id,summary,reporter,owner,description,type,status,priority,milestone,component,version,severity,resolution,keywords,cc,lang,patch,platform
956,Singleton PMCs with the active_destroy flag set cause segfaults when collected,darbelo,,"Here's an example dynpmc, called SegFaulty, drop the attached .pmc into src/dynpmcs/ and add it to the Makefile there (a simple s/dynlexpad/segfaulty/g should suffice) to build it. Parrot will segfault when the pmc is collected.

Not setting PObj_active_destroy_SET(SELF) on the PMC avoids the segfault.

As an example:

{{{
$ pwd
/home/darbelo/parrot/trunk/src/dynpmc
$ cat example.pir
.sub segfault :main
    $P0 = loadlib 'segfaulty'
    $P1 = new ""SegFaulty""

    say 'Nothing wrong here.'

.end
$ ../../parrot example.pir
Nothing wrong here.
Segmentation fault (core dumped) 

}}}

Examining that core dump with gdb yields the following backtrace:
{{{
(gdb) bt
#0  0x00000002050f61f0 in ?? ()
#1  0x00000002079a9395 in Parrot_pmc_destroy (interp=0x20178a400, pmc=0x20b5042d0) at src/pmc.c:113
#2  0x000000020795b24c in free_pmc_in_pool (interp=0x20178a400, pool_unused=0x202d35b00, 
    p=0x20b5042d0) at src/gc/mark_sweep.c:781
#3  0x000000020795a68d in Parrot_gc_sweep_pool (interp=0x20178a400, pool=0x202d35b00)
    at src/gc/mark_sweep.c:342
#4  0x0000000207959715 in gc_ms_finalize (interp=0x20178a400, arena_base=0x202d35400)
    at src/gc/gc_ms.c:234
#5  0x00000002079594f7 in gc_ms_mark_and_sweep (interp=0x20178a400, flags=4) at src/gc/gc_ms.c:160
#6  0x0000000207956c3d in Parrot_gc_mark_and_sweep (interp=0x20178a400, flags=4) at src/gc/api.c:805
#7  0x0000000207968e99 in Parrot_really_destroy (interp=0x20178a400, exit_code_unused=0, 
    arg_unused=0x0) at src/interp/inter_create.c:350
#8  0x0000000207947734 in Parrot_exit (interp=0x20178a400, status=0) at src/exit.c:91
#9  0x0000000000400ecf in main (argc=1, argv=0x7f7ffffddfc8) at src/main.c:65
}}}
",bug,closed,normal,,GC,trunk,medium,fixed,gc segfault dynpmcs,,,,all