Async memory leak when raising exception on ORC

Description

It seems there is a mem leak when raising exceptions from an async proc.

The command I ran:

$ nim c -d:danger --mm:orc --debugger:native --threads:off -d:useMalloc bug.nim && valgrind --leak-check=full --show-leak-kinds=all ./bug

import std/asyncdispatch

proc err {.async.} =
  raise newException(ValueError, "err1")
  #discard

proc amain {.async.} =
  await sleepAsync(1)
  try:
    await err()
  except ValueError:
    discard

proc main() =
  waitFor amain()

main()
doAssert not hasPendingOperations()
setGlobalDispatcher(nil)
GC_fullCollect()
echo "ok"

Nim Version

git hash: 2c8551556e5b51b7a7e487b1043b92d4ad34dbf0 active boot switches: -d:release

Current Output

Hint: mm: orc; opt: speed; options: -d:danger
63095 lines; 2.754s; 87.977MiB peakmem; proj: /home/esteban/AtomProjects/crap/bug.nim; out: /home/esteban/AtomProjects/crap/bug [SuccessX]
==145078== Memcheck, a memory error detector
==145078== Copyright (C) 2002-2017, and GNU GPL'd, by Julian Seward et al.
==145078== Using Valgrind-3.18.1 and LibVEX; rerun with -h for copyright info
==145078== Command: ./bug
==145078== 
ok
==145078== 
==145078== HEAP SUMMARY:
==145078==     in use at exit: 136 bytes in 2 blocks
==145078==   total heap usage: 19 allocs, 17 frees, 113,298 bytes allocated
==145078== 
==145078== 56 bytes in 1 blocks are indirectly lost in loss record 1 of 2
==145078==    at 0x484DCD3: realloc (in /usr/libexec/valgrind/vgpreload_memcheck-amd64-linux.so)
==145078==    by 0x10CC5F: _ZN6system11reallocImplE7pointer25range09223372036854775807 (malloc.nim:17)
==145078==    by 0x10CC5F: _ZN6system14alignedReallocE7pointer25range0922337203685477580725range0922337203685477580725range09223372036854775807 (memalloc.nim:383)
==145078==    by 0x10CC5F: prepareSeqAddUninit (seqs_v2.nim:121)
==145078==    by 0x10D697: _ZN6system3addE3varI3seqIN6system15StackTraceEntryEEE4sinkIN6system15StackTraceEntryEE (seqs_v2.nim:161)
==145078==    by 0x10D697: raiseExceptionEx (excpt.nim:504)
==145078==    by 0x1184E8: amain::amainX20X28AsyncX29_ (asyncmacro.nim:170)
==145078==    by 0x117297: amain::amainNimAsyncContinue (asyncmacro.nim:35)
==145078==    by 0x1188D0: bug::amain (asyncmacro.nim:293)
==145078==    by 0x118ADE: _ZN3bug4mainE (bug.nim:15)
==145078==    by 0x118ADE: NimMainModule (bug.nim:17)
==145078==    by 0x10A3F5: NimMainInner (asyncfutures.nim:234)
==145078==    by 0x10A3F5: NimMain (asyncfutures.nim:245)
==145078==    by 0x10A3F5: main (asyncfutures.nim:253)
==145078== 
==145078== 136 (80 direct, 56 indirect) bytes in 1 blocks are definitely lost in loss record 2 of 2
==145078==    at 0x484DA83: calloc (in /usr/libexec/valgrind/vgpreload_memcheck-amd64-linux.so)
==145078==    by 0x10CF3A: _ZN6system10alloc0ImplE25range09223372036854775807 (malloc.nim:11)
==145078==    by 0x10CF3A: _ZN6system13alignedAlloc0E25range0922337203685477580725range09223372036854775807 (memalloc.nim:353)
==145078==    by 0x10CF3A: nimNewObj (arc.nim:96)
==145078==    by 0x117507: _ZN3err18errX20X28AsyncX29_E (asyncfutures.nim:211)
==145078==    by 0x117507: err::errX20X28AsyncX29_ (asyncmacro.nim:250)
==145078==    by 0x116FAA: err::errNimAsyncContinue (asyncmacro.nim:33)
==145078==    by 0x118230: bug::err (asyncmacro.nim:293)
==145078==    by 0x118434: amain::amainX20X28AsyncX29_ (bug.nim:10)
==145078==    by 0x11725A: amain::amainNimAsyncContinue (asyncmacro.nim:33)
==145078==    by 0x1188D0: bug::amain (asyncmacro.nim:293)
==145078==    by 0x118ADE: _ZN3bug4mainE (bug.nim:15)
==145078==    by 0x118ADE: NimMainModule (bug.nim:17)
==145078==    by 0x10A3F5: NimMainInner (asyncfutures.nim:234)
==145078==    by 0x10A3F5: NimMain (asyncfutures.nim:245)
==145078==    by 0x10A3F5: main (asyncfutures.nim:253)
==145078== 
==145078== LEAK SUMMARY:
==145078==    definitely lost: 80 bytes in 1 blocks
==145078==    indirectly lost: 56 bytes in 1 blocks
==145078==      possibly lost: 0 bytes in 0 blocks
==145078==    still reachable: 0 bytes in 0 blocks
==145078==         suppressed: 0 bytes in 0 blocks
==145078== 
==145078== For lists of detected and suppressed errors, rerun with: -s
==145078== ERROR SUMMARY: 1 errors from 1 contexts (suppressed: 0 from 0)

Expected Output

No leaks

Possible Solution

No response

Additional Information

Valgrind does not show leaks when trying in Nim 1.6.20

nim-lang / Nim