point to lib, and appears to pick up the dlls correctly.    Would the exception result from a DLL dependency or environmental element that is required?   Could the ancient mono 2.4.4 bundled with ubuntu be interfering?

Thanks

Jonathan

[Jonathan Shore]

On further examination, it seems that when using mono_set_dirs (), is looking for:

lib/mono/4.0

AND

lib/mono/gac

Is there a way to avoid requiring the gac for an application with embedded mono?   A strace on all file open attempts shows that the gac is key to allowing the enumeration of types in System.Core.dll.   How do I work around this?  I don't want the file overhead of the gac if I can help it.  Just want to be able to indicate the 3 dependent assemblies.

Here are the calls (I have a very trimmed 2.10.6 distribution under "/home/jshore/Dev/EA/Isolated/dist"):

open("/home/jshore/Dev/EA/Isolated/lib/noarch/com.gf.core.dll", O_RDONLY) = 3

open("/home/jshore/Dev/EA/Isolated/dist/lib/mono/4.0/mscorlib.dll", O_RDONLY) = 3

...

open("/home/jshore/Dev/EA/Isolated/dist/lib/mono/gac/System.Core/4.0.0.0__b77a5c561934e089/System.Core.dll", O_RDONLY) = 3

open("/home/jshore/Dev/EA/Isolated/dist/lib/mono/gac/System/4.0.0.0__b77a5c561934e089/System.dll", O_RDONLY) = 3

Why doesn't mono look in lib/mono/4.0 for System.Core.dll?