[Haskell-cafe] strange ghc output

[Thomas Schilling]

2008/10/27 Dougal Stanton <dougal at dougalstanton.net>:

> This happens when, for example, your code imports a library which was
> compiled with a previous version of bytestring. Replacing bytestring
> on its own isn't enough to solve the problem. To make things more
> awkward, it could be several libraries which use the old bytestring.
> Using "ghc --make", it seems this error can be ignored, but it's
> annoying if you want to use the interactive GHC.

The problem is GHCi's linker.  It cannot deal with duplicate symbols,
while 'ld' can.  I know of no workaround to get it to work, though.
You could try to hide the new bytestring, so that ghci doesn't find
it.  FWIW, 6.10.1 will come with a recent version of bytestring, so
separately upgrading should no longer be necessary.