[Tcl-bugs] [ tcl-Bugs-1160057 ] Seg fault from usleep

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Bugs item #1160057, was opened at 2005-03-09 17:49
Message generated for change (Settings changed) made by dkf
You can respond by visiting: 
https://sourceforge.net/tracker/?func=detail&atid=110894&aid=1160057&group_id=10894

Category: 47. Threading
>Group: current: 8.4.9
Status: Open
Resolution: None
Priority: 5
Submitted By: Simon White (s_a_white)
Assigned to: Andreas Kupries (andreas_kupries)
Summary: Seg fault from usleep

Initial Comment:
Am trying to determine what may be going on in tcl that
causes this code to crash.  Using a main instead of tcl
to run the code it appears to work fine.

The computer is running MandrakeLinux 10.1:

kernel: 2.6.8.1-12mdksmp
gcc: 3.4.3-1mdk
glibc: 2.3.3-21mdk
tcl: 8.4.5-6mdk

Code:

#include <stdint.h>
#include <stdio.h>
#include <pthread.h>
#include <unistd.h>
#include <tcl.h>

class Message
{
public:
   Message();
   ~Message ();
};

Message::Message() {}
Message::~Message () {}

static void *RecallTaskEntry(void *_this)
{
   Message m;
   usleep(2000000);
   return 0;
}

extern "C" int createThread() {
  pthread_t Recallthread;
  pthread_create(&Recallthread,NULL,RecallTaskEntry, 0);
  usleep (50000);
  pthread_cancel (Recallthread);
  pthread_join   (Recallthread, NULL);
  return 0;
}

int TclCreateThread (ClientData clientData, Tcl_Interp
*interp,
                     int argc,CONST84 char *argv[])
{
  createThread ();
  return TCL_OK;
}

extern "C" int Thread_Init(Tcl_Interp *interp) {
   
Tcl_CreateCommand(interp,"createThread",TclCreateThread,
0, 0);
    return TCL_OK;
}

extern "C" int Thread_SafeInit(Tcl_Interp *interp) {
   return (Thread_Init(interp));
}

Code is C++ compiled as a shared library and run in tcl
via:

load libThread.so
createThread

The observed beviour is a segfault which results from
doing a pthread_cancel when the thread is in the
usleep.  The debugger output looks a little confused
like possible stack corruption.  However as explained
it works ok standalone outside of tcl.

Things that seem to make it work are:

- Removing the Message object from the thread.
- Removing Messages destructor.
- As a test using sleep and pause instead of usleep
appear to work.

Any ideas on what is causing this bug?

----------------------------------------------------------------------

Comment By: Nobody/Anonymous (nobody)
Date: 2005-03-10 22:42

Message:
Logged In: NO 

Have updated tcl to 8.4.9 and rebuilt the code.  Ran it up
using tclsh (didn't update tk) and still the seg fault
appears.  Interestingly I tried valgrind on tclsh and get
various complaints about mallocs/free's, but the seg fault
disappeared, hmmm.

----------------------------------------------------------------------

You can respond by visiting: 
https://sourceforge.net/tracker/?func=detail&atid=110894&aid=1160057&group_id=10894