I haven't investigated this closely, but when I try to compile with packman I get this:
-- <no location info>: error:
-- <command line>: can't load .so/.DLL for: /usr/lib/haskell-packages/ghc/lib/x86_64-linux-ghc-8.4.3/libHSpackman-0.5.0-Fv7reuyLHo03M7x4FerNmn-ghc8.4.3.so (/usr/lib/haskell-packages/ghc/lib/x86_64-linux-ghc-8.4.3/libHSpackman-0.5.0-Fv7reuyLHo03M7x4FerNmn-ghc8.4.3.so: undefined symbol: mblock_address_space)
I copied the code I needed into my app for the moment. Has anyone seen this error?