How to Set Up a C99 Development Environment

Sat, 26 Sep 2026 00:00:00 +0000

Introduction

So you’re starting a C course. Congratulations, you’re about to spend a lot of quality time with segmentation faults and loose all of your hair. Before any of that, though, there’s one boring-but-critical thing nobody warns you about: your setup has to match the grader’s setup.

Here’s the trap. Your code doesn’t get a grade because it works on your machine. It gets a grade because it compiles and runs on the grader’s machine, with the grader’s compiler and the grader’s flags. Those are almost never the same as your defaults, and the gap has gotten wider recently: modern compilers no longer default to C99. Fresh GCC (version 15 and up) defaults to C23, and Apple’s clang on macOS defaults to C17. Neither of those is C99.

Makefile on KMiguel's blog

How to Set Up a C99 Development Environment

Introduction