I'd prefer if it were more letters. It bothers me when API designers omit random letters just to save a few keystrokes. These are particularly egregious because I keep forgetting which letters they kept. Is it "chk"? or "ckd"? or "chd"? or something else?
I wrote a portability library that wraps these with compiler intrinsic and standard C fallbacks. I chose to spell out the full word in addition to making the type explicit. It's a lot more verbose of course but a lot clearer to read:
A 7 letter function to add two numbers and that returns a boolean... not entirely sure I'd call that 'sane'.