How do you separate global data running in different threads of TestStand

Question

I have created a DLL which I want to call from multiple threads of TestStand. I also need to have some global data that is local to each thread. VC++ allows me to use the declaration:
__declspec(thread) int foo
to create "Thread Local Storage"
(ie global data that is local in the each thread -- not shared between threads).
This works fine from a VC++ application, but when I try to access data declared with this from Test Stand I get the following error.
Win32error code 998 - Invalid access to memory location
This occurs when I try to set a variable declared using this convention in my DllMain function.
I get a -17502; System Level Exception when I access it from a function that I call in the DL
L.

Answer 1

Russell -
I found the following comment in Microsoft's MSDN and I know that TestStand dynamically loads DLLs:
If a DLL declares any nonlocal data or object as __declspec( thread ), it can cause a protection fault if dynamically loaded. After the DLL is loaded withLoadLibrary, it causes system failure whenever the code references the nonlocal __declspec( thread ) data. Because the global variable space for a thread is allocated at run time, the size of this space is based on a calculation of the requirements of the application plus the requirements of all of the DLLs that are statically linked. When you use LoadLibrary, there is no way to extend this space to allow for the thread local variables declared with __declspec( thread ). Use the TLS APIs, such as
TlsAlloc, in your DLL to allocate TLS if the DLL might be loaded with LoadLibrary.
Scott Richardson (NI)
Scott Richardson
National Instruments