Re: PSA: GHC can now be built with Clang

Please make sure that all bugs are reported back to the Clang devs. They are usually very fast in fixing them. I assume that the ${CPP} is in traditional mode? Cheers, Gabor On 6/19/13, Carter Schonwald wrote:

Awesome!

I'm actually hitting another CPP bug right now in building ghc head with clang head, also I'll reach out to an apple dude i know to find out if we can get any help from them on this or the related TLS issue.

On Wed, Jun 19, 2013 at 12:44 AM, Austin Seipp wrote:

...

Hi all,

As of commit 5dc74f it should now be possible to build a working stage1 and stage2 compiler with (an extremely recent) Clang. With some caveats.

You can just do:

$ CC=/path/to/clang ./configure --with-gcc=/path/to/clang $ make

I have done this work on Linux. I don't expect much difficulty on Mac OS X, but it needs testing. Ditto with Windows, although Clang/mingw is considered experimental.

The current caveats are:

* The testsuite will probably fail everywhere, because of some warnings that happen during the linking phase when you invoke the built compiler. So the testsuite runner will probably be unhappy. Clang is very noisy about unused options, unlike GCC. That needs to be fixed somewhere in DriverPipeline I'd guess, but with some refactoring. * Some of the stage2 libraries don't build due to a Clang bug. These are vector/primitive/dph so far. * There is no buildbot or anything to cover it.

You will need a very recent Clang. Due to this bug (preventing primitive etc from building,) you'll preferably want to use an SVN checkout from about 6 hours ago at latest:

http://llvm.org/bugs/show_bug.cgi?id=16363

Hilariously, this bug was tripped on primitive's Data.Primitive.Types module due to some CPP weirdness. But even with a proper bugfix and no segfault, it still fails to correctly parse this same module with the same CPP declarations. I'm fairly certain this is another bug in Clang, but I might be wrong. I'm trying to isolate it. Unfortunately Clang/LLVM 3.3 was just released and it won't see bugfix releases. But it will *probably* work if we just get rid of the CPP tomfoolery in primitive. I'll be testing it in the next few days to see if we can get 3.3 supported. (I'm sort of kicking myself in the head for not doing this a week or two ago...)

Anyway, there are some rough edges but it should be in shape for 7.8 I hope. It should be especially welcome for Mac users. (I'm also hoping modern Macs could even go all-clang-all-the-time if my fix for #7602 can go in soon...)

PS. If you use ASSERT, I just fixed a lot of instances of using that macro, involving whitespace between the name and arguments (commit d8ee2b.) Clang does not forgive you for this. Should I note this anywhere for the future in the wiki or something?

-- Regards, Austin - PGP: 4096R/0x91384671

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