[GHC] #8935: Obscure linker bug leads to crash in GHCi

[GHC]

#8935: Obscure linker bug leads to crash in GHCi
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        Reporter:  simonmar          |            Owner:  simonmar
            Type:  bug               |           Status:  patch
        Priority:  high              |        Milestone:  7.8.3
       Component:  Runtime System    |          Version:  7.8.1-rc2
      Resolution:                    |         Keywords:
Operating System:  Unknown/Multiple  |     Architecture:  Unknown/Multiple
 Type of failure:  GHCi crash        |       Difficulty:  Rocket Science
       Test Case:                    |       Blocked By:
        Blocking:                    |  Related Tickets:
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Comment (by dagit):

 Great and thanks for the examples!

 By the way, weak not making a difference is the other half of the point I
 wanted to make :) I'm glad we're on the same page. I feel like I've
 learned something useful that I can use elsewhere.

 You might also look at `RTLD_DEEPBIND` for doing the initial symbol match
 up (when you use `RTLD_LOCAL`). I can't be certain, but I think it may
 help when reloading a shared object (presumably with new definitions
 inside). As far as I can tell, that option was added specifically for uses
 like this (I found some mailing list threads about it). I suspect the
 point with that option is that it allows consistent behavior even if
 something you don't have control over passes `RTLD_GLOBAL` to `dlopen`. My
 prediction is that if you switch to using `RTLD_LOCAL`, then you won't
 need `RTLD_DEEPBIND` in 99% of cases.

 Also, I played with `RTLD_NEXT`, to see if I could locate the last symbol
 loaded, but I couldn't figure out when I had reached the end and I also
 wasn't able to lookup the symbol in the executable that way. I wish I
 understood what they mean by next.

 Thanks!

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8935#comment:38>
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