Do ghc-compiled binaries require GHC or are they self-contained?

If a friend wants to run my Haskell binaries, does he have to first install Haskell, or can he immediately run the binary by itself?

Is the answer the same on Mac, Windows, and Linux?

Solution 1:

GHC does produce stand-alone binaries that do not require GHC itself to be installed, however they do link against some dynamic libraries, most notably libgmp. The remaining libraries are commonly found out of the box on most Linux systems. I believe the situation is similar on Windows.

You can check which dynamic libraries you depend on using ldd on Linux. Here's what I get on Ubuntu Natty for a simple Hello World program:

$ echo 'main = putStrLn "Hello World"' > Hello.hs                                                   
$ ghc --make Hello.hs                                                                     
[1 of 1] Compiling Main             ( Hello.hs, Hello.o )
Linking Hello ...
$ ldd Hello                                                                                
    linux-vdso.so.1 =>  (0x00007fffe45ff000)
    libgmp.so.3 => /usr/lib/libgmp.so.3 (0x00007f8874cf9000)
    libm.so.6 => /lib/x86_64-linux-gnu/libm.so.6 (0x00007f8874a74000)
    librt.so.1 => /lib/x86_64-linux-gnu/librt.so.1 (0x00007f887486b000)
    libdl.so.2 => /lib/x86_64-linux-gnu/libdl.so.2 (0x00007f8874667000)
    libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007f88742d3000)
    libpthread.so.0 => /lib/x86_64-linux-gnu/libpthread.so.0 (0x00007f88740b4000)
    /lib64/ld-linux-x86-64.so.2 (0x00007f8874f7a000)

Solution 2:

GHC compiles Haskell to object code, with a linked runtime. That means that you do not need a Haskell compiler installed to execute Haskell programs.

The generated executable will use some variant of static and dynamic linking, for both C and Haskell library dependencies. Anything that is statically linked does not need to be installed on the user's machine. Anything that is dynamically linked must be installed.

To see what you need to ship along with the executable, on Linux (or Cygwin), use ldd. You can force static linking of almost everything by passing -static to GHC.

Solution 3:

If it's desirable to statically link some C libraries with your Haskell executable, on Linux you can use --whole-archive with the GNU linker; for example:

  ghc --make HelloZ.hs \
    -optl-Wl,--whole-archive \
      -optl/usr/lib/x86_64-linux-gnu/libffi.a \
      -optl/usr/lib/x86_64-linux-gnu/libz.a \
    -optl-Wl,--no-whole-archive

While they're quite common, libffi and libz are not ubiquitous (libffi is one that I often see in my Haskell binaries).

This approach was first suggested to me quite recently, on haskell-cafe.

Solution 4:

An installation of GHC is not required for most binaries. Some (e.g. xmonad) use Haskell as their configuration language; in those cases you will need a compiler.

There is also a question of static vs. dynamic linking. I believe the default for now is still static linking, in which case it should be quite easy to migrate a binary from one machine to the other (just need to have the same architecture and OS).