ghc passing -undef to preprocessor and thereby eliminating OS specific defines

Simon Marlow marlowsd at
Thu Jan 24 14:18:45 CET 2013

On 24/01/13 11:21, Nathan Hüsken wrote:
> Hey,
> I am trying to adapt some code in the libraries when compiling for
> android (i.E. because some things are different on android to other
> posix systems).
> So in C code I would just do "#ifdef __ANDROID__".
> While in the *.h and *.c files it seems to work, it does not work in
> *.hs files.
> I noted that the preprocessor is run like this:
> arm-linux-androideabi-gcc -E -undef -traditional -fno-stack-protector
> The "-undef" parameter is causing the __ANDROID__ define to be removed.
> Does it make sense to pass "-undef" to the preprocessor?
> Any other Ideas how I could adapt the code for android?

You want to use:

   #ifdef android_HOST_OS

the *_HOST_OS symbol is defined by GHC when it ivokes CPP.


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