macOS: Load frameworks without stating them first.

macOS Big Sur makes the following change to how frameworks are shipped
with the OS:

> New in macOS Big Sur 11 beta, the system ships with a built-in
> dynamic linker cache of all system-provided libraries. As part of
> this change, copies of dynamic libraries are no longer present on
> the filesystem. Code that attempts to check for dynamic library
> presence by looking for a file at a path or enumerating a directory
> will fail. Instead, check for library presence by attempting to
> dlopen() the path, which will correctly check for the library in the
> cache. (62986286)

https://developer.apple.com/documentation/macos-release-notes/macos-big-sur-11-beta-release-notes/

Therefore, the previous method of checking whether a library exists
before attempting to load it makes GHC.Runtime.Linker.loadFramework
fail to find frameworks installed at /System/Library/Frameworks.

GHC.Runtime.Linker.loadFramework now opportunistically loads the
framework libraries without checking for their existence first,
failing only if all attempts to load a given framework from any of the
various possible locations fail.

1 files changed, 14 insertions, 7 deletions

diff --git a/compiler/GHC/Runtime/Linker.hs b/compiler/GHC/Runtime/Linker.hs
index f94d225889..ccbb1791e9 100644
--- a/compiler/GHC/Runtime/Linker.hs
+++ b/compiler/GHC/Runtime/Linker.hs
@@ -1705,17 +1705,24 @@ loadFramework hsc_env extraPaths rootname
                                   Left _ -> []
                                   Right dir -> [dir </> "Library/Frameworks"]
               ps = extraPaths ++ homeFrameworkPath ++ defaultFrameworkPaths
-        ; mb_fwk <- findFile ps fwk_file
-        ; case mb_fwk of
-            Just fwk_path -> loadDLL hsc_env fwk_path
-            Nothing       -> return (Just "not found") }
-                -- Tried all our known library paths, but dlopen()
-                -- has no built-in paths for frameworks: give up
+        ; findLoadDLL ps }
    where
      fwk_file = rootname <.> "framework" </> rootname
-        -- sorry for the hardcoded paths, I hope they won't change anytime soon:
+
+     -- sorry for the hardcoded paths, I hope they won't change anytime soon:
      defaultFrameworkPaths = ["/Library/Frameworks", "/System/Library/Frameworks"]
 
+     findLoadDLL [] =
+       -- Tried all our known library paths, but dlopen()
+       -- has no built-in paths for frameworks: give up
+       return (Just "not found")
+     findLoadDLL (p:ps) =
+       do { dll <- loadDLL hsc_env (p </> fwk_file)
+          ; case dll of
+              Nothing -> return Nothing
+              Just _  -> findLoadDLL ps
+          }
+
 {- **********************************************************************
 
                 Helper functions