[GHC] #3: DiffArray should be instance of Show

[GHC]

#3: DiffArray should be instance of Show
--------------------------+--------------------
  Reporter:  magunter     |      Owner:  nobody
      Type:  bug          |     Status:  closed
  Priority:  normal       |  Milestone:
 Component:  hslibs/lang  |    Version:  5.0
Resolution:  Fixed        |   Keywords:
--------------------------+--------------------

Comment (by Sergei Trofimovich <siarheit@…>):

 In [changeset:"74897dece3ea92139b552bd711903ce630956df3/ghc"
 74897dec/ghc]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="74897dece3ea92139b552bd711903ce630956df3"
 Make rts/ThreadLabels.c threadsafe for debug runtime.

 rts/ThreadLabels.c has a global hashtable for each
 running haskell thread. It's not synchronized across
 OS threads.

 Was discovered when ran -debug build of ghc itself as:

     $ ghc-stage2 -j8 +RTS -A256M -l

 and glibc detected double-free corruption:

     #2  in __libc_message (do_abort=do_abort at entry=2,
         fmt=fmt at entry=0x7fe0bcebf368 "*** Error in `%s': %s: 0x%s ***\n")
     #3  in malloc_printerr (action=3, str=0x7fe0bcebf4c0 "double free or
 corruption (fasttop)",
         ptr=<optimized out>)
     #4  in _int_free (av=<optimized out>, p=<optimized out>, have_lock=0)
     #5  in stgFree (p=0x7fe060001820) at rts/RtsUtils.c:108
     #6  in freeHashTable (table=0x5929320, freeDataFun=0x36374df
 <stgFree>) at rts/Hash.c:360
     #7  in freeThreadLabelTable () at rts/ThreadLabels.c:37
     #8  in hs_exit_ (wait_foreign=rtsFalse) at rts/RtsStartup.c:403
     #9  in shutdownHaskellAndExit (n=0, fastExit=0) at
 rts/RtsStartup.c:481
     #10 in hs_main (...) at rts/RtsMain.c:91
     #11 in main (...) at ghc/hschooks.c:63

 Exposed itself after commit:

 > commit f6866824ce5cdf5359f0cad78c49d65f6d43af12
 > Author: Sergei Trofimovich <slyfox at gentoo.org>
 > Date:   Mon Aug 4 08:10:33 2014 -0500
 >
 >     ghc --make: add nicer names to RTS threads (threaded IO manager,
 make workers)

 Signed-off-by: Sergei Trofimovich <siarheit at google.com>

 Reviewers: austin, simonmar, ezyang, bgamari

 Reviewed By: ezyang, bgamari

 Subscribers: thomie

 Differential Revision: https://phabricator.haskell.org/D1146
 }}}

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/3#comment:2>
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