Bruno, you may be interested in this thread: http://gcc.gnu.org/ml/gcc/2007-06/msg00122.html.
It looks like for *printf-posix on mingw and other WOE32 environments, you will need to add a call to _set_printf_count_output to ensure that %n will work on mingw executables when run on Vista. (Thank goodness cygwin is immune to this stupidity.) I don't have access to Vista myself to try it out. -- Eric Blake
