variable scope/access in threads

Sat, 24 Mar 2007 20:16:53 CST
{ Please confine replies, as far as possible, to std C++. -mod/aps }

Hi All,

I have a question on the scope of variables for threads. The program
has a main thread which creates a few worker threads. The main thread
can access another class stored in another file, however, the worker
threads can't. I got link errors for the code inside of the worker
threads. The following contains code segments.

Multi_Queue is a class and getXXX() is a public member function inside
of Multi_Queue which is in another file.

// inside of the main thread
//global data
static Multi_Queue *test1;

int abc;
abc = test1->getXXX(); // no link error

// create worker threads
for (i=0;i<numWorker;i++)
       x = pthread_create(&workers[i], NULL, &workerThread, NULL);


// This is the worker thread
void *workerThread(void *inPtr)
int xyz = test1->getXXX(); // link error on getXXX

My question is why there is no link error in the main thread but in
the worker thread it has. A global variable, in this case
Multi_Queus, created in the main thread should be available in other
threads. Appreciate any insights.


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