It is not safe to pass NULL to dlclose(). At least on unix. I cannot
imagine it is a good idea on windows either.

Index: uisimulator/common/io.c
===================================================================
RCS file: /cvsroot/rockbox/uisimulator/common/io.c,v
retrieving revision 1.28
diff -u -r1.28 io.c
--- uisimulator/common/io.c 2 Mar 2006 01:08:38 -0000 1.28
+++ uisimulator/common/io.c 11 Mar 2006 06:30:36 -0000
@@ -361,7 +361,6 @@
 #else
         DEBUGF("dlopen(%s): %s\n", path, dlerror());
 #endif
- dlclose(*pd);
         return NULL;
     }

@@ -399,7 +398,6 @@
 #else
         DEBUGF("dlopen(%s): %s\n", path, dlerror());
 #endif
- dlclose(*pd);
         return NULL;
     }

--
Will Dyson