[Haskell-cafe] To LLVM or not to LLVM...

Heinrich Apfelmus apfelmus at quantentunnel.de
Wed Jan 29 09:55:19 UTC 2014

Ian Ross wrote:
>> A Cabal flag for the same purpose might make sense, IMHO, if there are
>> other build parameters that change when compiling with LLVM (like CPP
>> defines, etc.), but it's my understanding that this is not the case?
> Right.  I think I'll add a Cabal flag and worry about the reverse
> dependencies issue if the package ever has any!

You can specify a cabal flag to be switched on by default. Cabal will 
then switch off the flag automatically if it cannot satisfy the constraints.

So, if you can add a dependency on the LLVM tools in the 
"extra-libraries" field or elsewhere, you can use this automatic flag 
assignment to compile the LLVM version for people who already have the 
LLVM tools installed.

(Note that last time I checked, cabal will not try to download new 
packages in order to fulfill the constraints, though.)

Best regards,
Heinrich Apfelmus


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