beta page 2 - Dave's Blog

Wp64 Issues

2007 Aug 6, 3:43Miladin told me about the Visual Studio compiler's promising option Wp64 that finds 64bit portability issues when compiling in 32bit. If, for instance, you cast from a (long*) to a (long) you get a W4 warning. However, the #defines are still set for 32bit builds. This means that other parts of the code can make assumptions based on the #defines that are valid on 32bit but generate 64bit errors or warnings.

For instance, in winuser.h the public published Windows header file there's the following:

...
#ifdef _WIN64
...
WINUSERAPI
LONG_PTR
WINAPI
SetWindowLongPtrA(
    __in HWND hWnd,
    __in int nIndex,
    __in LONG_PTR dwNewLong);
...
#else  /* _WIN64 */
...
#define SetWindowLongPtrA   SetWindowLongA
...
#endif /* _WIN64 */
...

In 64bit everything's normal but in 32bit SetWindowLongPtrA is #defined to SetWindowLongA which takes a LONG rather than a LONG_PTR. So take the following code snippet:

...
LONG_PTR inputValue = 0;
LONG_PTR error = SetWindowLongPtrA(hWnd, nIndex, inputValue);
...

This looks fine but generates warnings with the Wp64 flag.

In 64 bit, p is cast to (LONG_PTR) and that's great because we're actually calling SetWindowLongPtrA which takes a LONG_PTR. In 32 bit, p is cast to (LONG_PTR) which is then implicitly cast to (LONG) because we're actually calling SetWindowLongA. LONG and LONG_PTR are the same size in 32bit which is fine but if you turn on the Wp64 flag there's a W4 warning because of the implicit cast from a larger size to a smaller size if you were to compile for 64bit. So even though doing a 32bit or 64bit compile would have worked just fine, if you turn on the Wp64 flag for 32bit you'd get an error here.

It looks like I'm the most recent in a list of people to notice this issue. Well I investigated this so... I'm blogging about it too!wp64 technical 64bit compiler c++ visual-studio setwindowlongptra

Thoughts on Polytope Tetris

2006 Nov 19, 9:25I've had a few thoughts recently on Polytope Tetris. Constructive thoughts:

• One dimensional view. It should be easy to just hack up the two dimensional view.
• Cross sectional view. I want to have a view that displays cross sections of the game space taken across one dimension all in a row. It'd be nice if this cross sectional view could use any other view to display each cross section, however I don't think the game's arch easily allows for that. Instead I may have to make it specific to the three dimensional view

Deconstructive thoughts:

• I went to the site the other day and saw that the project had an activity rating in the 90s. And this is while its still marked as Beta. I think I'm going to re-release the exact same bits under a new name and move it out of Beta or Alpha. I'll call it Platinum Edition.
• There are a number of issues with this whole project. I'm trying to get my thoughts down here.

project polytopetetris