How do I call SetWindowLong() in the 64-bit versions of Windows?

Question

In the header file WinUser.h, there is a part in which the constants of the second parameter of SetWindowLong() are defined.

// ...

#define GWL_WNDP         


        

Answer 1

Also make sure you're NOT defining the following:

#define NOWINOFFSETS

which makes GWL_*, GCL_*, ie. GetWindowLongPtr and family, as well as associated routines available.