ASan barfage during an HTTP::Server::Async run

gistfile1.txt

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==3058==ERROR: AddressSanitizer: heap-use-after-free on address 0x61600026c210 at pc 0x7fdac63de134 bp 0x7fdabe9c75f0 sp 0x7fdabe9c75e0
READ of size 8 at 0x61600026c210 thread T3
    #0 0x7fdac63de133 in MVM_interp_run src/core/interp.c:846
    #1 0x7fdac646c7a3 in start_thread src/core/threads.c:64
    #2 0x7fdac6679276 in uv__thread_start 3rdparty/libuv/src/unix/thread.c:49
    #3 0x344f207529 in start_thread (/lib64/libpthread.so.0+0x344f207529)
    #4 0x344ef0022c in __clone (/lib64/libc.so.6+0x344ef0022c)

0x61600026c210 is located 144 bytes inside of 640-byte region [0x61600026c180,0x61600026c400)
freed by thread T3 here:
    #0 0x7fdac6e1754f in __interceptor_free (/lib64/libasan.so.1+0x5754f)
    #1 0x7fdac64a0b02 in MVM_free src/core/alloc.h:29
    #2 0x7fdac64a1a60 in MVM_fixed_size_free src/core/fixedsizealloc.c:178
    #3 0x7fdac644e530 in MVM_frame_dec_ref src/core/frame.c:104
    #4 0x7fdac652e3ad in gc_free src/6model/reprs/MVMCode.c:70
    #5 0x7fdac64c0555 in MVM_gc_collect_free_nursery_uncopied src/gc/collect.c:549
    #6 0x7fdac64b031a in run_gc src/gc/orchestrate.c:308
    #7 0x7fdac64b09db in MVM_gc_enter_from_allocator src/gc/orchestrate.c:408
    #8 0x7fdac64b1032 in MVM_gc_allocate_nursery src/gc/allocation.c:32
    #9 0x7fdac64b1188 in MVM_gc_allocate_zeroed src/gc/allocation.c:49
    #10 0x7fdac64b1605 in MVM_gc_allocate_object src/gc/allocation.c:85
    #11 0x7fdac64f45a1 in MVM_repr_alloc_init src/6model/reprconv.c:13
    #12 0x7fdac660e572 in MVM_string_substring src/strings/ops.c:252
    #13 0x7fdac63e8a51 in MVM_interp_run src/core/interp.c:1335
    #14 0x7fdac646c7a3 in start_thread src/core/threads.c:64
    #15 0x7fdac6679276 in uv__thread_start 3rdparty/libuv/src/unix/thread.c:49

previously allocated by thread T3 here:
    #0 0x7fdac6e177c7 in malloc (/lib64/libasan.so.1+0x577c7)
    #1 0x7fdac64a0a29 in MVM_malloc src/core/alloc.h:2
    #2 0x7fdac64a17e3 in MVM_fixed_size_alloc src/core/fixedsizealloc.c:136
    #3 0x7fdac64a1810 in MVM_fixed_size_alloc_zeroed src/core/fixedsizealloc.c:144
    #4 0x7fdac64501eb in allocate_frame src/core/frame.c:306
    #5 0x7fdac6451622 in MVM_frame_invoke src/core/frame.c:441
    #6 0x7fdac652cfc7 in invoke_handler src/6model/reprs/MVMCode.c:10
    #7 0x7fdac1aec4a2 (+0x24a2)
    #8 0x7fdac66034c3 in MVM_jit_enter_code src/jit/compile.c:123
    #9 0x7fdac643d5eb in MVM_interp_run src/core/interp.c:4804
    #10 0x7fdac646c7a3 in start_thread src/core/threads.c:64
    #11 0x7fdac6679276 in uv__thread_start 3rdparty/libuv/src/unix/thread.c:49

Thread T3 created by T0 here:
    #0 0x7fdac6de3dba in pthread_create (/lib64/libasan.so.1+0x23dba)
    #1 0x7fdac66792bf in uv_thread_create 3rdparty/libuv/src/unix/thread.c:66

SUMMARY: AddressSanitizer: heap-use-after-free src/core/interp.c:846 MVM_interp_run
Shadow bytes around the buggy address:
  0x0c2c800457f0: fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd
  0x0c2c80045800: fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd
  0x0c2c80045810: fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd
  0x0c2c80045820: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c2c80045830: fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd
=>0x0c2c80045840: fd fd[fd]fd fd fd fd fd fd fd fd fd fd fd fd fd
  0x0c2c80045850: fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd
  0x0c2c80045860: fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd
  0x0c2c80045870: fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd
  0x0c2c80045880: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c2c80045890: fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd
Shadow byte legend (one shadow byte represents 8 application bytes):
  Addressable:           00
  Partially addressable: 01 02 03 04 05 06 07 
  Heap left redzone:       fa
  Heap right redzone:      fb
  Freed heap region:       fd
  Stack left redzone:      f1
  Stack mid redzone:       f2
  Stack right redzone:     f3
  Stack partial redzone:   f4
  Stack after return:      f5
  Stack use after scope:   f8
  Global redzone:          f9
  Global init order:       f6
  Poisoned by user:        f7
  Contiguous container OOB:fc
  ASan internal:           fe
==3058==ABORTING