Using Mono/.Net libraries that have native binding and you are receiving errors like “Unable to find the xxxx native library” or “DllImport error loading library”.

You can easily find where mono is looking for that native library by setting the MONO_LOG_LEVEL to debug and MONO_LOG_MASK filtering to only DLL related messages.

export MONO_LOG_LEVEL=debug
export MONO_LOG_MASK=dll
mono yourprogram.exe

I was recently using the mono-curses wrapper, or at least trying to ;-) and I knew my DYLD_LIBRARY_PATH was set properly to pick up the “libmono-curses.dylib” that I just built. But the program failed to run so I set the MONO_LOG_LEVEL and MONO_LOG_MASK env vars and re-ran the program. Yes it was finding the dylib OK but it was complaining about it being the wrong architecture…

Mono: DllImport attempting to load: 'libmono-curses.dylib'.
Mono: DllImport error loading library '/Users/administrator/Documents/Code/github/mono-curses/libmono-curses.dylib': 'dlopen(/Users/administrator/Documents/Code/github/mono-curses/libmono-curses.dylib, 9): no suitable image found.
Did find:  /Users/administrator/Documents/Code/github/mono-curses/libmono-curses.dylib: mach-o, but wrong architecture        

Checking with file and yes, it was a 32-bit version of the library:

file libmono-curses.dylib
libmono-curses.dylib: Mach-O dynamically linked shared library i386

I am compiling using a 64-bit version of Mono on OS-X and need 64-bit libraries (and native libs), so a quick fix in the mono-curses Makefile and re-compile and I have a 64-bit version (I’ll fork and fix the mono-curses project and post it to my GitHub).

file libmono-curses.dylib 
libmono-curses.dylib: Mach-O 64-bit dynamically linked shared library x86_64

After that, testing the C# ncurses wrapper went fine… ;-)

Mac OS X Framework and .dylib Search Path

The Framework and library search path is:

• A colon-separated list of directories in the user’s DYLD_FRAMEWORK_PATH environment variable.
• A colon-separated list of directories in the user’s DYLD_LIBRARY_PATH environment variable.

• A colon-separated list of directories in the user’s DYLD_FALLBACK_FRAMEWORK_PATH environment variable, which defaults to the directories:

    ~/Library/Frameworks
    /Library/Frameworks
    /Network/Library/Frameworks
    /System/Library/Frameworks
  

• A colon-separated list of directories in the user’s DYLD_FALLBACK_LIBRARY_PATH environment variable, which defaults to the directories:

    ~/lib
    /usr/local/lib
    /lib
    /usr/lib
  

Note: Mono will automatically append the appropriate suffix depending on the platform (.dylib on Mac, .so on Linux and .dll on Windows).