an empty initializer, such as uint8_t foo[] = { }; raises a warning: "use of GNU empty initializer extension" using -pedantic. This adds a dummy NUL byte that's not accounted in the len counter. So, now it produces: uint8_t foo[] = { 0x0 }; size_t foo_len = 0;

plus some doc improvements and a missing return

thanks Ben for noticing it!