C++ and S_ISDIR() problem

I'm trying to write a program that goes through folders recursively and lists 
what it finds in a specific format; however, I am having very strange 
problems with it in Ark Linux and I'm wondering if the problem is with AL, or 
if the posix headers have a major bug.

The problem so far is that S_ISDIR(...) is returning true in many cases on 
plain text files. This is my absolute first time using POSIX libraries in a 
program so I'm not even sure if I'm doing it right. 

I'll send the source code to anyone who thinks they can help on the 
understanding that although it doesn't have the GPL headers yet, it is a GPL 
application and all source code is licensed under the GPL.