C++ issues with Windows UAC

Question

I have a software written in C++ installed in some 1000 PC which is having some difficulties with windows UAC. I'm trying to make things work properly but I would need some help to understand the problem and find correct solution.

Situation is as follows: I need to write some data in some text / xml files, so I started (in XP) to write them in the executable folder. Not recommended, I know. When Vista kicked in, all files started being saved to the VirtualStore folder, which was fine for me, so I left things untouched. I had some issues back then with a couple of users (see problem 1) but I fixed them by hand and that was it. Now with Windows 8 I'm facing different problems (problem 2) and I want to fix them properly once and for all.

1. First problem: with Windows Vista it happened that some users eventually found their software "empty", as it was when just installed. All their work on it was gone. It turned out that suddendly Vista was looking for their files in C:\Program Files\{MyApp} instead of looking in the VirtualStore. Copying the files from VirtualStore to Program folders solved the problem, never understood why
2. Second problem: now with Windows 8 some users [a minority of them] experience a different, strange fact; my app does not seem to be able to create files in the VirtualStore, but it can edit existing files. So if I create the files manually, everything works. If not the app does not work: files are not modified neither in the program folder nor in the virtual store

Now I want to fix up things. My plan is to move all the files that need modifications in CSIDL_LOCAL_APPDATA and to have the software save stuff there. Only executables will be in the program folder. For backward compatibility, though, it seems I cannot use SHGetKnownFolderPath which seem to be Vista+ specific. So I would use SHGetFolderPath, which is deprecated, I know, but should work in XP and act as a wrapper of SHGetKnownFolderPath in Vista+, which is good for me.

My questions:

• any ideas about my problems 1 & 2? I'd like to understand them in order to be sure I defeated them complitely.
• is my plan UAC compliant? As far as I understand it is, but...
• any way to assure XP compatibility but for my workaround? I do not feel comfortable using deprecated functions, but I definitely do not want to have two versions (XP and Vista+) to deal with!

Thank you very much for any help you can provide. Luca

Answer 1

These are my ideas to problems 1 & 2: 1. If you are writing the files your application is working with, your files will be written in a sub-directory of C:\Program Files. In order to write files at this location (C:\Program Files), your application must be run as Administrator. For compatibility reasons Windows Vista will write data to VirtualStore, if you try to write data to directories where you need Administrator rights to write data to. 2. Windows 8 does not use VirtualStore anymore. Read access does not require Administrator rights, however. Yes, your plan is UAC compliant. Your program and the files your program uses must be saved in two different directories. I would use the ShGetFolderPath function in order to get the path of the AppData directory. Additionally this function is compatible with Windows XP. You might check the operating system version and use the appropriate function/interface for this version. GetVersion and GetVersionEx have been changed in Windows 8. This is why I recommend the use of the Version Helper functions for version checking purposes on Windows 8.