The question about the callbackdata parameter in the function PostDeferredCallToThread()

[David_Lee]

I find if using a local variable to pass to the PostDeferredCallToThread(), then in the callback function, it cannot be recevied correctly. But as NI document said, this variable is a user-defined, will avoid declaring the data object as a global variable. how to interpret the question?

David

[ebalci]

If you provide a pointer to the function the variable pointed by the pointer must be still in memory if you want to access it from that thread function.
One way of keeping the variable "alive" when you leave the scope of a function is to define it as static.

Dynamically allocated memory (malloc/calloc) is also accessible if not freed.
Suggested reading:
http://gribblelab.org/CBootcamp/7_Memory_Stack_vs_Heap.html

[David_Lee]

That also be the 'GLOBAL' .

[ebalci]

Sure, global variables can be used.

But I did not mention it since you asked how you can avoid the global variable.