SeqContextCVI - do I need it for every test?

Question

Assum there are 5 tests in the TS sequence.
Assume that each of the test requires access to the TS.
Question: Does every test has a different handle? and if so, I guess I must "handle" it to the CVI via a parameter like:
void __declspec(dllexport) __stdcall testNumLimit(CAObjHandle seqContextCVI, double *measurement,
char reportText[1024], short *errorOccurred, long *errorCode, char errorMsg[1024])
Will it work if I only do it in the first test, store the seqContextCVI as a global veriable and use it in the other 4 tests?
Thanks
Rafi

Answer 1

Rafi -
ActiveX/COM objects are reference counted, i.e. when the last reference to the object is released, the object is destoyed (memory deallocated).
In CVI, an CAObjHandle represents a reference to an object. When TestStand creates a CAObjHandle parameter to pass to a code module, CVI adds a COM reference to the object. When TestStand releases the CAObjHandle using CA_DiscardObjHandle, CVI releases the reference.
In a code module, if you want to maintain a handle that is passed to you and the caller releases what they pass, you must get your own CAObjHandle using the CVI function CA_DuplicateObjHandle. You are also expected to properly and timely call CA_DiscardObjHandle on the new CAObjHandle when it is no longer needed so the
object can be destroyed correctly, otherwise you have the potential for a memory leak because objects are no being released.
The problem with placing the object in a global is that you need to make sure that the release is done. If you are expecting a step later in the sequence to do it, what happens if the step is not called because of a error or a termination in the sequence?
Scott Richardson (NI)
Scott Richardson
National Instruments