druntime thread (from foreach parallel?) cleanup bug

[mw]

My program received signal SIGSEGV, Segmentation fault.

Its simplified structure looks like this:

```
void foo() {
   ...
   writeln("done");  // saw this got printed!
}

int main() {
   foo();
   return 0;
}

```

So, just before the program exit, it failed. I suspect druntime 
has a thread (maybe due to foreach parallel) cleanup bug 
somewhere, which is unrelated to my own code. This kind of bug is 
hard to re-produce, not sure if I should file an issue.

I'm using: LDC - the LLVM D compiler (1.30.0) on x86_64.


Under gdb, here is the threads info (for the record):

Thread 11 "xxx" received signal SIGSEGV, Segmentation fault.
[Switching to Thread 0x1555553df700 (LWP 36258)]
__GI___res_iclose (free_addr=true, statp=0x1555553dfdb8) at 
res-close.c:103
103     res-close.c: No such file or directory.


(gdb) info threads
   Id   Target Id         Frame
   1    Thread 0x155555515000 (LWP 36244) "lt" 0x0000155550af1d2d 
in __GI___pthread_timedjoin_ex (threadid=23456246527744, 
thread_return=0x0, abstime=0x0, block=<optimized out>) at 
pthread_join_common.c:89
* 11   Thread 0x1555553df700 (LWP 36258) "lt" __GI___res_iclose 
(free_addr=true, statp=0x1555553dfdb8) at res-close.c:103
   17   Thread 0x155544817700 (LWP 36264) "lt" 0x0000155550afac70 
in __GI___nanosleep (requested_time=0x155544810e90, 
remaining=0x155544810ea8) at 
../sysdeps/unix/sysv/linux/nanosleep.c:28


(gdb) thread 1
[Switching to thread 1 (Thread 0x155555515000 (LWP 36244))]
#0  0x0000155550af1d2d in __GI___pthread_timedjoin_ex 
(threadid=23456246527744, thread_return=0x0, abstime=0x0, 
block=<optimized out>) at pthread_join_common.c:89
89      pthread_join_common.c: No such file or directory.
(gdb) where
#0  0x0000155550af1d2d in __GI___pthread_timedjoin_ex 
(threadid=23456246527744, thread_return=0x0, abstime=0x0, 
block=<optimized out>) at pthread_join_common.c:89
#1  0x0000555555fb94f8 in 
core.thread.osthread.joinLowLevelThread(ulong) ()
#2  0x0000555555fd7210 in 
_D4core8internal2gc4impl12conservativeQw3Gcx15stopScanThreadsMFNbZv ()
#3  0x0000555555fd3ae7 in 
_D4core8internal2gc4impl12conservativeQw3Gcx4DtorMFZv ()
#4  0x0000555555fd3962 in 
_D4core8internal2gc4impl12conservativeQw14ConservativeGC6__dtorMFZv ()
#5  0x0000555555fc2ce7 in rt_finalize2 ()
#6  0x0000555555fc0056 in rt_term ()
#7  0x0000555555fc0471 in 
_D2rt6dmain212_d_run_main2UAAamPUQgZiZ6runAllMFZv ()
#8  0x0000555555fc0356 in _d_run_main2 ()
#9  0x0000555555fc01ae in _d_run_main ()
#10 0x0000555555840c02 in main (argc=2, argv=0x7fffffffe188) at 
//home/zhou/project/ldc2-1.30.0-linux-x86_64/bin/../import/core/internal/entrypoint.d:42
#11 0x0000155550163b97 in __libc_start_main (main=0x555555840be0 
<main>, argc=2, argv=0x7fffffffe188, init=<optimized out>, 
fini=<optimized out>, rtld_fini=<optimized out>, 
stack_end=0x7fffffffe178)
     at ../csu/libc-start.c:310
#12 0x00005555556dccca in _start ()


(gdb) thread 11
[Switching to thread 11 (Thread 0x1555553df700 (LWP 36258))]
#0  __GI___res_iclose (free_addr=true, statp=0x1555553dfdb8) at 
res-close.c:103
103     res-close.c: No such file or directory.
(gdb) where
#0  __GI___res_iclose (free_addr=true, statp=0x1555553dfdb8) at 
res-close.c:103
#1  res_thread_freeres () at res-close.c:138
#2  0x00001555502de8c2 in __libc_thread_freeres () at 
thread-freeres.c:29
#3  0x0000155550af0700 in start_thread (arg=0x1555553df700) at 
pthread_create.c:476
#4  0x0000155550263a3f in clone () at 
../sysdeps/unix/sysv/linux/x86_64/clone.S:95


(gdb) thread 17
[Switching to thread 17 (Thread 0x155544817700 (LWP 36264))]
#0  0x0000155550afac70 in __GI___nanosleep 
(requested_time=0x155544810e90, remaining=0x155544810ea8) at 
../sysdeps/unix/sysv/linux/nanosleep.c:28
28      ../sysdeps/unix/sysv/linux/nanosleep.c: No such file or 
directory.
(gdb) where
#0  0x0000155550afac70 in __GI___nanosleep 
(requested_time=0x155544810e90, remaining=0x155544810ea8) at 
../sysdeps/unix/sysv/linux/nanosleep.c:28
#1  0x0000555555fb8c3b in 
_D4core6thread8osthread6Thread5sleepFNbNiSQBo4time8DurationZv ()
#2  0x0000555555d9a0c2 in 
_D4hunt4util8DateTimeQj25_sharedStaticCtor_L406_C5FZ9__lambda4MFZv () at home/zhou/.dub/packages/hunt-1.7.16/hunt/source/hunt/util/DateTime.d:430
#3  0x0000555555fb89f4 in thread_entryPoint ()
#4  0x0000155550af06db in start_thread (arg=0x155544817700) at 
pthread_create.c:463
#5  0x0000155550263a3f in clone () at 
../sysdeps/unix/sysv/linux/x86_64/clone.S:95