Looks like SQLite is historically targetting a range of platforms that includes ones without a fully functional, standard-compliant printf(). Yes, that means it doesn't rely on much of anything elese provided by the C runtime and the operating system.

That reminds me: as an emebedded systems programmer, I've encountered a proper standards-compliant C compiler that allowed switching between a full, light and no version of printf() with a switch - you were allowed to omit just that one bit of the standard library for some significant savings in RAM and ROM usage. Of course, it was a little wonder for me at the time that a standards-compliant C compiler existed on that platform at all, but to realize that printf() function could often be the most heavy part of the application was another thing altogether... mind-expanding, really. The lesser C compiler vendors would just cut corners on the standard library implementation where they see fit, but that one left standard compliance as an option.