[GHC] #14346: 8.2.1 regression: heap corruption after safe foreign calls

[GHC]

#14346: 8.2.1 regression: heap corruption after safe foreign calls
-------------------------------------+-------------------------------------
        Reporter:  andrewchen        |                Owner:  (none)
            Type:  bug               |               Status:  infoneeded
        Priority:  highest           |            Milestone:
       Component:  Runtime System    |              Version:  8.2.1
      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 andrewchen):

 I managed to do a `rr` capture with `--chaos` mode.

 Here's the part in main where it does the comparison:
 {{{
 0x404581 <Main_main1_info+361>  mov    ecx,DWORD PTR [rax]
 0x404583 <Main_main1_info+363>  cmp    rcx,rbx                       //
 compares value with 0xDEADBEEF
 0x404586 <Main_main1_info+366>  jne    0x40443c <Main_main1_info+36> //
 goes to print "value mismatch"
 }}}
 {{{
 (rr) p/x $rcx
 $22 = 0x1
 (rr) p/x $rbx
 $23 = 0xdeadbeef
 (rr) p/x $rax
 $24 = 0x42000b7540
 }}}

 Putting a watch point on the the memory address and reverse continuing
 leads to this:
 {{{
 Old value = 1
 New value = -559038737
 0x0000000000470b42 in base_GHCziEventziPoll_new5_info ()
 => 0x0000000000470b42 <base_GHCziEventziPoll_new5_info+1218>:   49 89 04
 24     mov    QWORD PTR [r12],rax
 }}}
 {{{
 (rr) p/x $r12
 $27 = 0x42000b7540
 }}}

 Not sure what's going on there, but I hope this is of some help.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14346#comment:10>
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