Commits on Apr 27, 2023

1. [tests] Find a workaround for #xamarin/maccore@2668. …

   1. Mono changed dyld lookup to start looking in directories in
      NATIVE_DLL_SEARCH_DIRECTORIES before the actual given path, even when the
      given path is absolute [1].
   2. This turned out to break Mac Catalyst, because when a DllImport says a
      P/Invoke is in "/System/Library/Frameworks/SceneKit.framework/SceneKit",
      Mono would try loading by prefixing the directories in
      NATIVE_DLL_SEARCH_DIRECTORIES. We add the Contents/MonoBundle directory to
      NATIVE_DLL_SEARCH_DIRECTORIES, so Mono would try to load
      "/path/to/my.app/Contents/MonoBundle//System/Library/Frameworks/SceneKit.framework/SceneKit",
      and things would go wrong.
   3. We found a workaround: add "/" to NATIVE_DLL_SEARCH_DIRECTORIES. This works
      on Ventura, but apparently not on older macOS version, because the actual
      path we pass to dlopen ends up being "///System/Library/Frameworks/SceneKit.framework/SceneKit"
      (note the three initial slashes instead of a single slash).
   4. Add a second workaround, where we add a dll import resolver to load exactly
      the path we want to load.
   
   [1]: dotnet/runtime@5a1baeb
   [2]: dotnet/runtime#85255
   
   Technical sidenote:
   
   Why trying to load "/path/to/my.app/Contents/MonoBundle//System/Library/Frameworks/SceneKit.framework/SceneKit"
   turned out so bad on Mac Catalyst is not obvious. What happens is this:
   
   * The app calls 'dlopen ("/path/to/my.app/Contents/MonoBundle//System/Library/Frameworks/SceneKit.framework/SceneKit")'
   * dlopen checks if this is a Mac Catalyst override of a macOS system
     framework, by prefixing "/System/iOSSupport" and trying to load that. So
     dlopen would try to load "/System/iOSSupport/path/to/my.app/Contents/MonoBundle//System/Library/Frameworks/SceneKit.framework/SceneKit",
     which would obviously fail.
   * Then dlopen would try a few more fallbacks, eventually trying
     "/System/Library/Frameworks/SceneKit.framework/SceneKit", and successfully
     loading that library.
   * Unfortunately "/System/Library/Frameworks/SceneKit.framework/SceneKit" is
     the wrong library to load for Mac Catalyst ("/System/iOSSupport/System/Library/Frameworks/SceneKit.framework/SceneKit"
     is the correct version). These two libraries are incompatible, and calling
     one when you mean to call the other will do nasty things like corrupting the
     stack.

   

   rolfbjarne committed Apr 27, 2023
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