After going through the convoluted process of getting an app notarised so it can run on Mac OS X 10.15 Catalina, a problem popped up for some people:

System.TypeInitializationException: The type initializer for 'Keyboard' threw an exception. ---> System.TypeInitializationException: The type initializer for 'Sdl' threw an exception. ---> System.DllNotFoundException: libdl.so.2 at (wrapper managed-to-native) MonoGame.Utilities.FuncLoader+Linux.dlopen(string,int)

As you can see "Linux.dlopen" was being called and not the Mac function.

Lots of delving later I discovered the problem to be in CurrentPlatform.cs, in the DLLImport call for uname:

[DllImport ("libc")]
static extern int uname(IntPtr buf);

The call to uname was causing a dll not found crash. The full path needs to be specified for Macs to cover this problem.

Note I could not reproduce this problem but many of my customers could. I believe its connected to the fact that you have to do a hardened codesign and codesign the individual dylib libraries also in the MonoBundle part of the application.

I used the following to fix the code and keep it working for Linux also.
Replace the DllImport call with:

[DllImport ("libc", EntryPoint="uname")]
static extern int unameNoPath(IntPtr buf);
[DllImport ("/usr/lib/libc", EntryPoint="uname")]
static extern int unameWithPath(IntPtr buf);

and the uname() call with:

int unameResult;
try {
   unameResult = unameNoPath (buf);
} catch {
   unameResult = unameWithPath (buf);
}
if (unameResult == 0) {

There is also a bug in the file just after the uname() call - the return needs to be removed after the line

os = OS.MacOSX;

and instead add a check before the switch break:

if (os == OS.MacOSX)
   break;

os = OS.Linux;
break;

What version of MonoGame does the bug occur on:

• MonoGame 3.7

What operating system are you using:

• Mac OS X

What MonoGame platform are you using:

• DesktopGL