RE: Multithreading with C++

[Colovic (ext_evosoft) Aleksandar]

Hi, 

try declaring threadfun as class static function : void* 
CThread::threadfun(void* arg)
Attached is the working code. I built it with make cthread.cpp LDFLAGS=-lpthread


Cheers



-----Original Message-----
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Behalf Of Huber, George K 
RDECOM CERDEC STCD SRI
Sent: Donnerstag, 7. April 2005 19:02
To: linux-c-programming@vger.kernel.org
Subject: Multithreading with C++


All,

This may be a little off topic, but I though I would try here first.

I am writting a multi-threaded program and would like to have each 
thread `managed' by a class.  I have attempted to do this like this,
using the pthreads library:

<code>
====================begin cthread.h

class CThread
{
public:
    CThread(void*);
    ~CThread();

    ....

private:
    static CThread*     m_pThis;
    pthread_t             m_tid;
    static void*           threadfun(void*);

   ....
}

==================== begin cthread.cpp

CThread*  CThread::m_pThis = NULL;

CThread::CThread(void* arg)
{
    int      ret;

    m_pThis = this;
    if(0 != (ret = pthread_create(&m_tid, NULL, threadfun, arg)))
    {
         fprintf(stderr, "Thread creation failed");
   }
}   

void*  threadfun(void* arg)
{
     printf("Starting thread\n");
     ....
}

</code>

The code compiles without warnings or errors, except when I try and 
run the application I get a segmentation fault at the pthread_create.  
Trying to run under GDB, I am able to examine the value of the 
variables and they seem consisten with what I would expect

// stop on the pthread_create line in the constructor...

(gdb) print m_pThis
$1 = (CThread*) 0xfee756b0
(gdb) print this
$2 = (CThread*0xfee756b0
(gdb) print m_tid
$3 = 134514818               // to be expected because I have not initialized 
m_tid yet
(gdb) print &m_tid
$4 = (pthread_t*)0xfee756d8
(gdb) print threadfun
$5=&CThread::threadfun(void*)

// attempt the pthread_create line ....

Program received signal SIGSEGV, Segmenatation fault
0x0000000 in ?? ()
(gdb) where 
#0 0x00000000 in ?? ( )
#1 0x0804a6bb in CThread (this=0xfee756b0, args=0x0) at ....
#2 0x08049aad in daemon_main(argc=3, argv=0xfeec42d4) at ....
#3 0x08049193 in main(argc=3, argv=0xfeec42d3) at main.cpp: 83

Any idea on what is going on, or how to fix?

Thanks, 
George Huber

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cthread.h
Description: cthread.h

cthread.cpp
Description: cthread.cpp