SEGV when running t/spec/S17-promise/start.t as part of spectest using a small nursery and MVM_GC_DEBUG = 1

gistfile1.txt

dogbert@dogbert-VirtualBox ~/repos/rakudo $ gdb install/bin/moar core_start
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Reading symbols from install/bin/moar...done.
[New LWP 18138]
[New LWP 18148]
[New LWP 18162]
[New LWP 18137]
[New LWP 18158]
[New LWP 18157]
[New LWP 18147]
[New LWP 18159]
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
Core was generated by `/home/dogbert/repos/rakudo/nqp/MoarVM/../../install/bin/moar --execname=/home/d'.
Program terminated with signal SIGSEGV, Segmentation fault.
#0  by_offset (tc=tc@entry=0x12e9280, tss=tss@entry=0x7f4770393c90, bytecode_offset=232) at src/spesh/stats.c:122
122	        if (tss->by_offset[found].bytecode_offset == bytecode_offset)
[Current thread is 1 (Thread 0x7f477871c700 (LWP 18138))]
(gdb) bt
#0  by_offset (tc=tc@entry=0x12e9280, tss=tss@entry=0x7f4770393c90, bytecode_offset=232) at src/spesh/stats.c:122
#1  0x00007f47796d50c8 in incorporate_stats (tc=tc@entry=0x12e9280, simf=0x7f477156d8e0, frame_depth=frame_depth@entry=0, caller=caller@entry=0x0, sf_updated=sf_updated@entry=0x1bc8a28)
    at src/spesh/stats.c:338
#2  0x00007f47796d5bbe in save_or_free_sim_stack (sf_updated=0x1bc8a28, save_on_tc=0x7f4768121db0, sims=0x7f477161afd0, tc=0x12e9280) at src/spesh/stats.c:502
#3  MVM_spesh_stats_update (tc=tc@entry=0x12e9280, sl=<optimized out>, sf_updated=0x1bc8a28, in_newly_seen=in_newly_seen@entry=0x7f477871bb40, in_updated=in_updated@entry=0x7f477871bb48)
    at src/spesh/stats.c:643
#4  0x00007f47796d3938 in worker (tc=0x12e9280, callsite=<optimized out>, args=<optimized out>) at src/spesh/worker.c:20
#5  0x00007f477962ce41 in thread_initial_invoke (tc=0x12e9280, data=<optimized out>) at src/core/threads.c:59
#6  0x00007f4779603e7c in MVM_interp_run (tc=0x0, tc@entry=0x12e9280, initial_invoke=0x7, invoke_data=0xe8, invoke_data@entry=0x12eb1d0) at src/core/interp.c:149
#7  0x00007f477962cec6 in start_thread (data=0x12eb1d0) at src/core/threads.c:87
#8  0x00007f4778b306ba in start_thread (arg=0x7f477871c700) at pthread_create.c:333
#9  0x00007f477915641d in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:109
(gdb) info threads
  Id   Target Id         Frame 
* 1    Thread 0x7f477871c700 (LWP 18138) by_offset (tc=tc@entry=0x12e9280, tss=tss@entry=0x7f4770393c90, bytecode_offset=232) at src/spesh/stats.c:122
  2    Thread 0x7f477504f700 (LWP 18148) 0x00007f477911b30d in nanosleep () at ../sysdeps/unix/syscall-template.S:84
  3    Thread 0x7f476e7fc700 (LWP 18162) pthread_cond_wait@@GLIBC_2.3.2 () at ../sysdeps/unix/sysv/linux/x86_64/pthread_cond_wait.S:185
  4    Thread 0x7f477a0d0700 (LWP 18137) pthread_cond_wait@@GLIBC_2.3.2 () at ../sysdeps/unix/sysv/linux/x86_64/pthread_cond_wait.S:185
  5    Thread 0x7f476f7fe700 (LWP 18158) pthread_cond_wait@@GLIBC_2.3.2 () at ../sysdeps/unix/sysv/linux/x86_64/pthread_cond_wait.S:185
  6    Thread 0x7f476ffff700 (LWP 18157) pthread_cond_wait@@GLIBC_2.3.2 () at ../sysdeps/unix/sysv/linux/x86_64/pthread_cond_wait.S:185
  7    Thread 0x7f4775850700 (LWP 18147) pthread_cond_wait@@GLIBC_2.3.2 () at ../sysdeps/unix/sysv/linux/x86_64/pthread_cond_wait.S:185
  8    Thread 0x7f476effd700 (LWP 18159) __lll_lock_wait () at ../sysdeps/unix/sysv/linux/x86_64/lowlevellock.S:135
(gdb) l
117	                                  MVMuint32 bytecode_offset) {
118	    /* See if we already have it. */
119	    MVMuint32 found;
120	    MVMuint32 n = tss->num_by_offset;
121	    for (found = 0; found < n; found++)
122	        if (tss->by_offset[found].bytecode_offset == bytecode_offset)
123	            return &(tss->by_offset[found]);
124	
125	    /* If not, we need a new record. */
126	    found = tss->num_by_offset;
(gdb)