Is there a way to use ANSI C instead of ROBOTC to program Vex Robots?
So if you want to use GCC to program Vex Robots you are going to have to use PROS.
Or ConVEX (I could be wrong)
http://jpearman.github.io/convex/
Perhaps first of all carefully consider the reasons why you want ANSI C? RobotC is pretty good for it’s target audience, students getting started in C programming, but still retains most C language features. If you have to ask how do I program in ANSI C on a VEX Cortex then you’re probably better off using RobotC.
For the purposes of learning I see no value in adhering to strict C99 or C11. If you’re attempting to reuse code written in ANSI C to run on a VEX Cortex I’d suggest porting it to RobotC because you’ll learn a whole lot during that process.