[GHC] #12009: ASSERTION FAILED: file rts/LdvProfile.c, line 48

[GHC]

#12009: ASSERTION FAILED: file rts/LdvProfile.c, line 48
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        Reporter:  erikd             |                Owner:  erikd
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:  8.0.2
       Component:  Compiler          |              Version:  7.10.3
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  Runtime crash     |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by erikd):

 The following patch prevents the crash, but may result in in-correct heap
 profiling results:

 {{{#!diff
 diff --git a/rts/LdvProfile.c b/rts/LdvProfile.c
 index 1dfdc56..43a47aa 100644
 --- a/rts/LdvProfile.c
 +++ b/rts/LdvProfile.c
 @@ -184,7 +184,14 @@ processNurseryForDead( void )
      for (bd = MainCapability.r.rNursery->blocks; bd != NULL; bd =
 bd->link) {
          p = bd->start;
          while (p < bd->free) {
 +            // The start of the block may be zero filled which we need to
 skip
 +            // over.
              while (p < bd->free && !*p) p++; // skip slop
 +
 +            // In debug mode, with sanity checking enabled, start of the
 block
 +            // may be filled with `0xaa` so if we find it, we just break.
 +            IF_DEBUG(sanity, if (*((StgWord32*)p) == 0xaaaaaaaa) break;);
 +
              if (p >= bd->free) break;
              p += processHeapClosureForDead((StgClosure *)p);
          }
 }}}

 Maybe we could print a warning about inaccuracey if debug sanity checking
 is on in profiling mode.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12009#comment:5>
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