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1867 :: Segfault using times module with threads

• singularity (orginal) [2015-12-12T22:56:07+01:00] view original

  When compiling and running the following code (testme.nim) under Ubuntu 15.10 with the latest devel branch, I get a segfault pretty fast.

  
  import times, os
  
  var
    workerThread1: Thread[tuple[na: int]]
    workerThread2: Thread[tuple[na: int]]
  
  proc workerRun1(params: tuple[na: int]) {.thread.} =
    while true:
      let k = getDateStr()
      echo "1: ", k
      sleep(10)
  
  proc workerRun2(params: tuple[na: int]) {.thread.} =
    while true:
      let k = getDateStr()
      echo "2: ", k
      sleep(10)
  
  createThread(workerThread1, workerRun1, (na:0))
  createThread(workerThread2, workerRun2, (na:0))
  
  joinThread(workerThread1)
  joinThread(workerThread2)
  Run

  Output:

  
  2: 2015-12-12
  1: 2015-12-12
  2: 2015-12-12
  1: 2015-12-12
  2: 2015-12-12
  1: 2015-12-12
  2: 2015-12-12
  1: 2015-12-12
  1: 2015-12-12
  Traceback (most recent call last)
  testme.nim(15)           workerRun2
  times.nim(583)           getDateStr
  times.nim(444)           getLocalTime
  times.nim(403)           tmToTimeInfo
  times.nim(489)           getTzname
  SIGSEGV: Illegal storage access. (Attempt to read from nil?)
  Run

  Looking at getTzName() shows:

  
  ...
  
  var
    tzname {.importc, header: "<time.h>" .}: array[0..1, cstring]
  
  ...
  
  proc getTzname(): tuple[nonDST, DST: string] =
      return ($tzname[0], $tzname[1])
  Run

  It seems the $ operator is not thread safe. Is there any workaround I can use?

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• OderWat (orginal) [2015-12-13T00:06:34+01:00] view original

  On OS X this runs as expected with Nim current devel and 0.12.0 (since some minutes now). On a Debian Wheezy machine it crashes after some seconds for me too.

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• singularity (orginal) [2015-12-13T21:43:33+01:00] view original

  I played around a bit with getTzname() and it seems that sometimes during runtime tzname[0] or tzname[1] is nil. tzname was initialized using tzset() globally, though.

  
  var
    timezone {.importc, header: "<time.h>".}: int
    tzname {.importc, header: "<time.h>" .}: array[0..1, cstring]
  # we also need tzset() to make sure that tzname is initialized
  proc tzset() {.importc, header: "<time.h>".}
  # calling tzset() implicitly to initialize tzname data.
  tzset()
  Run

  I filed an issue on github: https://github.com/nim-lang/Nim/issues/3642

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