Converting Win16 C code to Win32

Question

In general, what needs to be done to convert a 16 bit Windows program to Win32? I'm sure I'm not the only person to inherit a codebase and be stunned to find 16-bit code lurking in the corners.

The code in question is C.

Answer 1

The original win32 sdk had a tool that scanned source code and flagged lines that needed to be changed, but I can't remember the name of the tool.

When I've had to do this in the past, I've used a brute force technique - i.e.: 1 - update makefiles or build environment to use 32 bit compiler and linker. Optionally, just create a new project in your IDE (I use Visual Studio), and add the files manually.

2 - build

3 - fix errors

4 - repeat 2&3 until done

The pain of the process depends on the application you are migrating. I've converted 10,000 line programs in an hour, and 75,000 line programs in less than a week. I've also had some small utilities that I just gave up on and rewrote (mostly) from scratch.

Answer 2

I agree with Alan that trial and error is probably the best way.

Here are some good tips.

Answer 3

Agreed that the compiler will probably catch most of the errors. Also, if you are using "near" and "far" pointers you can remove those designations -- a pointer is just a pointer in Win32.

Answer 4

Apart from getting your build environment right, Here are few specifics you will need to address:

1. structs containing ints will need to change to short or widen from 16 to 32 bits. If you change the size of the structure and this is loaded/saved to disk you will need write data file upgrade code.

2. Per window data is often stored with the window handle using GWL_USERDATA. If you widen some of the data to 32 bits, your offsets will change.

3. POINT & SIZE structures are 64 bits in Win32. In Win16 they were 32 bits and could be returned as a DWORD (caller would split return value into two 16 bit values). This no longer works in Win32 (i.e. Win32 does not return 64 bit results) and the functions were changed to accept a pointers to store the return values. You will need to edit all of these. APIs like GetTextExtent are affected by this. This same issue also applies to some Windows messages.

4. The use of INI files is discouraged in Win32 in favour of the registry. While the INI file functions still work you will need to be careful with Vista issues. 16 bit programs often stored their INI file in the Windows system directory.

This is just a few of the issues I can recall. It has been over a decade since I did any Win32 porting. Once you get into it it is quite quick. Each codebase will have its own "feel" when it comes to porting which you will get used to. You will probably even find a few bugs along the way.

Answer 5

There's a definitive guide in the article Porting 16-Bit Code to 32-Bit Windows on MSDN.