I can read and understand C well enough, having coded in it for about 40 years now... but I left C for Perl and Perl for Python, I try not to code in C when I don't have to, these days, as the P languages are more productive, overall.

But there has to be special handling somewhere for opening std*, because they are already open, unlike other files.  That is no doubt where the bug is.  Can you point me at that code?