darcs: internal error: update_fwd: unknown/strange object 57

[Simon Marlow]

David F. Place wrote:
> Trying to get the sources as instructed on the developer wiki:
> 
> /usr/local/bin/darcs get --partial http://darcs.haskell.org/ghc
> This is the GHC darcs repostory (HEAD branch)
> 
> For more information, visit the GHC developer wiki at
>   http://hackage.haskell.org/trac/ghc
> **********************
> darcs: internal error: update_fwd: unknown/strange object  57
>     Please report this as a bug to glasgow-haskell-bugs at haskell.org,
>     or http://www.sourceforge.net/projects/ghc/
> 
> I get this error using a version of darcs I downloaded from darwinports:
> 
> /opt/local/bin/darcs --version
> 1.0.5 (release)
> 
> and a precompiled binary which I downloaded from
> http://cbis.anu.edu.au/misc/darcs/
> 
> /usr/local/bin/darcs --version
> 1.0.6 (stable branch)
> 
> I am using MAC OS  X 10.4

This bug was fixed recentliy:

ghc/rts/GCCompact.c:
----------------------------
revision 1.24.6.4
date: 2005-12-02 16:17:41 +0000;  author: simonmar;  state: Exp;  lines: 
+1 -0
thread_obj: add missing case for FOREIGN (STABLE only; FOREIGN is gone
in the HEAD)

This accounts for crashes of the form "update_fwd: unknown/strange
object 57", which you might see if you run darcs with +RTS -c.
----------------------------

You need to ask your supplier of darcs binaries to use a 6.4.2 snapshot, 
or wait for the 6.4.2 release.

I'm not sure why in your case darcs is using the compacting collector. 
The compacting collector is turned off by default unless you explicitly 
request it using +RTS options, or the GHC_RTS environment variable.  I 
checked the darcs sources, and it doesn't appear to modify any RTS 
options that would enable compaction.  Do you have GHC_RTS set?

Cheers,
	Simon