The CE documentation mentions directories, too, but is silent on the 
FILE_FLAG_BACKUP_SEMANTICS use for them. Also, even using that flag, I 
can't open a directory under CE. It seems that this check is 
superfluous there.

I can also confirm that you get an error if you try to redirect stdin 
via the commandline to a dir even before the executable is even 
launched. The only way to still have a dir as stdin could be to use 
CreateProcess(), but I'm neither sure nor do I care about such abuses.

Do you want to remove the whole check for MS Windows then? Are you 
otherwise comfortable with the second part of the patch, the one about 
resolving argv[0]?