DllResolver fails with Ubuntu 22.04 (no libdl.so)

[imnasnainaec]

Describe the bug

Upon updating The Combine from 20.04 to 22.04, our backend encounters the following: System.DllNotFoundException : Unable to load shared library 'libdl.so' or one of its dependencies. This appears to be from the configuration in https://github.com/sillsdev/icu-dotnet/blob/master/source/icu.net/App.config that is enforced by https://github.com/sillsdev/icu-dotnet/blob/master/source/icu.net/NativeMethods/DllResolver.cs.

The error is further documented in sillsdev/TheCombine#1768

Environment

• Ubuntu 22.04
• icu.net 2.7.1 & 2.8.1

[ermshiperete]

This happens if the icu.net.dll.config doesn't get copied next to icu.net.dll, because that tells the name of the shared library to load (in this case libdl.so.2).

Also, when running under net6 you'll have to use the latest pre-release version 2.9.x - it seems that icu.net has to be build for net6 in order to pick up the config file.

See comment in sillsdev/TheCombine#1768.

[papeh]

Even when copying icu.net.dll.config and including its content in SIL.LCModel.Core.Tests/App.config, tests fail with

   System.DllNotFoundException : libdl.so assembly:<unknown assembly> type:<unknown type> member:(null)
  Stack Trace:
    at (wrapper managed-to-native) SIL.LCModel.Core.SpellChecking.SpellEngineLinux.dlopen(string,int)
  at SIL.LCModel.Core.SpellChecking.SpellEngineLinux.get_Library () [0x00014] in <8dfbb8a640e7481f8301a9226f75cf3f>:0 
  at SIL.LCModel.Core.SpellChecking.SpellEngineLinux.Hunspell_initialize (System.Byte[] affFile, System.Byte[] dictFile) [0x00000] in <8dfbb8a640e7481f8301a9226f75cf3f>:0 

(see https://github.com/sillsdev/liblcm/actions/runs/3688810619/jobs/6244040627)
Anything else I need to do?

[ermshiperete]

That's a rabbit trail. Note that this reference of libdl.so doesn't come from icu.net code but instead from SIL.LCModel.Core which is missing a dll mapping for libdl.so. So this is not a bug in icu.net.

See sillsdev/liblcm#267 (comment)