your cv/resume should say what you did at the company in your words, not necessarily what that company called it. If you are/were a software developer there call it like you see it. The only time a title causes a problem for me with an interview candidate is when they are being overly boastful. "I was The Supreme Being of Software Development" would put your resume in my trash can pretty fast.
HR is going to scan the cv/resume for buzz words, so yes software developer needs to be there if that is what you are and want to do at the new job. If foo and bar are unknown to the world, choose to include it as part of the description "I worked on an internal project code named foo" if you like but try to explain what it was in familiar terms. So to get through HR's filter it needs to use more common stuff like "programmed in C for Linux and Windows". And just flat out list a bunch of languages or terms, "knowledge and experience in C, C++, Perl, Python ....". That will get you through the HR filter into the interviewers hands. At the same time though, if you list all the languages you learned in college, but really didnt use them beyond college, I am going to figure that out in the interview and you will probably lose my vote at the post interview meeting. That falls into that being too boastful category for me. You dont have to be an expert but if you give me the "I took a class in it, but that was 3 years ago and I dont remember it now". Interview is over. If you are rusty on the topic but did know it I will figure that out and that is good for you. If you are fresh out of college and dont have much of a resume other than flipping burgers at McDonalds then list I took classes in ... instead of Knowledge and experience in ...
Notice how none of this has anything to do with the job title at some former job? If you are happy with your job, do not quit over this. The fact that you are asking this question and threatening to quit sounds like you have one foot already out the door at this place. Problem is your title will have changed by the time you actually get those interviews and you will then have to realize this fear.
They can call you whatever they want so long as they spell your name right on the paycheck. Even if the business cards they give you have a blank line for your name after the title "Generic Employee".