but fixed width data types are super freaking slow if your doing intensive processing.

I'm not buying it. I want to see your timings and proof. First of all, this only applies to a very few internal loops that don't touch disk, so you can use the "cross platform rule" for 99.999 percent of code. But if you are down to that last inner loop that runs your 3D video game, I'll admit you will need to have platform dependent code paths. But this describes an infinitesimally tiny subset of the code in the world. The rest of the time, write easy to understand cross platform less buggy code!

um.. what do you mean, exactly? all types in C are fixed bitwidth. but the uintx_t types make it obvious what what programmer wants.