[darcs-users] fromJust error in darcs-2.0.0

[Gwern Branwen]

On 2008.04.22 22:50:49 -0600, Greg Holtz <gh2377 at hotmail.com> scribbled 6.3K characters:
>    Hello,
>    That was a fast response!
>    I tried compiling with both --disable-optimize and --disable-mmap
>    (hints I got from the darcs.net binaries page under Solaris), but it
>    doesn't resolve this issue.
>
>    Unfortunately, I cannot volunteer the machine as a buildbot since
>    it's a work machine. However, I'm more than willing to compile things
>    and report my findings or bugs to help the community.
>
>    Is there any way to get more detailed information about the nature
>    of the error?

Depends on how much work you're willing to do.

# The best thing to do would be to run darcs in GHCi and use the breakpoint debugger to figure things out exactly. This is impossible to do. :)
# The second best thing to do would be to compile with profiling (--enable-profile); this is very painful as every library needs to be compiled for profiling (it can be done - I did it - but it's not pleasant or common). This is useful because you can then pass the RTS system an option to give a stack trace when it crashes, which would tell you the exact function and is half the battle.
# Third best would be to strace darcs and pore over its entrails. I doubt this would do much good.
# Fourth best would be to tediously narrow things down by editing in various calls to Debug.trace to sort of manually do a back-trace. As I and another discovered applying this technique to a ByteString-related crash, this is a very tedious task.

--
gwern
WWSP ASVC ISG Intiso Blenheim Operation intelsat 5.0i r00t 20
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