I want to P/Invoke to GetWindowLongPtr and SetWindowLongPtr, and I'm seeing conflicting information about them.
Some sources say that, on 32-bit platforms, GetWindowLongPtr is just a preprocessor macro that calls GetWindowLong, and GetWindowLongPtr doesn't exist as an entry point in user32.dll. For example:
- The pinvoke.net entry for SetWindowLongPtr has a static method that checks IntPtr.Size and then calls either SetWindowLong or SetWindowLongPtr, with a comment saying that "legacy OSes do not support SetWindowLongPtr". There's no explanation of what is meant by "legacy OSes".
- An answer on StackOverflow states "On 32bit systems GetWindowLongPtr is just a C macro that points to GetWindowLong".
So these sources seem to indicate that the *Ptr entry points simply aren't there in the version of user32.dll that ships with, say, 32-bit Windows 7.
But I see no indication of this in the MSDN documentation. According to MSDN, SetWindowLongPtr supersedes SetWindowLong, plain and simple. And according to the requirements section of the SetWindowLongPtr page, it appears that SetWindowLongPtr has been in user32.dll since Windows 2000 (both client and server editions). Again, no mention of the entry points being missing in 32-bit OSes.
I suspect that the truth is somewhere in between: that when you tell the C++ compiler to target older OSes (i.