Question

what is “__printflike__ modifier” exactly? what does this term mean?

Answer 1

At a guess it tells the compiler you’re using that a function takes arguments in the form [anything, ] format, ... where the format, ... part look like the arguments to printf. The __printflike__ attribute lets the compiler test the types in the argument list against the string format. This comes up when you write a function like log(format, ...) and use vsprintf to subordinate the formatting work to the usual standard library functions before sending the string to some special log interface.

If you are using GCC then it is probably a #define in your project something like:

#define __printflike__ __attribute__((format(printf, 1, 2)))

Where 1, 2 means that format, ... appear in positions 1 and 2.