It's on your hard drive. The call chain to where they are used in the kernel is about 5 functions deep, in xxxSetWindowData:
Originally Posted by CommonTater
If they were used as offsets, you wouldn't check for each one individually.
mov eax, [ebp+arg_4] ; where the index argument is on the stack
cmp eax, 0FFFFFFEBh ; GWLP_USERDATA
cmp eax, 0FFFFFFECh ; GWL_EXSTYLE
cmp eax, 0FFFFFFF0h ; GWL_STYLE
cmp eax, 0FFFFFFF4h ; GWLP_ID
cmp eax, 0FFFFFFF8h ; GWLP_HWNDPARENT
cmp eax, 0FFFFFFFAh ; GWLP_HINSTANCE
cmp eax, 0FFFFFFFCh ; GWLP_WNDPROC
jz short loc_BF8B3F64
; and this for everything else
push offset aSetwindowlongI ; "SetWindowLong: Invalid index 0x%x"