GHC 4.04 Mini-FAQ

This page lists known problems for the 4.04 release with workarounds.

• Linking a program causes the following error on Linux:

     /usr/bin/ld: cannot open -lgmp: No such file or directory
  

  The problem is that your system doesn't have the GMP library installed. If this is a RedHat distribution, install the RedHat-supplied gmp-devel package, and the gmp package if you don't already have it. There have been reports that installing the RedHat packages also works for SuSE (SuSE don't supply a shared gmp library).

• My program fails with

      fatal error: No threads to run!  Deadlock?
  

  The primary cause of this message is trying to use trace at the same time as writing to stdout or stderr (eg. putStr (trace "foo" "bar") will illustrate the error). The problem is caused by overzealous locking in our I/O library, but we don't have a complete fix at this time. A workaround is to start your program like this:

      main = seq stderr $ do ...
  

  This allows you to trace while writing to stdout, but tracing while writing to stderr will still cause a deadlock.