unhandled ELF relocation(RelA) type 42

[alang9]

On a machine running ubuntu 16.04 and ghc 8.0.2.

When running cabal install --only-dep -fllvm-ptx in the accelerate-examples repo, it tries to install accelerate-llvm, but fails with this error:

ghc: accelerate-examples/.cabal-sandbox/lib/x86_64-linux-ghc-8.0.2/llvm-hs-4.0.1.0-2aLaGcp4OtZ2HmPfg2V9k8/HSllvm-hs-4.0.1.0-2aLaGcp4OtZ2HmPfg2V9k8.o: unhandled ELF relocation(RelA) type 42

ghc: unable to load package `llvm-hs-4.0.1.0'
cabal: Leaving directory '/tmp/cabal-tmp-25178/accelerate-llvm-1.0.0.0'

In contrast, running stack build seems to work fine

[tmcdonell]

I guess this is related to #369? Probably cabal isn't applying the -fshared-llvm flag again, whereas it is (presumably) explicit in your stack.yaml file?

[tmcdonell]

Otherwise this is presumably GHC#12147 which should be in GHC-8.0.2 (?).

[alang9]

I confirmed that it's applying the -fshared-llvm flag.

From ghc-pkg --package-db=.cabal-sandbox/x86_64-linux-ghc-8.0.2-packages.conf.d describe llvm-hs:

hs-libraries: HSllvm-hs-4.0.1.0-2aLaGcp4OtZ2HmPfg2V9k8
extra-libraries:
    stdc++ LLVM-4.0

[tmcdonell]

Hm, I'm not sure what cabal might be doing differently to stack; maybe this is a cabal bug?

It could be worth trying cabal [new-]build --with-gcc $GCC --ghc-options "-pgmc=${GCC}", where $GCC points to a recent version (>=5 ?).

-v2 might also have useful information.

[alang9]

so far I've been able to reproduce the error on 2 machines running ubuntu 16.04, but I failed to reproduce it on 3 machines running 14.04.

Also, if I use cabal install -j 1, the error doesn't occur either.

When running with --verbose=3, the output around the error looks like this:

*** gcc:
/usr/bin/gcc -fno-stack-protector -DTABLES_NEXT_TO_CODE -B[...]/accelerate-examples/.cabal-sandbox/lib/x86_64-linux-ghc-8.0.2/llvm-hs-4.0.1.0-2
aLaGcp4OtZ2HmPfg2V9k8 -B/usr/lib/llvm-4.0/lib --print-file-name 'libstdc++.so'
*** gcc:
/usr/bin/gcc -fno-stack-protector -DTABLES_NEXT_TO_CODE -B[...]/accelerate-examples/.cabal-sandbox/lib/x86_64-linux-ghc-8.0.2/llvm-hs-4.0.1.0-2
aLaGcp4OtZ2HmPfg2V9k8 -B/usr/lib/llvm-4.0/lib --print-file-name 'liblibstdc++.so'
Loading package llvm-hs-4.0.1.0 ... linking ... ghc: [...]/accelerate-examples/.cabal-sandbox/lib/x86_64-linux-ghc-8.0.2/llvm-hs-4.0.1.0-2aLaGcp4OtZ2HmPfg2V9k8/HSllvm-hs-4.0.1.0-2aLaGcp4OtZ2HmPfg2V9k8.o: unhandled ELF relocation(RelA) type 42

[tmcdonell]

paging @cocreature, who may be interested as this seems to involve llvm-hs (though I have no idea what the root cause is)

[cocreature]

I don’t know what’s could be causing the error (apart from the things fixed in 8.0.2) but here are a few things that might be interesting:

1. Try cloning the llvm-hs repository and build everything in there including the tests (that’s basically equivalent to building executables that link against llvm-hs so linker errors should appear there as well).
2. What’s the output of gcc --version, cabal --version, llvm-config --version and ghc --version?
3. Can you reproduce the error using cabal new-build?
4. Can you provide instructions on how to reproduce this (ideally for a clean docker image of 16.04). In particular, how did you install LLVM, ghc and cabal?

[tmcdonell]

guessing this is fixed now or no longer relevant with llvm-5? please reopen if you have further problems.