PSA: GHC 7.10, cabal, and Windows.

Posted by Michael Snoyman - 19 May, 2015

Since we've received multiple bug reports on this, and there are many people suffering from it reporting on the cabal issue, Neil and I decided a more public announcement was warranted.

There is an as-yet undiagnosed bug in cabal which causes some packages to fail to install. Packages known to be affected are blaze-builder-enumerator, data-default-instances-old-locale, vector-binary-instances, and data-default-instances-containers. The output looks something like:

Resolving dependencies...
Configuring data-default-instances-old-locale-0.0.1...
Building data-default-instances-old-locale-0.0.1...
Failed to install data-default-instances-old-locale-0.0.1
Build log ( C:\Users\gl67\AppData\Roaming\cabal\logs\data-default-instances-old-locale-0.0.1.log ):
Building data-default-instances-old-locale-0.0.1...
Preprocessing library data-default-instances-old-locale-0.0.1...
[1 of 1] Compiling Data.Default.Instances.OldLocale ( Data\Default\Instances\OldLocale.hs, dist\build\Data\Default\Instances\OldLocale.o )
C:\Users\gl67\repos\MinGHC\7.10.1\ghc-7.10.1\mingw\bin\ar.exe: dist\build\libHSdata-default-instances-old-locale-0.0.1-6jcjjaR25tK4x3nJhHHjFM.a-11336\libHSdata-default-instances-old-locale-0.0.1-6jcjjaR25tK4x3nJhHHjFM.a: No such file or directory
cabal.exe: Error: some packages failed to install:
data-default-instances-old-locale-0.0.1 failed during the building phase. The
exception was:
ExitFailure 1

There are two workarounds I know of at this time:

  • You can manually unpack and install the package which seems to work, e.g.:

    cabal unpack data-default-instances-old-locale-0.0.1
    cabal install .\data-default-instances-old-locale-0.0.1
  • Drop down to GHC 7.8.4 until the cabal bug is fixed

For normal users, you can stop reading here. If you're interested in more details and may be able to help fix it, here's a summary of the research I've done so far:

As far as I can tell, this is a bug in cabal-install, not the Cabal library. Despite reports to the contrary, it does not seem to be that the parallelization level (-j option) has any impact. The only thing that seems to affect the behavior is whether cabal-install unpacks and installs in one step, or does it in two steps. That's why unpacking and then installing works around the bug.

I've stared at cabal logs on this quite a bit, but don't see a rhyme or reason to what's happening here. The bug is easily reproducible, so hopefully someone with more cabal expertise will be able to look at this soon, as this bug has high severity and has been affecting Windows users for almost two months.


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