[Mono-list] DllImport and modifying library search path

Uli Hertlein uli at xdt.com.au
Fri Feb 11 02:26:17 EST 2011

Hi guys,

I'm trying to come up with a way to transparently pick up the correct OS and CPU dependent 
.dll/.so/.dylib from within my application.

Assume I have the following directory structure:

The DllImport only specifies the 'base' library name, i.e.
[DllImport("Sdk", EntryPoint="foo")]

At runtime I assemble the directory based on Environment.Is64BitProcess and 
Environment.OSVersion.Platform to end up with e.g. "Linux64" or "Win64".

Now, to pickup the correct shared library I thought I'd prefix the the respective search path 
(LD_LIBRARY_PATH on Linux, DYLD_LIBRARY_PATH on OS X, and PATH on Windows) with this directory. 
This is then set using 'Environment.SetEnvironmentVariable("LD_LIBRARY_PATH", dllSearchPath)'

On Windows/CLR this works fine, but on Mono (Linux and Windows, mono-2.10 preview) it doesn't.

I've noticed (with MONO_LOG_LEVEL=debug) that Mono is trying to lookup the DllImport before my main 
even runs, as opposed to when the call to the lib is actually made.

So I am wondering if
- Mono is caching that first lookup (which fails, because the search path isn't set properly)
- Mono makes a copy of the search path and hence doesn't notice later changes to the environment 

Or something else?  Any ideas?

Ulrich Hertlein
Research and Development   mailto:uli at xdt.com.au
XDT Pty Ltd                http://www.xdt.com.au

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