In Visual C++4.2, the Standard C++ header files contained a typedef that equated bool with int. In Visual C++ 5.0 and later, bool is implemented as a built-in type with a size of 1 byte. That means that for Visual C++ 4.2, a call of sizeof(bool) yields 4, while in Visual C++ 5.0 and later, the same call yields 1. This can cause memory corruption problems if you have defined structure members of type bool in Visual C++ 4.2 and are mixing object files (OBJ) and/or DLLs built with the 4.2 and 5.0 or later compilers.
The __BOOL_DEFINED macro can be used to wrap code that is dependent on whether or not bool is supported.
I'm currently having problems with memory access violations when passing a ctypes.wintypes.BOOL to a DLL and I wouldn't be surprised if it's because I'm passing 4 bytes when it's expecting 1 byte.