faq_404.shtml

---
title: GHC 4.04 Mini-FAQ
---

<h2>GHC 4.04 Mini-FAQ</h2>

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

<ul>
   <li>Linking a program causes the following error on Linux:
<pre>
   /usr/bin/ld: cannot open -lgmp: No such file or directory
</pre>
  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).
  </li><p>

  <li><p>My program fails with
<pre>
    fatal error: No threads to run!  Deadlock?
</pre>
  The primary cause of this message is trying to use <tt>trace</tt> at
  the same time as writing to <tt>stdout</tt> or <tt>stderr</tt>
  (eg. <tt>putStr (trace "foo" "bar")</tt> 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:
<pre>
    main = seq stderr $ do ...
</pre>
  This allows you to trace while writing to <tt>stdout</tt>, but
  tracing while writing to stderr will still cause a deadlock.
  </li>
</ul>