printf and similar stdio string formatting functions have caused a non-trivial amount of security exploits. If the compiler can statically check that your form

printf and similar stdio string formatting functions have caused a non-trivial amount of security exploits. If the compiler can statically check that your format string is valid and type checks, you can prevent this entire class of exploits. https://en.wikipedia.org/wiki/Printf#Vulnerabilities https://en.wikipedia.org/wiki/Printf#Vulnerabilities