SIGSEV with `try` and `closure` iterators

[Graveflo]

Nim Version

latest devel

Description

This is as far as I have been able to isolate the issue:

import std/[asyncdispatch]

proc blahAsync() {.async.} =
  try:
    await sleepAsync(1)
  finally:
    discard

try:
  try:
    raise newException(ValueError, "")
  finally:
    waitFor blahAsync()
except:
  discard

edit: seems to have nothing to do with unittest

for some reason the finally in blahAsync causes something strange to happen.

Current Output

Traceback (most recent call last)
/usr/lib/nim/lib/pure/asyncfutures.nim(162) nimscraps
SIGSEGV: Illegal storage access. (Attempt to read from nil?)

Expected Output

Unhandled exception:  [ValueError]
  [FAILED] something

Known Workarounds

re-raise in blahAsync works but that is impractical

Additional Information

No response

[Graveflo]

seems to be something wrong with the bare execpt too. If the outermost except is changed to finally it doesn't SIGSEV, but does not raise an exception. If the finally in blahAsync is changed to bare except it still fails.

edit: actually things like except ValueError also cause the bug... further:

import std/[asyncdispatch]

proc blahAsync() {.async.} =
  try:
    await sleepAsync(1)
  finally:
    discard

try:
  raise newException(ValueError, "")
finally:
  waitFor blahAsync()

does not raise an exception at all, so it's gotta be something with async ??

[Graveflo]

okay. I was able to eliminate asyncdispatch by reducing the expanded macro code. Looks like closure iterators might be involved

iterator someit(): int {.closure.} =
  try:
    yield 1
  finally:
    discard

try:
  raise newException(ValueError, "")
except:
  for x in someit():
    discard

maybe related to #24978

[yglukhov]

Fixed in #25030