How to make C (P/invoke) code called from C# “Thread-safe”

Question

I have some simple C-code which uses a single global-variable. Obviously this is not thread-safe, so when I call it from multiple threads in C# using P/invoke, things screw up.

Answer 1

The good news, you can create a __declspec(naked) function as a member of C++ (non-CLI) class:

class A {
    int n;
public:
    A() { n = 0; }
    void f(int n1, int n2);
};

__declspec(naked) void A::f(int n1, int n2)
{
    n++;
}

The bad news, you will need COM to be able to use such class. That's right: asm wrapped in C++, wrapped in COM, wrapped in RCW, wrapped in CLR...