The trouble stems from the C Standard being copyrighted. Hence, anyone writing online documentation is forced to rewrite and rephrase what the Standard says. The Standard is written in very precise language, and is vetted by the best and most persnickety C programmers.

But the various rewrites and rephrases? Nope. If you absolutely, positively want to get it right, refer to the C Standard.

printf is particularly troublesome. The interactions between argument types and the various formatting flags is not at all simple.

Other sources of error are the 0 handling of `n` functions, and behavior when a NaN is seen.