How do I install dependencies when cross compiling haskell code?
I've successfully created a ghc cross compiler, that allows me to compile haskell code for armv6h (raspberry pi in my case) from my x64 linux machine. I've successfully run a hello world program on the raspberry.
No I want to build my real app, which has a lot of dependencies on other haskell modules. When I compile for x64 I simply do
cabal install dependenciy1 depenency2 ...
I know I could make my own programm a cabal-project an automate this step. But that's not the point here.
When I try to use the cross-compiler
arm-unknown-linux-gnueabi-ghc --make myapp.hs
It tells me about modules it could not find. Of course, they are not installed!
I read https://ghc.haskell.org/trac/ghc/wiki/Building/CrossCompiling and according to that I tried
cabal --with-ghc=arm-unknown-linux-gnueabi-ghc --with-ghc-pkg=arm-unknown-linux-gnueabi-ghc-pkg --with-ld=arm-unknown-linux-gnueabi-ld install random
random is the depenency I'm trying to install here. I get the following error:
Resolving dependencies...
Configuring random-1.0.1.3...
Failed to install random-1.0.1.3
Last 10 lines of the build log ( /home/daniel/.cabal/logs/random-1.0.1.3.log ):
/home/daniel/.cabal/setup-exe-cache/setup-Cabal-1.18.1.3-arm-linux-ghc-7.8.3.20140804: /home/daniel/.cabal/setup-exe-cache/setup-Cabal-1.18.1.3-arm-linux-ghc-7.8.3.20140804: cannot execute binary file
cabal: Error: some packages failed to install:
random-1.0.1.3 failed during the configure step. The exception was:
ExitFailure 126
When I do
file /home/daniel/.cabal/setup-exe-cache/setup-Cabal-1.18.1.3-arm-linux-ghc-7.8.3.20140804
I get
/home/daniel/.cabal/setup-exe-cache/setup-Cabal-1.18.1.3-arm-linux-ghc-7.8.3.20140804: ELF 32-bit LSB executable, ARM, EABI5 version 1 (SYSV), dynamically linked (uses shared libs), for GNU/Linux 3.10.2, not stripped
No wonder it can't execute it. It's compiled for arm.
Am I missing something here? My goal is to pull in all dependencies, then create a statically linked app that I can deploy on my raspberry.
To understand this error, you need to know how cabal install works internally. In essence, it will perform the following steps:
Setup.hs (this file is used for customization of the build system, for example, you can implement some hooks to run additional haskell code in the configure phase). setup configure <configure flags> && setup build && setup install The problem is now that cabal install uses the GHC given by --with-ghc also for step 2, but the executable produced by that step must run on the host system!
A workaround is to do the steps manually, which means you have full control. First, get the source:
$ cabal get random
Downloading random-1.0.1.3...
Unpacking to random-1.0.1.3/
$ cd random-1.0.1.3
Then, compile Setup.hs , using the host ghc:
$ ghc ./Setup.hs -o setup
And finally, configure, build and install. As suggested by @Yuras in a comment, we also add the -x option for running hsc2hs :
$ ./setup configure ----with-ghc=arm-unknown-linux-gnueabi-ghc --with-ghc-pkg=arm-unknown-linux-gnueabi-ghc-pkg --with-ld=arm-unknown-linux-gnueabi-ld --hsc2hs-options=-x
$ ./setup build && ./setup install
There is already a cabal issue about this: https://github.com/haskell/cabal/issues/2085
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