crossgen2 doesn't call DllMain on the JIT

[BruceForstall]

This is specific to PAL, Linux implementations.

The JIT uses the DllMain() DLL_PROCESS_DETACH event to call jitShutdown(), which is output various information under various debugging modes, and close stdout if being unloaded.

More importantly, SuperPMI uses DLL_PROCESS_ATTACH to initialize the PAL (on Unix), initialize the logger, and DLL_PROCESS_DETACH to shutdown the logger. Because the PAL isn't initialized, SuperPMI crashes (issue: #47960)

@dotnet/crossgen-contrib @dotnet/jit-contrib

[BruceForstall]

AFAICT, crossgen2 doesn't call ICorJitCompiler::ProcessShutdownWork() either.

[jkotas]

Can we change SuperPMI to use jitStartup / ICorJitCompiler::ProcessShutdownWork for the initialization/shutdown instead of depending on the Win32 DllMain emulator?

crossgen2 doesn't call ICorJitCompiler::ProcessShutdownWork() either

I agree that we should fix this one.

[BruceForstall]

Can we change SuperPMI to use jitStartup / ICorJitCompiler::ProcessShutdownWork for the initialization/shutdown instead of depending on the Win32 DllMain emulator?

I'm sure we could make that work.

I hadn't noticed before, but even though the JIT uses DllMain DLL_PROCESS_DETACH to call its jitShutdown() function, jitShutdown() is also called by the ProcessShutdownWork() API (and the JIT makes sure shutdown only happens once). It appears that possibly only the DllMain shutdown code gets called if, by the comments, "FreeLibrary has been called or the DLL load failed". Maybe we don't need to worry about those cases.

[trylek]

Fixed by #49531, closing.

[BruceForstall]

@trylek, #49531 only worked around the problem, and only for SuperPMI. The problem still exists: we either need crossen2 to call DllMain on attach and detach, like on Windows, or we need a new "shutdown" API call.