I'm modifying an old C++ program to run on Vista. It does not require Admin privileges.

I've changed the code to put logfiles in \ProgramData\MyApp\. These logfiles are written with the stdio functions (fopen, fprintf, fclose).

Here's the problem:

1. UserA runs the program first, it creates \ProgramData\MyApp\MyLogFile.txt

2. UserB runs the program next, it tries to append to MyLogFile.txt and gets access denied.

I tried creating a null SECURITY_DESCRIPTOR and passing that to CreateFile(). That does create a file with "no permissions assigned", but it seems as if the first user to write to the file takes ownership and afterwards all the other non-admin users are out of luck.

It's important that all users share the same logfiles, but it's also important that I change as little code as possible.