Re: shared variable

[Fernando Nasser <fnasser at cygnus dot com>]

Nicolas Vignal wrote:
> 
> Hello
> 
> I know that shared variable must be lock. But behaviour of software under
> debugger and reality should be the same. 

Not really.  There is timing involved and debuggers introduce "artifact".  Results can be unpredictably different.




> If you try this little code under
> the last linux gdb snapshot you will see a difference.
> 
> On console I have :
> 
> I create the thread number 1026
> I am the thread number 1026
> 
> Under gdb :
> 
> I am the thread number -1
> I create the thread number 1026
> 
> Regards
> 
>         Nicolas
> 
> #include <stdio.h>
> #include <pthread.h>
> 
> pthread_t threadID=-1;
> 
> int function(void)
> {
>   printf("I am the thread number %d\n",threadID);
> 
>   while (1);
> 
>   return 0;
> }
> 
> int main(int argc, char *argv[])
> {
> 
>   pthread_create(&threadID, NULL, function, NULL);
>   printf("I create the thread number %d\n",threadID);
> 
>   return 0;
> }

-- 
Fernando Nasser
Red Hat - Toronto                       E-Mail:  fnasser@redhat.com
2323 Yonge Street, Suite #300
Toronto, Ontario   M4P 2C9