your last point is a good one. How do i know if my sketch is linking to an external library? the IDE does this linnking automatically, when i'm making use of "string functions" for example, right?
Actually, I have no idea wether the IDE links to a single library containing all the function or to multiple small ones that are used selectively. Usually, you have all the string functions and other stdlib stuff in a single library, but it may be different for those little microcontrollers since code size is a concern. I'm also new to this, I was just imagining this may be an issue.
Anyways, I assume that somewhere down the toolchain, some sort of "dead code stripping" may be applied, stripping away any symbols that are not referenced in your program i.e. functions that you do not call. I don't think uploading lots of functions you never use into 8K or so flash space made too much sense?
Maybe someone who is better informed could clarify this? Thanks!