multithread with egcs/(C++) and RedHat 5.0

["Torbjörn Eriksson" <pt96ter@palantir.proj.ide.hk-r.se>]

[-- Warning: decoded text below may be mangled, UTF-8 assumed --]
[-- Attachment #1: Type: text/plain, Size: 2735 bytes --]

Hello,

First of all, I apologize if this question shouldn't bee here at all.
I'm quite new at programming threads, so I don't really know if this
problem is related to egcs at all.

Background: We're 4 students working on a project at University of
Karlskrona-Ronneby i southern Sweden. We decided to develop our project
in C++ on a Linux box, (RedHat 5.0). After doing some research we found
out that gcc ver. 2.7.2 doesn't work with threads, and that egcs would.

Our problem is that system calls like readdir_r and localtime_r causes
segmention faults, this is a printout from gdb.

#0  0x4004c93c in __pthread_mutex_lock () at mutex.c:135
#1  0x4004e28c in __fresetlockfiles () at lockfile.c:87
#2  0x400a7053 in _IO_fread (buf=0xbffff7a0, size=44, count=1,
fp=0x804e250)
    at iofread.c:44
#3  0x400c546e in __tzfile_compute (timer=1074773704,
    use_localtime=1074807804, leap_correct=0xbffff860,
leap_hit=0xbffff8cc)
    at tzfile.c:283
#4  0x400c4413 in tzset_internal () at tzset.c:197
#5  0x400c518c in __tz_convert () at tzset.c:561
#6  0x400c1c2f in localtime (t=0xbffff8cc) at localtime.c:49
#7  0x8048f1c in ThreadClass::Notify () at ThreadClass.cc:103
#8  0x8048e48 in ThreadClass::ScanDir (this=0x804c1d0) at
ThreadClass.cc:66
#9  0x8048daa in ThreadClass::Listen (this=0x804c1d0) at
ThreadClass.cc:44
#10 0x8048bfe in main () at main.cc:23

I do'nt know, but I suspect that we might start the thread in an illegal
way

pthread_t
ThreadClass::Run()
{
  pthread_attr_init(&myThreadAttr);
  pthread_attr_setscope(&myThreadAttr, PTHREAD_SCOPE_SYSTEM);

  if (pthread_create(&myThread, &myThreadAttr, SpawnThread, this)==0)
    {
      return myThread;
    }else
      return (0);
}

// this one is declared as static void* in ThreadClass.hh
//  ThreadClass::Listen is a ordinary member function returning void*

void*
ThreadClass::SpawnThread(void* arg)
{
  return (((ThreadClass *) arg)->Listen());
}

Listen memberfunction just sleeps for a while and then it calls ScanDir
that does a readdir_r on a directory, when a file is found it calls
Notify with the filename

void
ThreadClass::Notify(char* filename)
{
  struct stat sbuf;
  struct tm   tptr;

  if (!lstat(filename, &sbuf))
    {
      localtime_r(&(sbuf.st_mtime), &tptr);
    }
}

In localtime_r, the program causes a segm. fault

We have installed
gcc version egcs-2.90.27 980315 (egcs-1.0.2 release)
and the prerequisits that the rpm asked for.

We will be very grateful for any help or suggestions, and, once again,
I'm sorry if  this question doesn't belong here, but after browsing
through this mail archive and searching the net, it seemed to be a good
place to start.

Thorbjörn Eriksson
pt96ter@student.hk-r.se
pt96ter@palantir.proj.ide.hk-r.se