Oddity with 'cabal install' in GHC 7.4.1

Conal Elliott conal at conal.net
Sun Feb 5 08:22:25 CET 2012

Hi Andres,

Thanks for the reply! Note that I get this message even running 'cabal
install' a second time after changing nothing. Is that scenario an example
of what you mean by a "potentially dangerous cabal invocation"? I've been
unable to avoid this error message by any other means that (a) 'ghc-pkg
unregister <package>' or (b) '--force-reinstall'. So far,
'--solver=modular' hasn't helped. So I'm hoping for something less
aggressive. In particular, in case nothing has changed, I want 'cabal
install' to succeed (exit code 0) so that my automated build & install &
release processes will continue rather than get stopped.

Regards, - Conal

On Sat, Feb 4, 2012 at 9:51 PM, Andres Löh <andres.loeh at googlemail.com>wrote:

> Hi Conal.
> On Sun, Feb 5, 2012 at 12:36 AM, Conal Elliott <conal at conal.net> wrote:
> > Since upgrading to 7.4.1, if I 'cabal install' successfully and then
> 'cabal
> > install' a second time without first doing a 'ghc-pkg unregister
> > <package-name>', I get the following complaint:
> >
> > [...]
> The warning is intended to prevent you from breaking your system
> without knowing that you know that you're running a potentially
> dangerous cabal invocation.
> The --force-reinstalls flag should always make it build. If it
> doesn't, it's a bug.
> In addition, I'm planning to make the warning a little bit less
> aggressive before the release.
> > The only path I've found so far that's willing to rebuild or even say
> > nothing needs rebuilding (when nothing does) is to 'ghc-pkg unregister'
> and
> > then 'cabal install' again. I'm getting the same behavior on Red Hat 5
> and
> > Mac OS 10.6.8, both compiled from sources.
> I'd be surprised if the OS matters. But as I said, I've not yet
> encountered a situation where it wouldn't build given
> --force-reinstalls.
> Cheers,
>  Andres
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