random crash caused by createThread

[kvinwang]

proc testCreateThread(): Thread[int] =
  createThread(result, proc(a: int) = discard, 0)

let t = testCreateThread()
t.joinThread()

Crashes without any hint.

In threads.nim

    if pthread_create(t.sys, a, threadProcWrapper[TArg], addr(t)) != 0:

it use the addr(t) directly. so it has problem if t is on stack.

[genotrance]

Works fine on Windows, crashes on Linux.

[timotheecour]

so the problem is indeed that pthread_create(t.sys, a, threadProcWrapper[TArg], addr(t)) != 0: consumes a stack address that gets invalidated, and nim doesn't flag this as illegal. Thread already has =copy disabled with {.error.} but that's unrelated and doesn't prevent this.

possible solution: use escape analysis, refs #14976 to detect this and at least issue a warning.

[Varriount]

so the problem is indeed that pthread_create(t.sys, a, threadProcWrapper[TArg], addr(t)) != 0: consumes a stack address that gets invalidated, and nim doesn't flag this as illegal. Thread already has =copy disabled with {.error.} but that's unrelated and doesn't prevent this.

possible solution: use escape analysis, refs #14976 to detect this and at least issue a warning.

Can you explain a bit more?

[Araq]

createThread is a sharp tool and you cannot use it in this way.

[kvinwang]

createThread is a sharp tool and you cannot use it in this way.

I don't think this is a responsible answer.

[Araq]

Too bad.