I tried 9.4.4 (haven't tried the new PR yet) and it still occurs:
bt
#0 heapCensusBlock (bd=0x42664029c0, census=0x4ea6ba0) at rts/ProfHeap.c:1110
#1 heapCensusChain (census=census@entry=0x4ea6ba0, bd=0x42664029c0) at rts/ProfHeap.c:1277
#2 0x00000000034defb3 in heapCensus (t=t@entry=59661024641) at rts/ProfHeap.c:1310
#3 0x00000000034ff54e in GarbageCollect (collect_gen=<optimized out>, collect_gen@entry=1,
do_heap_census=do_heap_census@entry=true, is_overflow_gc=is_overflow_gc@entry=true,
deadlock_detect=deadlock_detect@entry=false, gc_type=gc_type@entry=2, cap=cap@entry=0x4e915b0,
idle_cap=<optimized out>) at rts/sm/GC.c:968
#4 0x00000000034e8ecc in scheduleDoGC (pcap=pcap@entry=0x7f517f7fddd0, task=task@entry=0x7f5194000bc0,
force_major=force_major@entry=false, is_overflow_gc=<optimized out>,
deadlock_detect=deadlock_detect@entry=false) at rts/Schedule.c:1859
#5 0x00000000034e9a9f in schedule (initialCapability=initialCapability@entry=0x4e4a200,
task=task@entry=0x7f5194000bc0) at rts/Schedule.c:580
#6 0x00000000034eb1fc in scheduleWorker (cap=cap@entry=0x4e4a200, task=task@entry=0x7f5194000bc0)
at rts/Schedule.c:2644
#7 0x00000000034eff16 in workerStart (task=0x7f5194000bc0) at rts/Task.c:444
#8 0x00007f51a843cb43 in start_thread (arg=<optimized out>) at ./nptl/pthread_create.c:442
#9 0x00007f51a84cea00 in clone3 () at ../sysdeps/unix/sysv/linux/x86_64/clone3.S:81
Maybe a different error then, if 9.4 is still crashing?
I've encountered this segfault as well (or at least a similar one) on 9.2.5, running a program with "-hc". Backtrace:
(gdb) bt
#0 heapCensusBlock (bd=0x4248e00800, census=0x3169ae0) at rts/ProfHeap.c:1099
#1 heapCensusChain (census=census@entry=0x3169ae0, bd=0x4248e00800) at rts/ProfHeap.c:1267
#2 0x0000000002011413 in heapCensus (t=t@entry=35268392127) at rts/ProfHeap.c:1300
#3 0x0000000002018ac9 in GarbageCollect (collect_gen=<optimized out>, collect_gen@entry=1, do_heap_census=do_heap_census@entry=true,
is_overflow_gc=is_overflow_gc@entry=true, deadlock_detect=deadlock_detect@entry=false, gc_type=gc_type@entry=2,
cap=cap@entry=0x3157be0, idle_cap=<optimized out>) at rts/sm/GC.c:967
#4 0x000000000200a959 in scheduleDoGC (pcap=pcap@entry=0x7f3fb4ff8dd0, task=task@entry=0x7f3f98000bc0,
force_major=force_major@entry=false, is_overflow_gc=<optimized out>, deadlock_detect=deadlock_detect@entry=false)
at rts/Schedule.c:1860
#5 0x000000000200b3dd in schedule (initialCapability=initialCapability@entry=0x313e370, task=task@entry=0x7f3f98000bc0)
at rts/Schedule.c:579
#6 0x000000000200c32c in scheduleWorker (cap=cap@entry=0x313e370, task=task@entry=0x7f3f98000bc0) at rts/Schedule.c:2645
#7 0x0000000002005ed7 in workerStart (task=0x7f3f98000bc0) at rts/Task.c:445
#8 0x00007f3fe015db43 in start_thread (arg=<optimized out>) at ./nptl/pthread_create.c:442
#9 0x00007f3fe01efa00 in clone3 () at ../sysdeps/unix/sysv/linux/x86_64/clone3.S:81