[GHC] #11234: GHCi on Windows segfaults

[GHC]

#11234: GHCi on Windows segfaults
----------------------------------------+-------------------------------
           Reporter:  Phyx-             |             Owner:  Phyx-
               Type:  bug               |            Status:  new
           Priority:  high              |         Milestone:  8.0.1
          Component:  Runtime System    |           Version:  7.11
           Keywords:                    |  Operating System:  Windows
       Architecture:  Unknown/Multiple  |   Type of failure:  GHCi crash
          Test Case:                    |        Blocked By:
           Blocking:                    |   Related Tickets:
Differential Rev(s):                    |         Wiki Page:
----------------------------------------+-------------------------------
 GHCi on Windows has had a segfault for while now on `x86_64`. During the
 upgrade of `GCC` in Phab:D1123 I noticed that test `prog003` was failing
 with a segfault.

 Currently the segfault exist in both versions but on `x86` it's
 particularly easy to trigger.

 In my case I can't even start ghci.

 {{{
 $ inplace/bin/GHC-stage2.exe --interactive
 GHCi, version 7.11.20151213: http://www.haskell.org/ghc/  :? for help
 Segmentation fault/access violation in generated code
 }}}

 The segfault does not seem to happen when linked to the debug rts, and
 running with `+RTS -Ds -RTS` doesn't report anything special.

 Compiling with `devel2` so the rts gets compiled with `-g` the stack trace
 is not very useful.

 {{{
 (gdb) run --interactive
 Starting program: /home/Tamar/ghc/inplace/bin/ghc-stage2 --interactive
 [New Thread 108480.0x1960c]
 [New Thread 108480.0x19b2c]
 [New Thread 108480.0x19c30]
 [New Thread 108480.0x1a0a8]
 [New Thread 108480.0x1a93c]
 [New Thread 108480.0x13954]
 [New Thread 108480.0x14440]
 GHCi, version 7.11.20151213: http://www.haskell.org/ghc/  :? for help

 Program received signal SIGSEGV, Segmentation fault.
 0x06843aa5 in ?? ()
 (gdb) bt
 #0  0x06843aa5 in ?? ()
 #1  0x04b82cfc in ?? ()
 #2  0x8d078902 in ?? ()
 #3  0xc689fd47 in ?? ()
 #4  0xff04c583 in ?? ()
 #5  0x83c70065 in ?? ()
 #6  0x0000033c in ?? ()
 #7  0x00000008 in ?? ()
 #8  0x04e9c689 in ?? ()
 Backtrace stopped: Cannot access memory at address 0x47c70cc8
 }}}

 And the output of `p4`

 {{{
 (gdb) p4 0x06843aa5
 0x6843ab0:      0x330073
 0x6843aac:      0x790073 <c1CgU_info+131>
 0x6843aa8:      0x6d005c <c1rsa_info+715>
 0x6843aa4:      0x3a0045
 }}}

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11234>
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