Re: [Haskell-cafe] OS X ghci problem

On Sat, Jul 13, 2013 at 5:32 PM, Anthony Cowley wrote:

On Jul 13, 2013, at 8:04 PM, Jason Dagit wrote:

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On Sat, Jul 13, 2013 at 4:39 PM, Mark Lentczner wrote:

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Bizarre - this just happened to me today, too. Anyone? Did you figure out a work around? For the record, I'm trying to bring Euterpea up.

After some digging, experimenting, asking around, and head scratching my best guesses are:

* GHCi's custom linker isn't doing the right thing (some versions of llvm/clang gave crashes like this and it was a linker bug for them, you can find reports on sites like StackOverflow). * We need to feed .m files to clang instead of ghc/gcc * GHCi needs to be built with Cocoa in mind (is it already?) * Some rts component of objective-c is not properly initialized (ARC vs. -fobjc-gc vs. -fnext-step, etc)

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My system is OS X 10.8.4, and I'm running HP 2013.2, so 7.6.3. And GLFW-0.5.1.0.

In terms of experimentation, you can hand desugar the objective-c code in the GLFW init and when I do that I get segfaults. Also, the address mentioned in the objective-c exception has a suspicious value, which would further implicate the linker. Add to that, it works for a compile program (which uses the system linker, IIRC).

Basically, I'm pretty sure it's GHCi's linker to blame here but I don't have a smoking gun.

Jason

I thought I'd had some success desugaring the Objective-C code, but I never went the whole way, so perhaps I just didn't get to the segfault. What I do for GLFW is use a dylib, then you don't rely on GHCi's static-ish linker. The only wrinkle is figuring out where you want the dylib. I think homebrew will put one in /usr/local/lib, which works out nicely, but they don't have GLFW 3 yet. Another option is to build the dylib yourself from the GLFW source bundled with the GLFW-b package, then tell cabal where to find it.

Thanks. It hadn't occurred to me that the previous packaging had better success precisely because it built a dylib first.

It's worth the trouble, as having a GHCi-based workflow for graphics work is wonderful. A fancy Setup.hs that works out installation paths could generate the dylib, and I thought such code existed in the past. Was some problem found with that approach?

Yes, I wrote the Setup.hs/Makefile in the previous GLFW-b version that built glfw as a dylib. The problem is that Hackage no longer accepts that packaging because it doesn't like the extra-lib-dirs. Working around the (somewhat) arbitrary constraints that cabal/hackage imposes is rather annoying. There is no "trust me, this package works" option. It just assumes that a relative path in extra-lib-dirs can never work and rejects the package upload :( Jason