Re: Multithreading with C++

[Ron Michael Khu <ronkhu@ntsp.nec.co.jp>]

i've encountered a similar problem a few months ago...
have u tried declaring AND defining the threadfun() function OUTSIDE of 
the class??


Huber, George K RDECOM CERDEC STCD SRI wrote:

>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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>
>  
>