Building GHC on FreeBSD is currently supported on 8.4-RELEASE or later, on i386 (x86) and amd64 (x86_64) architectures. One might be able to build GHC on different architectures and earlier versions but they are not maintained actively. Note that 8.4-RELEASE is used for the FreeBSD nightly builds (amd64 head, i386 head).
Note that this section is primarily intended for developers and early adopters.If you are just want to install GHC on your system, simply use the devel/hs-haskell-platform port instead. This port does all the things described below for you. It is usually kept updated to match the latest Haskell Platform specifications.
In order to be able to build GHC from source, the following ports have to be installed.
Probably it is possible to use a vanilla binary distribution to bootstrap the build, but one must note that it is built on 8.4-RELEASE, hence it will require installing misc/compat8x in order to make it work on 9.x and later systems.
In addition to the required ones, there are some further ports to install for extras.
devel/binutils (for a more up-to-date version of the GNU toolchain, see Notes)
FreeBSD stores locally installed third-party software (i.e. the ports mentioned above) under a separate prefix, called LOCALBASE here, which is /usr/local/ by default. Thus the preferred way of invoking the configure script is as follows.
The --disable-large-address-space disables the runtime's two-step allocator, which isn't currently supported on FreeBSD prior to 11.1 and GHC earlier than 8.6 (see #12695 (closed)).
On systems earlier than 10.0-RELEASE, one has to configure iconv(3) as well. For 10.0-RELEASE and later, iconv(3) functions are part of the base system libraries, so these flags is not needed any more.
After configure ran successfully, invoke GNU make as usual. Note that GNU make is called gmake under FreeBSD as make is the BSD make.
$ gmake -j `sysctl -n hw.ncpu`
Here is a random list of thoughts about things that are good to know when working on FreeBSD.
The Alex and Happy ports may not be up-to-date enough for building GHC (as they are tracking the versions specified in the Haskell Platform). Install cabal-install and install those tools using cabal instead.
The FreeBSD base system contains GCC and the GNU toolchain in older (pre-10.0) versions. GCC is technically stuck at version 4.2.1 which may not be optimal for building GHC these days. Hence it is highly recommended to use the GNU toolchain (devel/binutils) and GCC ( lang/gcc) from the Ports Collection instead.
Clang is the default base system compiler for FreeBSD 10.0 or later. So one may try to build GHC using Clang on such systems (however, Clang can also be installed on earlier versions from the lang/clang33 port). It should work, but have not yet been extensively tested.
The FreeBSD base system is shipped with a version of ncurses but this may not be the latest. Unfortunately, when devel/ncurses is installed one should add some extra lines to mk/build.mk to tell GNU make we want to use ncurses from $LOCALBASE (see above) instead, otherwise terminfo (which uses ncurses) becomes linked to ncurses in the base:
The GHC source code have an in-tree version of libffi and gmp which may work by accident -- especially if the version of libgmp.so and libffi.so matches the version installed by the ports. But using them is not recommended as they could result in various strange build and run-time errors. See the configure options to work around them.
In an extremely high-speed environment it might happen that gmake restarts multiple times, c.f. #7592 (closed). This is because timestamp precision for the VFS layer is set to a POSIX-friendly value by default. Adjusting the vfs.timestamp_precision sysctl(3) variable can help.
Building GHC sources and Haskell sources in general could be sped up by setting up a tmpfs(5) partition. (This is not created by the default install.) Just replace the /tmp partition with a tmpfs-backed entry in /etc/fstab:
tmpfs /tmp tmpfs rw,mode=777 0 0
and use your original /tmp partition as a swap device (substitute ada0s1 with your device):