Re: variable scope in threads
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
static Multi_Queue *test1;
abc = test1->getXXX(); // no link error
// create worker threads
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.
Only if all of the code (main thread & worker threads)
is in ONE source file.
You declared 'test1' as 'static', so it is NOT global;
it's only visible within the source file where it
One (of several) solutions might look like this:
// in main.cpp
// in worker.cpp
extern Multi_Queue *test1;
When main.cpp & worker.cpp are compiled and then
Linked together, code in 'worker.cpp' will have
access to 'test1'.
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