What is New in Cross Compiling Haskell

May Edition

With GHC 8.6.1 being released soon, the windows for patches was closing fast. While not necessarily cross compilation related, I was still able to get a patch in the infamous load command size limit issue on macOS.

Interestingly windows suffers from a similar issue. On windows we have a command argument size limit of 32k character from Windows 7 onwards. Cabals (and to that extend also Stacks, and all other tools that use Setup.hs ) tendency to put libraries into their own folders results in one library search path per library. Thus once you have accumulated enough dependencies in your transitive dependency closure, you will see the gcc.exe: error: CreateProcess: No such file or directory (or realgcc.exe ) errors. Now you might be wondering why? Arn’t we using response files? And indeed we use response files to pass the arguments to gcc . However gcc internally does not seem to use response files for the library search paths when passing them off to collect2 and as such fail over. Of course we can hack this rather crudely in ghc , but the real solution is to fix gcc .

Now on to cross compilation related news: I’ve spent some more time looking at -target but got nothing useful to report yet. I also started looking on the llvm-ng backend and making it ready for the upcoming ghc 8.6.1 release. This included mostly adapting new code gen paths for new primops in 8.6.1.

I’m also trying to speedup the llvm-ng backend to be less space and time consuming and hope to be able to provide prebuilt cross compiler binaries for 8.6.1 in a timely manner around the 8.6.1 alpha/beta releases.

Finally a shout out to obsidian.systems for releasing obelisk!