[GHC] #3874: GHC.Exts.traceEvent segfaults

[GHC]

#3874: GHC.Exts.traceEvent segfaults
-------------------------------+--------------------------------------------
    Reporter:  cjs             |       Owner:                 
        Type:  bug             |      Status:  new            
    Priority:  normal          |   Component:  Runtime System 
     Version:  6.12.1          |    Keywords:  event, eventlog
          Os:  Linux           |    Testcase:                 
Architecture:  x86_64 (amd64)  |     Failure:  None/Unknown   
-------------------------------+--------------------------------------------
 When I call the GC.Exts.traceEvent function (argument: "hello") with event
 logging enabled (i.e., compiled with -eventlog and run with -ls) my
 program generates a segmentation fault. Here is the gdb backtrace:
 {{{
 #0  0x00007f3ad6744a2f in vfprintf () from /lib/libc.so.6
 #1  0x00007f3ad677039a in vsnprintf () from /lib/libc.so.6
 #2  0x00000000004476c4 in postLogMsg (eb=0x8160d0, type=19,
     msg=0x7f3ad5d7e010 "hello", ap=0x0) at rts/eventlog/EventLog.c:403
 #3  0x0000000000447853 in postUserMsg (cap=0x69b780,
     msg=0x7f3ad5d7e010 "hello") at rts/eventlog/EventLog.c:433
 #4  0x000000000043b012 in traceUserMsg (cap=0x69b780,
     msg=0x7f3ad5d7e010 "hello") at rts/Trace.c:290
 #5  0x000000000044e237 in stg_traceEventzh ()
 #6  0x0000000000000000 in ?? ()
 }}}
 It's not at all clear to me what could be going wrong here.

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/3874>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler