Visual C++ :: Can Two Functions In Same DLL Be Called By Two Threads?

I write a DLL MyDLL.dll with Visual C++ 2008, as follows:

(1)MFC static linked
(2)Using multi-thread runtime library.

In the DLL, this is a global data m_Data shared by two export functions, as follows:

ULONGLONG WINAPI MyFun1(LPVOID *lpCallbackFun1) {
...
Write m_Data(using Critical section to protect)

[Code]....

Although MyThread1 and MyThread2 using critical section to protect the shared data m_Data, I will still suspend MyThread1 before accessing the shared data, to prevent any possible conflicts.

The problem is:

(1)When the first invoke of MyFun2, everything is OK, and the return value of MyFun2(that is nResult2) is 1 , which is expected.

(2)When the second, third and fourth invoke of MyFun2, the operations in MyFun2 are executed successfully, but the return value of MyFun2(that is nResult2) is a random value instead of the expected value 1. I try to using Debug to trace into MyFun2, and confirm that the last return statement is just return a value of 1, but the invoker will receive a random value instead of 1 when inspecting nResult2.

(3)After the fourth invoke of MyFun2 and return back to the next statement follow MyFun2, I will always get a "buffer overrun detected" error, whatever the next statement is.

I think this looks like a stack corruption, so try to make some tests:

1.I confirm the /GS (Stack security check) feature in the compiler is ON.

2.If MyFun2 is invoked after MyFun1 in MyThread1 is completed, then everything will be OK.

3.In debug mode, the codeline in MyFun2 that reads the shared data m_Data will not cause any errors or exceptions. Neither will the codeline in MyFun1 that writes the shared Data.